RE: AC motor speed control question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Stephen Mathieson" <sm-at-uwmail-dot-com> 

You can buy a variable speed AC drive (I got mine on e-bay.)  Building one
would be pretty tricky.

Remember that if it is an AC motor then speed is determined by line
frequency and not voltage. Many "AC" motors are actually DC motors with an
internal rectifier. This type of motor you should be able to drive directly
with a variac for speed control.

Stephen A. Mathieson

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, October 17, 2004 6:10 PM
To: tesla-at-pupman-dot-com
Subject: AC motor speed control question

Original poster: "michael curtiss" <lucknau-at-yahoo-dot-com>

Hi all,

I accidently sent a blank email as my first post ever
to this group.  My apologies.

I'm building an SRSG, and want to make a speed
controller circuit for my AC motor.

What I've been reading is that there's a danger of
kickback spikes when trying to vary AC current with
something like a variac.  There're a lot of references
out there to a motor speed control circuit on John
Freau's site, but the link no longer exists.  I'm
wondering if anyone knows of a good way (and/or
schematic) to safely vary the speed of an AC motor.

thanks,
Michael Curtiss