AC induction motor brake

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Hukshawn

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Something I don't know much about is motors. Having been a residential electrician for a number of years, it's just not something we dealt with. Anyways.

Can any induction motor with a centrifugal switch be wired to brake itself?
And if so, how?

My Bridgeport clone 2hp motor is eating the dust and I'm contemplating whether to fix it, or just replace it. If I replace it, I want it to have a brake. Cause I find myself using the brake on the mill every time I shut the machine off. It would be nice to not have to take that step each time. Especially for power tapping.
I understand the brake isn't instant, the centrifugal switch needs to collapse in order to brake. But with the mill's natural resistance in the belts/gears, it wouldn't take long.

Thoughts and opinions are desired. Especially if I'm way our in left field here.


(If I replace it, I have a friend with an actual Bridgeport with a 3 phase pancake motor. I would likely give him the motor to fix and use. Then he wouldn't have to use a poorly operating, cobbled together rotary phase converter. That would be my good deed for the month)
 
If you go the replace route get yourself a 3 phase motor and VFD. The VFD parameters can be programmed for quick deceleration. Perfect for power tapping.
 
While that would be my first choice, to even have variable speed, that option may be too expensive at this time. I have to sell a few items I don't use in order to obtain the motor.
 
I have a 2hp motor but it's 3450 rpm. Too fast for the mill which is 1750 or something.
 
it seems to me that the brake could be wired in using a normally open switch, either manually depressed for operation of the brake or you could get a lot more complicated and use a relay, and/or another switch (maybe a double throw) to disconnect motor power and apply brake power.
the possibilities are endless :grin:
 
I've been reading some articles and this is much more complicated than I realized at first... Darnnit.
 
Can you run a single phase motor from a VFD? I have that other 2hp motor, but it's 3450 rpm. Too fast for the mill. It's single phase.
 
Can any induction motor with a centrifugal switch be wired to brake itself?
And if so, how?

As far as I know, there is no way to just rewire the motor to brake itself. You will need to install an electric brake, which as Mike said, can be operated via a manually operated switch or a relay. I have worked on many electric motors with electric brakes and from my experience, the VFD would likely be less costly and offer many other benefits.

Ted
 
Ac motors without permanent magnets don't generate enough back emf to give an effective braking action- it could be done dynamically but it's difficult, you'd need a shaft encoder and electronics- too much hassle
Mark
 
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