Situation:
Cornered grounded delta (Bastard 3 phase) (L1-grnd=480) (L2-grnd=0) (L3-grnd=480) phase to phase = 480.

20HP Baldor 460 motor rated for VFDs and 4to1 turn down.

SquareD Altivar 21 drive rated for 20HP.

SquareD told me the drive would handle the input of the cornered grounded delta. I hooked the system up and suffered a few nuisance ground faults and then the windings of the motor went to ground.

I'm really wondering about the input to the drive. Any help would be appreciated.
Thanks

 

ABB drives can handle asymmetrical feed as long as they don't have any EMI reduction components installed.

 

Tally... Can you provide the actual L1-L2, L2-L3 and L3-L1 measurements?

Regards, Phil Corso

 

L1-L2=484, L2-L3=483, L1-L3=486

Thanks
Tally

 

Tally... the figures you provided result in a NEMA, and IEC Voltage Unbalance Factor (VUF) of 0.34% and 0.36%, respectively. Thus, supply voltage unbalance can be ruled out.

1) Do you have comparable figures for the line-volts, and line-amps at the drive's output or the motor's input?

2) Can you provide detail on the motor failure- mode?

Regards,
Phil