50 Hz motors on 60 Hz system

[Isaiah]

Back in the 80s, we had to supply an air compressor with a 460V, 50Hz motor. I can’t remember where it went, but it was an odd duck, for sure. I think we had GE re-nameplate a 440V (maybe 415V?), 50 HZ which dropped the service factor from 1.15 to 1.0.

Jaref, just out of curiosity if I ran 3, 1/C XHHW, along with 3 EGCs in a Triplex configuration would this be ok in PVC conduit?


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[Jraef]

Jaref, just out of curiosity if I ran 3, 1/C XHHW, along with 3 EGCs in a Triplex configuration would this be ok in PVC conduit?


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It would not matter much to the motor. It might bother other things nearby. It’s a pretty boring radio station.

 

[zbang]

It’s a pretty boring radio station.

Maybe not so much underground, but ya, same song on repeat.

 

[LarryFine]

Maybe not so much underground, but ya, same song on repeat.

And you can't even dance to it.

 

[ptonsparky]

Maybe not so much underground, but ya, same song on repeat.

My older Well VFD was in metallic conduit out to about 10' from the house to where it transitions to PVC then 150' +- to well. The Song was certainly there when attempting to listen to any AM broadcast. Cheap fix was, don't attempt.

I've a newer VFD installed now but don't know if its playing the same song or not.

 

[Knightryder12]

These motors are pretty big. I'd be concerned about ground current through the frame causing bearing damage. I've seen it happen, even with short cable runs.

Are these motors not VFD rated? If they are VFD rated it would be safe to presume that they have the shaft ground protection/shield installed.

 

[Jraef]

Are these motors not VFD rated? If they are VFD rated it would be safe to presume that they have the shaft ground protection/shield installed.

If only that were true... There is no enforcement mechanism for what "inverter rated" (or "duty" or "ready" etc.) means and a lot of companies, even good ones, play games with that. I have done a couple of projects where OEMs supplied 1/2HP evaporative cooler fans with Baldor "Inverter Ready" motors, we had MULTPLE failures within weeks, despite doing all of the right things with regard to wiring and grounding, even load reactors. Turned out they had no special insulation, no shaft grounding, nothing special about them whatsoever. So "Inverter Ready" meant absolutely nothing other than having Class H insulation. To their credit though, Baldor replaced them in both projects, so over 100 motors in total, with ones that said they met "NEMA MG-1, Part 31", which spells out specific design criteria.

 

[Tip DS]

It would be best if you used a VFD cable. Yes, you can connect a VFD to a motor and make it work with a non-VFD cable. You can hook up a transformer to convert from one voltage to another without grounding the neutral - that will also work. In both cases, just connecting it and justifying the method by saying, "It worked without issue" isn't sound justification. In the case of the non-VFD cable, you WILL see insulation degradation over time due to the voltage spikes created by the interference patterns associated with the harmonics inherent to non-linear electrical manipulations in the drive. If you're installing on a skid that will be thrown away in 5 years, then sure - do it the wrong way & don't worry about the long-term effects.

 

[Knightryder12]

If only that were true... There is no enforcement mechanism for what "inverter rated" (or "duty" or "ready" etc.) means and a lot of companies, even good ones, play games with that. I have done a couple of projects where OEMs supplied 1/2HP evaporative cooler fans with Baldor "Inverter Ready" motors, we had MULTPLE failures within weeks, despite doing all of the right things with regard to wiring and grounding, even load reactors. Turned out they had no special insulation, no shaft grounding, nothing special about them whatsoever. So "Inverter Ready" meant absolutely nothing other than having Class H insulation. To their credit though, Baldor replaced them in both projects, so over 100 motors in total, with ones that said they met "NEMA MG-1, Part 31", which spells out specific design criteria.

We have not had that issue around here. The only issue we have had is when they do not put an inverter rated motor in.