Rotary Converter AND VFD?

JMackessy · Apr 22, 2002

Is there any advantage to using a rotary
phase converter and then a VFD running on it
to power a three phase motor? I currently run
the Bridgeport's 1HP motor on a 7.5 HP rotary
converter, I have a 5 HP VFD I want to use,
and it will run the motor with single phase power coming into the VFD. Will I get better
power using both? Will this help to equalize
the three legs? -JM

D. Thomas · Apr 22, 2002

My experience has been that a VFD will produce converted power that more closely resembles true 3 phase as far as motor torque/hp utilization, than any rotary converter will, so would seem a bit silly to run a VFD from a rotary converter. The exception is with CNC equipment, where the square wave of the VFD will fry RC networks/filters. But for simple manual machine applications like this one, the VFD is king.

amaranth · Apr 24, 2002

Generally, although it depends on the particular manufacturer, you need to derate a 3 phase VFD when running it on single phase, somewhere around 50%. So your 5 hp VFD can run a 2.5 hp 3 ph motor from single phase. If you were running it close to it's design limits, or there was something funny in the design that absolutely required 3 ph input, then you might want to hook it to a phase converter. In this case though, it's not necessary.

Paul

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Rotary Converter AND VFD?

JMackessy

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D. Thomas

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amaranth

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