Seam Annealer

Good morning. Is anyone has experience in seam annealer. If yes I'm having problem with our unit. Today even the company that design and manufacture it was not able to help me. Is run awhile and the system shut down the AC SCR firing board. We have replace SCR, diodes, firing board, lost phase detector, snubber almost everything but the problem still remain. Breaker didn't trip, fuses are ok. We have the unit since 3 years it never happen. This problem start last month just like that.

see below the alarm

ACI/AUX TRIP: AC Interrupter Fault. Trips off unit, trips main breaker.
This fault indicates that the main breaker is off, as well as the AC Rectifier which charges the DC bus of the unit. A break in the E-Stop chain will also engage this fault.

If all E-Stops (or door switches or cap pressure switches) are cleared, then engage the main breaker, and pressing Reset will start the AC Rectifier, charge the DC bus, and clear this fault, making the inverter ready for Heat On operation.

This fault also indicates a loss of a phase/wrong rotation on the input 3-phase voltage to the main breaker. Check the lost phase detector next to the main breaker, if the red fault LED is on, a lost/wrong phase situation is present.