Refinement of the welding machine. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Refinement of the welding machine. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Electrician's Handbook

Using my own experience, I made a welding machine for electric arc welding. Then I decided to improve the accessories for the welding machine: a head protective shield, an electrode holder, a current-carrying clamp. I started with the head protective shield: the fixation of its positions was broken in the existing one. I purchased an EOS-2 head protective shield with an electronic-optical control of the light filter in the distribution network. Good device. Its use significantly improves the working conditions of the welder and the quality of the welding work performed. But soon the shield stopped working. The solar battery has failed.

It was not possible to restore the operation of the electron-optical light filter. I decided to remove it from the shield and replace it with a home-made electromechanical one controlled from the electrode holder remote control. As a result of this and subsequent improvements, a welding machine was assembled and tested in operation, the diagram of which is shown in Fig. 1 .

Finalization of the welding machine
Fig. 1

The welding machine contains:

- the block of inclusion and protection (BVZ) - A1;
- head shield with an electromechanical light filter block - block A2;
- welding transformer - unit A3;
- electrode holder - block A4;
- current-carrying clamp (TPZ).

Consider the operation of the device block by block.

BVZ turns on the welding machine with the SA2 toggle switch from the control panel located on the electrode holder (block A4), automatically disconnects from the network in emergency situations and when the temperature of the welding transformer windings rises above 65 ° C. It contains a QF1 circuit breaker, a K1 relay, a K1 relay winding power supply, made on a T1 mains transformer, VD2-VD5 rectifier diodes, a smoothing capacitor C1 and a parametric stabilizer R1, VD1. When the contacts of the toggle switch SA2 are closed, the winding of the relay K1 is connected to the output of the stabilizer. The relay is activated and with its contacts K1.1 supplies mains voltage to the winding I of the transformer T1. The stabilizer maintains the rated voltage on the relay winding K1 during the operation of the welding machine.

Resistor R1 - C5-37, it can be replaced by two MLT-2 resistors with a resistance of 910 ohms connected in parallel. Relay K1 - RKS 3, passport RS4.501.200. In case of unreliable operation of the relay, you should install a Zener diode VD1 with a high stabilization voltage (15 ... 18 V) and reduce the resistance of the resistor R1 to 200 ... 270 Ohms. Automatic switch imported from MONTEL for a current of 30 A. Transformer T1 is made on a magnetic circuit ShlO-20x16 mm. The primary winding contains 2400 turns of PEV-2 wire with a diameter of 0,14 mm, the secondary - 280 turns of PEV-2 wire with a diameter of 0,31 mm. You can also use any network step-down transformer with a power of 2.3 W with a voltage on the secondary winding of 25.27 V. Connector X1 - connector ONTS-VG-5/16.

The installation of high-current circuits of the unit is carried out with a BPVL wire with a cross section of 6 mm2, control circuits - with a MGSHV 0,2 wire. The block is placed in a case made of sheet plastic 2 mm thick, on the basis of which there are clamps XT1 and XT2, connector X1. The elements of the stabilizer are placed on a printed circuit board made of one-sided foil-coated fiberglass-stolite 1,5 mm thick and fixed on the base of the block using corners and M3 screws. On the cover of the block there is a carrying handle made of gety-nax. A photograph of the BVZ with the cover removed is shown in fig. 2.

Finalization of the welding machine
Fig. 2

In the head shield (block A2), instead of the removed, as already mentioned above, block of the electron-optical light filter, a self-made block of the electromechanical light filter (EMS) was installed. EMC closes the viewing window of the welding shield with a light filter during welding and opens it after welding. The EMC block is controlled from the control panel located on the electrode holder (block A4). In the initial position, the SA1 three-position toggle switch, located on the electrode holder console, is in the middle neutral position. The DC motor (hereinafter referred to as the motor) M1 and the time relay assembled on the elements VT1, C1-C3, R1 and R2 are de-energized. The time relay controls the duration of the engine, which is 0,8.1 s.

When switching the toggle switch SA1 to one of the extreme positions through the diode bridge VD1-VD4 and the open transistor VT1 of the time relay, the supply voltage from the battery GB1 is supplied to the motor winding M1. The diode bridge ensures the connection of the time relay in the required polarity when the direction of rotation of the motor changes (lowering or raising the filter frame). Its shaft begins to rotate and, through the mechanism for lowering / raising the frame of the filter, sets the frame itself in motion. It opens or closes the viewing window of the welding shield. After 0,8.1 s, the capacitors C1-C3 will be charged, the current through the transistor VT1 and the motor winding will decrease to units (tens) of milliamps. When the device is turned on for a long time, in order to prevent premature discharge of the GB1 battery, the SA1 toggle switch should be set after lowering (raising) the frame to the neutral position.

M1 engine - EG-5330VD-2BH from a cassette recorder, electronic speed stabilizer removed. Battery GB1 - four elements R14S, connector X2 - PC7, capacitors C1-C3 - imported oxide, diodes VD1-VD4 (germanium 1602a) are replaceable by Schottky diodes for a current of at least 200 mA and a reverse voltage of more than 10 V.

Structurally, the EMC unit consists of a base, fixed on the welding shield, and two covers. Connector X1, a container with a GB1 battery, an M1 motor with a mechanism for lowering/raising the frame, elements of a time relay with a diode bridge are fixed on the base. In the middle part of the base of the block, there is a viewing window 90x40 mm in size, in front of which there is a frame with a C300 protective light filter 102x52 mm in size. The elements of the time relay, the diode bridge and the X1 connector are placed on a printed circuit board made of foil fiberglass with a thickness of 1,5 mm. A photograph of the head shield with the covers removed is shown in fig. 3.

Finalization of the welding machine
Fig. 3

Welding transformer T1 of block A3 is designed according to the criterion of the smallest mass. It provides an open-circuit voltage of 65 V on the secondary winding, a welding current of 140.150 A at PV (load duration) of 60% and work with welding electrodes with a diameter of 3 mm. It has no schematic and design features. Protection of the windings of the welding transformer against overheating is made on the thermal switches ST1 and ST2, installed on top of the windings I and II of the transformer T1. The contacts of the thermal switches through connector X3 are connected in series to the winding circuit of the relay K1 of block A1 (through connector X1) and the contacts of the toggle switch SA2 of the control panel. They open the power supply circuit of the K1 relay winding when the welding transformer windings are heated above 65 ° C, disconnecting the machine from the mains.

Thermoswitches KSD 301-65 are fixed with EP-6 epoxy glue on fiberglass plates 40x40 mm in size, 1,5 mm thick. The plates themselves are fixed on the windings of the T1 transformer with fiberglass bandages. The transformer is placed in a plastic case, on which clamps XT3, XT4, XT5, XT6 and connector X3 are mounted. The magnetic circuit of the transformer is grounded. Connector X3 - connector ONTS-VG-5/16.

Finalization of the welding machine
Fig. 4

The electrode holder (block A4, photo in Fig. 4) is self-made, it supplies current to the welding electrode. A control panel is mounted on the electrode holder, consisting of toggle switches SA1 and SA2. As mentioned above, the SA2 toggle switch turns the welding machine on and off, and SA1 controls the operation of the light filter in the protective shield unit (block A2). Toggle switch SA1 - P2T-1L (three-position), SA2 - P1T4-1PV. The electrode holder is made in the form of a housing with a handle and a built-in control panel, a box for fastening the head of the electrode holder with a fixed head. The handle has a through hole with a diameter of 18 mm along the axis, through which a power wire passes from the XT5 clamp to the head and wires from the control panel. The handle is attached to the body of the electrode holder with M3 screws.

The box-type case is assembled from fiberglass plates 2 mm thick. The plates are attached to a frame made of 1,5 mm thick sheet steel. The SA1 toggle switch is installed on the frame. The switch is controlled by a slider that reciprocates under the action of the thumb or forefinger of the welder. Toggle switch SA2 is fixed on the bottom plate of the case. The box for attaching the head of the electrode holder is assembled from fiberglass plates 4 mm thick. The plates of the box are fastened with the help of U-shaped profiles made of steel 1 mm thick and homemade rivets with a diameter of 2 mm with sunken heads. The heads of the rivets are recessed into the plates by 1 mm, and the recesses are filled with epoxy putty. The power wire leading to the welding electrode is attached to the head with an M6 brass screw with a plastic-reinforced nut with a star-shaped handle. This fastening allows you to rotate the head of the electrode holder at an angle of 90 °.

The screw fixes the welding electrode. The hole in the head with a diameter of 8 mm for the welding electrode is reinforced with a copper tube with an outer diameter of 8 mm, an inner diameter of 6 mm. The tube is flared and has a through hole for the passage of a screw that fixes the welding electrode. Reinforcement of the head with a copper tube and the use of a brass screw eliminates the "sticking" of the welding electrode to the elements of the head. The main attention in the manufacture of this block is given to the requirements of electrical safety.

Finalization of the welding machine
Fig. 5

The current-carrying clamp (TPZ, photo in Fig. 5) is self-made, not shown in the diagram. It serves to supply welding current to the parts to be welded (to the "mass"). Spring-type TPZ, as the safest, is made in the form of oversized pliers. It consists of sponges, current-carrying inserts, springs on the axis and handles. Sponges TPZ are made of steel 1 mm thick. Having opened the throat of the sponges - 30 mm, the compression force of the sponges - 1,5 kg. TPZ handles are made of textolite and fixed with rivets and M4 screws, one of which is connected to a terminal with a current-carrying power wire from the XT6 clamp.

All high-current wires coming from the XT1-XT6 clamps are homemade. They are made of relatively inexpensive stranded copper wire of the PRN brand with a cross section of 25 mm2. Each wire has a termination at the end for connection to the corresponding terminals of the welding machine. End caps are made of pieces of copper tube with a diameter of 10 mm. The ends of the wires are tin-plated and embossed into end caps. The BVZ control wires coming from the X1 connector are MGGShV-0,2. Both of these wires and the wire from the XT5 clamp are placed in a common protective sheath made of tarpaulin. The wire from the XT6 clamp, connected to the TPZ, is also placed in a canvas sheath.

When developing the design, due attention was paid to reliable electrical insulation of the blocks. Their cases are made of insulating materials, low-voltage power supplies of 6 V (block A2) and 12 V (block A1) are used, and all wires are protected, as already mentioned above, from electrical, mechanical and thermal damage by additional shells.

When performing welding work, it is necessary to strictly follow the rules of electrical safety so as not to get an electric shock. A current of 0,1 A is life-threatening. Before carrying out welding work, it is necessary to check the external inspection of the welding machine for the absence of mechanical damage, including damage to the wire insulation. The magnetic circuit of the welding transformer T1 in block A3 must be grounded. Work should be carried out only while standing on an insulating mat in tarpaulin gloves. In work, it is necessary to be guided by the requirements and rules for the technical operation of consumer electrical installations and safety regulations for the operation of consumer electrical installations.

Author: L. Stepanov

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