[Milsurplus] multi phase AC power

[J. Forster]

I'm not a real expert, but did look into this a while back There are a few possibles:

Capacitor phase converter. These are fairly cheap and have a cap phase shifter and Scott connected transformer. As I remember it did not make good 3 phase, but it was OK for motors up to a few HP and likely OK for 3 phase power supplies where the input is transformer isolated and then rectified. As I remember, the lines are not symmetric about neutral, so an isolated load is a must. The efficiency is pretty good.

Rotary phase converters: These can either be belt driven or the Georator style. Big, HEAVY, and can be noisy. The phase relation of the output is stable and is symmetric about neutral. I have a roughly 1 KVA one as a 400 Hz, 3 phase supply. It keeps the floor down well !!  IMO, the belt driven ones are less desirable.

Solid State Static:  These are nice and can sometimes be gotten cheap. Unfortunately, the bigger ones take 3 phase input power, so you are back where you started. They don't have much stored energy, so may have trouble starting loads. OTOH, they are often dial-a-frequency, which is nice. Caution is required though. I once applied 40 Hz to a 400 Hz transformer. It cooked pretty quickly. Again, big and heavy in larger sizes, but often cheap due to lack of demand.

The best choice really depends on your needs.

-John



gl4d21a at juno.com wrote:

> Group:
>
> All this discussion of single phase, 3 phase, Y, delta, etc., put me in mind of a piece of information I found on one of the constant voltage transformer manufacturer's web site.  The statement was that the output of a CVT is shifted around 120° with respect to the input.  This caught my attention, as it seems I often would like to generate some 3 phase power from a single phase source.  So, now if I can find some device which will produce a few hundred watts at -120°, I'll have something.  I thought of using the input phase and this +120° as two legs of an open Y, but I suspect that would be pretty inefficient.  I suppose I could connect a second CVT to the output of the first and generate 240°, and I may try that sometime when I have my collection of Solas out at one time.  Any power experts out there who have gone through all this?
>
> 73,
> George
> W5VPQ