motors: 50 Hz vs 60 Hz

[Ragin Cajun]

Have a current project where the client has two extruder systems. Both are used equipment and came from United States facilities.

One extruder drive motor (Siemens) is dual rated at:

315KW, 380/660V, 578/333A, 50 Hz, 1490 rpm

AND

353KW, 440V, 538A, 60HZ, 1780 rpm.

Voltage range is 360-400/630-690 at 50 Hz and 420-460V on 60Hz. FLA's are 549-610/318-349A at 50Hz and 515-564A at 60 Hz.

Never seen a dual Hz rated motor before!
Perhaps because the extruded motor is on a VFD?


The other extruder line has all 50Hz rated motors but all were supposedly run at 60Hz,

What gives?

The V/Hz for the 50Hz rating is 7.6, and at 60 Hz it's 7.333. I'm sure that the plant voltage originally was 460V (or even 480V) which puts the v/Hz at 7.6666.
So from a V/Hz standpoint, they are very close.

I thought that you can't / shouldn't run 50Hz motors on 60Hz, at least for FVNR motors. Motors on VFD's are different.. What did I miss?

Some of the motors are on VFS, and other are oil pumps, cooling fans, etc.

Am I making a mountain out of a mole hill?

 

[GoldDigger]

You should not run 60Hz motors on 50Hz without reducing the voltage, to avoid saturation of the iron elements of the motor's magnetic circuit.
You also should not casually run 50HZ motors on 60Hz without taking into consideration the increased mechanical load. For a fan or impeller pump, the 60/50 speed increase corresponds to a factor of 1.72 increase in power. If you can make a pulley or gear change to fix the speed, no problem.

 

[Joethemechanic]

I've seen that 50/60 hz rating on some smaller motors. I think they were SEW Eurodrives. If I remember correctly the 50 hz rating was 380 volts, although I could be wrong. It was on machinery that came from Germany