The DC current has reached the rated value, and the DC voltage and intermediate frequency voltage are low

May 11, 2022

Fault phenomenon: when the equipment is running, the DC current has reached the rated value, but the DC voltage and intermediate frequency voltage are low. Observe the intermediate frequency voltage waveform with an oscilloscope. The waveform is normal and the front angle of the inverter is also normal.

Fault analysis and treatment: this fault phenomenon does not belong to the fault of medium frequency power supply, but is caused by the low impedance of the load, so the load impedance must be readjusted.

a. In the circuit of boosting load, this fault phenomenon will be caused by the damage of series compensation capacitor, its removal and no replacement, or blindly requiring high power and uncontrolled increase of compensation capacitor, so that the compensation amount of load is over compensated. The solution is to readjust the compensation amount of the compensation capacitor so that the equipment can operate at rated power.

b. The inductor has inter turn short circuit. If the inductor has inter turn short circuit, the impedance of its load will also be reduced. There are two possibilities of inter turn short circuit: the copper tube of the inductor is directly short circuited; The fixed bakelite column of the inductor is severely carbonized. Because the carbon has conductive characteristics, it causes the inductor turn to turn. The carbonized bakelite makes the turn to turn direct connection, resulting in turn to turn short circuit. The solution is to eliminate the phenomenon of inter turn short circuit.