Good Day All.

Can someone please explain to me how the this circuit works?

The above circuit is from my Power Performance FMTC1020R Router.

It is used to control the motor speed from 11,500-34,000rpm.

I am used to dealing with DC voltage, and using PWM to control motor speeds.

But when it comes to AC, I don't know a grate deal.

I have a very healthy respect for mains voltages.

If someone could try and explain to me how the above circuit works I would be very gratefull.

Best Regards.

 

Looks to me as a simple modification of a common light dimmer circuit.

D1 would be a diac though so the symbol is wrong.

SW1 would enable full on, VR2 would be the control and VR1 would be a trimmer adjustment.