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RE: phase shifter helps lock wimpy motors



Original poster: "Basura, Brian by way of Terry Fritz <twftesla-at-uswest-dot-net>" <brian.basura-at-unistudios-dot-com>

John/all,

I'll test out John's suggestion to return the Variac to non-reso mode
before powering down and see if this eliminates the braking issue (although
it's just a noticeable effect and not a problem when the capacitor is the
correct size).

BTW - Here is the capacitor sizes I came up with utilizing a W10 Variac and
various motors.

1800rpm, 1/3hp	- 168ufd
1800rpm, 1/2hp - 180ufd
3600rpm, 1/2hp - 270ufd

When working up a capacitor for your configuration make sure to monitor the
voltage, minimize resonant rise, and be very cautious about using too much
capacitance (or the motor may brake VERY HARD upon power down).

Regards,
Brian B.

 -----Original Message-----
From: 	Tesla list [mailto:tesla-at-pupman-dot-com] 
Sent:	Tuesday, January 09, 2001 12:04 PM
To:	tesla-at-pupman-dot-com
Subject:	phase shifter helps lock wimpy motors

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<FutureT-at-aol-dot-com>

Hello coilers,


<snip>

Another thought comes to mind.  Brian spoke of the problem
with self-braking of a larger motor at power-down.  Simply 
setting the variac at a non-reso position before shutdown may
stop the self-braking?  (assuming the cap is not too large)
Again, here, it would be good to set the rough phase of the
motor, such that the coil normally runs with the sync motor
at a non-reso position on the variac.  This way the power can
be shut down without first resetting the variac to a non-reso
position.

<snip>

For those who have not seen it, the phase shifter circuit for easy
remote adjustment of the phase of sync rotary gaps is at:

        http://hometown.aol-dot-com/futuret/page3.html

John Freau