VAXen at home
wdonzelli at gmail.com
Fri Oct 19 14:08:04 CDT 2007
> My experience with these things (admittedly only with machine tools)
> shows a strong tendency for less-than-perfect (i.e. 120 degree) phase-
> to-phase relationships and fairly drastic phase-to-phase voltage and
> current variations. They work with motors, but none allows for full
> motor nameplate loading (usually around 80 percent of nameplate). My
> take is that they work "sort of". Heaven only knows how a power
> supply would behave attached to one of these things.
I doubt it would be SO bad that the power supply would not work
properly. Most have constant voltage transformers to take care of
problems like this anyway, and if one of the phases is really out of
whack in the voltage department, it can be bucked or boosted with an
A small phase shift in one of the phases really will not do much. Any
fans or pumps will basically not care (and help correct the error as
well). In a full three phase rectifier, the ripple just will not go
out of control if a phase if off even by 30 degrees. And if it is, put
another big cap or two in the circuit.
All this assumes that the three phase converter is not some little
wimpy motor, but something with a lot of balls. The bigger the
converter, the smaller the problems, but the larger the electric bill.
> My feeling is that if you have to power some three-phase big iron
> from a single-phase source, it's probably better to take a look at
> one of the modern (and expensive) solid-state converters--or get some
> real three-phase distribution installed.
If the iron gets too big, it will suck up too much power for
reasonable use in a house anyway. The proper thing to do is buy or
rent some industrial space with real power.
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