On Apr 12, 5:30*pm, "vaughn" wrote:
"David Nebenzahl" wrote in message

s.com...

Is the spindle motor in your DVD player AC? How about the spindle motor on
your hard drive?

No magic there! *Spindle motors simplyt substitute solid state switching for
mechanical commutation. *Actually, what is fed to the windings of a spindle
motor (though you may "nictpick" by calling it pulsating DC) actually more
resembles 3-phase AC. *In fact, the windings of a spindle motor are usually
connected in a wye or delta configuration, sound familiar?



You do agree that those are all examples of "rotating machinery", don't you?

I agree that spindle motors are examples of rotating machinery. *I don't agree
that proves any particular point for you.

Vaughn

Exactly so. Every single electric motor without exception runs on AC.
The correct term for the above is synchronous motors. Stepper motors
are a similar sort of thing for other applications.
http://en.wikipedia.org/wiki/Synchronous_motor#Uses
http://en.wikipedia.org/wiki/Stepper_motor

In days of yore "DC motors" were used where speed control was
neccessary.
The AC was created by the armature and brushes.
Changing frequencies was not cheaply possible by any other way.
Nowadays it is very easily possible and "DC motors" have virtually
disappeared.