how to work this ac motor speed control circuit using 2AC input?

Please let mo konw how to working this curcuit. I think Left one both ac input. So, SCR always turn on and off. than ac motor contineuly rotate isn' it?...
But, this pic shows downscaling elevator moving circuit. I want some explain. plz someone help me..

left 15V both AC, right R1.T1 are 220V AC

Picture of how to work this ac motor speed control circuit using 2AC input?
iceng3 years ago

First pic is an SCR DC circuit

Second pic is a Triac and controls flow in both directions AC.

Both the SCR ( Silicone_Controlled_Rectifier ) and Triac are trigger ON devices.

After that they will conduct forever ! or until you interrupt the current or until you reverse the voltage as happens in a AC Mains......

The Triac is actually back to back SCRs with a single gate trigger.

Your circuit might work (run the motor) if both optical isolators are turned on at the same time.

If the motor is an induction by directional machine without a start winding then direction is selected by R5 as you say but still it will not work with SCRs.


iceng3 years ago

Sorry it wont run the AC motor because the SCRs are DC only power devices !

Even if you were to use AC Triacs the motor would only start and run one way !

The way to reverse a single phase AC motor is to reverse either winding.


mr.kdy (author)  iceng3 years ago

Changing mothod is push R5 botton

mr.kdy (author)  iceng3 years ago

I know SCR only turn on when +pulse. So, I guess when trigger 0, thatit optocupler working SCR are turn off. than ACmotor doesnt rotate. if opto turn off SCR turn on when posstive pulse sending, result R1T1 pos pulse are passing SCR1.

if trigger 2 0 R1T1 pulse allabove pass so more high speed rotate.

that assume is dint correct???