Understand that I have no actual experience with rotary phase converters...
...but what I've read about them suggests an RPC motor 1.5X to 2X the size of the motor you're going to run. If that guideline holds true in your case, you should be okay. It may depend on how much of a starting load is on the machine's motor.
Try it and see what happens!
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Law of Logical Argument - Anything is possible if you don't know what you are talking about.
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