Creating a PM Induction Generator from Induction Motor

[AaronWeber]

Hello this is my first post, please let me know if I'm breaking any rules, I'm still a bit hazy on them.

I am in the process of making a permanent magnet induction generator from and old washing machine induction motor. The motor is rated 1725 rmp, 115 volts 6.3 amps at 1/3 horsepower. It is a single phase motor. I intend to use it for a wind turbine so running the rotor 5% above rated rpm's is not an option. Instead I would like to drill out the rotor and put in cylindrical Neodymium magnets 3/8" diameter by 1" length. If i want to run the engine at low RPM (say 0 to 600 for a turbine) how many magnets would I need to use to achieve an output of 500 watts or more, if that is possible.

Thanks all.

 

[anorlunda]

ping @jim hardy

 

[jim hardy]

Well what an an interesting project. I've thought about it for years but never acted on the thought.

Having never done this i can only suggest you'll need as many as you can fit into the rotor.

Washing machine motors are usually multispeed so you'll want to give your rotor the same number of poles as on the winding you select. I'd use the lowest speed winding (the one with the most poles)

We had an old thread on re-purposing washing machine motors here
https://www.physicsforums.com/threa...g-machine-motor-to-power-a-grain-mill.833300/
that'll help you identify the windings

I found a paper on PM machines
https://pdfs.semanticscholar.org/75ba/b56b1709df4c72bf8a52dbae35dd2715c18a.pdf
and here's an image from it of a four pole rotor (page 42 of the 115 page PDF)
annotated with my thoughts about the biggest problem i foresee

you'll need to provide a wide annulus around your cylindrical magnets, at least twice the air gap of the motor,
so that flux doesn't find a shortcut through iron back to the other end of your magnets.

Honestly i'd look into modifying an automobile alternator.
There are plenty of Youtubes on making GM alternators into PM machines,
but look around junkyards - the larger the diameter the better low speed performance you'll get. Old Chryslers from early 60's were quite wide as best i remember.

old jim

 

[anorlunda]

I moved this thread from the spring cleaning workshop to EE forum so that everyone can see @jim hardy 's great reply.

Thanks Jim.