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I have a single 1HP VFD running two 1/3HP induction motors.
Supply voltage to drive 460, motors rated for 460v/60hz/3450rpm (2 pole).
For reasons unknown, when given a speed command of 60hz, the drive was only putting out 320vac.
The drives people at both my vendor and the manufacturer were both stumped to why. The motors seemed to be running fine for many days and the shipment day for the machine had arrived....so out the door it went.
After a few days at the customer, the motor burned up one of its coils. The motor is rated 0.7FLA, and due to low loading, it never actually pulls that much. In fact, when putting out 320vac the drive was also only putting out 0.6A to run both motors. 0.6A total, not per motor. Even if it was 0.6A to just one motor (which it wasn't because they were both spinning furiously) how would that cook the motor?
The OL to the motor never opened up (presumably because the current never exceeded the 0.8A setting) so how did the motor get ruined?
I've searched the net for V/Hz ratio info. All anyone says is that its important. I've read what happens if the V/Hz ratio is too high, but can't find a treatment of what happens if its too low....
Anyone with any insight/experience on this?
Supply voltage to drive 460, motors rated for 460v/60hz/3450rpm (2 pole).
For reasons unknown, when given a speed command of 60hz, the drive was only putting out 320vac.
The drives people at both my vendor and the manufacturer were both stumped to why. The motors seemed to be running fine for many days and the shipment day for the machine had arrived....so out the door it went.
After a few days at the customer, the motor burned up one of its coils. The motor is rated 0.7FLA, and due to low loading, it never actually pulls that much. In fact, when putting out 320vac the drive was also only putting out 0.6A to run both motors. 0.6A total, not per motor. Even if it was 0.6A to just one motor (which it wasn't because they were both spinning furiously) how would that cook the motor?
The OL to the motor never opened up (presumably because the current never exceeded the 0.8A setting) so how did the motor get ruined?
I've searched the net for V/Hz ratio info. All anyone says is that its important. I've read what happens if the V/Hz ratio is too high, but can't find a treatment of what happens if its too low....
Anyone with any insight/experience on this?