Variable speed AC Mains motor drive

[eem2am]

Hello,

There is a way of doing a Variable Speed Drive for an AC mains motor by simply using a microcontroller and a opto-Triac driver.

...but do you know of a schematic for this?

I cannot find anything liek it on the internet.

Domestic shower pumps use this technique.

There is absolutely no need to have a DC Link.

 

[FvM]

What's you're intended control method? Phase angle control?

According to torque versus slip characteristic of an asynchronous motor, speed control by voltage (respective phase angle) variation has very limited capabilities. But it can work with fans or rotary pumps that tend to stabilize the speed despite of the motor's torque characteristics. They are basic dimmer circuits, but providing a more stable and symettrical phase angle than a lamp dimmer and suited for inductive load.

 

[eem2am]

-Its the software engineer who will be doing the control software and its difficult to get time to speak with him.

He has asked me for a mains zero-crossing detector signal.....so obviously he needs the zero-crossing in order to do his variable speed driving of the AC Motor.

(Its a brushed AC mains motor)

The engineering manager told me that its a rough-and-ready way of getting variable speed...but cheap.

He mentioned that the control method would be "slipping" the motor.

I think its kind of like the same way a cheap electric drill has speed control.