28 Apr
2005
28 Apr
'05
2:33 p.m.
Paul Koning wrote:
The problem will be that some devices work well if they have a large
amount of inductance in their power supplies, such as conventional
power supplies will have.
If they are switcher power supplies, they tend not to react very nicely
to having a solid state inverter feed them.
This is the why, and is only answerable on a case by case basis.
I didn't see a mention of the most obvious case, and that is not 3 phase,
but
that a lot of systems took in 208 three phase and did a rotating
conversion
to 400 hz.
>>>> "Simon" == Simon Fryer <fryers at gmail.com> writes:
Simon> All, On 4/27/05, Kevin Handy <kth at srv.net> wrote:
<chomp chomp>
Simon> The PWM works pretty well for induction motors. I would expect
Simon> big iron to have some issues.
Why? I would expect power supplies to be every bit as tolerand of
distorted waveforms as motors are, even assuming that these converters
produce major distortion.
Simon> Depending on how the three phases are used for the big iron,
Simon> it may be possible for all three phases to be wired the
Simon> same. That is electrically connect all three phases together,
Simon> to a single phase supply. This can only be done if each phase
Simon> is used independently of the others (separate
Simon> transformers/SMPS). If there is anything in the machine that
Simon> wants all three phases - find a nice clean sinusoidal source.
Motors will -- disk drives for example. The larger disk drives (DEC
RP04 class, for example) use three phase motors. They also are picky
about the phase order being right, otherwise they spin on the wrong
direction which is not a Good Thing.