Toroidal welding transformer from available parts. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / welding equipment
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Many amateur welders dream of a toroidal transformer. After all, it has long been known that the weight and size characteristics of toroids are much better than those of "Sh" and "P"-shaped transformers. So, with the same characteristics, the toroid is 1,3-1,5 times smaller. The reason why many do not undertake the manufacture of 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 a used industrial welding transformer. To do this, it is disassembled, and a donut is assembled from plates measuring 90X450 mm. The required cross-sectional area of the core depends on the number of plates.
In principle, the plates can also be used from the power transformers of old tube color TVs. Transformer TC270, TCA310 are being reassembled. U-shaped cores are broken into plates with a hammer blow, which are straightened on an anvil.
To make a donut, you first need 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, the second plate is inserted end-to-end with it, and so on, until the inner diameter of the donut is 120 mm. If the bagel is made from TS270 transformers, then the diameter must be recalculated to achieve the required cross-sectional area. You can make two bagels and put them together. 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. From electric cardboard we make two rings with an outer diameter of 270 mm, an inner diameter of 110 mm, and a strip 90 mm wide. We apply the blanks from the electric cardboard to the donut and wrap it with tape on a woven basis, you can wrap it with tape from the degaussing loop of kinescopes. The primary winding is wound with a PEV-2 wire with a diameter of 2,0 mm, the number of turns for 220 V is approximately 170. This largely depends on the assembly density 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 - 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, but wound with MGTF 0,35 wire. Tape insulation is laid between the windings.
After testing the transformer, you can begin to manufacture the control circuit. 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. Capacitor C1 is charged by a positive half-wave through resistors R2 and R1. When the voltage on it reaches about six volts, a breakdown occurs of an analogue of a low-voltage dinistor assembled on a zener diode VD6 and a thyristor VS3, and the thyristor VS3 opens through the VD1 diode. 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.
(click to enlarge)
The adjustment consists in adjusting the required welding current control zone with the resistor R1.
As SA1, you can use any machine for 25 A KD209A can be replaced "by KD202V-KD202M or any others for a current of more than 0,7 A and a voltage of more than 70 V. The KUKLA thyristor can be replaced with KU201-KU202. Resistors R1 and R2 - for power not less than 10 W. C1 - K50-6.VD1, VD2, VS1, VS2 for a current of 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, and the secondary, if necessary, can be increased.
Author: Abramov S.M.
See other articles Section welding equipment.
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