380v 50hz spindle motor running on 60hz

[JimH07]

Hi,

We are working on a Wotan mill that our customer purchased via an auction. This mill had previously been retrofitted to run off 240vac, 60hz. We replaced the control and axis drives and now blow fuses when reversing the spindle. I discovered that the spindle motor is rated at 380vac at 50hz.

Based on what I have read about running motors rated at 50hz on 60hz, I've come to the conclusion that this motor should be running at 480vac, and that the only difference from rated would be an increase in rpm from 1420 to 1704. Am I correct in my assumptions?

Nameplate info from motor:
9.2 KW
380/660V
20.5/11.8A
Frec 50 Rpm 1420

220vac is currently being supplied to the machine, but 480vac is available.

Jim H.
Eagle Machine Tool

 

[waross]

Yes you are correct. The motor should be fed from a 480 volt circuit. (380V x 5/6 = 456V, 480 volts nominal supply = 460 volts utilization voltage, 456V vs 460V = close enough.)
respectfully

 

[Marke]

At the reduced voltage, your torque available will be less than a quarter. This could be low enough to prevent the motor from reaching full speed and under the stall condition, the current will be three time rated current (due to the reduced voltage) and this would cause the fuses to fail.

Best regards,

Mark Empson

http://www.lmphotonics.com