My unit a 380V two-phase electric welding machine, 3KW welding power about iron, boot no reaction can not be welded, sometimes a little spark, general principle is that, a line directly into the welding machine coil, a line through the thyristor into the coil, controlled silicon trigger circuit, trigger by the time relay control circuit, I have changed the SCR (1600V 100A), the fault still, I would like to ask how to check, the SCR is two-way? Where will the trouble occur?
The no-load voltage of the two circuit is usually 10-18 volts. If the voltage is normal, there is a certain rust in each part of the circuit, resulting in poor contact. Just keep it clean. If the voltage is abnormal, check the control loop and transformer.
As the two time no voltage, it shows that the transformer does not work or work, but the voltage does not output, because it is a spot welder, so the two voltage will not be very high, usually that is, a few volts. So, in dealing with the fault, first of all, to check whether the transformer one or two winding is intact, and whether the input and output connections are reliable. If you are normal, it is necessary to consider the trigger circuit of silicon controlled rectifier, thyristor can be shorted, then supply power, two times the output voltage measurement is normal, if not normal, may be the power line, if the normal is SCR trigger circuit or the problem.
1, K - power switchUsed to connect (or cut off) contact with mains power (220V, 50 Hz)2, RT - starting resistanceWhen the welding machine is started, the filter electrolytic capacitor should be charged. In order to avoid excessive surge current damage to the switch and trigger circuit breaker tripping, access start at boot time to limit the inrush current resistance. After normal operation, the starting resistor is shorted by the relay. In actual circuit, in order to avoid the damage of starting resistance caused by inrush current, the starting resistance adopts thermistor (PTC and NTC), they have good shock resistance.3, J1 - relayAfter the switch is switched on, the current is charged by the starting resistor to the filter electrolytic capacitor. When the capacitor voltage reaches a certain value, the auxiliary power supply starts to work, the 24V power is supplied, the relay is pulled in, and the starting resistance is short circuited.4, DB - silicon bridgeThe silicon bridge is used for primary rectification, and the DC current of the 308V is rectified by rectifying the mains 220V and 50 Hz alternating current.5, C1 - electrolytic filter capacitorAfter rectification, the output DC current of 308V is pulsating DC, and the capacitor plays a smoothing role6, R - discharge resistanceAfter the shutdown, there is a high voltage in the filter capacitor. For safety purposes, the resistor will be used to drain the power.7, C2 - high frequency filter capacitorIn the high frequency inverter, the high frequency current is needed for the switch tube, while the reason of the electrolytic filter capacitor is the inductance and lead inductance of the filter
