[TheForge] Fwd: Shop tools & layount (3-phase converter)

Wed Jan 21 00:52:00 2004

If you don't have the capacitor on the idler motor, you can spin it either
direction to start and that will reverse the motor on the machine.
Darrell

http://www.machinemaster.com
----- Original Message ----- 
From: <[email protected]>
To: <[email protected]>
Sent: Tuesday, January 20, 2004 6:49 PM
Subject: Re: [TheForge] Fwd: Shop tools & layount (3-phase converter)

> Thanks for the links, I had pulled those down at the time, but haven't
> looked at it since.    I am going to have to spend some time thinking
> about this to reconcile it as well as take some readings myself.    When
> I scoped mine years ago, I didn't get anything like his display,
> although my old EICO scope was pretty feeble already at that point.
> Regarding efficiency, if the single phase input were only driving one
> winding, then in fact the phase converter is generating two phases,
> which would  mean all of the energy required by your load is coming
> through one winding.  So if you are running a five horse motor as a
> load,  your pulling 18 amps through the idler winding.    Looking at his
> schematic though, I just figured this one out and it is quite bright.
> The single phase is supplying two of the windings, but his capacitor
> between the input legs to the idler is effectively a static phase
> converter and is creating a second phases for the idler, which is then
> generating yet another phase.   Creative.   He is then balancing the
> phases with the other two capacitors.  You get a perfect waveform when
> the load is perfectly balanced with the capacitance.  This is not the
> same as just hooking up a a three phase motor and spinning it up as an
> idler.  But now I am curious about something else that I will have to
> look at -- that is reversing a three phase motor only require swapping
> any two legs.  If there is only two phases without the capacitor, then
> swapping them won't reverse it.  That is pretty easy to check this
> weekend in the shop.    Regarding efficiency,  most phase converter
> manufacturers recommend 80-90% max nameplate HP continuous on a rotary
> and 75% for a static for your load motor.
>
> Charles
>
> Steve Smith wrote:
>
> > A lot of good stuff that is going to result in me doing a lot more
> > reading and embarking on yet another research project in the garage
> > that I don't have time for
>
>
>
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