VFD on a generator

J. Hoffman

J. Hoffman

Knifemaker / Craftsman / Service Provider
Joined
Jan 1, 2011
Messages
1,774
I have a local shop wanting to run a 3 phase machine using a VFD, but their only power is from a generator. I know VFDs don't like GFCI circuits, does anyone know how they run on a generator?
 
It all depends on the generator. I have been at hammer-ins where a generator ran a grinder and VFD. I think most modern generators are more compatible.
The simple answer is to plug the VFD machine into a generator a=nd see if you get a fault.
 
I would guess it depends on how dirty the power is from the generator. If it’s a pure sign output it would probably be better. If you want to be really safe I would run the power into a power conditioner to get it cleaned up and the voltage stabilized for the VFD.
 
See if the generator has an AVR (automatic voltage regulator). And if the generator is only for that machine, sounds like the wire runs may be short, which means very little impedance to knock down spikes, etc, so may want to add a line reactor in front of the VFD, or an isolation transformer in front of the whole machine. But if the gen is running through a whole building worth of cabling before getting to the machine, may not be an issue.
 
Most VFDs should be pretty tolerant of dirty power. The AC voltage is getting rectified and turned into DC in the first stage of the VFD before the VFD processes it into the frequency it needs. This inherently cleans up the power. The biggest issue you might have is low voltage errors as the generator surges or idles down. Keep it out of eco mode and always have a small (few hundred watts) resistive load on it to help stabilize the generator if you have issues with voltage swings
 
Backyard has a good point.
Plug a large fan or spotlight (about 2 to 3 amps load) into the generator to be on all the time. This makes the generator always under load and it won't drop back when you change things on the VFD or create spikes.
 
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I have run small items in my shop during power outages with a high quality diesel generator, and also a cheep pos gas generator. The variable frequency drives worked without problem
 
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