Speed Control for Clutch Motor

[Tigweldor]

I live in Germany.

National companies like Kobold, Quick, Efka have always delivered top quality.

The older the mechanism - the more "German" it was in design - and with as little as possible plastic in the whole concept.

And a lot more "service friendly" than many new "let´s produce cheap" construction concepts.

I can not speak for (newer) clones of them, stemming from far east of Asia.

 

Edited May 5 by Tigweldor

[dikman]

To answer your original question, no, you can't use an electronic speed control on a single-phase motor as those controllers are designed to work on "universal" motors that use brushes, not squirrel cage AC induction motors like your clutch motor. The advantages of a servo are they're relatively compact, are already set up to connect the foot pedal and are pretty cheap these days. If you've already got a 3-phase motor and VFD then obviously your costs will be minimal but you will need to source/fabricate a foot pedal with a built-in rheostat to control the VFD. 

I have fitted VFD/3-phase combos to my lathe, belt grinder and drill press but personally I won't even consider it for a sewing machine, servos are a much neater solution.

Edited May 5 by dikman

[AlZilla]

1 hour ago, dikman said:

To answer your original question, no, you can't use an electronic speed control on a single-phase motor as those controllers are designed to work on "universal" motors that use brushes, not squirrel cage AC induction motors like your clutch motor

I'm glad you jumped in with that. I've been trying to remember what it was that was bugging me about this thread.

Nice job!

[MarlinDave]

I was in Harbor Freight today and they had a $17  router speed control. Thought I would try this out. Plugged in the sewing machine, set the speed control to full speed, and turned on the machine. Blew the 8 amp glass fuse in the speed control before the machine turned over. I replaced the fuse and tried it on a small drill press, and it did okay, but would not run full speed on direct. Cant imagine it doing much with a 1 1/2HP router, but ill try that tomorrow.  The clutch motor has a wing nut rod which limits clutch travel. I reset it and I can pretty much sew one to two stitches at a time. 

[Tigweldor]

 If you've already got a 3-phase motor and VFD then obviously your costs will be minimal but you will need to source/fabricate a foot pedal with a built-in rheostat to control the VFD.

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Wrong.

The VFD just lowers the overall rpm of a motor by reducing the Hz factor in the current that the motor receives - which in the US straight from a wall outlet is 60Hz (cycles per second),  in the EU it is 50 Hz.

You lower that frequency to 30 Hz - you will have reduced motor speed to half of its´original value.

No special rheostat needed - all stays stock - you just plug your machine into the VFD outlet and control it with the settings made within the VFD.

I currently own 6 sewing machines - all with 3-phase clutch motors and VFD controlled.

2 Adlers (4 and 5), 2 Pfaffs (138), one Dürkopp (239) and an Adler 30-7 - which does not have a clutch motor, but a gear reduction motor

Edited May 6 by Tigweldor

[Digit]

@Tigweldor I believe @dikman suggests to replace the clutch pedal with a pedal that controls the VFD and somehow lock the clutch motor into a direct drive (because the OP finds the clutch impossible to control). As I mentioned: this risks overheating the motor because it is not designed to run at slow speeds.

If you're going out of your way to transform a clutch motor into a servo-ish motor, then I think it's better to replace it with a proper servo.

[Tigweldor]

yes - in the beginning I was also weary of overheating the motors cause they run at reduced rpm = reduced cooling.

But : the older 3 phase motors have massive copper windings - they can stand the heat.

When I run my Adler 5 for about 2 hours of sewing (between 22 and 28 Hz) - the motor gets warm - but not so hot that you can not lay your hand upon it.

Now had I bought 6 servo motors for my sewing machines - I´ld have been out around 1000 bucks of hard earned cash - a VFD plus board plus socket plus wall plug and cable comes to less than a 100 bucks.

You figure out the math on that one.

Edited May 6 by Tigweldor

[GerryR]

If you want to control the VFD with a foot pedal rather than from the control panel of the VFD, you can get an inexpensive TIG welder pedal (Ebay) that contains the potentiometer (pot) needed by the VFD for external speed control.  I mentioned this in another thread.  (Not all TIG pedals have the pot included, some just contain a switch, so you have to be careful when ordering.)  Just lock the clutch on the 3-phase clutch-motor and use the foot pedal to regulate speed.  The one I'm using on my machine is called a "HITBOX" (www.unitweld.com) and I got it off Ebay.  It contains two pots, one the foot pedal operates and another that can be used to limit top speed that is mounted on the box and has a control knob.  Just my $.02

@Tigweldor  Very neat solution!!

Edited May 6 by GerryR

[dikman]

Thanks Gerry, that's what I meant, guess it wasn't clear enough. Without a foot pedal of some sort with a potentiometer the only way to vary the speed of the sewing machine is by using the inbuilt VFD speed control which requires using your hand - no problem if you have three hands. I'm a bit confused, however, as it sounds like some are talking about controlling the existing clutch motor just by adding a VFD? That can't be done with the clutch motors I have had as they were single phase induction motors which can't be controlled with a VFD. If it was that simple then belt grinder manufacturers wouldn't have to use three phase motors on their products and could save money.

Bottom line is for most people the simplest option is to replace the clutch motor with a servo, they are relatively inexpensive, are a straight bolt on replacement and use less power than a single/three phase motor.

[Digit]

6 hours ago, dikman said:

I'm a bit confused, however

That's something you get when everyone chips in with their own situation and experiences in mind and little to no knowledge about the OP's.

I have one three-phase clutch motor that I managed to drive (at constant speed) using a cheap VFD and I have one sewing machine powered by a servo. I love the servo but a VFD was cheaper to convert my clutch-motor-powered skiver to single-phase than buying a servo for that machine.
You have single-phase clutch motors, so you advise in that direction and Hans has a whole shop full of three-phase motors so he advises on a plug-in VFD setup.
Everyone's situation is different, so everybody will come up with different solutions. The good thing is that in this way we can all learn from each other.

The best the OP can do is to distill all the advice he got and apply it to his situation.