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Re: Help with my rotary gap (and other tuning problems).....

Original poster: FutureT@xxxxxxx

In a message dated 7/17/05 2:33:12 PM Eastern Daylight Time, tesla@xxxxxxxxxx writes:



The variac is an Ohmite 3 amp 0-135v.....and the motor is an Oriental .03A
7.5w. I'm using a 47uF cap for adjustment.



I tried that type of motor with the phase shifter one time.  I assume you
meant to say 0.3A.   I found that 7uF was too large, and 2.5uF was
a little too small but it worked.  Probably about 4uF would be good.
But you should do a test to verify the proper resonant rise.
Some of those motors use a run cap.  Maybe you left it off?  By
using a little larger run cap you can get more power out of those motors
BTW.  I think I used 3uF instead of the 2uF that it came with.
47uF for the phase shift cap seems much too large to me.


I know someone who used the same (except a different variac) setup and it
worked well....



It's a mystery to me how it could have worked well.


The variac has numbers on it (1-5). Just by experimenting with it, it seems
they are "standard", with 3 being the tap, etc.



Yes, you want one connection to the beginning of the variac coil, and one to
the tap.  Only two connections are made to the variac.  I suppose terminal
# 1 and # 4 are the ends of the coil.  So one wire should be connected to
either terminal #1 or # 4 (but not both).  The other wire goes to # 3, the tap.


I had it hooked up in a variety of configurations on none worked, the fuses
blew each time. Eventually I could find one that works? I had the variac
setup as in variable inductor set in series with the "inlet" of the motor.



Well assuming you have the correct setup, try a 4uF cap or so.  Also
make sure the run cap is installed on the motor if it calls for one.

Cheers,
John