sirius softstarters blowing up fuses 1

[vilhal]

Hello

We have a small pumping station with 2 37kW pumps.
We added two sirius softstarters (2 phases controlled) with line contactors.
Control voltage and lighting are connected to 2nd phase with their own fuses.
First time we tried to start softstarter, plc and kwh meter burned.
After that every time we try to start softstarter lighting fuse blows.
Lights dont flicker or anything, just after a few seconds fuse blows.
Very weird since controlvoltage and lighting have their own fuses.
Both are from 2nd phase which is the same phase that directly goes through the softstarter.
Without softstarter, controlled only with contactor the pumps run fine and there's no problems with fuses.
Also when trying to start with softstarters there's a constant sound. Like it's not even trying to up the voltage, only the 2nd phase going through.
Softstarter leds show phase failure / missing load.

Hopefully someone has some solution to this before we throw away the softstarters and buy frequency converters just to find out it doesnt fix the problem.

Thank You.

 

[LionelHutz]

It's no secret. We already have a number of them in the field. It's a modular multi-level converter design. A 5kV system would have a 18-pulse transformer creating a ~6kVDC bus. The DC bus feeds 6 cells in series per phase.