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

[William Noble <william_b_noble@xxxxxxx>]

if anyone is near Los angeles and wants it, I have available a 2 HP 3 phase motor, 220/440V, 1735 RPM - weighs about 100 pounds, scrap value is around $10 to $15 based on its weight - $20 and it's yours.  with three phase, you can control the motor accurately with a VFD (for speed) including synchronizing it to 60 hz, so maybe this will help.  It has a 1" diameter shaft, so it is heavy and rigid enough to take a lot of abuse.  It is at risk of going to the scrap dealer, so if you have interest, drop me a note.
 
> To: tesla@xxxxxxxxxx
> Date: Tue, 17 Nov 2009 16:22:00 -0500
> From: futuret@xxxxxxx
> Subject: [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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