[TheForge] Electric motor speed control

[Paul Sperbeck]

Hi Dave
This is one instance where having a three phase motor is a big plus. See the
following link to dealers electric...
http://www.dealerselectric.com/inventory.htm
Scroll down to the end of the page or so and they list a number of
fractional h/p variable frequency drives.
If you are looking to control a fan or blower motor, the simplest solution
is to find a universal type motor( one with brushes) and use a dc speed
controller or a fan speed controller( one that is rated for inductive
loads). I have ignored my own advice and used a heavy duty light dimmer from
Menards in conjunction with a old champion blower, and it works quite well.
The dimmer is the push on push off style, and the blower will run under 20
rpm or so. It will not start at that low a speed though. You must set the
speed higher and then back it down. Most likely would not happen with a
fancier muter speed controller similar to
http://www.grainger.com/Grainger/productdetail.jsp?xi=xi&ItemId=1611576601&c
citem= this kind of controller is designed for 90 v dc motors, but a 110 v
universal motor will run on this type of control at about 85% of max rpm. I
have run across 90v motors as surplus, and if you have a robotics repair
company around you, you might be able to pick up 90 servo motors with bad
encoders... sometimes they just toss the motors and replace the whole unit.
Here are some more motors... http://www.kansaswindpower.net/motors.htm



Paul C. Sperbeck

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-----Original Message-----
From: theforge-bounces at mailman.qth.net
[mailto:theforge-bounces at mailman.qth.net]On Behalf Of Dave Brown
Sent: Thursday, September 09, 2004 12:17 PM
To: TheForge
Subject: [TheForge] Electric motor speed control


Hey kids .... what's the deal on electric motors and varying the speed?  If
I understand it, you can do it with some AC motors, but not with all AC
motors?  What kind can you do it with and how do you do it.  Light dimmers
don't work?  But the Ceiling fan speed controls will?

Take for example my Westinghouse, 1/4hp, 120v, 2-pole (L1 and L2, no L3),
reversible motor.  How can I vary the speed of this beast?  <grin>

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