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240V 1PH to 380V 3PH questions


Feb 2, 2022
I apologize if this is covered somewhere else, but I haven't found anything similar to my situation so far in the past postings here. I've been reading the forum for a long time, so I know asking questions without doing your research is definitely poor form. This isn't strictly a machine tool question, but it has enough similarities that youse guys are going to have the right answer. I don't have all the exact details of the machinery at my fingertips, but can fill them in once I get back to the shop in the morning. But the gist of it is this:

I have a fuel injector test bench that I will need to get powered up. Machine needs 380V 3 phase input. The bench is equipped with a 15hp motor to drive the high pressure pumps, and has a 2000w immersion heater to heat the fluid tanks. Currently (ha!) it is being fed from a 240V 3 phase service through a transformer to boost the voltage to 380V.

The heater circuit is dumb - wired into the bench's internal fuse panel and is regulated by it's own built-in thermostat. The motor control is more sophisticated - the motor is driven with an ABB VFD, controlled by the bench's internal computer system. So, 380V 3PH into the ABB unit, 380V 3PH out to the motor. I can say that the motor is being commanded for a relative soft and slow ramp-ups to target RPM - it's easier on the equipment to sneak up to 25,000 psi I suppose.

Now, the problem. My lease is up in a couple months, and for a host of reasons I'm inclined to move to greener pastures. My biggest problem is finding a small affordable space in the area that has 3 phase service. I'm leaning towards getting a rotary phase converter and installing it between the electrical service and the transformer (changing out the VFD in the test bench is a non-starter).

My question, after all that, is this: Is putting a 240V 1PH to 240V 3PH RPC upstream of a boost transformer an acceptable solution? It isn't a high utilization piece of equipment, so I can accept some lack of efficiency.

Does anyone make a "Magic Box" that inputs 240V 1PH and spits out 380V 3PH in the 15KW range, that would let me ditch the transformer?


Hot Rolled
Dec 24, 2019
If you can supply smooth-ish 550-750V DC to the DC link terminals, the VFD will be happy. A sufficient capacitor bank, rectifier, and voltage doubler (Delon circuit) will work for this.

There was a manufacturer or two that made boxes for this purpose, but I can no longer find them.

Ideally you would probably add a bit of series inductance to improve the current waveform a bit.