Portable pulse electric welding machine. Scheme, description

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Portable pulse electric welding machine. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / welding equipment

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This electric welding machine with an external welding gun is designed for welding stainless steel sheet with a thickness of 0,08-0,15 mm to massive steel parts, as well as for welding steel wire with a diameter of up to 0,3 mm.

Portable pulse electric welding machine. The design of the welding gun
Fig. 1

Description of work

The device works as follows. When the contacts of the SA1 switch are closed (see Fig. 2), the supply voltage of 220 V is supplied to the primary winding of the TV1 transformer. Capacitor C1, connected through the closed contacts of switch SA3 to the rectifier bridge D5-D8, is charged. The primary winding of the transformer TV2 is de-energized, since the trinistor VS1 is closed.

Fig. 2

When the switch button SA3 is pressed, the charged capacitor C1 is connected to the control electrode of the trinistor through a variable resistor R1. The discharge current of the capacitor opens the trinistor, and the mains voltage is supplied to the primary winding of the welding transformer TV2. If the secondary winding of the welding transformer is connected to the parts to be welded, then a powerful current pulse arises in it, which causes a strong heating of the metal at the point of contact of the welding electrode. The duration of the current pulse depends on the parameters of the timing circuit R1C1. With the ratings of the elements of this circuit, the maximum pulse duration (excluding the internal resistance of the trinistor) is approximately equal to:

i_и =R1C1 =100×1000×10^-6=0,1 s

During this time, the current in the secondary winding can reach 300 ... 250 A. This is quite enough for durable welding of foil parts up to 0,15 mm thick to massive structures, for example, from 1Kh18N10T alloy steel.

The optimal welding mode is set by the tuning resistor R1.

Design

Structurally, the welding machine consists of two parts: a power unit and a welding gun, which are interconnected by a flexible multi-core cable. Almost all elements of the device are located on the chassis of the power unit.

The device of the welding gun is shown in fig. 1. The body 7 of the gun is made in the form of two parts of the same shape, milled from sheet textolite 12 mm thick. The holder 3 of the welding electrode 2, the backlight lamp 8 with the push-button switch 4 "Illumination", the microswitch 6 "Impulse" are mounted in the body. The connecting cable 5 is a flexible twenty-four-wire rubber-insulated cable with an outer diameter of 11 mm and a cross section of each wire of 0,75 mm². Five wires of the cable are used to connect the microswitch and the backlight, and the remaining nineteen wires are soldered directly into the holder 3 of the electrode. The holder is made of a copper bar of rectangular or square section. The electrode is a copper rod with a diameter of 8 mm. The electrode must be securely fixed in the holder. At the same time, it should be possible to change the electrode. To solder the foil, the tip of the electrode is sharpened with a cone turning into a sphere with a diameter of 1 ... 1,5 mm. To weld the foil, an electrode with a flat working end is used.

The capabilities of the device can be significantly expanded. If you use a copper-plated graphite electrode with a diameter of 6 ... 8 mm, you can weld tinned copper conductors with a diameter of up to 0,3 mm. Very well, such conductors are welded to any tinned and silver-plated parts, as well as to non-tinned copper foil.

Details

Transformer TV1 can be any, providing a voltage of 8 ... 10 V (to charge the capacitor) and 3 ... 6 V (to power the backlight) on the secondary windings.

The TV2 transformer is assembled from Sh40 plates, the thickness of the set is 70 mm. The primary winding contains 300 turns of wire PEV-2, 08. The secondary winding of this transformer consists of 10 turns of insulated wire or bus with a cross section of at least 20 mm². The "grounding" connecting conductor of the secondary winding is made of the same section. Its length should be no more than 2 ... 2,5 m. Between the primary and secondary windings of the transformer, it is necessary to lay several layers of varnished fabric as insulation.

D1-D4	D232A
D5-D8	D226B
VS1	PTL-50
С1	1000uF-25V
R1	100 ohm

Exploitation

A properly assembled device starts work immediately, without any adjustment. The quality of welding depends on the selected welding current, which is set by the trimming resistor R1 "mode".

Attention!

Take precautions with this electrical appliance.

Publication: cxem.net

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