Toroidal welding transformer from available materials. Encyclopedia of radio electronics and electrical engineering

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Many amateur welders dream of a toroidal welding transformer. After all, it has long been known that the weight and size characteristics of toroids are much better than those of W- and U-shaped transformers. So, with the same characteristics, the toroid is 1,3-1,5 times smaller. The reason why many do not undertake to make such a transformer is the lack of iron. This article will help you find a way out of this situation.

The design involves the manufacture of a toroidal transformer from an industrial welding transformer that has served its time. To do this, it is disassembled and a bagel is assembled from plates measuring 90×450 mm. The required core area depends on the number of plates. Plates can be used from old tube color TVs. Transformers of the TC270, TCA310 types are disassembled, the U-shaped cores are broken into plates with a hammer blow, which are straightened on the anvil.

To make a donut, it is necessary to rivet a hoop of plates with an outer diameter of 260 mm. Then the first plate is inserted inside the hoop, holding it with your hand so that it does not unwind, butt to it - the second, etc. until the inner diameter of the donut is 120 mm. If the donut is made from transformers of the TS270 type, then the diameter must be recalculated to achieve the required cross-sectional area. It can be recommended to make two donuts and fold them in half, in this case the outer and inner diameters of the donut can be left unchanged.

The edges of the toroid are processed with a file. Two rings with an outer diameter of 270 mm, an inner diameter of 110 mm and a strip 90 mm wide are made of electric cardboard. They apply blanks from electric cardboard to a donut and wrap it with fabric-based electrical tape, you can wrap it with tape from the degaussing loop of kinescopes. The primary winding is wound with PEV-2 D2,0 mm wire, the number of turns rated for 220 V is approximately 170 - this largely depends on the density of the assembly of the plates. The exact number of turns can be verified experimentally. If the no-load current is more than 1 ... 2 A, then it is necessary to wind the turns, if less, then you can unwind. The secondary winding is wound with a PV3 wire with a cross section of 15 ... 20 mm, 30 turns. The third winding also contains 30 turns and is wound with MGTF-0,35 wire. Between the windings we lay insulation from the braid.

After testing the transformer, you can begin to manufacture the control circuit (see figure). It is a phase current regulator. The alternating voltage taken from the third winding of the transformer is rectified by a bridge on diodes VD5-VD8. A positive half-wave through the resistors R1, R2 charges the capacitor C1.

(click to enlarge)

When the voltage reaches about 6 V, a breakdown occurs of an analog of a low-voltage dinistor assembled on a zener diode VD6 and a thyristor VS3, and the thyristor VS3 opens through the VD1 diode, while the capacitance C1 is discharged. The same thing happens with a negative half-wave, only the VD4 diode and the VS2 thyristor open. Resistor R3 serves to limit the current through the analogue of the dinistor.

The adjustment consists in adjusting the required welding current control zone with the resistor R1.

As SA1, you can use any machine for a current of 25 A. Instead of VD3-VD8, diodes KD202V-KD202M or any for a current of more than 0,7 A and a voltage of 70 V. Instead of KU101A, you can use KU201KU202. Resistors R1, R2 for a power of at least 10 watts. C1 type K50-6. VD1, VD2, VS1, VS2 for current 160...250 A with any voltage group. They must be installed on radiators with a cooling area of ​​at least 100 cm2. Winding 3 of the transformer is designed for a voltage of 40 V, the secondary winding can be increased if necessary.

Author: S.M. Abramov

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