Chris Loiacono <chris@MAIL2ASI.COM> wrote:
> Has anyone looked at microchip's an 843 lately?
> It's a nice example of a variable voltage-variable frequency drive for
> three-phase induction motors.
>
> It is shown with a three-phase source that is rectified and filtered.
> I began thinking (scary, eh?!) that this could be fed by a 2 wire single
> phase line also...and rectified with even less parts...
>
> couldn't it?
>
> Assuming line current is not an issue, this would result in a 3-phase
> induction motor controller that could be run from a single phase line.
> I don't believe I've ever seen such a product...
> It seems there would be nice demand for such a thing since many places do
> not have 3-phase power available....Hmmmm
>
> Am I on to something here, or am I overlooking the obvious - or not so
> obvious?

Your single-phase AC to DC converter needs to be able to store enough
energy (BIG capacitors) to supply significant load currents at times when
the single-phase line is at or near zero.

Since 3-phase power is typically used for motors > 1 HP and other
electrical loads > 1 KW, line current is *most definitely* an issue!

I was just recently thinking about this issue when the capacitor went bad
in my 1.5 HP capacitor-start pool pump, and I was wondering if I could
replace it with a solid-state circuit to shift the phase for the starting
winding. I realized that no matter what, some sort of energy storage device
would be needed, so I just replaced the capacitor.

-- Dave Tweed

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