Someone asked the other day about a phase converter to power their 3-phase lathe or mill motor from 120 volts or 240 volts single phase.
I think a VFD is a better alternative than a rotary or static phase converter, and I think a much cheaper alternative too.
And the VFD would act as a phase converter, as well as a speed controller, but you would have to be careful to maintain enough ventilation for the motor when it is slowed down.
I looked at the Mitsubishi cut sheet, and I don't see a range for input voltages, but it may be better to use a 240 volt single phase input into a VFD, instead of 120 volts, if possible.
For smaller motors, a 120 volt input would be ok.
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I would offer a suggested modification: a VFD
may be better ... will
often be cheaper ... but circumstances can vary.
One reason a VFD is often considered better is because it allows variable speed; another is that it is quieter. When might a rotary be better? When more than just the primary motor needs the 3-phase input, especially when one wants to preserve the original control structure and/or the machine has its own system for variable speed. Another situation is when more than one machine at a time needs 3-phase - one rotary converter can serve multiple machines (depending on size and configuration), but generally speaking a VFD can only serve one machine. Finally, a rotary phase converter is likely to be much simpler to operate; to really take advantage of all that a VFD can do, it will require programming or setup.
In terms of cost, VFDs have dropped to incredibly low levels, at least for import units - here's the first thing that popped up in a search on Amazon, a 3-hp unit for well under $100:
https://www.amazon.com/FAHKNS-Variable-Frequency-Inverter-Converter/dp/B0BZP6JGLD/ (no affiliation or experience with this unit or company). I seriously doubt that one will find even a used rotary converter for that price, and definitely not a new one.
But ... a rotary phase converter can still be cheaper, if one has access to the component parts as scrap. In my case, I picked up a 3-hp 3-phase motor for free from the scrap metal bin at work (with permission); the end bell was cracked through, but I was able to tig braze it back together with no problems. I also picked up various contacters (relays), capacitors, and control transformers (to produce 24v AC) for free from a friend with an HVAC business - he was happy for me to take all I wanted from his "bone pile." With these components in hand, plus some scrap wood out of my stash to make a convenient box to hold it all, the only things I had to buy were the twist-lock 3-phase outlet and a pair of large push-button momentary switches (one red, one green). Total cost was around $20, giving me a 3-hp rotary phase converter that has worked perfectly for many years to power my 2-hp Bridgeport variable-speed mill. Recently I picked up an old Powermatic tablesaw with a near-new Baldor 5-hp 3-phase motor and magnetic start switch. I wondered if I could start that using my 3-hp RPC, even though in theory that is too small ... somewhat to my surprise, it starts right up and runs perfectly.
