I have run motors on smaller VFDs unloaded once or twice and it worked but I
don't remember how far out I was

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I got a good deal on a couple of little VFD's. They take 120 volt
single phase and put out 240 volt 3 phase and are not very big, but
they are only rated for 1/4 hp. And me without any 1/4 hp three phase
motors.

But at the scrap yard, I ran across a 1/2 hp three phase motor that
had a key taped in place on the shaft. May not have ever been used.
There were no wire nuts on the power leads and it did not look like
they had ever had a wire nut on them.

So can you run an unloaded motor off a VFD that is only rated at half
the motors hp? Well the answer is that you can not at least with the
VFD that I was trying. After a second or so, the vfd would stop and
show an error code. But wait, the motor can be connected for either
240 or 480 volts. Meaning it has two sets of windings. Connect is
parallel for 240 volts and in series for 480 volts.

Or you can connect just one set of windings, and voila a 1/4 hp
motor. Works with the VFD just fine.


Dan