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- Feb 13, 2017
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This is a duplicate post from an answer to a beginner's question. Any serious thoughts will be greatly appreciated.
This will be a "theoretical" or hypothetical thought. It just struck me, not very hard, but I have zero experience in the matter. Just the theoretical knowledge of a retired engineer........ Now, it seems that every one is all wound up with converting to 3 phase motors and using the electronicly synthesized variable frequency from the VFDs.
It would seem to me that while single phase motors aren't quite as stable rotationally as a three phase, they do get their speed regulation from frequency, same as a 3 phase motor. By that thought, what would be the problem of acquiring a 3 phase VFD and running a single phase motor from it until such time as the motor conversion could take place? It should run well enough from 30 to 90 hertz, in either case. With a 4 pole motor, synchrounous speed of 1800 (less slip) at 60 hz, the yield would be from 900 to 2700 rpm. I doubt many people would need to excede either speed. Just change the pulley there.
There would be some limitations, I'm sure. A three phase motor would have a usable output somewhat slower than a single phase. And I assume it would be necessary to disable the phase loss for one leg. But what I see in my mind, a single phase motor should be able to run on a three phase device. Making the voltage match-up, of course. A good many of my machines will work on 120 or 240 volt. Depending on hook-up, of course. 3 phase motors will run on 240 or 480. So, 240 is the common link. For short runs, wire size shouldn't be that expensive.
It was just a thought that came up as I was thinking about the author's question.
This will be a "theoretical" or hypothetical thought. It just struck me, not very hard, but I have zero experience in the matter. Just the theoretical knowledge of a retired engineer........ Now, it seems that every one is all wound up with converting to 3 phase motors and using the electronicly synthesized variable frequency from the VFDs.
It would seem to me that while single phase motors aren't quite as stable rotationally as a three phase, they do get their speed regulation from frequency, same as a 3 phase motor. By that thought, what would be the problem of acquiring a 3 phase VFD and running a single phase motor from it until such time as the motor conversion could take place? It should run well enough from 30 to 90 hertz, in either case. With a 4 pole motor, synchrounous speed of 1800 (less slip) at 60 hz, the yield would be from 900 to 2700 rpm. I doubt many people would need to excede either speed. Just change the pulley there.
There would be some limitations, I'm sure. A three phase motor would have a usable output somewhat slower than a single phase. And I assume it would be necessary to disable the phase loss for one leg. But what I see in my mind, a single phase motor should be able to run on a three phase device. Making the voltage match-up, of course. A good many of my machines will work on 120 or 240 volt. Depending on hook-up, of course. 3 phase motors will run on 240 or 480. So, 240 is the common link. For short runs, wire size shouldn't be that expensive.
It was just a thought that came up as I was thinking about the author's question.
Bill Hudson