phase converters for big iron

[jim stephens]

Paul Koning wrote:

> >>>>> "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.
>

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> 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.