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Re: [TCML] Variable RSG



John and all,
I have used the phase shifter circuit successfully with a hysteresis type motor. As mentioned, with a hysteresis motor, the synch point can move on each start. You can switch it on and off several times until the phase is correct. Not the most convenient but otherwise you need a salient pole or a modified induction motor.
Jim Zimmerschied
  ----- Original Message ----- 
  From: FutureT@xxxxxxx<mailto:FutureT@xxxxxxx> 
  To: tesla@xxxxxxxxxx<mailto:tesla@xxxxxxxxxx> 
  Sent: Wednesday, April 09, 2008 5:13 PM
  Subject: Re: [TCML] Variable RSG



  In a message dated 4/9/2008 6:51:35 P.M. US Eastern Standard Time,  
  quarkster@xxxxxxx<mailto:quarkster@xxxxxxx> writes:

  >Let's also make sure that everyone is talking about the same type  of motor. 
  When we're talking about a >motor for use with a Synchronous  Rotary Spark 
  Gap, and "synchronizing" the rotor angular position >with the  sine wave of the 
  AC power supply, we are usually talking about a "salient  pole" type motor, 
  >either factory-made (like used in a Teletype machine) or  a modified (flats 
  machined on rotor) >synchronous induction  motor.

  >  Miles' original post dealt with  adjusting the phase of a "syncronous" 
  motor, and there was no mention >of  salient-pole modification.

  >  I've experimented  with John Freau's phase adjust circuit using 
  salient-pole motors, and it works  as >advertised.

  >  However, I've never tried it  on an un-modified synchronous motor 
  (conventional squirrel-cage induction  >motor). Does it work on an regular 
  squirrel-cage motor?

  >  Regards,
  >  Scott Hanson


  Scott, all,
   
  A conventional squirrel-cage induction motor is not a synchronous  motor.  
  Such a motor
  will always slip and run slower than the synch speed.  Such a  motor only 
  becomes
  synchronous when it's modified by grinding the flats.  Commercial  synch 
  motors of
  the salient pole types are sometimes called reaction synch  motors.  Still 
  another
  type of synch motor is the hysteresis synch motor.  This type will  lock into 
  a
  different phase position each time it's turned on.  It didn't seem  clear to 
  me which type
  of 2HP motor the poster was using.  I got the impression it may  have been a 
  hysteresis
  type since he said it locked into various phase positions.  But if  he has a 
  regular
  induction motor, then he'd need to grind flats onto it before it could  
  possibly run
  in synch fashion.  My phase shift circuit cannot work with a  un-modified 
  regular induction motor.  It has to be modified first by  grinding flats.  
  The key
  will be what is written onto the name-plate of the motor.  If it  says 1725, 
  or
  3450 rpm, then it's an induction motor, not a synch motor.  A  synch motor 
  will say 1800 rpm, or 3600 rpm (1500 rpm or 3000 rpm in countries 
  using 50Hz AC power).   
   
  I've never tried my phase shift circuit on a hysteresis type motor.   I think 
  I
  remember that someone said they tried it and it worked, but I'm not  sure.  
  In any case since my circuit can only give 90 degrees of electrical phase  
  shift, 
  a few starts of a hysteresis motor may be needed before it can be 
  brought successfully into phase using the circuit (assuming the  circuit
  works at all with a hysteresis motor).
   
  Cheers,
  John









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