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

[theforge@mailman.qth.net]

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