Before welding, the capacitor energy storage spot welding machine needs to charge the energy storage capacitor first. At this time, the circuit for discharging the energy storage capacitor to the welding transformer is disconnected. During the welding process, the energy storage capacitor discharges rapidly to the welding transformer. At this time, the charging circuit should ensure reliable disconnection.
The charging thyristor valve requires sufficient withstand voltage, generally selecting a withstand voltage of 2-3 times the power supply voltage for the tube. In addition to requiring sufficient withstand voltage, the discharge thyristor valve also needs to withstand large current surges and reliably turn off after the discharge current reaches a certain value. This is extremely important in the control of the welder. Otherwise, when the discharge ends and the charging thyristor valve is turned on, the charging circuit will directly supply power to the welding transformer, causing a short circuit in the circuit.
Therefore, the circuit design must adopt interlocking control of the charging and discharging thyristor valves. Some also apply a reverse voltage pulse to both ends of the discharge thyristor valve before the charging thyristor valve is turned on to ensure reliable turn-off of the discharge thyristor valve before the charging thyristor valve is turned on.
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Post time: Mar-08-2024