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Re: Teletype motor (fwd)
Original poster: List moderator <mod1@xxxxxxxxxx>
---------- Forwarded message ----------
Date: Mon, 14 May 2007 23:14:04 EDT
Subject: Re: Teletype motor (fwd)
In a message dated 5/14/2007 7:49:22 P.M. Pacific Daylight Time,
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
good digital stroboscope with no "drift". It takes the entire adjustment
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
prop gap, it always starts at the same phase angle, no matter which
it starts near.
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.
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