VFDs and rotary phase converter

Carlos and Fitch were discussing VFDs and rotary phase
converters.

VFDs have trouble using single phase because of two
factors: the size of the input diodes and the ripple
voltage. However, if they have implemented some sort
of phase checking for current draw, then you are out
of luck with either the rotary converter or direct
connect because you will get a phase fault.

If the VFD has power factor correction, the ripple
voltage may cause a problem.

Static phase converters cut out once they have started
the motor, rotary doesn't have to, but you still don't
get full rated power out of the motor.

I do think you should be able to drive the motor with
an undersized VFD, but it depends on their control
scheme and how much you overdrive the VFD. It
probably will have reduced life.
Eric


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