Speed Control for Clutch Motor

[MarlinDave]

Hello, 

I have a Consew 225 with a clutch motor. Too fast for my use for leather. Built a belt and pulley speed reducer, approximately 3 to 1 ratio. Helps but not where I need to be. Lengthened the arm on the clutch motor linkage and getting close. I wondered about an electric speed reducer like you use to plug a router or other power tools into. Anybody ever tried one of these? I built a speed control with a light dimmer switch yesterday. Worked a while but at some point the motor kicked out and I was able to get it going again. Did not expect this to work but wanted to try. Not enough power (600 watts maybe). Would try a router speed control if it would be safer for the motor. I know about servo motors, but really don't need to spend that much right now as I pretty much give all my work away. Thanks. 

[kgg]

1 hour ago, MarlinDave said:

I wondered about an electric speed reducer like you use to plug a router or other power tools into.

Your clutch motor is probably a 1 hp (745 watts) and with a typical speed of 1750 rpm. That motor on startup could have a inrush current draw of 6 times that of normal current draw (~6amps) on initial startup. Anytime you reduce the input voltage on a motor the motor will run hotter and it will draw more current in order to keep it's wattage rating until it blows the motors inline fuse or circuit breaker in the main electrical panel.

My opinion is that you have done almost all the normal mods except for reducing the size of the pulley on the motor. However until you master feathering the clutch you got what you got or until you install a servo motor which will set you back about $150 USD.

[MarlinDave]

It has the smallest motor pulley as well. 

[Wizcrafts]

1 hour ago, MarlinDave said:

It has the smallest motor pulley as well. 

Aside from learning to feather the clutch, you're best alternative is to swap the motor out for a servo motor. like this one.

[Tigweldor]

I would advise you to just add a VFD to reduce motor rpm.

I built a portable unit (s) - you can then use it on different machines.

If you build one - you might as well build two - very little more effort needed.

Sell the better looking one - the one left over cost nigh none.

hope that helps you out,

Hans

Who actually prefers the superior ability to feather a mechanical clutch system manually via pedal over the electronic version and runs all of his 3-phase clutch motors over such device(s) as shown in the pics.

It´s sort of like driving a truck with a manual or automatic tranny - on the automatic you cant really feather the clutch.

Anyway, this is definitely one of the most fruitful DIY projects you can make for yourself - trust me.

I actually consider it as a TOOL to manipulate the motor to perform the way I need it for my exact application.

You will never ever want to miss it again.

You can program in a stop mode - so your motor comes to a complete stop within x amount of secs when you press the stop button or by switch - it transforms the old clutch motors into a whole different beast.

Edited May 5 by Tigweldor

[MarlinDave]

Thanks for the ideas. I considered a VFD for some 3 phase machine shop items I have. Built rotary converters for 2, one came with a static converter box. I was always scared of VFDs because so many have problems with them. The clutch is not smooth at all - grabs all at once. It takes off fast, then slows. 

[Tigweldor]

Naaaah - the only prob is, that you have to sit down and read/learn how to set the parameters within the different programs and sub-programs of your particular VFD.

And they are all a tad different - but lots of info an the internet.

You just gotta go through all that data entry step by step for the first time or to change/readjust settings to your likings - but all in all they are "bullet proof"

Edited May 5 by Tigweldor

[Digit]

I've had a positive experience with a cheap Chinese VFD (see Powering three-phase skiver motor), but note that clutch motors are designed for continuous running at a constant speed. Their built-in cooling fan is designed to provide adequate cooling at that speed. If you lower rpm for any prolonged time, the motor will draw more current (increasing heat production) and lower the fan speed (decreasing cooling). The combination will risk your motor to overheat and burn through.

You say the clutch isn't operating smoothly. Could it be that it's clutch plate deteriorated from long-time use at slipping speeds?

I have no experience with clutch motor clutches, but does anyone perhaps know if these are wet or dry? And if wet, maybe the oil has leaked out and needs replacing?

[Tigweldor]

The clutch motors usually all have conical bell type clutch plates and the clutch lining is very similar to brake lining.

Often after woken up from decade long slumber, oil and grease have hardened, rust has formed - action is inferior - service is needed.

A well tuned and properly set up mechanical clutch system is a pleasure to operate - at least on my motors they are - and that is no witch-craft.

As to skivers - many people think that by having activated the sharpening wheel and sparks have quit flying - the bell knife is now sharp. Well only half way home - you still have to eliminate the burr from the inside of the bell knife. You omit that step - results will be poor. Cussing will get loud. Manufacturers and engineers blamed. All cause of the burr.

Edited May 5 by Tigweldor

[MarlinDave]

The motor was new on the machine when I got it. Might have 20 hours on it. 

[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.

---------------------------------------------------------------

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.

[AlZilla]

Here's a search on practical machinist about this very subject and it's a rabbit trail of complications with no clear answer. Single phase motors are harder than 3 phase and lose torque when you slow them down. I coughed up the money for a purpose designed servo. I wanted to spend my time sewing, not reinventing the wheel.

https://www.practicalmachinist.com/search-entire-site/#gsc.tab=0&gsc.q=speed control single phase motor&gsc.sort=

Years ago I wanted to slow down a drill press and used a tread mill motor to do it. I just mounted the entire control panel on the wall behind the press and used the speed control knob. It's working great to this day, it just lacks finesse.

[Tigweldor]

In my up to date experience, most industrial (sewing) machines use 3-phase motors and single phase motors are usually found on the "home" models for private citizens.

Simply because in the industry, 3-phase wiring is standard procedure to power motor driven implements - not so in every home or apartment/condo or garage workshop.

Also a 3-phase motor is more efficient in converting electrical into mechanical energy - due to the construction of its´ magnetic fields.

You can regulate the speed of most single phase motors with a potentiometer (dimmer switch) - but current not needed/used will be transformed into heat.

This is why most speed controls have a max. wattage rating that they can handle - the same goes for a VFD - you buy one built for max. 1,5kW and try to run a 4kW motor on that - it will not last long due to overload and overheating.

Plus you have to take into consideration : starting current is most often manyfold of the actual current needed , once running rpm has been reached.

 

The nice thing about a VFD though is, that it can convert single phase house hold current into 3-phase current needed to run any 3-phase motor.

With the added benefit of being able to control output frequency = motor speed and the ability to severely cut down on run on time after the motor is shut of = motor brake.

On some VFDs you can also increase starting current to give it a boost to 125% or 150% of current needed - a "starting ramp" so to speak. 

I will say it again - they are a pretty bullet proof apparatus once set up and as you can tell by the dates on my pics - I have been using them for years with success, even long before the pics were taken.

And I am talking real hands-on experience - not some theoretical mumbo-jumbo why they can´t and will not work on a three phase clutch motor.

As to the motor overheating - in the industry, motor speed is controlled with VFDs - they would not use such units if it meant that the motor would burn out in short time. They do such calculations with a very sharp pencil.

Another benefit : as more and more people are switching to servo motors - the availability of used 3-phase clutch motors in good condition has increased - while at the same time prices for them have dropped. Since I use them, I see that as a win-win situation (for me at least).

 

Greetings

Hans

Edited May 7 by Tigweldor

[Digit]

53 minutes ago, Tigweldor said:

in the industry, motor speed is controlled with VFDs - they would not use such units if it meant that the motor would burn out in short time

Slight nuance: in the industry motors are built to specifications. If a motor needs to be able to run between a range of rpms, the cooling system is calculated to those rpms. Clutch motors are not designed to provide a range of rpms at the axle; that's what the clutch is for: transform a fixed rpm to a range of rpms (plus heat dissipation on the clutch plate).

I'm not saying that a clutch motor can't be speed-regulated; they can, just like any motor; but that's taking them out of their spec and into the realm of safety margins. As long as you don't venture into extremes you're safe. The older the motor, the more likely it has been overdesigned and can take some thrashing.

[Tigweldor]

Jup - you got that one right.

Some of my 3-phase clutch motors weigh (almost) as much as the sewing machine that it powers.

And if I do go way below 20Hz - they do get very warm.

I have tested them with an infra red thermometer - at the speeds that I run them at, they do not exceed 60° to 65°C.

And that is a temp, that most all industrial motors can cope with.

[GerryR]

Many of the three phase motors produced today are "inverter" rated and are spec'd to run from 10 to 90 Hz (175-2295 rpm) and are usually attached to a gearbox.  In my particular case, a 5:1 gearbox giving 35 to459 rpm final output.  Further reduction from the motor pulley to the sewing machine pulley keeps you well above the 10 Hz minimum with plenty of low speed control.  Couple that with the VFD setup which allows the top speed to be programmed so that the full range of the pot, in this case foot pedal, is from 0 to programmed top rpm and you have very fine speed control.  (The DCservos operate the same way as far as programmed top speed is concerned.)