What can be cooked from squid: quick and tasty

The operating modes are set using a potentiometer. Together with capacitors C2 and C3, it forms phase-shifting chains, each of which, triggered during its half-cycle, opens the corresponding thyristor for a certain period of time. As a result, the primary winding of the welding T1 turns out to be adjustable 20-215 V. Transforming in the secondary winding, the required -Usv allow you to easily ignite the arc for welding at alternating (terminals X2, X3) or rectified (X4, X5) current.

Fig. 1. Self-made welding machine based on LATR.

A welding transformer based on the widespread LATR2 (a), its connection to the circuit diagram of a home-made adjustable welding machine for alternating or direct current (b) and a voltage diagram explaining the operation of the transistor controller of the electric arc combustion mode.

Resistors R2 and R3 bypass the control circuits of thyristors VS1 and VS2. Capacitors C1, C2 reduce to an acceptable level of radio interference accompanying an arc discharge. A neon lamp with a current-limiting resistor R1 is used in the role of an indicator light HL1, signaling that the device is switched on to the household power grid.

To connect the "welder" to the apartment wiring, a conventional plug X1 is used. But it is better to use a more powerful electrical connector, which is commonly called "Euro plug-Euro socket". And as a switch SB1, a VP25 "bag" is suitable, designed for a current of 25 A and allowing you to open both wires at once.

As practice shows, it makes no sense to install any kind of fuses (anti-overload machines) on the welding machine. Here you have to deal with such currents, when exceeded, the protection at the input of the network into the apartment will necessarily work.

For the manufacture of the secondary winding from the base LATR2, the casing, the current collector slider and the fastening fittings are removed. Then, on the existing 250 V winding (127 and 220 V taps remain unclaimed), reliable insulation (for example, made of varnished cloth) is applied, on top of which a secondary (step-down) winding is placed. And this is 70 turns of an insulated copper or aluminum bus, having a diameter of 25 mm2. It is acceptable to perform the secondary winding from several parallel wires with the same overall cross-section.

Winding is more convenient for two people. While one, trying not to damage the insulation of adjacent turns, carefully pulls and lay the wire, the other holds the free end of the future winding, protecting it from twisting.
The upgraded LATR2 is placed in a protective metal casing with ventilation holes, on which a circuit board made of 10-mm getinax or fiberglass with a SB1 packet switch, a thyristor voltage regulator (with a resistor R6), an HL1 light indicator for connecting the device to the network and output terminals for welding on alternating (X2, X3) or constant (X4, X5) current.

In the absence of a basic LATR2, it can be replaced with a home-made "welder" with a magnetic core made of transformer steel (core section 45-50 cm2). Its primary winding should contain 250 turns of PEV2 wire with a diameter of 1.5 mm. Secondary is no different from that used in the modernized LATR2.

At the output of the low-voltage winding, a rectifier unit with power diodes VD3-VD10 is installed for direct current welding. In addition to these valves, more powerful analogs are quite acceptable, for example, D122-32-1 (rectified current - up to 32 A).
Power diodes and thyristors are installed on heat sinks, heat sinks, each with an area of ​​at least 25 cm2. The axis of the adjusting resistor R6 is brought out from the casing. A scale with divisions corresponding to specific values ​​of direct and alternating voltage is placed under the handle. And next to it is a table of the dependence of the welding current on the voltage on the secondary winding of the transformer and on the diameter of the welding electrode (0.8-1.5 mm).

Of course, homemade electrodes made of carbon steel "wire rod" with a diameter of 0.5-1.2 mm are also acceptable. Workpieces with a length of 250-350 mm are covered with liquid glass - a mixture of silicate glue and crushed chalk, leaving unprotected 40-mm ends required for connecting to a welding machine. The coating is thoroughly dried, otherwise it will start "shooting" during welding.

Although for welding you can use both alternating (terminals X2, X3) and constant (X4, X5) current, the second option, according to welders' reviews, is preferable to the first. Moreover, polarity plays an important role. In particular, when the "plus" is applied to the "ground" (welded object) and, accordingly, the electrode is connected to the terminal with the "minus" sign, the so-called forward polarity takes place. It is characterized by the release of more heat than with reverse polarity, when the electrode is connected to the positive terminal of the rectifier, and the "mass" - to the negative. Reverse polarity is used when it is necessary to reduce the generation of heat, for example, when welding thin metal sheets. Almost all the energy released by the electric arc is spent on the formation of a weld, and therefore the penetration depth is 40-50 percent greater than with a current of the same magnitude, but of straight polarity.

And a few more very significant features. An increase in the arc current at a constant welding speed leads to an increase in the penetration depth. Moreover, if the work is carried out on alternating current, then the last of the named parameters becomes 15-20 percent less than when using direct current of reverse polarity. The welding voltage has little effect on the penetration depth. But the width of the seam depends on Usv: with increasing voltage, it increases.

Hence, an important conclusion for those involved in, say, welding when repairing a car body made of thin sheet steel: the best results will be obtained by direct current welding of reverse polarity with a minimum voltage (but sufficient for stable arc burning).

The arc must be kept as short as possible, the electrode is then consumed evenly, and the penetration depth of the metal being welded is maximum. The seam itself turns out to be clean and durable, practically free of slag inclusions. And you can protect yourself from rare splashes of the melt, which are difficult to remove after the product has cooled down, by rubbing the near-weld surface with chalk (the drops will roll off without adhering to the metal).

Excitation of the arc is carried out (after applying the corresponding -Usv to the electrode and "mass") in two ways. The essence of the first is in a light touch of the electrode to the parts to be welded, followed by its removal by 2-4 mm to the side. The second method resembles striking a match over a box: sliding the electrode over the surface to be welded, it is immediately taken away a short distance. In any case, you need to catch the moment of the arc and only then, smoothly moving the electrode over the seam formed immediately, maintain its quiet combustion.

Depending on the type and thickness of the welded metal, one or another electrode is selected. If, for example, there is a standard assortment for a St3 sheet with a thickness of 1 mm, electrodes with a diameter of 0.8-1 mm are suitable (this is basically the design in question). For welding on 2-mm rolled steel, it is desirable to have a more powerful "welder" and a thicker electrode (2-3 mm).
For welding jewelry made of gold, silver, cupronickel, it is better to use a refractory electrode (for example, tungsten). It is possible to weld less oxidation-resistant metals using carbon dioxide protection.

In any case, work can be performed both with a vertically positioned electrode and tilted forward or backward. But sophisticated professionals say: when welding with an angle forward (meaning an acute angle between the electrode and the finished seam), a more complete penetration and a smaller width of the seam itself are provided. Welding with a backward angle is recommended only for overlapping joints, especially when you have to deal with profile rolled products (angle, I-beam and channel).

An important thing is the welding cable. For the device under consideration, a copper stranded (total cross-section of about 20 mm2) in rubber insulation is the best fit. The required amount is two one and a half meter sections, each of which should be equipped with a carefully crimped and soldered terminal lug for connection to the "welder". For direct connection with the "mass", a powerful crocodile clip is used, and with an electrode - a holder resembling a three-pronged fork. You can also use a car "cigarette lighter".

Personal safety must also be taken care of. In electric arc welding, try to protect yourself from sparks, and even more so from splashes of molten metal. It is recommended to wear loose-fitting canvas clothing, protective gloves and a mask that protects the eyes from the harsh radiation of an electric arc (sunglasses are not suitable here).
Of course, we must not forget about the "Safety rules when performing work on electrical equipment in networks with a voltage of up to 1 kV". Electricity does not forgive carelessness!

The basis of the first design welding machine- laboratory transformer LATR for 9 A. The casing and all the fittings are removed from it, only the winding remains on the core. In the transformer of the welding machine, it will be primary (network). This winding is insulated with two layers of electrical tape or varnished cloth. A secondary winding is wound over the insulation - 65 turns of a wire or a set of wires with a total cross section of 12-13 mm 2. The winding is reinforced with electrical tape.The transformer is installed on an insulating stand made of textolite or getinax inside a casing made of sheet steel or duralumin with a thickness of no more than 3 mm. Holes with a diameter of 8-10 mm are made in the cover of the casing, on the rear and side walls for ventilation. A steel bar handle is reinforced from above.

An indicator light, a switch for 220 V, 9 A and the terminals of the secondary winding are brought out to the front panel - a cable with an electrode holder is attached to one of them, a cable is connected to the other, the other end of which is pressed against the workpiece during welding. In addition, this last terminal must be grounded during operation. The indicator lamp of alternating current of the type CH-1, CH-2, M.N-5 signals the switching on of the apparatus.

The electrodes for this apparatus must have a diameter of no more than 1.5 mm.

For a welding machine of the second design(fig. 126) it is necessary to make a transformer. A core with a cross section of about 45 cm 2 is collected from the W-shaped transformer iron, a primary (network) winding is wound on it - 220 turns of a 1.5 mm PEL wire. Taps are made from the 190th and 205th turns, after which the winding is insulated with two or three layers of electrical tape or varnished cloth.

A secondary winding is wound over the insulated primary winding.

It contains 65 turns of wire or a set of wires with a total cross-section of 25-35 mm 2. It is best to use PEL or PEV 1.0-1.5 mm wires in the set. As in the first design, the finished transformer is fixed on an insulating support and placed in a casing. The walls of the casing must be at least 30 mm away from the transformer. On the front panel, in addition to the light, the switch and the terminals, a switch is brought out that regulates the current strength.

In a welding machine of this design, electrodes with a diameter of 1.5 and 2 mm can be used.

When working, you must wear a mask. You cannot connect this device to a home network, since it consumes about 3 kW. The device can be used in a workshop if there is an electrical network to which it is allowed to connect devices with a power of up to 5 kW.

Attention! Check grounding before starting work.

Wear dry tarpaulin clothing and gloves during welding. Place a rubber mat under your feet. Do not work without a mask.

Do-it-yourself welding in this case does not mean welding technology, but home-made equipment for electric welding. Working skills are acquired through industrial practice. Of course, before you go to the workshop, you need to master the theoretical course. But you can only put it into practice if you have something to work on. This is the first argument in favor of taking care of the availability of the appropriate equipment while mastering welding on your own.

Second, a purchased welding machine is expensive. Renting is also not cheap, because the probability of its failure with unskilled use is great. Finally, in the hinterland, getting to the nearest location where you can rent a welder can simply be long and difficult. All in all, it is better to start the first steps in welding metals with making a welding machine with your own hands. And then - let him stand in the barn or garage until the occasion. It is never too late to spend money on branded welding, if it goes well.

What are we going to talk about

This article discusses how to make equipment at home for:

• Electric arc welding with alternating current of industrial frequency 50/60 Hz and direct current up to 200 A. This is enough to weld metal structures approximately to the fence from corrugated board on a frame from a professional pipe or welded garage.
• Microarc welding of wire twists is very simple and useful when laying or repairing electrical wiring.
• Spot impulse resistance welding - can be very useful when assembling products from a thin steel sheet.

What we will not talk about

First, let's skip gas welding. The equipment for it costs pennies in comparison with consumables, you can't make gas cylinders at home, and a homemade gas generator is a serious risk to life, plus carbide is expensive now, where it still goes on sale.

The second is inverter arc welding. Indeed, the semiautomatic welding inverter allows the novice amateur to cook quite critical designs. It is lightweight and compact and can be carried by hand. But the retail purchase of inverter components, which allows you to consistently maintain a high-quality seam, will cost more than the finished device. An experienced welder will try to work with simplified homemade products and refuse - "Give me a normal machine!" Plus, or rather a minus - to make a more or less decent welding inverter, you need to have quite solid experience and knowledge in electrical engineering and electronics.

The third is argon arc welding. Whose light hand the assertion that it is a hybrid of gas and arc, is unknown. In fact, this is a kind of arc welding: the inert gas argon does not participate in the welding process, but creates a cocoon around the working area, isolating it from air. As a result, the weld is chemically clean, free from impurities of metal compounds with oxygen and nitrogen. Therefore, non-ferrous metals can be cooked under argon, incl. dissimilar. In addition, it is possible to reduce the welding current and arc temperature without compromising its stability and to weld with a non-consumable electrode.

It is quite possible to make equipment for argon-arc welding at home, but gas is very expensive. It is hardly necessary to cook aluminum, stainless steel or bronze in the order of routine economic activity. And if you really need to, it is easier to rent argon welding - compared to how much (in money) gas will go back into the atmosphere, this is a penny.

Transformer

The basis of all "our" types of welding is a welding transformer. The procedure for calculating it and design features significantly differ from those of power supply (power) and signal (sound) transformers. The welding transformer operates intermittently. If designed for maximum current as continuous transformers, it will turn out to be prohibitively large, heavy and expensive. Ignorance of the features of electric arc welding transformers is the main reason for the failure of amateur designers. Therefore, we will walk through the welding transformers in the following order:

• a little theory - on the fingers, without formulas and zaum;
• features of the magnetic cores of welding transformers with recommendations for choosing from accidentally turned up;
• tests of the second-hand available;
• calculation of the transformer for the welding machine;
• preparation of components and winding of windings;
• trial assembly and debugging;
• commissioning.

An electrical transformer can be likened to a storage tank for a water supply. This is a rather deep analogy: a transformer operates due to the reserve of magnetic field energy in its magnetic circuit (core), which can many times exceed that instantly transmitted from the power supply network to the consumer. And the formal description of losses due to eddy currents in steel is similar to that for water losses due to infiltration. Power losses in the copper of the windings are formally similar to the pressure losses in pipes due to viscous friction in the liquid.

Note: the difference is in the loss for evaporation and, accordingly, in the scattering of the magnetic field. The latter in the transformer are partially reversible, but they smooth out the peaks of energy consumption in the secondary circuit.

External characteristics of electrical transformers

An important factor in our case is the external current-voltage characteristic (VVAC) of the transformer, or simply its external characteristic (VX) - the dependence of the voltage on the secondary winding (secondary) on the load current, with a constant voltage on the primary winding (primary). For power transformers, VX is rigid (curve 1 in the figure); they are like a shallow vast basin. If it is properly insulated and covered with a roof, then water loss is minimal and the pressure is quite stable, no matter how consumers turn the taps. But if there is a gurgle in the drain - sushi oars, the water is drained. With regard to transformers, the power engineer must keep the output voltage as stable as possible to a certain threshold, less than the maximum instantaneous power consumption, be economical, small and light. For this:

• The steel grade for the core is chosen with a more rectangular hysteresis loop.
• Structural measures (core configuration, calculation method, configuration and arrangement of windings) in every possible way reduce dissipation losses, losses in steel and copper.
• The induction of the magnetic field in the core is taken less than the maximum allowable for the transmission of the current form, because its distortion reduces efficiency.

Note: transformer steel with "angular" hysteresis is often called magnetic hardness. This is not true. Hard magnetic materials retain strong residual magnetization, they are made by permanent magnets. And any transformer iron is soft magnetic.

It is impossible to cook from a transformer with a rigid VX: the seam is torn, burnt out, the metal is splashed. The arc is inelastic: I almost moved it with the electrode, it goes out. Therefore, the welding transformer is already made similar to a conventional water tank. Its IQ is soft (normal dissipation, curve 2): as the load current increases, the secondary voltage decreases smoothly. The normal scatter curve is approximated by a straight line falling at an angle of 45 degrees. This allows, due to a decrease in efficiency, to briefly remove several times more power from the same iron, or, respectively. to reduce the weight and dimensions and the cost of the transformer. In this case, the induction in the core can reach the saturation value, and for a short time even exceed it: the transformer will not go into a short circuit with zero power transfer, like a "silovik", but will heat up. Quite long: the thermal time constant of the welding transformers is 20-40 minutes. If you then let it cool down and there was no unacceptable overheating, you can continue to work. The relative drop in the secondary voltage ΔU2 (it corresponds to the swing of the arrows in the figure) of normal dispersion increases smoothly with an increase in the amplitude of oscillations of the welding current Iw, which makes it easy to keep the arc in any type of work. The following properties are provided:

• The steel of the magnetic core is taken with a more "oval" hysteresis.
• Normalize reversible scattering losses. By analogy: the pressure has dropped - consumers will not pour out a lot and quickly. And the operator of the water utility will have time to turn on the pumping.
• The induction is chosen close to the limit for overheating, this allows, by reducing the cosφ (parameter equivalent to efficiency) at a current significantly different from sinusoidal, to take more power from the same steel.

Note: reversible leakage losses means that some of the lines of force penetrate the secondary through the air bypassing the magnetic circuit. The name is not quite apt, as well as "useful scattering", since "Reversible" losses for the efficiency of a transformer are no more useful than irreversible ones, but they soften the VC.

As you can see, the conditions are completely different. So, is it imperative to look for iron from a welder? Optional, for currents up to 200 A and peak power up to 7 kVA, but this will be enough on the farm. By design and design measures, as well as with the help of simple additional devices (see below), we will obtain curve 2a on any BX gland, somewhat more rigid than normal. In this case, the efficiency of energy consumption of welding is unlikely to exceed 60%, but for occasional work it is not scary for oneself. But on delicate works and low currents, it will be easy to keep the arc and welding current, without much experience (ΔU2.2 and Ib1), at high currents Ib2 we will get an acceptable weld quality, and it will be possible to cut metal up to 3-4 mm.

There are also welding transformers with steeply dipping VX, curve 3. This is more like a pumping pump: either the output flow is in the nominal value regardless of the feed height, or it does not exist at all. They are even more compact and lightweight, but in order to withstand the welding mode on a steeply dipping VX, it is necessary to respond to fluctuations ΔU2.1 of the order of a volt in a time of the order of 1 ms. Electronics can do it, therefore transformers with "steep" VX are often used in welding semiautomatic devices. If from such a transformer you cook by hand, then the seam will go sluggish, undercooked, the arc is again inelastic, and when you try to ignite it again, the electrode now and then sticks.

Magnetic cores

The types of magnetic cores suitable for the manufacture of welding transformers are shown in Fig. Their names begin with a letter combination acc. standard size. L means tape. For a welding transformer L or without L - there is no significant difference. If the prefix contains M (SHLM, PLM, SHM, PM) - ignore without discussion. This iron of reduced height, unsuitable for the welder, with all other outstanding advantages.

Magnetic cores of transformers

The letters of the type are followed by the numbers denoting a, b and h in Fig. For example, at Ш20х40х90 dimensions cross section core (central rod) 20x40 mm (a * b), and the height of the window h - 90 mm. Core cross-sectional area Sс = a * b; window area Sok = c * h is needed for accurate calculation of transformers. We will not use it: for an accurate calculation, you need to know the dependences of losses in steel and copper on the value of induction in the core of a given standard size, and for them - the steel grade. Where can we get it if we wind it on random hardware? We will calculate using a simplified method (see below), and then we will bring it to the test. It will take more work, but we will get welding on which you can actually work.

Note: if the iron is rusty from the surface, then nothing, the properties of the transformer will not suffer from this. But if there are spots of tarnishing flowers on it, this is a marriage. Once upon a time, this transformer was very overheated and the magnetic properties of its iron were irreversibly deteriorated.

Another important parameter of the magnetic circuit is its mass, weight. Since the specific gravity of steel is unchanged, it determines the volume of the core, and, accordingly, the power that can be taken from it. For the manufacture of welding transformers, magnetic cores of mass are suitable:

• Oh, OL - from 10 kg.
• P, PL - from 12 kg.
• Ш, ШЛ - from 16 kg.

Why Sh and ShL are needed more heavily is understandable: they have an "extra" lateral rod with "shoulders". The OL can be easier, because there are no angles in it for which an excess of iron is needed, and the bends of the magnetic field lines are smoother and for some other reasons, which are already in the next. section.

The prime cost of transformers on tori is high due to the complexity of their winding. Therefore, the use of toroidal cores is limited. A torus suitable for welding can, firstly, be removed from the LATR, a laboratory autotransformer. Laboratory, so it should not be afraid of overloads, and the LATR iron provides VC close to normal. But…

LATR is a very useful thing, first. If the core is still alive, it is better to restore the LATR. Suddenly it is not needed, you can sell it, and the proceeds will be enough for welding suitable for your needs. Therefore, it is difficult to find "bare" LATR cores.

Second - LATRs with power up to 500 VA are weak for welding. From iron LATR-500, you can achieve welding with an electrode of 2.5 in the mode: cook for 5 minutes - it cools down for 20 minutes, and we heat up. As in the satire of Arkady Raikin: mortar bar, brick yok. Brick bar, mortar yok. LATRs 750 and 1000 are very rare and useful.

The torus, which is also suitable for all its properties, is the stator of the electric motor; welding from it will turn out even for an exhibition. But it is no easier to find it than the LATR iron, and it is much more difficult to wind it on it. In general, a welding transformer from an electric motor stator is a separate topic, there are so many difficulties and nuances. First of all - with the winding of a thick wire on the "donut". Without experience in winding toroidal transformers, the probability of spoiling an expensive wire, and not getting welding, is close to 100%. Therefore, alas, with the cooking apparatus on the troidal transformer will have to be postponed.

Armor cores are structurally designed for minimal dispersion, and it is practically impossible to normalize it. Welding on a conventional W or SL will turn out to be too tough. In addition, the conditions for cooling the windings on Ш and ШЛ are the worst. The only armored cores suitable for a welding transformer are of increased height with spaced wafer windings (see below), on the left in Fig. The windings are separated by dielectric non-magnetic heat-resistant and mechanically strong gaskets (see below) with a thickness of 1 / 6-1 / 8 of the core height.

Plates of armored magnetic cores and wafer windings

The core Ш is loaded (assembled from plates) for welding necessarily over the cover, i.e. yoke-plate pairs are alternately oriented back and forth relative to each other. The method of normalizing scattering by non-magnetic gap for a welding transformer is unsuitable, because losses are irreversible.

If you turn up a lined Ш without a yoke, but with a notch of the plates between the core and the bulkhead (in the center), you are in luck. Signal transformer plates are loaded, and steel on them, to reduce signal distortion, goes to give normal VC initially. But the likelihood of such luck is very small: signal transformers for kilowatt powers are a rare curiosity.

Note: do not try to collect a high Ш or ШЛ from a pair of ordinary ones, as on the right in Fig. A continuous straight gap, albeit very thin, is irreversible scattering and steeply dipping VX. Here, the dissipation losses are almost the same as the evaporation losses of water.

Winding transformer windings on a bar core

Rod cores are most suitable for welding. Of these - those charged in pairs of identical L-shaped plates, see Fig., Their irreversible scattering is the smallest. Second, the windings P and PLov are wound in exactly the same halves, half turns for each. The slightest magnetic or current asymmetry - the transformer hums, heats up, but there is no current. The third thing that may seem unobvious to those who have not forgotten the school rule of the gimbal is that the windings are wound on the rods in one direction... Is there something wrong? Does the magnetic flux in the core have to be closed? And you twist the gimbals along the current, not along the turns. The directions of the currents in the semi-windings are opposite, and the magnetic fluxes are shown there. You can also check if the protection of the wiring is reliable: supply the network to 1 and 2 ', and close 2 and 1'. If the machine gun does not immediately knock out, then the transformer will howl and shake. However, who knows what you have with the wiring. Better not.

Note: you can also find recommendations - winding the windings of the welding P or PL on different rods. Like, VX is softening. That's how it is, but a special core is needed for this, with rods of different sections (secondary housing on the smaller one) and recesses that release the lines of force into the air in the desired direction, see Fig. on right. Without this, we will get a loud, shaking and gluttonous, but not a boiling transformer.

If there is a transformer

A 6.3 A circuit breaker and an AC ammeter will also help determine the suitability of an old welder lying around God knows where and the devil knows how. An ammeter is needed either a non-contact induction (current clamp) or an electromagnetic switch for 3 A. A multimeter with alternating current limits will be unacceptable to lie, because the shape of the current in the circuit will be far from sinusoidal. Another - a liquid household thermometer with a long neck, or, better, a digital multimeter with the ability to measure temperature and a probe for this. A step-by-step procedure for testing and preparing for further operation of the old welding transformer is as follows:

Calculation of the welding transformer

In runet, you can find different methods for calculating welding transformers. Despite the apparent inconsistency, most of them are correct, but with full knowledge of the properties of steel and / or for a specific series of standard types of magnetic cores. The proposed methodology was developed in Soviet times, when instead of a choice there was a shortage of everything. For the transformer calculated according to it, VX falls a little steeply, somewhere between curves 2 and 3 in Fig. at the beginning. For cutting, this is suitable, and for thinner work, the transformer is supplemented external devices(see below), stretching VX along the current axis to curve 2a.

The basis of the calculation is usual: the arc burns stably under a voltage of Ud 18-24 V, and its ignition requires an instantaneous current 4-5 times higher than the nominal welding current. Accordingly, the minimum no-load voltage Uхх of the secondary will be 55 V, but for cutting, since everything possible is squeezed out of the core, we take not the standard 60 V, but 75 V. There is no other way: it is unacceptable for TB, and the iron will not pull out. Another feature, for the same reasons, is the dynamic properties of the transformer, i.e. its ability to quickly switch from a short circuit mode (say, when closed by drops of metal) into a working one, is maintained without additional measures. True, such a transformer is prone to overheating, but since it is its own and in front of our eyes, and not in the far corner of a workshop or site, we will consider this permissible. So:

• According to the formula from clause 2 before. the list we find the overall power;
• We find the maximum possible welding current Iw = Pg / Ud. 200 A are provided if 3.6-4.8 kW can be removed from iron. True, in the 1st case, the arc will be sluggish, and it will be possible to cook only with a two or 2.5;
• We calculate the operating current of the primary at the maximum allowable mains voltage for welding I1рmax = 1.1Pg (VA) / 235 V. In fact, the norm for the network is 185-245 V, but for a home-made welder at the limit this is too much. We take 195-235 V;
• Based on the found value, we determine the operating current circuit breaker as 1.2I1рmax;
• We accept the current density of the primary J1 = 5 A / sq. mm and, using I1рmax, we find the diameter of its wire in copper d = (4S / 3.1415) ^ 0.5. Its full diameter with self-isolation is D = 0.25 + d, and if the wire is ready - tabular. To work in the "brick bar, yok solution" mode, you can take J1 = 6-7 A / sq. mm, but only if the required wire is not available and is not expected;
• We find the number of turns per volt of the primary: w = k2 / Sс, where k2 = 50 for Ш and П, k2 = 40 for ПЛ, ШЛ and k2 = 35 for О, ОЛ;
• We find the total number of its turns W = 195k3w, where k3 = 1.03. k3 takes into account the energy losses of the winding for dissipation in copper, which is formally expressed by a somewhat abstract parameter of the winding's own voltage drop;
• We set the stacking coefficient Ku = 0.8, add 3-5 mm each to a and b of the magnetic circuit, calculate the number of layers of the winding, medium length turn and length of wire
• We calculate in a similar way the secondary at J1 = 6 A / sq. mm, k3 = 1.05 and Ku = 0.85 for voltages of 50, 55, 60, 65, 70 and 75 V, in these places there will be taps for rough adjustment of the welding mode and compensation for fluctuations in the supply voltage.

Winding and finishing

Wire diameters in the calculation of windings are usually more than 3 mm, and varnished winding wires with d> 2.4 mm in widespread sale rare. In addition, the welder's windings experience strong mechanical loads from electromagnetic forces, therefore, finished wires are needed with an additional textile winding: PELSH, PELSHO, PB, PBD. They are even more difficult to find and very expensive. The length of the wire per welder is such that cheaper bare wires can be insulated on their own. An additional advantage - twisting to the desired S several stranded wires, we get a flexible wire, which is much easier to wind. Anyone who has tried to manually lay a tire of at least 10 squares on the carcass will appreciate it.

Isolation

Let's say there is a 2.5 sq. mm in PVC insulation, and the secondary needs 20 m by 25 squares. We prepare 10 coils or coils of 25 m each.We wind off about 1 m of wires from each and remove the standard insulation, it is thick and not heat-resistant. We twist the bare wires with a pair of pliers into an even tight braid, and wrap it, in order of increasing insulation cost:

• Masking tape with 75-80% overlap, i.e. in 4-5 layers.
• Mitcal tape with an overlap of 2 / 3-3 / 4 turns, i.e. 3-4 layers.
• Cotton tape with an overlap of 50-67%, 2-3 layers.

Note: the wire for the secondary winding is prepared and wound after winding and testing of the primary, see below.

A thin-walled home-made frame will not withstand the pressure of the turns of a thick wire, vibrations and jerks during operation. Therefore, the windings of welding transformers are made frameless biscuit, and on the core they are fixed with wedges made of textolite, fiberglass or, in extreme cases, bakelite plywood soaked in liquid varnish (see above). The instructions for winding the windings of the welding transformer are as follows:

• We prepare a wooden boss with a height in the height of the winding and with dimensions in diameter 3-4 mm larger than a and b of the magnetic circuit;
• We nail or fasten temporary plywood cheeks to it;
• We wrap the temporary frame in 3-4 layers with a thin plastic wrap with an approach to the cheeks and a twist on their outer side so that the wire does not stick to the tree;
• We wind a pre-insulated winding;
• On the winding, we soak twice before flowing through with liquid varnish;
• after the impregnation dries, carefully remove the cheeks, squeeze out the lug and tear off the film;
• we tie the winding in 8-10 places evenly around the circumference with a thin cord or propylene twine - it is ready for testing.

Lapping and homework

We load the core into a biscuit and tighten it with bolts, as expected. The winding tests are carried out completely similar to the tests of the questionable finished transformer, see above. Better to use LATR; Iхх at an input voltage of 235 V should not exceed 0.45 A per 1 kVA of the overall power of the transformer. If it is more, the primary organization will be killed. Winding wire connections are made on bolts (!), Insulated with a heat-shrinkable tube (HERE) in 2 layers or cotton tape in 4-5 layers.

According to the test results, the number of turns of the secondary is corrected. For example, the calculation gave 210 turns, but in reality Iхх got into the norm at 216. Then we multiply the calculated turns of the secondary sections by 216/210 = 1.03 approx. Do not neglect the decimal places, the quality of the transformer largely depends on them!

After finishing, the core is disassembled; tightly wrap the biscuit with the same masking tape, calico or "rag" tape in 5-6, 4-5 or 2-3 layers, respectively. Wind across the turns, not along them! Now we soak it again with liquid varnish; when dry - twice undiluted. This biscuit is ready, you can make a secondary one. When both are on the core, we once again test the transformer on Ixx (suddenly it curled somewhere), fix the biscuits and impregnate the entire transformer with normal varnish. Phew, the most dreary part of the work is over.

But we still have it too cool, have you forgotten? It needs to be softened. The simplest way- the resistor in the secondary circuit is not suitable for us. Everything is very simple: on a resistance of only 0.1 Ohm at a current of 200, 4 kW will dissipate by heat. If we have a welder for 10 or more kVA, and we need to weld thin metal, a resistor is needed. Whatever the current is set by the regulator, its emissions during arc striking are inevitable. Without active ballast, they will burn through the seam in places, and the resistor will extinguish them. But to us, low-powered, it will not be of any use to him.

Adjusting the reactive coil welding mode

The reactive ballast (inductance coil, choke) will not take away excess power: it will absorb current surges, and then smoothly give them to the arc, this will stretch the VX as it should. But then you need a choke with dispersion control. And for him - the core is almost the same as that of the transformer, and rather complicated mechanics, see fig.

Homemade ballast welding transformer

We will go the other way: we will apply active-reactive ballast, in the old welders colloquially called the gut, see fig. on right. Material - steel wire rod 6 mm. The diameter of the turns is 15-20 cm. How many of them are shown in Fig. it can be seen that this gut is correct for power up to 7 kVA. The air gaps between the turns are 4-6 cm. The active-reactive choke is connected to the transformer with an additional piece of welding cable (hose, simply), and the electrode holder is attached to it with a clip-clothespin. By selecting the attachment point, it is possible, coupled with switching to secondary taps, to fine-tune the operating mode of the arc.

Note: active-reactive choke in operation can be heated red-hot, therefore, it needs a non-combustible thermo-resistant dielectric non-magnetic lining. In theory, a special ceramic lodgment. It is permissible to replace it with a dry sand pillow, or already formally in violation, but not rough, the welding gut is laid on bricks.

But other?

Primitive welding electrode holder

This means, first of all, the electrode holder and the return hose connector (clamp, clothespin). They, since we have a transformer at the limit, you need to buy ready-made, and such as in Fig. on the right, don't. For a welding machine for 400-600 A, the quality of contact in the holder is not perceptible, and it will also withstand just winding the return hose. And our self-made, working with an effort, it seems to be unclear why.

Further, the body of the device. It needs to be made of plywood; desirably bakelite impregnated as described above. The bottom - from 16 mm thick, the panel with the terminal block - from 12 mm, and the walls and cover - from 6 mm, so that they do not come off during carrying. Why not sheet steel? It is a ferromagnet and in the stray field of the transformer can disrupt its operation, because we are drawing out everything that is possible from it.

As for the terminal blocks, the terminals themselves are made from bolts from M10. The basis is the same textolite or fiberglass. Getinaks, bakelite and carbolite are not suitable, they will soon crumble, crack and exfoliate.

Trying a constant

DC welding has a number of advantages, but the VC of any DC welding transformer is toughened. And ours, designed for the minimum possible power reserve, will become unacceptably tough. The choke-gut will no longer help here, even if it were running on direct current. In addition, expensive 200 A rectifier diodes must be protected from current and voltage surges. We need a return-absorbing infra-low frequency filter, FINCH. Although it looks reflective, the strong magnetic coupling between the halves of the coil must be taken into account.

DC arc welding circuit

The scheme of such a filter, known for many years, is shown in Fig. But immediately after its implementation by amateurs, it turned out that the operating voltage of the capacitor C is small: voltage surges during arc ignition can reach 6-7 values ​​of its Uхх, i.e. 450-500 V. Further, capacitors are needed to withstand the circulation of high reactive power, only and only oil and paper (MBGCH, MBGO, KBG-MN). About the mass and dimensions of single "cans" of these types (by the way, and not cheap) gives an idea of ​​the trace. fig., and on the battery they will need 100-200.

Oil-paper capacitors

With the magnetic core, the coils are easier, although not entirely. For him, 2 PLs of the TS-270 power transformer from old tube TVs - "coffins" (data are available in reference books and in the Russian Internet), or similar, or SHL with similar or large a, b, c and h are suitable. SL is assembled from 2 submarines with a gap, see fig., 15-20 mm. Fix it with textolite or plywood spacers. Winding - insulated wire from 20 sq. mm, how much will fit in the window; 16-20 turns. They wind it in 2 wires. The end of one is connected to the beginning of the other, this will be the midpoint.

Armored magnetic circuit with non-magnetic gap

The filter is adjusted along an arc at the minimum and maximum values ​​of Uхх. If the arc is at least sluggish, the electrode sticks, the gap is reduced. If the metal burns at maximum, they increase or, which will be more effective, cut off part of the side rods symmetrically. So that the core does not crumble from this, it is impregnated with liquid, and then normal varnish. Finding the optimum inductance is quite difficult, but then welding works flawlessly on alternating current.

Microarc

The purpose of micro-arc welding was mentioned at the beginning. The “equipment” for it is extremely simple: a step-down transformer 220 / 6.3 V 3-5 A. One electrode - the wire twisting itself (copper-aluminum, copper-steel can be used); the other is a graphite rod, like the lead from a 2M pencil.

Now more computer power supplies are used for micro-arc welding, or, for pulsed micro-arc welding, capacitor banks, see the video below. On direct current, the quality of work, of course, improves.

Video: homemade twist welding machine

Contact! There is a contact!

Resistance welding in industry is mainly used for spot, seam and butt welding. At home, primarily in terms of energy consumption, pulsed point is feasible. It is suitable for welding and welding thin, from 0.1 to 3-4 mm, steel sheet parts. Arc welding will burn through a thin wall, and if a part is a coin or less, then the softest arc will burn it entirely.

Spot resistance welding scheme

The principle of operation of spot resistance welding is illustrated in Fig: copper electrodes compress the parts with force, a current pulse in the steel-steel ohmic resistance zone heats the metal to the point that electrodiffusion occurs; the metal does not melt. The current is needed for this approx. 1000 A per 1 mm of thickness of the parts to be welded. Yes, a current of 800 A will take sheets of 1 and even 1.5 mm. But if this is not a craft for fun, but, for example, a galvanized corrugated fence, then the first strong gust of wind will remind you: "Man, but the current was rather weak!"

Nevertheless, resistance spot welding is much more economical than arc welding: the open-circuit voltage of the welding transformer for it is 2 V. It is the sum of 2-contact steel-copper potential differences and the ohmic resistance of the penetration zone. The transformer for resistance welding is calculated similarly to it for arc welding, but the current density in the secondary winding is taken from 30-50 A / sq. mm. The secondary of the contact welding transformer contains 2-4 turns, is well cooled, and its utilization factor (the ratio of welding time to idling and cooling time) is many times lower.

Runet has a lot of descriptions of homemade pulse-point welders from unusable microwaves. They are, in general, correct, but in repetition, as it is written in "1001 Nights", there is no benefit. And old microwave ovens are not piled up in the trash heaps. Therefore, we will deal with constructions less known, but, by the way, more practical.

Simple homemade installation contact welding

In fig. - device of the simplest apparatus for impulse spot welding... It can weld sheets up to 0.5 mm; for small crafts, it fits perfectly, and magnetic cores of this and larger standard size are relatively affordable. Its advantage, in addition to simplicity, is the clamping of the running rod of the welding tongs with a load. A third hand would not hurt to work with a contact-welding impulse, and if one has to squeeze the pliers with force, then it is generally inconvenient. Disadvantages - increased risk of accidents and injuries. If you accidentally give an impulse when the electrodes are brought together without the parts to be welded, then plasma will hit from the tongs, metal splashes will fly, the wiring protection will be knocked out, and the electrodes will fuse tightly.

Secondary winding - 16x2 copper bus. It can be drawn from strips of thin sheet copper (it will turn out to be flexible) or made from a piece of a flattened pipe for supplying the refrigerant of a household air conditioner. Manually insulate the bus as described above.

Here in fig. - drawings of an impulse spot welding apparatus are more powerful, for sheet welding up to 3 mm, and more reliable. Thanks to a rather powerful return spring (from the carapace of the bed), accidental convergence of the pliers is excluded, and the eccentric clamp provides a strong stable compression of the pliers, which greatly affects the quality of the welded joint. In which case the clamp can be instantly reset with one blow to the eccentric lever. The disadvantage is the insulating nodes of the ticks, there are too many of them and they are complicated. Another one is the aluminum pliers rods. Firstly, they are not as strong as steel, and secondly, they are 2 unnecessary contact differences. Although the heatsink on aluminum is certainly excellent.

About electrodes

Resistance welding electrode in insulating sleeve

In an amateur environment, it is more expedient to insulate the electrodes at the installation site, as shown in Fig. on right. The house is not a conveyor belt, the device can always be allowed to cool down so that the insulating sleeves do not overheat. Such a design will make it possible to make the rods from a durable and cheap steel professional pipe, and also lengthen the wires (up to 2.5 m this is permissible) and use a contact welding gun or remote pliers, see Fig. below.

In fig. on the right, one more feature of electrodes for spot resistance welding is visible: a spherical contact surface (heel). Flat heels are more durable, so electrodes with them are widely used in industry. But the diameter of the flat heel of the electrode should be equal to 3 thicknesses of the adjacent material to be welded, otherwise the penetration spot will be burned either in the center (wide heel) or along the edges (narrow heel), and corrosion will go from the welded joint even on stainless steel.

Resistance Welding Gun and Remote Pliers

The last thing about electrodes is their material and dimensions. Red copper quickly burns out, so purchased electrodes for resistance welding are made of copper with a chromium additive. These should be used, given the current copper prices, this is more than justified. The diameter of the electrode is taken depending on the mode of its use, based on a current density of 100-200 A / sq. mm. The length of the electrode according to the conditions of heat transfer is not less than 3 of its diameters from the heel to the root (the beginning of the shank).

How to give impetus

In the simplest home-made devices for pulse-contact welding, a current pulse is given manually: they simply turn on the welding transformer. This, of course, is not good for him, and welding is either lack of penetration or burnout. However, it is not so difficult to automate the feeding and normalization of welding pulses.

Diagram of a simple pulse shaper for resistance welding

A diagram of a simple, but reliable and proven by long-term practice of the welding pulse generator is given in Fig. The auxiliary transformer T1 is a conventional power transformer of 25-40 W. Winding voltage II - according to the backlight lamp. You can instead put 2 LEDs connected in antiparallel with a damping resistor (usual, 0.5 W) 120-150 Ohm, then the voltage II will be 6 V.

Voltage III - 12-15 V. You can 24, then the capacitor C1 (ordinary electrolytic) is needed for a voltage of 40 V. Diodes V1-V4 and V5-V8 are any rectifier bridges for 1 and from 12 A, respectively. Thyristor V9 - for 12 or more A 400 V. Optothyristors from computer power supplies or TO-12.5, TO-25 are suitable. Resistor R1 is a wire-wound resistor that regulates the pulse duration. T2 transformer - welding.

1.1. General information.

Depending on the type of current used for welding, a distinction is made between welders direct and alternating current. Welding machines using low direct currents are used for welding thin sheet metal, in particular, roofing and automotive steel. The welding arc in this case is more stable and at the same time welding can occur both on direct and on reverse polarity of the applied constant voltage.

On direct current, you can weld with electrode wire without coating and electrodes, which are designed for welding metals with direct or alternating current. To give arc burning at low currents, it is desirable to have an increased open-circuit voltage U xx up to 70 ... 75 V on the welding winding. For AC rectification, as a rule, bridge rectifiers on powerful diodes with cooling radiators are used (Fig. 1).

Fig. 1 Schematic diagram of a bridge rectifier of a welding machine, indicating the polarity when welding thin sheet metal

To smooth out voltage ripples, one of the CA terminals is connected to the electrode holder through a T-shaped filter consisting of a choke L1 and a capacitor C1. The choke L1 is a coil of 50 ... 70 turns of a copper bus with a branch from the middle with a section of S = 50 mm 2 wound on a core, for example, from a step-down transformer OSO-12, or more powerful. The larger the cross section of the iron of the smoothing choke, the less likely it is that its magnetic system will saturate. When the magnetic system enters saturation at high currents (for example, when cutting), the inductance of the choke decreases abruptly and, accordingly, the current will not be smoothed. In this case, the arc will burn unstably. Capacitor C1 is a bank of capacitors such as MBM, MBG or the like with a capacity of 350-400 μF for a voltage of at least 200 V

Characteristics of powerful diodes and their imported counterparts are possible. Or follow the link to download a guide to diodes from the series "To help radio amateurs No. 110"

For rectification and smooth regulation of the welding current, circuits are used on powerful controlled thyristors, which allow you to change the voltage from 0.1 xx to 0.9U xx. In addition to welding, these regulators can be used to charge batteries, power electric heating elements, and other purposes.

In AC welding machines, electrodes with a diameter of more than 2 mm are used, which allows welding products with a thickness of more than 1.5 mm. In the process of welding, the current reaches tens of amperes and the arc burns quite steadily. In such welding machines, special electrodes are used, which are intended only for welding with alternating current.

For normal operation of the welding machine, a number of conditions must be met. The output voltage must be sufficient to reliably ignite the arc. For an amateur welding machine U xx = 60 ... 65V. For the safety of work, a higher open-circuit output voltage is not recommended; for industrial welding machines, for comparison, U xx can be 70..75 V.

Welding stress value I sv should ensure stable burning of the arc, depending on the diameter of the electrode. The magnitude of the welding voltage Uw can be 18 ... 24 V.

The rated welding current must be:

I sv = KK 1 * d e, where

I sv- the value of the welding current, A;

K 1 = 30 ... 40- coefficient depending on the type and size of the electrode d e, mm.

The short-circuit current should not exceed the rated welding current by more than 30 ... 35%.

It is noted that stable arc burning is possible if the welding machine has a falling external characteristic, which determines the relationship between the current strength and the voltage in the welding circuit. (fig. 2)

Fig. 2 Falling external characteristic of the welding machine:

At home, as practice shows, it is quite difficult to assemble a universal welding machine for currents from 15 ... 20 to 150 ... 180 A. In this regard, when designing a welding machine, one should not strive to completely overlap the range of welding currents. It is advisable at the first stage to assemble a welding machine for working with electrodes with a diameter of 2 ... 4 mm, and at the second stage, if it is necessary to work at low welding currents, to supplement it with a separate rectifier device with smooth regulation of the welding current.

Analysis of the designs of amateur welding machines at home makes it possible to formulate a number of requirements that must be met in their manufacture:

• Small size and weight
• Powered by 220 V
• The duration of operation should be at least 5 ... 7 electrodes d e = 3 ... 4 mm

The weight and dimensions of the apparatus directly depend on the power of the apparatus and can be reduced by reducing its power. The operating time of the welding machine depends on the material of the core and the heat resistance of the insulation of the winding wires. To increase the welding time, it is necessary to use steel with a high magnetic permeability for the core.

1. 2. Selecting the type of core.

For the manufacture of welding machines, mainly rod-type magnetic cores are used, since they are more technologically advanced in design. The core of the welding machine can be drawn from plates of electrical steel of any configuration with a thickness of 0.35 ... 0.55 mm and pulled together with studs isolated from the core (Fig. 3).

Fig. 3 Rod type magnetic circuit:

When choosing a core, it is necessary to take into account the dimensions of the "window" to fit the windings of the welding machine, and the area of ​​the transverse core (yoke) S = a * b, cm 2.

As practice shows, one should not choose the minimum values ​​of S = 25..35 cm 2, since the welding machine will not have the required power reserve and it will be difficult to obtain high-quality welding. And hence, as a consequence, the possibility of overheating the device after a short time of work. To avoid this, the cross-section of the core of the welding machine should be S = 45..55 cm 2. Although the welding machine will be somewhat heavier, it will work reliably!

It should be noted that amateur welding machines on toroidal cores have electrical specifications 4 ... 5 times higher than that of the rod, and hence small electrical losses. It is more difficult to make a welding machine using a toroidal type core than with a rod-type core. This is mainly due to the placement of the windings on the torus and the complexity of the winding itself. However, with the right approach, they give good results. The cores are made of tape transformer iron rolled into a torus-shaped roll.

Rice. 4 Toroidal magnetic circuit:

To increase the inner diameter of the torus ("window"), a part of the steel tape is unwound from the inside and wound onto the outside of the core (Fig. 4). After rewinding the torus, the effective cross-section of the magnetic circuit will decrease, so you will have to partially rewind the torus with iron from another autotransformer until the cross-section S is equal to at least 55 cm 2.

The electromagnetic parameters of such iron are most often unknown, so they can be determined experimentally with sufficient accuracy.

1. 3. Choice of wire windings.

For the primary (mains) windings of the welding machine, it is better to use a special heat-resistant copper winding wire in cotton or fiberglass insulation. Wires in rubber or rubber-fabric insulation also have satisfactory heat resistance. It is not recommended to use wires in polyvinyl chloride (PVC) insulation for operation at elevated temperatures due to its possible melting, leakage from the windings and short-circuiting of turns. Therefore, PVC insulation from the wires must either be removed and wrapped along the entire length of cotton insulating tape, or do not remove at all, but wrap the wire over the insulation.

When selecting the cross-section of the winding wires, taking into account the periodic operation of the welding machine, a current density of 5 A / mm2 is allowed. The power of the secondary winding can be calculated using the formula P 2 = I sv * U sv... If welding is carried out with an electrode de = 4 mm, at a current of 130 ... 160 A, then the power of the secondary winding will be: Р 2 = 160 * 24 = 3.5 ... 4 kW, and the power of the primary winding, taking into account losses, will be of the order of 5 ... 5.5 kW... Based on this, the maximum current in the primary winding can reach 25 A... Therefore, the cross-sectional area of ​​the wire of the primary winding S 1 must be at least 5..6 mm 2.

In practice, it is advisable to take the cross-sectional area of ​​the wire a little more, 6 ... 7 mm 2. For winding, a rectangular bus or copper winding wire with a diameter of 2.6 ... 3 mm is taken, excluding insulation. The cross-sectional area S of the winding wire in mm2 is calculated by the formula: S = (3.14 * D 2) / 4 or S = 3.14 * R 2; D is the diameter of the bare copper wire, measured in mm. In the absence of a wire of the required diameter, winding can be carried out in two wires of a suitable cross-section. When using an aluminum wire, its cross-section must be increased 1.6 ... 1.7 times.

The number of turns of the primary winding W1 is determined from the formula:

W 1 = (k 2 * S) / U 1, where

k 2 - constant coefficient;

S- cross-sectional area of ​​the yoke in cm 2

You can simplify the calculation by using the special program Welding calculator for the calculation.

When W1 = 240 turns, taps are made from 165, 190 and 215 turns, i.e. every 25 turns. A larger number of network winding taps, as practice shows, is impractical.

This is due to the fact that due to a decrease in the number of turns of the primary winding, both the power of the welding machine and U xx increase, which leads to an increase in the arc burning voltage and a deterioration in the quality of welding. By changing only the number of turns of the primary winding, it is not possible to overlap the range of welding currents without deteriorating the quality of welding. In this case, it is necessary to provide for switching the turns of the secondary (welding) winding W 2.

The secondary winding W 2 must contain 65 ... 70 turns of an insulated copper bus with a cross section of at least 25 mm2 (preferably with a cross section of 35 mm2). Flexible stranded wire such as welding wire and three-phase power stranded cable are also suitable for winding the secondary winding. The main thing is that the cross-section of the power winding is not less than the required one, and the insulation of the wire is heat-resistant and reliable. With insufficient wire cross-section, winding in two or even three wires is possible. When using an aluminum wire, its cross-section must be increased by 1.6 ... 1.7 times. The leads of the welding winding are usually led through copper lugs for terminal bolts with a diameter of 8 ... 10 mm (Fig. 5).

1.4. Features of winding winding.

There are the following rules for winding the windings of the welding machine:

• Winding should be done on an insulated yoke and always in one direction (eg clockwise).
• Each layer of the winding is insulated with a layer of cotton insulation (fiberglass, electric cardboard, tracing paper), preferably impregnated with bakelite varnish.
• The terminals of the windings are tinned, marked, secured with cotton tape, and a cotton cambric is additionally put on the terminals of the network winding.
• If the insulation of the wire is of poor quality, winding can be done in two wires, one of which is a cotton cord or cotton thread for fishing. After winding one layer, the winding with cotton thread is fixed with glue (or varnish) and only after it dries is the next row wound.

The mains winding on a bar-type magnetic circuit can be positioned in two main ways. The first method allows you to get a more "hard" welding mode. In this case, the mains winding consists of two identical windings W1, W2, located on different sides of the core, connected in series and having the same wire cross-section. To adjust the output current, taps are made on each of the windings, which are closed in pairs ( Rice. 6 a, b)

Rice. 6. Ways of winding CA windings on a rod-type core:

The second way of winding the primary (mains) winding is winding a wire on one of the sides of the core ( rice. 6 c, d). In this case, the welding machine has a steeply dipping characteristic, it cooks "softly", the arc length has less effect on the value of the welding current, and, consequently, on the quality of welding.

After winding the primary winding of the welding machine, it is necessary to check for the presence of short-circuited turns and the correctness of the selected number of turns. The welding transformer is connected to the network through a fuse (4 ... 6 A) and if there is an alternating current ammeter. If the fuse burns out or gets very hot, this is a clear sign of a short-circuited loop. In this case, the primary winding must be rewound, paying particular attention to the quality of the insulation.

If the welding machine hums strongly, and the consumed current exceeds 2 ... 3 A, then this means that the number of turns of the primary winding is underestimated and it is necessary to wind up some more turns. A working welding machine should consume no more than 1..1.5 A of current at idle, do not heat up and not hum too much.

The secondary winding of the welding machine is always wound on both sides of the core. According to the first method of winding, the secondary winding consists of two identical halves, connected to increase the stability of the arc counter-parallel (Fig. 6 b). In this case, the cross-section of the wire can be taken slightly less, that is, 15..20 mm 2. When winding the secondary winding according to the second method, first, 60 ... 65% of the total number of its turns are wound on the side of the core free of windings.

This winding is mainly used to ignite the arc, and during welding, due to a sharp increase in the dissipation of the magnetic flux, the voltage across it drops by 80 ... 90%. The remaining number of turns of the secondary winding in the form of an additional welding winding W 2 is wound over the primary. Being power, it maintains the welding voltage, and therefore the welding current, within the required limits. The voltage across it drops in welding mode by 20 ... 25% relative to the open circuit voltage.

The winding of the windings of the welding machine on a toroidal core can also be done in several ways ( Rice. 7).

Methods of winding the windings of the welding machine on a toroidal core.

Switching windings in welding machines is easier to do with copper lugs and terminals. Copper lugs at home can be made from copper pipes of a suitable diameter 25 ... 30 mm long, fixing the wires in them by crimping or soldering. When welding in various conditions (strong or low-current network, long or short supply cable, its cross-section, etc.), by switching the windings, the welding machine is set to the optimal welding mode, and then the switch can be set to the neutral position.

1.5. Setting up the welding machine.

Having made a welding machine, a home electrician must adjust it and check the quality of welding with electrodes of various diameters. The setup process is as follows. To measure welding current and voltage, you need: an alternating current voltmeter for 70 ... 80 V and an alternating current ammeter for 180 ... 200 A. Connection diagram measuring instruments shown in ( Rice. eight)

Rice. eight Schematic diagram of connecting measuring devices when setting up a welding machine

When welding with various electrodes, the values ​​of the welding current - Iw and the welding voltage Uw are removed, which must be within the required limits. If the welding current is small, which happens most often (the electrode sticks, the arc is unstable), then in this case, by switching the primary and secondary windings, the required values ​​are set, or the number of turns of the secondary winding is redistributed (without increasing them) in the direction of increasing the number of turns wound over the mains windings.

After welding, it is necessary to check the quality of welding: the depth of penetration and the thickness of the deposited metal layer. For this purpose, the edges of the products to be welded are broken or sawn. It is advisable to draw up a table based on the measurement results. Analyzing the data obtained, choose optimal modes welding for electrodes of various diameters, remembering that when welding with electrodes, for example, 3 mm in diameter, electrodes 2 mm in diameter can be cut, because cutting current is more than welding current by 30 ... 25%.

The welding machine must be connected to the network with a wire with a cross section of 6 ... 7 mm through an automatic machine for a current of 25 ... 50 A, for example AP-50.

The diameter of the electrode, depending on the thickness of the metal to be welded, can be selected based on the following ratio: de = (1 ... 1.5) * B, where B is the thickness of the metal to be welded, mm. The length of the arc is selected depending on the diameter of the electrode and is on average (0.5 ... 1.1) de. It is recommended to perform welding with a short arc of 2 ... 3 mm, the voltage of which is 18 ... 24 V. An increase in the length of the arc leads to a violation of the stability of its combustion, an increase in losses for waste and spattering, and a decrease in the depth of penetration of the base metal. The longer the arc, the higher the welding voltage. The welding speed is chosen by the welder depending on the grade and thickness of the metal.

When welding on straight polarity, the plus (anode) is connected to the part and the minus (cathode) is connected to the electrode. If it is necessary that less heat is generated on the part, for example, when welding thin-sheet structures, then welding is used in reverse polarity. In this case, the minus (cathode) is attached to the workpiece to be welded, and the plus (anode) is attached to the electrode. This not only provides less heating of the workpiece to be welded, but also accelerates the process of melting the electrode metal due to the higher temperature of the anode zone and greater heat supply.

Welding wires are connected to the welding machine through copper lugs for terminal bolts from the outside of the welding machine body. Poor contact connections reduce the power characteristics of the welding machine, deteriorate the quality of welding and can cause them to overheat and even fire the wires.

With a short length of welding wires (4..6 m), their cross-sectional area should be at least 25 mm 2.

During welding work, it is necessary to observe fire safety rules, and when setting up the device and electrical safety - during measurements with electrical devices. Welding must be carried out in a special mask with C5 protective glass (for currents up to 150 ... 160 A) and gloves. All switching in the welding machine must be done only after disconnecting the welding machine from the mains.

2. Portable welding machine based on "Latra".

2.1. Design feature.

The welding machine operates on a 220 V AC mains. unusual shape magnetic circuit, thanks to which the weight of the entire device is only 9 kg, and the dimensions are 125x150 mm ( Rice. nine).

For the magnetic circuit of the transformer, tape transformer iron is used, rolled into a roll in the shape of a torus. As you know, in traditional designs of transformers, the magnetic core is recruited from W-shaped plates. The electrical characteristics of the welding machine, thanks to the use of a torus-shaped transformer core, are 5 times higher than those of machines with W-shaped plates, and the losses are minimal.

2.2. Improvements to "Latra".

For the core of the transformer, you can use the ready-made "LATR" type M2.

Note. All latras have a six-pin block and voltage: at the input 0-127-220, and at the output 0-150 - 250. There are two types: large and small, and are called LATR 1M and 2M. Which one I don't remember which one. But, for welding, it is precisely a large LATR with rewound iron that is needed, or, if they are serviceable, then the secondary windings are wound with a bus and after that the primary windings are connected in parallel, and the secondary ones in series. In this case, it is necessary to take into account the coincidence of the directions of the currents in the secondary winding. Then it turns out something similar to a welding machine, although it cooks, like all toroidal ones, a little harsh.

You can use a torus-shaped magnetic core from a burnt-out laboratory transformer. In the latter case, first remove the fence and fittings from the Latra and remove the burnt winding. The cleaned magnetic circuit, if necessary, is rewound (see above), insulated with an electric cardboard or two layers of varnished cloth and the transformer windings are wound. The welding transformer has only two windings. For winding the primary winding, a piece of PEV-2 wire with a length of 170 m, a diameter of 1.2 mm ( Rice. ten)

Rice. ten Winding the windings of the welding machine:

For the convenience of winding, the wire is pre-wound on a shuttle in the form of a 50x50 mm wooden rail with slots. However, for greater convenience, you can make a simple device for winding toroidal power transformers

Having wound the primary winding, they cover it with a layer of insulation, and then the secondary winding of the transformer is wound. The secondary winding contains 45 turns and is wound copper wire in cotton or glassy insulation. Inside the core, the wire is located turn to turn, and outside - with a small gap, which is necessary for better cooling. A welding machine manufactured according to the above method is capable of giving a current of 80 ... 185 A. A schematic electrical diagram of the welding machine is shown on rice. eleven.

Rice. eleven Schematic diagram of the welding machine.

The work will be somewhat simplified if it is possible to purchase a working Latr for 9 A. Then they remove the fence, the current collector slider and the fastening fittings from it. Next, the terminals of the primary winding for 220 V are determined and marked, and the remaining terminals are reliably isolated and temporarily pressed against the magnetic circuit so that they are not damaged when winding a new (secondary) winding. The new winding contains the same number of turns and the same brand and the same wire diameter as in the above version. The transformer in this case gives a current of 70 ... 150 A.
The manufactured transformer is placed on an insulated platform in the previous casing, having previously drilled holes in it for ventilation (Fig. 12))

Rice. 12 Variants of the casing of the LATRA-based welding machine.

The conclusions of the primary winding are connected to the 220 V network with a SHRPS or VRP cable, while an AP-25 disconnecting machine should be installed in this circuit. Each terminal of the secondary winding is connected to a flexible insulated wire PRG. The free end of one of these wires is attached to the electrode holder, and the free end of the other is attached to the work piece. This end of the wire must also be grounded for the safety of the welder. Adjustment of the welding machine current is carried out by connecting in series to the wire circuit of the electrode holder pieces of nichrome or constantan wire d = 3 mm and 5 m long, coiled up with a "snake". The snake is attached to the asbestos sheet. All wire and ballast connections are made with M10 bolts. Moving the wire connection point along the "snake", set the required current. The current can be adjusted using electrodes of different diameters. For welding with such an apparatus, electrodes of the E-5RAUONII-13 / 55-2,0-UD1 type dd = 1 ... 3 mm are used.

When carrying out welding work, to prevent burns, it is necessary to use a fiber protective shield equipped with an E-1, E-2 light filter. A headdress, overalls and mittens are required. Protect the welding machine from moisture and prevent it from overheating. Approximate modes of operation with an electrode d = 3 mm: for transformers with a current of 80 ... 185 A - 10 electrodes, and with a current of 70 ... 150 A - 3 electrodes. after using the specified number of electrodes, the device is disconnected from the network for at least 5 minutes (or better about 20).

3. Welding machine from a three-phase transformer.

The welding machine, in the absence of "LATRA", can be made on the basis of a three-phase step-down transformer 380/36 V, with a capacity of 1..2 kW, which is designed to supply low voltage power tools or lighting (Fig. 13).

Rice. 13 General view of the welding machine and its core.

Even an instance with one blown winding is suitable here. Such a welding machine operates on a 220 V or 380 V alternating current network and with electrodes up to 4 mm in diameter allows welding metal 1 ... 20 mm thick.

3.1. Details.

The terminals for the terminals of the secondary winding can be made from a copper tube d 10 ... 12 mm and a length of 30 ... 40 mm (Fig. 14).

Rice. fourteen The design of the terminal of the secondary winding of the welding machine.

On one side, it should be riveted and a hole d 10 mm should be drilled in the resulting plate. Carefully stripped wires are inserted into the terminal tube and crimped with light hammer blows. To improve the contact on the surface of the terminal tube, you can make notches with a core. On the panel located at the top of the transformer, the standard screws with M6 nuts are replaced by two screws with M10 nuts. It is advisable to use new screws and nuts made of copper. The terminals of the secondary winding are connected to them.

For the terminals of the primary winding, an additional board is made of sheet textolite with a thickness of 3 mm ( fig. 15).

Rice. 15 General view of the scarves for the conclusions of the primary winding of the welding machine.

10 ... 11 holes d = 6mm are drilled in the board and M6 screws with two nuts and washers are inserted into them. After that, the board is attached to the top of the transformer.

Rice. 16 Schematic diagram of the connection of the primary windings of the transformer for voltage: a) 220 V; b) 380 V (secondary winding is not specified)

When the device is powered from a 220 V network, its two extreme primary windings are connected in parallel, and the middle winding is connected to them in series ( fig. 16).

4. Electrode holder.

4.1. Electrode holder from pipe d¾ ".

The simplest is the design of the electric holder, made of a pipe d¾ "and a length of 250 mm ( fig. 17).

On both sides of the pipe at a distance of 40 and 30 mm from its ends, cut out recesses with a hacksaw half the diameter of the pipe ( fig. 18)

Rice. eighteen Drawing of the body of the electrode holder from the pipe d¾ "

A piece of steel wire d = 6 mm is welded to the pipe above the large recess. A hole d = 8.2 mm is drilled on the opposite side of the holder, into which an M8 screw is inserted. A terminal from the cable going to the welding machine is connected to the screw, which is clamped with a nut. A piece of rubber or nylon hose with a suitable inner diameter is put on top of the pipe.

4.2. Electrode holder made of steel corners.

Convenient and simple in design, the electrode holder can be made of two steel corners 25x25x4 mm ( rice. 19)

They take two such corners with a length of about 270 mm and connect them with small corners and bolts with M4 nuts. The result is a box with a section of 25x29 mm. In the resulting housing, a window is cut out for the retainer and a hole is drilled to install the axis of the retainers and electrodes. The latch consists of a lever and a small key made of 4 mm steel sheet. This part can also be made from a corner of 25x25x4 mm. To ensure reliable contact of the latch with the electrode, a spring is put on the latch axis, and the lever is connected to the body with a contact wire.

The handle of the resulting holder is covered insulating material, which is used as a cut of a rubber hose. The electrical cable from the welding machine is connected to the housing terminal and fixed with a bolt.

5. Electronic current regulator for welding transformer.

An important design feature of any welding machine is the ability to adjust the operating current. such methods of current regulation in welding transformers are known: shunting with the help of chokes of all kinds, changing the magnetic flux due to the mobility of the windings or magnetic shunting, the use of active ballast resistors and rheostats. All of these methods have both advantages and disadvantages. For example, the disadvantage of the latter method is the complexity of the design, the bulkiness of the resistances, their strong heating during operation, and the inconvenience when switching.

The most optimal is the method of stepwise current regulation, by changing the number of turns, for example, by connecting to the taps made when winding the secondary winding of the transformer. However, this method does not allow for wide adjustment of the current, therefore it is usually used to adjust the current. Among other things, the regulation of the current in the secondary circuit of the welding transformer is associated with certain problems. In this case, significant currents pass through the regulating device, which is the reason for the increase in its dimensions. For the secondary circuit, it is practically impossible to find powerful standard switches that would withstand currents up to 260 A.

If we compare the currents in the primary and secondary windings, it turns out that the current in the primary winding circuit is five times less than in the secondary winding. This suggests the idea of ​​placing a welding current regulator in the primary winding of the transformer, using thyristors for this purpose. In fig. 20 shows a diagram of a thyristor-based welding current regulator. With the utmost simplicity and accessibility of the element base, this regulator is easy to operate and does not require adjustment.

Power regulation occurs when the primary winding of the welding transformer is periodically disconnected for a fixed period of time at each half-cycle of the current. In this case, the average value of the current decreases. The main elements of the regulator (thyristors) are connected opposite and parallel to each other. They alternately open with current pulses generated by transistors VT1, VT2.

When the regulator is connected to the network, both thyristors are closed, the capacitors C1 and C2 begin to charge through the variable resistor R7. As soon as the voltage on one of the capacitors reaches the voltage of the avalanche breakdown of the transistor, the latter opens, and the discharge current of the capacitor connected to it flows through it. Following the transistor, the corresponding thyristor opens, which connects the load to the network.

By changing the resistance of the resistor R7, you can adjust the moment of turning on the thyristors from the beginning to the end of the half-period, which in turn leads to a change in the total current in the primary winding of the welding transformer T1. To increase or decrease the adjustment range, you can change the resistance of the variable resistor R7 up or down, respectively.

Transistors VT1, VT2, operating in avalanche mode, and resistors R5, R6 included in their base circuits, can be replaced by dinistors (Fig. 21)

Rice. 21 Schematic diagram of replacing a transistor with a resistor with a dinistor, in the current regulator circuit of a welding transformer.

the anodes of the dinistors should be connected to the extreme terminals of the resistor R7, and the cathodes should be connected to the resistors R3 and R4. If the regulator is assembled on dinistors, then it is better to use devices of the KN102A type.

Transistors of the old type P416, GT308 have proven themselves well as VT1, VT2, but these transistors, if desired, can be replaced with modern low-power high-frequency transistors with similar parameters. Variable resistor type SP-2, and fixed resistors type MLT. Capacitors of the MBM or K73-17 type for an operating voltage of at least 400 V.

All parts of the device using surface-mounted assembled on a textolite plate with a thickness of 1 ... 1.5 mm. The device has a galvanic connection with the mains, therefore all elements, including thyristor heat sinks, must be isolated from the case.

A properly assembled welding current regulator does not require special adjustment, you just need to make sure that the transistors work in an avalanche mode or, when using dinistors, in their stable turn on.

A description of other structures can be found on the website http://irls.narod.ru/sv.htm, but I want to warn you right away that many of them have at least controversial points.

Also on this topic you can see:

http://valvolodin.narod.ru/index.html - a lot of GOSTs, schemes of both self-made devices and factory

http://www.y-u-r.narod.ru/Svark/svark.htm the same site of a welding enthusiast

All the best, write to © 2005

Resistance welding, in addition technological merits application, has another important advantage - simple equipment for it can be made independently, and its operation does not require specific skills and initial experience.

1 Principles of design and assembly of resistance welding

Contact welding, assembled by hand, can be used to solve a fairly wide range of tasks of a non-serial and non-industrial nature for the repair and manufacture of products, mechanisms, equipment from various metals both at home and in small workshops.

Resistance welding ensures the creation of a welded joint of parts by heating the area of ​​their contact with an electric current passing through them while simultaneously applying a compressive force to the joint area. Depending on the material (its thermal conductivity) and the geometric dimensions of the parts, as well as the power of the equipment used to weld them, the contact welding process should proceed with the following parameters:

• low voltage in the power welding circuit - 1–10 V;
• in a short time - from 0.01 seconds to several;
• high welding pulse current - most often from 1000 A or higher;
• small melting zone;
• the compressive force applied to the weld should be significant - tens to hundreds of kilograms.

Compliance with all these characteristics directly affects the quality of the resulting welded joint. You can only make devices for yourself, as in the video. The easiest way is to assemble an unregulated AC welding machine. In it, the process of joining parts is controlled by changing the duration of the supplied electrical impulse. To do this, use a time relay or cope with this task manually "by eye" using a switch.

Homemade spot resistance welding is not very difficult to manufacture, and to complete its main unit - a welding transformer - you can pick up transformers from old microwave ovens, televisions, latvians, inverters and the like. The windings of a suitable transformer will need to be rewound in accordance with the required voltage and the welding current at its output.

The control scheme is selected ready-made or developed, and all other components and, in particular, for the contact welding mechanism are taken based on the power and parameters of the welding transformer. The contact-welding mechanism is manufactured in accordance with the nature of the forthcoming welding works according to any of the known schemes. Welding tongs are usually made.

Everything electrical connections must be of high quality and have good contact. And connections using wires are made of conductors with a cross section corresponding to the current flowing through them (as shown in the video). This is especially true for the power section - between the transformer and the clamp electrodes. With poor contacts of the circuit of the latter, there will be large energy losses at the joints, sparking may occur, and welding may become impossible.

2 Diagram of a device for welding metal up to 1 mm thick

To connect parts by contact, you can assemble according to the diagrams below. The proposed device is designed for welding metals:

• sheet, the thickness of which is up to 1 mm;
• wires and rods up to 4 mm in diameter.

Main technical characteristics of the device:

• supply voltage - alternating 50 Hz, 220 V;
• output voltage (on the electrodes of the contact welding mechanism - on the pincers) - alternating 4–7 V (no-load);
• welding current (maximum pulse) - up to 1500 A.

Figure 1 shows a schematic electrical diagram of the entire device. The offered resistance welding consists of a power section, a control circuit and circuit breaker AB1, which serves to turn on the power of the device and protect in case of emergency situations... The first unit includes a welding transformer T2 and a non-contact thyristor single-phase starter of the MTT4K type, which connects the primary winding of T2 to the mains.

Figure 2 shows a diagram of the windings of a welding transformer with an indication of the number of turns. The primary winding has 6 terminals, by switching which you can perform a stepwise coarse adjustment of the output welding current of the secondary winding. In this case, pin No. 1 remains permanently connected to the network circuit, and the remaining 5 are used for adjustment, and only one of them is connected to the power supply for operation.

The scheme of the MTT4K starter, produced in series, is shown in Fig. 3. This module is a thyristor switch, which, when its contacts 5 and 4 are closed, switches the load through contacts 1 and 3 connected to the open circuit of the primary winding of Tr2. MTT4K is designed for load with maximum voltage up to 800 V and current up to 80 A. Such modules are produced in Zaporozhye at Element-Converter LLC.

The control scheme consists of:

• power supply unit;
• direct control circuit;
• relay K1.

Any transformer with a capacity of no more than 20 W can be used in the power supply unit, designed to operate from a 220 V network and outputting a voltage of 20-25 V on the secondary winding. It is proposed to install a diode bridge of the KTs402 type as a rectifier, but any other with similar ones can be used. parameters or assembled from individual diodes.

Relay K1 is used to close contacts 4 and 5 of the MTT4K key. This happens when voltage is applied from the control circuit to the winding of its coil. Since the switched current flowing through the closed contacts 4 and 5 of the thyristor switch does not exceed 100 mA, almost any low-current electromagnetic relay with an operating voltage within 15-20 V is suitable as K1, for example, RES55, RES43, RES32 and the like.

3 Control chain - what does it consist of and how does it work?

The control circuit acts as a time relay. Turning on K1 for a given period of time, it sets the duration of the effect of an electric pulse on the parts to be welded. The control circuit consists of C1-C6 capacitors, which must be electrolytic with a charging voltage of 50 V or higher, P2K switches with independent latching, KH1 buttons and two resistors - R1 and R2.

The capacitance of the capacitors can be: 47 μF for C1 and C2, 100 μF for C3 and C4, 470 μF for C5 and C6. KH1 must be with one normally closed and the other normally open contacts. When AB1 is turned on, the capacitors, connected with P2K to the control circuit and the power supply (in Fig. 1, this is only C1), begin to charge, R1 limits the initial charging current, which significantly increases the service life of the capacitors. Charging occurs through the normally closed contact group of the KH1 button, which was switched at that time.

When KH1 is pressed, the normally closed contact group opens, disconnecting the control circuit from the power supply, and the normally open one closes, connecting the charged capacities to the K1 relay. The capacitors are discharged and the discharge current triggers K1.

An open normally closed contact group KH1 prevents the relay from being energized directly from the power supply. The greater the total capacity of the discharging capacitors, the longer they are discharged, and, accordingly, K1 closes contacts 4 and 5 of the MTT4K key for a longer time, and the longer the welding pulse. When the capacitors are completely discharged, K1 will shut off and resistance welding will stop working. To prepare it for the next impulse, KH1 must be released. The capacitors are discharged through the resistor R2, which must be variable and serves to more accurately control the duration of the welding pulse.

4 Power section - transformer

The proposed resistance welding can be assembled, as shown in the video, on the basis of a welding transformer made using a magnetic circuit from a 2.5 A transformer. Such are found in LatRs, laboratory instruments and a number of other devices. The old winding must be removed. At the ends of the magnetic circuit, it is necessary to install rings made of thin electrical cardboard.

They are folded along the inner and outer edges. Then the magnetic core must be wrapped over the rings with 3 or more layers of varnished cloth. To make the windings, wires are used:

• For primary 1.5 mm in diameter, it is better in fabric insulation - this will contribute to a good impregnation of the winding with varnish;
• For a secondary diameter of 20 mm, stranded in organosilicon insulation with a cross-sectional area of ​​at least 300 mm 2.

The number of turns is shown in Fig. 2. Intermediate conclusions are made from the primary winding. After winding, it is impregnated with EP370, KS521 varnish or the like. A cotton tape (1 layer) is wound over the primary coil, which is also impregnated with varnish. Then the secondary winding is laid and the varnish impregnation is done again.

5 How to make pliers?

Contact welding can be equipped with pliers, which are mounted directly into the body of the device itself, as in the video, or external in the form of scissors. The first, from the point of view of performing high-quality, reliable insulation between their nodes and ensuring good contact in the circuit from the transformer to the electrodes, is much easier to manufacture and connect than remote ones.

However, the clamping force developed by such a structure, if the length of the movable arm of the pliers is not increased after the electrode, will be equal to the force generated directly by the welder. Remote pliers are more convenient to use - you can work at some distance from the device. And the effort developed by them will depend on the length of the handles. However, it will be necessary to make good enough insulation from textolite bushings and washers in the place of their movable bolted connection.

When making pincers, it is necessary to foresee in advance the necessary overhang of their electrodes - the distance from the body of the apparatus or the place of the movable connection of the handles to the electrodes. This parameter will determine the maximum possible distance from the edge of the sheet metal to the place where welding is performed.

Tick ​​electrodes are made from copper or beryllium bronze rods. You can use the tips of powerful soldering irons. In any case, the diameter of the electrodes must be no less than that of the wires supplying them with current. To obtain welding cores of the desired quality, the size of the contact pads (electrode tips) should be as small as possible.