Phase controller question.

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Original poster: "Christoph Bohr" <cb-at-luebke-lands.de> 

Hello all.

Two small questions about phase controllers:


1st:
Will it effect the operation of the classic phase controller circuit, when 
I use a stepdown (auto)transformer after the phase controller
to attach a motor that runs at lower voltage?
I know what you want to say: Put your transformer before your controller, 
but in this specific case it would be much easier for me to put the
stepdown xformer after the controller.
To be honest. I already tried and it sorta worked, but the angle about 
which I can vary the phase seems very, very small and I
am simply not sure if I migh be messing things up.However, I get a 8V 
resonant rise in the middle of the variacs range.
Motor is a 220V 370W 3000rpm motor the runs at 90V 0.5A after modification 
( Do'h ), so I need the 90V supply voltage.

2nd:
Can someone give me a good initial value for the cap size in the above 
szenario? I only own a 10µF and two 7µF caps that should be suitable.
Controller operation voltage would be either 90 or 230V, my variac is a 
230/250V 10A unit, motor specs are given above.

Best regards

Christoph Bohr