Re: SRSG remote phase controller

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "steve" <steve_vance-at-cablelynx-dot-com> 

John,

Thanks for the info. I get it now.  The old swap and see system.
I know it well ;^)

Steve
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, January 25, 2004 3:16 PM
Subject: Re: SRSG remote phase controller


 > Original poster: FutureT-at-aol-dot-com
 >
 > In a message dated 1/25/04 2:15:56 PM Eastern Standard Time,
 > tesla-at-pupman-dot-com writes:
 >
 > >to determine the capacitor size. Could someone help me out? Also, I have
 > >a 3.5 amp variac laying around. Is there some reason this wouldn't work?
 > >the motor only draws 1.5A.
 > >
 > >Thanks
 > >Steve Vance
 > >
 >
 >
 > Steve,
 >
 > Your variac will work fine for the phase shifter.
 > To select the cap size,  try a certain value for example 25uF
 > and see how it works.  Measure the voltage across the motor
 > terminals when the circuit is all built and working and see
 > if the motor voltage goes 5 volts higher than the line input
 > voltage at any position of the variac.  In other words sweep
 > the variac knob slowly through its range and see if the voltage
 > across the motor ever goes 5 volts higher than the line voltage.
 > For example if line voltage is 120 volts,  you're looking for
 > a max of 125 volts across the motor at the point when the
 > variac gives the max voltage across the motor.  This max
 > voltage could occur at anyplace on variac dial, perhaps
 > 1/3rd of the way to the end or whatever.  You're looking for
 > a slight resonant rise.  This helps the phase shifter to keep
 > the motor locked for the full ranged of the variac knob.  I mean
 > locked in sync at the sync rpm.  If you get more than a 5 volt rise
 > across the motor, then use a smaller capacitor.  If you get
 > less than a 5 volt rise over line voltage across the motor, then
 > use a larger capacitor.  It's a trial and error thing to find the
 > correct cap value.   Also the
 > rise does not need to be exactly 5 volts over the line.  It can
 > be a rise of perhaps 3 volts to 7 volts.  Some systems even
 > work with no resonant rise at all.   With no rise, the motor
 > may drop out of sync before the end of the variac's range.
 > You have to try it and see what happens.  Every motor and
 > combo is different.  You have to go though the trials to see.
 > If the motor loses lock near the end of the variac, some folks
 > simply limit the knob range so they don't lose lock.  Let
 > me know if my explanation is still not clear.
 >
 > John
 >
 >
 >