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Other Stuff => Other Topics => Topic started by: tubesornothing on January 24, 2010, 05:52:18 pm

Title: Slowing an AC induction Motor
Post by: tubesornothing on January 24, 2010, 05:52:18 pm: This might be similar to G Hoffman's thread, but a little twist.

I bought myself a used industrial sewing machine for making amp covers. It is excellent, but holy crap it is fast. Efiin scarey fast. I can probably get a smaller drive pulley, but since I got a couple of variacs kicking around, I am curious - can I use a variac to control the speed with no ill effect? It looks like a typical 1hp 1720RPM induction motor.

thanks
ToN
Title: Re: Slowing an AC induction Motor
Post by: jjasilli on January 24, 2010, 06:36:57 pm: Checkout ths thread: http://www.electro-tech-online.com/electronic-projects-design-ideas-reviews/10476-looking-ac-motor-speed-control-circuit.html

Also see: Inductive motors require a variable frequency control. http://www.aaroncake.net/Circuits/acmotcon.asp

http://www.fairchildsemi.com/an/AN/AN-7511.pdf
Title: Re: Slowing an AC induction Motor
Post by: tubesornothing on January 24, 2010, 07:24:52 pm: Hey thanks. Yeah I kinda thought it wouldn't just be a voltage adjustment. I just re-read PRR's response to G Hoffman leslie motor control thread. http://www.el34world.com/Forum/index.php?topic=7982.0 He basically says the same thing. Since this is an industrial sewing machine, its not the typical universal motor. Its same size as a 15A table saw motor.

I think I need to re-gear it (pulleys). I just finished stitching up a couple of tarp zippers. If I knew what I was doing, I could have done the 8 ft of zipper in about 30 seconds. This thing rips.
Title: Re: Slowing an AC induction Motor
Post by: PRR on January 25, 2010, 06:45:29 pm: "Sewing machines" traditionally use "Universal motors", NOT induction motors.

The no-load speed is another clue.

Does it have brushes? Does it spark?

> It looks like a typical 1hp 1720RPM induction motor.

Then maybe it IS an induction motor. But why 1 whole Horse for sewing? Why 1800 when 3600 is cheaper and it must have a belt anyway?
Title: Re: Slowing an AC induction Motor
Post by: tubesornothing on January 25, 2010, 08:50:04 pm: This is not a home sewing machine - it is an industrial machine. 1hp motor - for sure induction (i.e. not universal - no brushes anywhere). These babies are designed to run flat out, but there speed can be varied somewhat because it has a clutch (no kidding, a real live clutch). I spoke with the local sewing shop (which also sells the industrial machines) they sold me a pulley for $10. He did try to upsell me to a DC motor with speed ranges - but I did not want to fork out the $300
Title: Re: Slowing an AC induction Motor
Post by: billcreller on January 29, 2010, 09:11:23 pm: I've used one of those industrial type machines. lots of power for heavy material. Don't remember if it was variable speed.