Re: Teletype motor (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: List moderator <mod1@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Mon, 14 May 2007 23:14:04 EDT
From: FutureT@xxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: Teletype motor (fwd)

 
In a message dated 5/14/2007 7:49:22 P.M. Pacific Daylight Time,  
tesla@xxxxxxxxxx writes:

Using an  unmodified Staco Type 291 (3A, .4 kVA), my  little Oriental 
motor  gets a full 45 mechanical degrees of adjustment. I  verified this with 
a  
good digital stroboscope with no "drift". It takes the  entire  adjustment 
range 
of the variac to do so.
It was very  picky about the value of the additional  cap.
I did  discover, with the good stroboscope, that the  Oriental is in fact 
a  hysteresis type. When it restarts, it is in a different  shaft position.  
However, using it as a standard 1800 rpm/120 bps/4 stationary   electrode 
Blake 
prop gap, it always starts at the same phase angle, no  matter  which 
electrode 
it starts near.

-Phil  LaBudde



Phil,
 
Are you sure then that it is a hysteresis motor?  It sounds to  me
like it is *not* a hysteresis motor.  A true hysteresis  motor will lock
into random phases, not phases that are 90 degrees separated.
An 1800rpm motor that locks at only 90 degree positions is a  typical salient
pole or reaction type sync motor.  
 
I realize that folks often say that a salient pole or reaction motor
always locks up in the same phase position.  This however is not
true.  What is meant is that the motor always locks into a  correct
phase position.  For an 1800 rpm motor, there are 4 correct  phase
positions, and for a 3600 rpm motor there are 2 correct phase  positions.
By *correct*, I mean correct for use in synchronous spark gaps
for Tesla coil use.  
 
It sounds like you did a good job selecting your cap value for the
phase shifter circuit.  
 
John



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