Thread: Motor Speed Controllers

You've got to be a bit careful here because not all electric motors can be speed-controlled. There are two types of motor - only the ones with carbon brushes can be used with a variable controller.

You need to be careful with your advice too - these are variable frequency drives and are designed to work with non-brushed ac motors.

Thanks Chrisp. That's a great innovation because I have a couple of non-brushed motors that I'd love to step down. I understood that only brushes would work. Obviously not.

One of mine is an ancient bench grinder that would be great in a slower application because it has a fair bit of oomph. BUT, and there's always a BUT, it's a bit exe and almost the cost of a ready-to-go device.

I stand corrected.

I think youll find that these controllers are for 3 phase motors.

They take in 240v ac and convert it to dc then turn it into 3 phase 240 or 220 volt ac which is then controlled through varying the frequency input some other smarts are also available which make them attractive.

I think you would be hard pressed to run single phase via a frequency controller.

The motors are not hard to obtain just remember to make sure of the voltage requirement.

Three phase motors are much better for torque and if you have a questionable power supply i.e. limited current availability the controllers are ideal as the motor starting can be ramped up and down like a soft starter to suit the conditions.

Because the motor is 3 phase reversing is easy and usually done through the v/f drive unit.




Peter