Over-current action after the induction melting furnace presses the start button

First, the phenomenon of failure 

After pressing the IF start button, the overcurrent protection action causes the rectifier to be pulled into the inverter state.

Second, failure analysis and processing 

For the newly installed intermediate frequency power supply, check whether the voltage polarity is correct, whether the polarity of the inverter pulse is correct, and whether the lead angle is too small. Since there is no polarity problem for the already operated intermediate frequency power supply, it can be detected from the following aspects.

(1) Use a multimeter to measure the damage of the thyristor and the fast fuse. If it is damaged, replace the thyristor fast fuse melt.

(2) Check if the load circuit is short-circuited and the load is too heavy.

(3) Use an oscilloscope to check if the lead angle is too small, if the inverter pulse has interference, and if the thyristor characteristics deteriorate.

(4) Check if the overcurrent protection setting value has changed. If it changes, it should be re-tuned.

(5) Check if the current feedback is too large. If the feedback amount is too large, the oscillation will stop. If it is normal, check if the voltage feedback signal is off.

(6) Check if the DC output voltage of the rectifier circuit is too low and whether the insulation of the IF power load circuit is reduced.