There was this in the feedback "Back EMF Looped, AC Motor Speed Controller Circuit I have tried this circuit and it does not work.....'
Max.

well, that sucks ... back to the drawing board...

 

That would make for a rather lousy speed controller, since it would only be able to extract up to 50% of the motor's total power. And it would maybe cause "jumpy" behavior...

To say nothing of being useless for an induction motor.
Max.

 

To say nothing of being useless for an induction motor.
Max.

Yeah... but I'm trying to control a universal motor type... I'm trying to sim that thing in LTspice, using a simple inductor and a resistance to represent the load... see if that works.

 

So maybe the circuit is powering the motor on the positive half of the sinewave, and it's using the negative side to "measure" the back EMF

And if that's the case... then that thing is indeed an SCR and not a Triac...

 

Here's my sim... and the thing doesn't seem to work...

 

There was this in the feedback "Back EMF Looped, AC Motor Speed Controller Circuit I have tried this circuit and it does not work.....'
Max.

Hello,

Very good, so now we know. Whoever made this circuit would have to be contacted to find out what they were trying to do.

 

Looks like the sort of circuit you'd find on the Destructables web-site .
In the sim, make U1 a triac, R1=10k, C2=1u and then the triac does fire. However, R3 has little control over the trigger point.

 

Hello,

Very good, so now we know. Whoever made this circuit would have to be contacted to find out what they were trying to do.

Also to confirm whether Triac or SCR used and nature of the motor.
Max.

 

Also to confirm whether Triac or SCR used and nature of the motor.
Max.

I'm almost certain this dude intended to use an scr, look at my posts 43 and 44

 

Sorry, I was not directing it to you, it was a sort of rhetorical question to the test poster of the F.B. on the article site.
He doesn't say what he used and the motor type.
Max.

 

Hi,

Yes, the multiple ambiguities we find here says much about the designers experience and thus about the circuit functionality. If we read between the lines we see there's nothing useful there either.