Multi-welding all-rounder. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / welding equipment

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Why "multi-welding"? Because this welding transformer (CT) has many important additional functions. If in a traditional "welder", which has a magnetic circuit assembled from U- and W-shaped plates, sometimes there is nowhere to squeeze at least one or two auxiliary turns, then in the proposed donut-shaped design there was plenty of free space. As a result, he is able to cook "five" on alternating / direct current, charge batteries, melt metal, supply safe voltage to electric burners in "Skillful Hands" circles, and also perform a lot of other things. It’s time to even put the question in a different way: what other winding and for what purposes does the user of such a ST want to have in addition ?!

Indeed, the core of the "welder", which has the form of a "donut", called a torus in mathematics and technology, has a great future. Realizing this, but not having at their disposal special industrial-made toroidal magnetic circuits intended exclusively for transformers, do-it-yourselfers are forced to adapt cylindrical ersatz from stators of old electric motors with a power of 1-1,5 kW for their ST. For this, the cases of electric motors are usually simply broken, the windings laid in the grooves are discarded as unnecessary, the protrusions of the poles are cut down. super goals" - cook steel with a "five"!

I am convinced that it is not necessary to distort electric motors, even if they have become unusable - a zealous owner can always rewind the burnt windings and replace worn out bearings. A rebuilt engine is capable of much more...

And for the toroidal magnetic circuit I propose, 5-6 kg of transformer steel scrap is enough. Moreover, even the same amount of roofing iron (annealed) can be content here as a starting material.

The technology for manufacturing a magnetic circuit from such raw materials is quite simple (Fig. 1). All scrap of flat transformer steel is cut with scissors into strips of approximately the same width.

Rice. 1. Formation of a toroidal magnetic circuit: 1 - the base of the mold; 2 - outer cylinder-formwork ("corolla" of the gear for starting the starter of the GAZ-53 car); 3 - inner cylinder-formwork (60 mm piece of steel pipe 100x6, slightly machined, wrapped with two or three layers of paper); 4 - initial mass (plates 60-70 mm wide, cut from scrap from W- and U-shaped plates of transformer steel, covered with quick-drying office-type glue, gum arabic or oil paint and laid in overlap, followed by filling voids with roofing waste)

Practice shows that most often you have to deal with rectangles 60-70 mm wide or slightly smaller analogues cut from U- and W-shaped plates. All "iron transformer" and roofing waste are also used. After lubrication on both sides with some quick-drying glue such as stationery ("liquid" glass), gum arabic or even cheap oil paint, they are tightly laid with a slight overlap in the formwork (as when pouring a hollow concrete column) from improvised materials.

In the author's technology, the inner cylinder of the formwork (Fig. 1) is a 60 mm piece of steel pipe 100x6 mm. Inside, it must be machined slightly into a cone and wrapped (in order to later be easier to remove from the "cast" magnetic circuit) with two or three layers of paper strip. And as an external one, a removable "corolla" of the gear is used (internal diameter of the order of 250 mm) - from the starter start system of the GAZ-53 car.

Of course, you can use for formwork and other suitable blanks that can withstand the mechanical stresses that occur during the "casting" of the toroidal magnetic circuit. And they are considerable, especially when small plates have to be hammered into all the slotted holes (it is desirable that they correspond to the width of the set).

Once the glue has dried, the toroidal core is almost ready. True, it is still necessary to make one-sidedly rounded half-rings - "semi-blinds" of insulating material on it. At least from plywood - for better laying of future windings and avoiding short circuits on the sharp edges of the magnetic circuit. This will also be facilitated by the preliminary wrapping of the torus with two or three layers of keeper tape, fiberglass or a fabric strip impregnated with drying oil.

Now about the windings of the "welder". Science claims, and practice clearly proves that the transformer operates in the most favorable mode for it, if a current equal to 1 A passes through its windings through 2 mm5 of the cross section of the copper wire. Under extreme conditions, this figure can increase to 13 A, but with the wires get very hot and burn out.

For welding, even with a 3-mm electrode, a current of at least 80 A is required. This means that the cross section of the conductors of a copper cable or a power (welding) bus must correspond to it. Taken with a solid margin, it is usually in the range from 25 to 35 mm2 for a good-quality home-made welding transformer.

Based on the already mentioned "minimum welding" 80 A and taking into account the widely practiced ratio of turns of the mains and power windings of approximately 5: 1, we find: the current of the mains winding must be at least 16 A. It follows that for mounting the mains winding it is necessary to take a copper wire with a cross section not less than 3,2 mm2. However, the best, perhaps, option is PEV2 with a diameter of 2-2,5 mm.

It is generally accepted (and this is confirmed by practice) that with a "cast" magnetic circuit having a cross-sectional area for transformer steel equal to 40 cm2, each turn of the winding will correspond to a voltage of 1 V. Given the possible instability of the power supply, the network winding should be made with a margin.

Landmark - 250 turns. In this case, after the 190th, it is desirable to provide (without cutting the wires!) Every ten turns of taps. Of course, the switch for them must be sufficiently reliable, with good electrical contact to avoid large energy losses and strong heating during the operation of the ST.

In fact, winding the network winding is a rather difficult operation. It has to be done with the help of long wooden shuttles (Fig. 2). Do everything carefully, avoiding overlapping turns, the formation of knots and damage to the layer of insulating varnish on the wire. Otherwise, interturn short circuits and overheating of the transformer can be expected.

Rice. 2. Laying turns of the network winding of the "welder" (interlayer insulating gaskets are conventionally not shown): 1 - toroidal magnetic circuit; 2 - one-sided rounded half-ring - "semi-bulb" made of insulating material (2 pcs.); 3 - mounting insulating gasket (2-3 layers of keeper tape, fiberglass or fabric strip impregnated with drying oil); 4 - wire of the network winding (PEV2, diameter 2-2,5); 5 - wooden shuttle

If the core is placed on two supports with a soft coating (lining), which excludes damage to the wire insulation when winding the ST, then the whole work will take about two hours. It is desirable to finish it "in one pass" so that the winding does not weaken and turns out to be as dense as possible, with insulating gaskets between the layers.

After the network is wound up, it's a good idea to check it at idle. If even for a long time of operation the magnetic circuit with the winding becomes only barely warm, then everything is in order. Significant heating is evidence that either there are few turns, or there is an interturn short circuit (or even a breakdown of the winding on the case!).

Secondary - welding, or power - should be laid on the two-three-layer insulation of the network winding. And this is from 40 to 80 turns of a copper bus or a stranded cable. The latter is preferable for the following reasons: you can immediately make welding sleeves from it; winding is greatly facilitated; the service life of the welding winding increases while simplifying the operating conditions, which is especially important when experimenting with such a CT. In addition, the connection of the rectifier is simplified and it becomes possible to effectively control the welding current and voltage by performing an elementary operation - winding or unwinding the cable turns.

For self-made not too powerful welding machines, the following work schedule is desirable: a minute for welding, two for a technological break to cool the ST. A good result is the use of small fans. Probably, even more can be achieved when using the simplest heat-radiating radiators for cooling the "welder", as well as mineral oils that can improve the insulation of the MT windings.

A solid welding transformer must have a steeply falling characteristic. This can be achieved by dividing the winding into two equal parts. On one side of the core, half of the network and half of the power winding are wound, and on the other, the rest (and so as not to be confused later - in the same sequence).

It is not superfluous, apparently, to recall that a transformer is a reciprocal device: if an alternating voltage is connected to any winding for which it is designed, then those for which they are intended appear on others. By the way, many radio amateurs do the same when determining the windings in an unknown transformer.

Considering the foregoing, it is not at all necessary to wind the network (primary) winding of the vehicle first, and already on top of it - the welding (secondary). The sequence of winding, as well as their serial numbers, is only a condition for a faster and more familiar orientation in the circuit diagram of the "welder". Therefore, if, say, you need to wind one of the windings with a fairly rigid tire, when laying which you will have to resort to a mallet, then, of course, it is more convenient to place such "copper" first on the core so as not to damage the more pliable and vulnerable wires of the remaining windings.

And further. If there is enough wire for one winding, and very little for the other winding, then first proceed to the one where your options are limited. Because with a clear shortage of a cable or bus for the power (welding) winding, but in the presence of powerful diodes-semiconductor valves, it becomes profitable to abandon welding on alternating current in favor of direct current (Fig. 3). In this case, the voltage from the ST, and hence the number of turns in the welding winding, is sufficient to have a minimum. If the bus is with damaged insulation, then it is recommended to first anneal it with cooling in water (copper will become soft), insulate it with shellac and fiberglass, and only then proceed to winding it on the magnetic circuit.

Fig. 3. Schematic solution of a welding rectifier with a current regulator for a self-made multi-welding transformer (R1 - a spiral of nichrome wire with a diameter of 3-5 mm with a movable knife-like contact)

Often, do-it-yourselfers have difficulty connecting the power cable to the product to be welded: either the contact is bad, or there is nothing to “grab” to. Two options for devices can help in such situations (Fig. 4): magnetic contact and crocodile clip. Both homemade products are extremely simple to manufacture, quickly and conveniently attached. In the absence of proper contact, it is enough to rub them a little on the part.

Rice. 4. Variants of devices for ground contact - magnetic (a) and crocodile clip (b): 1 - welding cable; 2 - handle; 3 - steel lining; 4 - ring magnet - "stuck"; 5- screw (quantity and location - according to the place of installation); 6 - half of a home-made "toothy jaw" of a clothespin (from a piece of steel pipe of a suitable size, 2 pcs.); 7 - steel axle, riveted on both sides; 8 - spring

It is also a good idea to equip the CT network winding with a standard AP automatic machine, designed for at least 30 A, - with its help it is convenient to turn off the transformer in the pauses between welding. This will significantly save electricity, create favorable conditions for timely cooling of the device, and make work safer. Well, the presence of a powerful rectifier (Fig. 3) will, as already noted, make it possible to use the resulting unit when charging batteries or organizing multi-station power supply, for example, low-voltage soldering irons and electric burners in "Skillful Hands" school circles. Moreover, such a unit is truly indispensable, for example, when performing electroplating work at home or starting a car in cold conditions.

It is very interesting and promising to equip the ST with an additional winding containing only one full turn of an annealed copper bus 5x50 mm or a thick stranded copper cable with a diameter of about 20 mm (with trailers made of pieces of a thick-walled copper pipe). As practice has shown, with the help of such a winding it is possible to perform hot free forging, hardening and burnishing, soldering and surfacing; bending of a metal strip, pipe, thick steel bar, "round timber", brittle wire; casting of tin, zinc, lead; unscrewing "stuck" bolts, studs and nuts; spot welding, hot fitting and a number of other operations.

How to make a smooth adjustment of the current? Yes, at least in the way mentioned above - by adjusting the power (cable) winding. When part of it is unwound from the magnetic circuit, the voltage decreases with a simultaneous increase in the current from the ST, but, in particular, the conditions for ignition of the arc worsen. And vice versa: cable winding leads to an increase in the transformed voltage with a simultaneous decrease in the current strength given to the load. In this case, the electric arc ignites better.

Or another option, when the welding cable is connected to the product not directly, but through several turns of high-resistance wire (for example, nichrome). How many resistant turns - so many levels of adjustment of the welding current. The arc is ignited in all cases in almost the same way.

CT current adjustment can be carried out using a combined valve made of transformer steel and non-ferrous metal. In this case, a transverse cut is made on the magnetic circuit.

Plumbers, motorists, repairmen and just DIY enthusiasts, this "welder" with such versatile properties is for you.

Author: R. Kravtsov, Yeysk, Krasnodar Territory

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