SCR VOLTS

If an imbalance of voltage is seen across the SCRs on an inverter bridge, heat will be turned off. The voltage across 1 SCR on the bridge, and the total voltage across both is monitored. If one is not half the other, this fault will activate and won’t clear until the voltage on both SCRs of the bridge is even, between 300-350VDC (units more than 500kW will have two bridges, 2 SCRs on each). It will also activate if the DC voltage falls below its normal value.

This fault indicates such a voltage imbalance, and typically means that either an SCR or diode has failed in the rectifier bridge. A shorted filter or series resonant capacitor can also cause this problem.


 * If the pins that hold up the SCRs on the inverter or rectifier bridges are not positioned correctly, the SCRs are not flush with the clamping mechanism.

VIPs