Variable Speed Control Hacks ?

You're right. There is only a start capacitor on that particular grinder. Whether a single phase motor has only a start cap, or both a start and run cap has nothing to do with "how they do things in Taiwan" as run capacitor motors generate more torque than induction only motors. I assumed grizzly used such a motor for their grinder. Doesn't change what you said about the start circuit.
 
I just did some research of run caps, and realize i misunderstood running caps. I was told once it was to restart a stall motor, but now i see they actually cause a phase shift which helps a motor under load. I need to read more.
 
ERRN said:
I got a grizzly and burned it out straight away doing this before I was more informed. Expensive lesson...
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Out of curiosity do you know what you burned up? The windings? Capacitor? Something else?
 
No I’m not sure. I don’t know enough about them still to know what I burned out. I plugged it in to a router controller that I use in guitar building to control heat level on a silicone heat blanket for bending sides. I ran it pretty slow and I suspect that was what did it.
I could always pull it apart and look if someone could tell me what to look for if it would be beneficial for informational purposes.
 
kuraki said:
Because the torque loss in a single phase induction motor is so severe. You can vary the speed. That part works. But when you do it becomes next to unusable. That loss in torque is the symptomatic of the oscillating magnetic field and the loss of inertia in the stator when it's speed is reduced. A 3ph motor has a revolving magnetic field and therefore can produce full torque from zero rpm.

Torque loss in the face of work results in higher power draw. Using a variac to vary voltage means increasing current draw at lower voltage. This is what will heat the motor and "burn out" the windings.

They work on universal motors with brushes and comutators because of how they're wound and in effect the commutator creating a large number of poles that don't exist in an induction motor.

If it worked we would all do it. I've even gone so far as attempting to run a 1ph motor off a VFD. Same problem.

Why don't you think a Grizzly single phase grinder has starting caps? It has both start and run caps.
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Sorry just now seen, it. Using the reply function helps with such things you know ;)
Well now that you say it it certainly has a relatively high loss in torque, thanks, forgot about that.
EDIT: forgot about the caps: I didn't think it would have starting caps because you wait until a grinder is up to speed until you start grinding so you don't need that much torque on startup. At least that's what I was thinking
 
Stacy E. Apelt - Bladesmith said:
SV-97,
You are going to have to trust us engineer types and take our word for it. I would think if you hade electrical engineering technician training you would have understood the hints I gave. Kuraki and Drew elaborated more on those topics.

Short answer - No, it won't work.
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Well your response wasn't exactly helpful but rather seemed like "I'll just throw out fancy words to sound smart". Kurakis answer was helpful.
 
OK, I'll delete my fancy words and let it go. All I was trying to do was tell you it won't work. - Goodbye.
 
SV-97 said:
Well your response wasn't exactly helpful
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Perfect way to derail a thread. Almost troll like. Ie: self proclaimed expert, arguemenetive(sp) with people that have real world experience.
 
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