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Alternator To Motor - Page 2

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Posted by JIMMIE on May 10, 2009, 9:40 pm

Alternators can be used as stepper motors. I think there was an
article in"Nuts & Volts" several years back. I think it was a Don
Lancaster article.
He may have something on his website.


Posted by Martin Riddle on May 10, 2009, 8:45 pm

He wants  to convert a alternator to a motor. To replace the pancake
motors used on scooters.

Which IMO is not a good idea, they're not designed for that.  Buy a good
dc motor.


Posted by Jim Rojas on May 10, 2009, 9:12 pm
Plus the fact that I can get 3000+ RPM from an alternator without too
much excessive heat or wear. A scooter motor won't last very long that
those speeds. I also looked into stepper motors, and treadmill motors.
But I am looking for something I wont have a hard time getting
replacement parts for. Alternators are in abundance, usually $0-20 at
any salvage yard.

Jim Rojas

Posted by Tim Jackson on May 11, 2009, 7:30 am
 Jim Rojas wrote:

I guess you could drive one with a 3-phase inverter, but it wouldn't be
very efficient and you wouldn't get much torque; plenty of rpm though,
they're rated at least 10,000.  You'd need a lot of Hz to get there.
Battery powered high-speed motor inverters aren't lying around, the only
ones I've seen are heavies, for fork lift trucks or trams.  There are
such things as brushless servo motors which use basically the same idea,
they are industry standard for motion control these days, and tend to
replace pancake motors.  But they aren't cheap, I think a motor +
inverter set typically comes in about $000 or something like that,
depending on size.

Tim Jackson

Posted by Don Kelly on May 12, 2009, 5:09 am

In Theory and with some considerable extra costs- you could do it. If you
apply DC to the terminals of an automotive alternator, you will get nothing.
You would have to  strip the diodes out and provide an appropriate 3 phase
drive- at this stage you have something that is far more expensive and
complex than the alternatives.
 As Tim has indicated- you can get something that works- at a greater cost
and effort than the alternatives.  The speed of an alternator is frequency
dependent - do you have a variable frequency polyphase source?
Alternatively- go with the pancake motor that is designed to do the job
efficiently and properly rather than try to adapt something designed to do
another job efficiently  and appropriately. If you picked up an old
generator(DC) as used prior to the adoption of alternators for automotive
applications, the conversion would be much simpler.

So- what do you want to accomplish? That is the primary consideration- then
consider the alternative approaches to this.

Don Kelly
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