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[TCML] Using hysteresis motors, and modifying induction motors for sync operation



The problem is that the phase controller only gives about 90 degrees of electrical phase
shift, and you may need more than that, depending on where the hysteresis motor
decides to phase up.  But in that case, if you try a few more starts, then surely by randomness,
you'll start up at a point where the phase controller can phase it in.  I *think* someone
said my phase controller design works with hysteresis motors, I may have tried it myself,
but I can't remember.   

To avoid those problems, it's easy to create a salient pole sync motor by
converting an induction motor for sync operation.  For a 1725 rpm motor
grind 4 flats, for a 3450 rpm motor grind two flats on the motor armature (properly called
a rotor).  For the 1725 rpm motor, the width of the flats should be about 1/4 the rotor
diameter, and for the 3450 rpm motor, the flats should be about 1/2 the rotor diameter.  
There's another method which can be used to determine the width of the flats, which
involves identifying and using the width of the dead poles of the motor's run windings,
within the motor stator.

The milling or grinding of the flats does not have to be super-accurate.  I just use
a large file, or hand grinder.  The procedure is much more critical for 3600 rpm
motors than for 1800 rpm motors because of the balance issue at higher rpm's.
It's best to use a mill for the procedure, and measure carefully of course, whatever
method you use.  I usually get a little vibration after my modifications, but it's so 
slight, it doesn't cause any problem.  

Avoid the use of shaded pole induction motors which are wimpy and often of poor quality
and design.  You can use centrifugal switch start, capacitor run, or capacitor start
induction motors.  If the electrode spark rotor is very heavy, then a capacitor start
motor will help the starting and synch-up by providing a greater starting torque.   

John


-----Original Message-----
From: Andrew Robinson <teslamad@xxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Tue, Nov 17, 2009 3:43 pm
Subject: Re: Re: [TCML] SRSG Update. Very cool pictures!


UGH... You learn something new everyday. Some times for a price. It is in fact that type of motor. Arg! Since the design is finalized and the motor portion is complete I guess I will press on until anywaz and test this until I find a better motor. I do have access to a mill. Several in fact. Dont know how accurate I can make it though. Dont know anything about converting an induction motor. For now I guess I'll design a phase controller. Think this will work? Guess I'll just have to adjust the motor via the controller each time I start it up. Sigh 
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