VFD for clutch motor

[4squareleather]

Just got my first sewing machine, Consew 206-RB 3, and it has a clutch motor.  I see many folks installing servo motors with a speed reducing pulley.  Being an electrician my first thought was to just put a VFD (variable frequency drive) on the current clutch motor.  has any one done this?  its essentially the same thing as the servo motor but i think it would eliminate the need for a reducing pulley.  

[toxo]

If this is doable as a retro fit and is robust and consistent you should expect an offer for the patent from every servo manufacturer sometime soon.

[dikman]

Hmm, being an electrician I would have thought you'd be aware that VFD's are used with 3-phase motors, all the clutch motors I've come across have been single phase.

Toxo is right.

[Uwe]

I looked into using a VFD drive a few years back. I bought a nice VFD and a 3-phase motor and set it up on a test stand with a pedal for speed input. Alas, I soon abandoned that project - it was just not a practical solution in my mind. I highly recommend going the brushless servo motor route instead.

Edited March 25, 2021 by Uwe

[dikman]

6 minutes ago, Uwe said:

I looked into using a VFD drive a few years back. I bought a nice VFD and a 3-phase motor and set it up on a test stand with a pedal for speed input. Alas, I soon abandoned that project - it was just not a practical solution in my mind. I highly recommend going the brushless servo motor route instead.

I agree. While it can be done the question is why bother? Servos provide a much neater, relatively inexpensive solution.

[Northmount]

You should also recognize that the slower the induction motor goes, the lower the torque.  And as the speed is reduced, so is the motor cooling.  If you don't have experience with sewing leather, you will find that you are likely to want to go to lower speeds than your VFD will run the motor at.  At that low a speed, you are likely to let the smoke out.

[4squareleather]

2 hours ago, dikman said:

Hmm, being an electrician I would have thought you'd be aware that VFD's are used with 3-phase motors, all the clutch motors I've come across have been single phase.

Toxo is right.

They make single phase in/out vfd.  Thank you for your help. 

[4squareleather]

2 hours ago, Northmount said:

You should also recognize that the slower the induction motor goes, the lower the torque.  And as the speed is reduced, so is the motor cooling.  If you don't have experience with sewing leather, you will find that you are likely to want to go to lower speeds than your VFD will run the motor at.  At that low a speed, you are likely to let the smoke out.

Ok makes sense about the torque loss. My thought was if you could slow the RPM’s down it would be easier to feather the clutch motor to a more manageable speed.  

[4squareleather]

2 hours ago, Uwe said:

I looked into using a VFD drive a few years back. I bought a nice VFD and a 3-phase motor and set it up on a test stand with a pedal for speed input. Alas, I soon abandoned that project - it was just not a practical solution in my mind. I highly recommend going the brushless servo motor route instead.

Figured I wasn’t the only one with that thought.  

[dikman]

21 hours ago, 4squareleather said:

They make single phase in/out vfd.

Yes, I know, I thought it would be a great idea for a bench grinder but when I did more research I found that it's not a good way to run a motor. If it was that simple people wouldn't bother with changing their lathe/belt grinder motors to 3-phase in order to use a VFD. Unlike a 3-phase motor a single phase loses torque and overheats as the speed is reduced, making it very inefficient. As Northmount said.