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single phase synchronous motor speed control

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Well, here's a little something for ya'll to ponder...

The other day I bought a Laminator off the clearance rack at a discount store (it was cheap enough, and I was hoping to use it to replace my failing 30 year old Laminator I use for PCB Transfer Paper).

The transfer process is naturally a temp/time thing, and unfortunately this Laminator runs way too fast (and the temp not adjustable). So I figure I can change the speed somehow.

So I pop it open and find this little gearmotor (Kaili TY-50BF), a little web research shows it's a synchronous motor.

Since the speed of a synchronous motor is dependent on frequency rather that voltage, a typical "triac motor controller" wont work, so I'm thinking about some little MOSFET inverter circuit that pumps out 120vac with an adjustable frequency, and I've found examples on the web using different means of digital timing.

Now, I have an old V120-22-T1 sitting in my shop, and was thinking I could write some little PWM code to flip-flop the drive to a couple MOSFETs and set the frequency I want?

Anybody done something like this who can provide some guidance?

BTW, was going to add a couple pics, but I cant seem to capture a .png that meets the 14kB requirement???

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You could totally do that.  

Check this guy's video out  -


He's in Arduino land, but you can bypass that part.  He goes into the 120V drive circuit and has determined that small IGBTs work better than MOSFETS.  So it's like a regular VFD - you rectify the incoming 120V to get a high voltage bus and then chop it to feed your motor.

Keep us posted on your findings.

Joe T.

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On 2/18/2023 at 3:24 AM, John_R said:

Anybody done something like this who can provide some guidance?

I have experimented with different ways of controlling synchronous motors. The use of hard switching and PWM modulation requires a specialized controller. The simplest PWM from a PLC requires quite a large number of components to implement frequency control. This is due to the fact that you have high-voltage motor circuits and need to isolate the control circuits (upper and lower transistors in the H-bridge).

In my opinion, the cheapest way to implement your task is to use a specialized IC - a set for implementing frequency control. Below are two manuals about a IC and a ready-made board for implementing a sine wave with an adjustable frequency for your motor.


I installed such a circuit board in a UPS with burned-out MCU and got a good inverter with the ability to adjust the frequency and voltage, similar to a frequency converter, but in a single-phase version.


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