Replies

1. 
   dgreen | May 14, 2006 03:52am | #1

   Here's a place to start.

   http://www.controlres.com/ac.htm

1. 
   Mike&L | May 14, 2006 07:14am | #2

   Thanks,

   This is a great start, but these excellent controls are for shaded pole and split capacitor motors - typical of fan motors.  What I need is an industrial control for a standard induction motor.

   Thanks for the effort, however.

   Mike

1. 
   dgreen | May 14, 2006 07:28am | #4

   Sorry about the false lead, I was thinking the Nimbus worked with induction motors but after looking at the specs. I see I was mistaken...

2. 
   user-152474 | May 14, 2006 07:22am | #3

   Would a variac,(variable transformer) work?

1. 
   Mike&L | May 14, 2006 07:35am | #5

   A variac in concert with a rectifier circuit would work great to control a DC motor, but wouldn't work in this instance - with falling voltage, an induction motor tries to compensate to maintain it's speed by drawing more current - it soon overheats and burns out.

   I've done some more internet searching since my initial question, and conclude that, while what I want to do is theoretcally possible, it is not practical given the lack of availability of appropriate off-the-shelf controls. 

   Mike

1. 
   dgreen | May 14, 2006 07:38am | #6

   The way a lot of manufacturers do it is with a three phase motor and a variable speed electronic controller. No help to you though.

3. 
   JohnWW | May 14, 2006 10:03pm | #7

   Mike,

   It isn't possible to use a control to slow down a single phase induction motor, basic physics works against doing so for several reasons.  Also the centrifugal switch needed for starting single phase motors will kick in as the motor speed drops, engaging the motor's starting coils that will begin to overheat in just a few seconds if left engaged. 

   What you need is a three phase motor and and an inverter type speed controller which does control the speed by varying the frequency.  While any three phase motor will run on an inverter, a motor designed for inverter control will hold up better.

   John White, Shop Manager, Fine Woodworking Magazine 

1. 
   Mike&L | May 14, 2006 10:15pm | #8

   Thanks for the input.

   It would be so cool to be able to control the motor speed in an induction motor, but it clearly isn't to be.

   In any event, it's nice to know difinitively that it isn't practical.

   Mike D

4. 
   Eric | May 14, 2006 10:18pm | #9

   Mike,

   I'd check McMaster Carr: http://www.mcmaster.com/

   If they don't have it, it will be really really hard to find.

   Cheers,

   Eric

5. 
   gmitch | May 15, 2006 03:36am | #10

   Click the following link to TB Woods website.  These controllers are AC Inverters.  There are quiet a few company's out there that make this type of inverter Baldor, AC Tech, or Leeson.  You can check with Motion Industries in your area to buy through.  AC Tech is probably the least expensive of the bunch.

   http://www.tbwoods.com/products.php?level=4&GID=47&PID=31&MID=2

   Greg

   Endeavor to persevere

1. 
   Mike&L | May 15, 2006 05:17am | #11

   This is very cool.  I'll look into this.

   Thanks

   Mike

1. 
   RickL | May 15, 2006 03:58pm | #12

   http://www.factorymation.net/s.nl;jsessionid=ac112b1b1f43a16d1a6c25344f1d9858f61af7ec6e95.e3eTaxmKbNaNe3yRc3ePbh4Ne6fznA5Pp7ftolbGmkTy?sc=2&category=11

   factorymation has the best prices I've seen on inverters. You cannot get variable speed on a single phase inducton motor.