switched reluctance motors

snipped-for-privacy@gmail.com wrote: > Hi, > > Anyone know where I can find small (100 W or so) switched reluctance motors for sale? (Yes, I used Google, and the best I could come up with was these guys, who 1. make motors too large for me at the moment, and 2. seem awfully reluctant to give specs or pricing).

can hunt for used ones to scavenge)? > > Thanks, > > Michael

Mine was a spare from some type of medical imaging device. I forgot what company made it, never found full specs. They're easy to identify at surplus stores as they have virtually no cogging when you spin the rotor and have more leads than an synchronous motor.

Eastern Air Devices still makes them, try ebay for used ones.

Thanks!

I did some more digging since I posted and it looks like the Maytag Neptune experimented with switched reluctance motors too.

Michael

Hey wait a minute. Are hard drive motors switched-reluctance ones, or basically brushless DC (with permanent magnets)?

Michael

snipped-for-privacy@gmail.com prodded the keyboard with:

Brushless DC with permanent magnets.

Oh ok. Thanks.

Michael

Out of curiosity, what are you planning on doing?

I can't help you with finding any, alas.

I was hoping to see how to drive one by exciting the various windings by using a microcontroller to provide pulses to transistors in sequence.

I was also hoping to take it apart to see how it is constructed: must everything be laminated, or would solid iron work, or what.

Long-term, perhaps make an r/c airplane out of a small one, or a fan.

It's really quite an interesting motor design. I like how it doesn't need rare earth magnets (imported from China, right?)

Thanks,

Michael

I'm pretty sure that if you looked the weight needed to generate a given amount of power at reasonable efficiency, a motor with rare-earth magnets would win hands-down.

IIRC, there are rare earth mines in the US that haven't operated since forever -- so there's a supply in the continental US if we ever go to war with China, and if either country is still standing after the first day.

There's supposed to be nodules of fairly high-grade rare-earth ore lying at the bottom of the Pacific ocean in international waters, just waiting for someone to dive down and pick them up. Unfortunately, the cost of "just" diving down and picking them up is far more than the cost of stuff from China.

But -- keep us posted.

Yep, I really want one to study it thoroughly, really. I hadn't realized these motors are so rare. It's even more surprising considering they were first developed in the '30s... the 1830s.

Yeah, they're supposed to be a little on the heavy side.

Are you referring to Molycorp's mine in California?

Oh well. This could save the ore for when it's really needed, someday in the future.

Thanks,

Michael

There won't be anything interesting in there. Stator will be like that of stepper motor, and the rotor will just have some poles, probably a number that doesn't match that of the stator.

It will be too weak and heavy for sure for a plane. They're made to be cheap, not strong, and I suspect the no-cogging effect when freewheeling is another factor they even produce them at all. The drag is virtually nothing when turning the shafts on them.

need rare earth magnets (imported from China, right?) > > Thanks, > > Michael

bankruptcy

That's the one I know about. Wikipedia says the stuff's all over. I think the issue is that you have to tear up a whole bunch of ground to get enough ore -- in the US we respect environmentalists, in China they shoot them, or make them work in the mines. So China has mines.