Welding - your own. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Welding - your own. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / welding equipment

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Almost a quarter I also deal with electric welding machines (ESA). I was convinced that the most suitable "welder" in terms of weight and power is with a toroidal magnetic circuit (for example, from a burned-out electric motor with a power of 3-5 kW).

Based on my own experience and the practice of other home-made designers, I also consider it appropriate to emphasize that the no-load current of a good-quality welding transformer, designed for connection to a household 220-volt network, should be about 0,5-1 A. With a smaller value of this parameter, it drops power, with more - the magnetic circuit is heated, and with it the entire ESA.

I can’t help but note: if the connection of the “welder” is planned to a network with a voltage of 220-380 V, then it is highly desirable to have an additional, 160-volt winding on top of the primary winding (the required number of turns is specified by the voltmeter), after which comes the secondary, welding.

The case of such a self-made ESA can be made, for example, from a perforated metal sheet with a thickness of 1-1,5 mm. At its base, the toroidal transformer itself is installed on insulating supports, fixed from above by a clamping insulator bar with two M10 studs. Perforations with a diameter of 20 mm - to create a natural forced ventilation, which is necessary for our "welder".

Rice. 1. Homemade "welder" assembly (click to enlarge): 1 - shock absorber support (4 pcs.); 2 - M10 stud bracket with two washers and a pair of nuts (4 sets); 3 - lining with slots for ventilation: 4 - M8 stud with two washers and a pair of nuts (2 sets); 5 - base with ventilation holes; 6 - insulating lining (getinaks textolite or wooden plank s10-15, 4 pcs.); 7 - magnetic circuit (from an electric motor with a power of 3-5 kW); 8 - insulating substrate (fiberglass, 2-3 layers); 9 - primary network winding (220-380 V, no-load current 0,5-1 A); 10 - additional winding, designed for 160 V; 11 - secondary welding winding; 12 - protective shell of the welding transformer (fiberglass, 2-3 layers); 13 - scarf (4 pieces); 14 - carrying handle (metal pipe 20x3, 2 pcs.) 15 - clamping bar (textolite, getinax or wooden plank s10-15); 16 - terminal panel (13 mm fiberglass or other heat-resistant insulator); 17 - light indicator (MTX-90 thyratron with 60 kiloohm MLT-0,25 or "neonka" TN-02 with a series-connected resistor of the order of 120 kOhm); 18 - terminal 220 V (2 pcs.): 19 - welding terminal (M10 bolt with two nuts, a pair of washers and a wing nut, brass or copper, 2 sets); 20 - "limit switch" of the welding winding (copper or brass, sheet s1,5, 2 pcs.); material children. pos. 3,5 and 13 - metal sheet s1-1,5; type and number of fasteners for cladding and terminal panel not shown

The cladding is attached to the base (for example, with screws and brackets-corners): also from a metal sheet, but already with a "slotted" perforation. The distance between the walls and the transformer should, as practice shows, be at least 30 mm - again, to facilitate air cooling conditions.

From above, the body is stiffened with scarves, to which handle brackets are attached. The basis of each of these handles is a pipe 20x2 mm with side holes with a diameter of 10,3 mm at the ends, into which M10 studs are inserted and welded through the end window.

At the final stage of the assembly, a panel of 10 mm fiberglass (or other equally heat-resistant insulator) is installed with network and more powerful welding terminals located on it, as well as an "On" light indicator. As the latter, an MTX-90 thyratron with a 60-kiloohm resistor or a "neonka" MN3 (TN-0,2) with a series-connected MLT-0,25 resistance of 120 kOhm can be used.

To adjust the current during welding, it is recommended to use a homemade rheostat. The basis is a 100-mm piece of asbestos-cement pipe with a diameter of 200-250 mm. As a resistant winding, a spring is used (steel chromium-vanadium wire with a diameter of 3-4 mm, winding - on a cylindrical blank with a diameter of 40 mm), for example, from a seeder.

Welding - own
Rice. 2. Ring rheostat: 1 - base-insulator (asbestos-cement pipe); 2 - resistant winding (cylindrical spring from a seeder, steel chrome-vanadium wire with a diameter of 3-4, a coil with a diameter of 40, the ends are annealed and, after installation in place, are bent under the M8 bolt); 3 - terminal (M8 bolt with a nut and two washers, 2 sets); 4 - welding cable with "limit switch"; 5 - carrying handle (steel strip 40x2); 6 - welding cable with two "terminals"; 7 - crimp-insulator (rubber hose 20x3, L50); 8 - knife contact (copper strip 25x5, L110)

The ends of the spring blanks are heated red-hot, passed through the holes drilled for them inside the asbestos-cement pipe-base and bent with pliers under the M8 bolt. The beginning of the resulting resistant winding is connected to the 1st welding cable using a self-made terminal consisting of an M8 bolt, a nut and two washers. Well, the adjustable current collection is carried out using a copper knife-regulator inserted between the coils of the rheostat spring.

Of course, it is useful to equip the ESA with a sufficiently powerful rectifier, which will allow you to perform high-quality DC welding. As practice shows, the most acceptable are technical solutions based on the so-called rectifier bridge on diodes capable of supplying a direct current of at least 100 A to the load. For the purpose of better cooling, it is desirable to supply each of the semiconductor valves with a radiator having a heat transfer area of about 200 cm2 .

Pretty good performance, for example, for a rectifier bridge, consisting of two groups of powerful bipolar diodes V200 and VL200, the design of which (with "anodic" or, conversely, "cathode" heat removal and having distinctive housings, respectively, green or crimson ) makes it easy to combine them into a super-compact block with "plus-minus" and "minus-plus" contact-radiator groups, between which a rubber gasket is installed (see "Model designer" No. 5'97 and No. 9'02).

For reliable ignition of the arc, a capacitor or choke is usually used. However, the latter is preferable due to its inherent high energy-intensive and operational qualities. The design itself depends on the magnetic circuit used. The most accessible for many is the "hardware" of burned-out transformers. More precisely - packages of standard configurations made of electrical steel.

Rice. Fig. 3. Scheme of the rectifier-throttle unit, as well as possible options for a welding choke on a rod magnetic circuit (a) and on an armored one (b), composed of two typical rod cores (click to enlarge): 1 - magnetic circuit (package assembled from the most available plates transformer steel); 2 - insulating gasket (2-3 layers of glass insulating tape); 3 - winding (35-40 turns of cable with a total cross section of copper conductors 25 mm2 or aluminum 35-40 mm2); 4 - coupling bracket (metal corner 15x15 or 25x25, 4 pcs.); 5 - coupler (stud with two nuts and Grover washers, 4 or 8 sets)

Good chokes are obtained, in particular, when, as a magnetic circuit for them, there is a rod core 30 mm wide and a package thickness of 150-250 mm (from an old power supply unit) or two paired ones, adapted as a kind of armor with a package 100-150 mm thick. The winding contains from 35 to 40 turns of a well-insulated wire (conductive bus, cable) with a cross section of 35-40 (aluminum) or 25 (copper) mm2. Advantage: any electrode can be used.

It is these chokes that are easy to integrate into rectifiers or arrange as separate blocks. If you have to do a lot of welding and also use 4 mm electrodes, then you can not do without forced air cooling. In this case, it is desirable to install the fan itself directly on the ESA rectifier.

In the last author's version, I had to go for the installation of more powerful radiators from 500-ampere diodes. The result was a home-made ESA, which, in terms of its technical and operational parameters, is capable of being, as they say, on an equal footing with industrial-made welding machines.

Author: A. Pevnev, Dimitrovgrad, Ulyanovsk region

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