Re: 3 phase power converters
Gene writes:
> Three phase, at most any frequency can be had a lot cheaper at up to
> 10 horse or so by using a suitably sized VFD.
Yes. Don't buy a static or rotary converter for a single machine. They
only make sense these days if you can build them at no cost with stuff
you have laying around.
Put an external fan on your motor. If you are going to operate at those
frequencies a thermistor in the windings would also be a good idea. The
motor is very inefficient down there so you want to keep an eye on the
temperature even with forced cooling. The thermistor can also control
the fan.
You can get more torque at high frequencies if you up the voltage, but
most VFDs can't do that. Besides, you'd be pushing the voltage rating
on the insulation.
One reason to consider a motor-generator set (or utility supplied three
phase) for a shop full of VFD-equipped three-phase machines is that VFDs
operating from single phase are limited by the need for large filter
capacitors.
--
John Hasler
jhasler@newsguy.com
Elmwood, WI USA
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