# How to slow down a electric motor

#### spike1947

Joined Feb 4, 2016
84
Hi
I have a electric motor from a houshold vacuum cleaner that I want to power a small blacksmiths forge , but it is to powerfull , what I was wanting to do was try to slow the motor down with a resistor ! .
Would that be possible .

cheers

spike

#### Dodgydave

Joined Jun 22, 2012
8,465
Use a light dimmer, these are usually Universal type motors in hoovers, and respond well to dimmers.

#### wayneh

Joined Sep 9, 2010
16,114
Another approach is to just let it run but throttle the air flow, for instance with a damper.

#### spike1947

Joined Feb 4, 2016
84
I thought about that , but would it not overheat the motor ! .

cheers

spike

#### spike1947

Joined Feb 4, 2016
84
Use a light dimmer, these are usually Universal type motors in hoovers, and respond well to dimmers.
Yes tks for that , and I think I may have one kicking about somewere , So can I discount the resister way then ! .

cheers

spike

#### spike1947

Joined Feb 4, 2016
84
Use a light dimmer, these are usually Universal type motors in hoovers, and respond well to dimmers.
Just thinking with the light dimmer , would it take the current ie 1200Kw motor ! .

Joined Jul 18, 2013
19,156
You need to get the power tool version, either that or DIY version if the former is not available where you are.
Throttling the output, lowers the motor current but heating may occur due to reduced air flow.
Max.

#### spike1947

Joined Feb 4, 2016
84
You need to get the power tool version, either that or DIY version if the former is not available where you are.
Throttling the output, lowers the motor current but heating may occur due to reduced air flow.
Max.
That sounds expensive ! .

cheers

spike

#### AlbertHall

Joined Jun 4, 2014
8,504
I thought about that , but would it not overheat the motor ! .

cheers

spike
No, the motor will be fine.

Joined Jul 18, 2013
19,156
That sounds expensive ! .

cheers

spike
Which?
The Triac or the throttle?
Max.

Joined Jul 18, 2013
19,156
You could look at the wall mount ceiling fan variety of controllers and check the No. of the Triac used and beef it up, if needed.
Max.

#### spike1947

Joined Feb 4, 2016
84
You could look at the wall mount ceiling fan variety of controllers and check the No. of the Triac used and beef it up, if needed.
Max.
Was thinking of building a thyrister controller ! .

#### spike1947

Joined Feb 4, 2016
84
Would there be any diagrams around to do that ! .

#### wayneh

Joined Sep 9, 2010
16,114
I thought about that , but would it not overheat the motor ! .

cheers

spike
Unlikely, but you could build in a slipstream to keep a small airflow over the motor even if the main flow is cutoff. The motor will act like a vacuum cleaner motor when you block airflow. It’ll speed up a little because there’s a reduced load.

Joined Jul 18, 2013
19,156
There are several for ~ $2.00 each on ebay and Ali express etc, AC 220V 2000W SCR Voltage Regulator Dimming Dimmers Speed Controller Max. #### wayneh Joined Sep 9, 2010 16,114 I agree that’s an excellent solution unless you need fine control at the very low end, for instance the ability to choose 2% versus 4% flow. #### DNA Robotics Joined Jun 13, 2014 505 I have used just a 10 amp diode to slow some power tools. It just gets a half wave. I think I got that idea from a Makita sander. #### thedoc8 Joined Nov 28, 2012 128 I thought about that , but would it not overheat the motor ! . cheers spike I think if you divert the airflow instead restricting it, the motor won't overheat. Might be very loud. Thread Starter #### spike1947 Joined Feb 4, 2016 84 There are several for ~$2.00 each on ebay and Ali express etc,
AC 220V 2000W SCR Voltage Regulator Dimming Dimmers Speed Controller

Max.
I have used just a 10 amp diode to slow some power tools. It just gets a half wave. I think I got that idea from a Makita sander.

Interesting , tks

#### spike1947

Joined Feb 4, 2016
84
There are several for ~ \$2.00 each on ebay and Ali express etc,
AC 220V 2000W SCR Voltage Regulator Dimming Dimmers Speed Controller

Max.
Thanks just what I am wanting , trouble is if they are from China I may not get it untill quite a few weeks time , I could really do with making one , have lots of electronic parts , would anyone have a schematic of this type of controler ! .

cheers spike