Speed Control for Clutch Motor

[MarlinDave]

Interesting but my machine has a single phase motor. I have single phase shop power and some 3 phase shop machines (lathe,mill, welder) running on converters. I would convert all these to single phase if not so expensive. I got a free 10 hp 3 phase compressor and swapped motors to single phase to dodge the converter hassle. 

[Tigweldor]

Now that is an interesting philosophy - as most people upgrade their shop wiring to 3-phase sooner or later and never look back to regret it.

Nice thing about 3-phase wiring - you can also run single phase motors on that - you just use/hook up one phase and omit the other two.

The wiring does not care - neither does the motor.

Greetings

Hans

[MarlinDave]

Where I live I would likely have to pay the utility $100,000 to get three phase to do projects  give away. 

[AlZilla]

3 phase is not in homes in the US, generally. I buy electric motors when I see them at yard sales and such and never see a 3 phase motor.

[dikman]

13 hours ago, Tigweldor said:

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.

 

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.

 

Things must be different on your side of the world. Every industrial sewing machine I've bought came with a single-phase clutch motor, 240v/50 Hz, all of which I either sold or scrapped and replaced with servos as the most cost-effective and practical solution.

The reason I did that is because those clutch motors CANNOT be controlled with a simple dimmer control/potentiometer device - the controller will immediately blow up if you try. As I mentioned before, those controllers are intended for universal-type motors as used in power tools, hair dryers, fans etc, not single phase induction motors. I wonder how many unsuspecting people buy those cheap controllers on ebay thinking they can slow down their grinder or drill press only to have them go poof when they try?

Trying to make a single-phase motor variable speed is a complex issue and not worth the trouble/cost, as you say three-phase motors are the best option in that case (if you don't want a servo).

[Tigweldor]

Well, as it is stated in the side bar - I live in Germany.

Over here, ALL industrial wiring is/has always been 3-phase --- hence : all industrial sewing machine motors are 3-phase.

And it does not matter if you buy an old Quick, Kobold or EFKA motor - for industrial application they are all 3-phase motors.

In days gone past (before the internet), it used to be difficult to obtain used industrial sewing machines - the manufacturers of sewing machines had contracts with the industry and when it came time to replace models - they would rather scrap entire machines than selling them on the second hand market for use in private homes. All said : there was really no second hand market for used industrial sewing machines as we have it nowadays.

This was to promote sales of "home use" sewing machines - which then came with single phase motors.

 

As to exports to the outback and the islands around Australia - they most likely did furnish them with single phase motors as you guys did not have extensive 3-phase wiring throughout your countries, until a very short time ago.

Edited May 8 by Tigweldor

[kgg]

49 minutes ago, Tigweldor said:

Over here, ALL industrial wiring is/has always been 3-phase

In North America the standard residential / small business electrical service is single phase 120 / 240 volts at 60 Hz on a 200 Amp service drop. There are smaller older service drops, old 60 Amp, 100Amp but typically 200 Amp is the norm. Over 200 Amp service drops do require a different metering installation but in rural areas a single phase 300 Amp service drop like mine is not that uncommon particularly if there are other out buildings like barns / garages on the property.

Most commercial applications, at least in Canada, will have three phase service drops but usually peel off 120 Volts for small motor usage like what is used with sewing machines.

kgg

[Tigweldor]

Over here in Germany, many (better : most) residential homes have 3-phase wiring to the fuse panel as well - since all electric stoves/ovens are wired 3-phase.

The national electrical code is pretty strict about that - has been for many decades.

We only have 50 Hz over here - on older imported record players and cassette tape decks you had to dial in wanted frequency on the back of the machine - else the turn table/motor would be "wonky"/out of tune. Some record players without that switch even came with 2 different drive belt pulleys for the motor - one for 50Hz , the other for 60Hz in order to obtain proper 45 or 33 rpm.

Edited May 8 by Tigweldor

[Wyowally]

My introduction to clutch motors was on an old Necchi BV. The motor was installed in New York where assembly for imports took place. Upside down, so the lube ports were on the bottom! After fixing that, I addressed the cork surface clutch. There were many ways to adjust alignment, but all crude threads. Perfect engagement of the clutch and plates took some work.  I renewed the cork surface by lightly engaging a sanding disc between the plates using the engagement lever carefully.

This old motor/clutch combo is nearly silent and feathers nicely. Alignment had to be perfect. My time is worth about 25 cents/hour, so I pulled it off. 

Point is, perfect alignment, good running motor and good clutch surfaces will make for easier feathering.

[dikman]

At least two of my machines were ex-factory, one from a car manufacturer (when we used to build our own cars) and both were single-phase. It is rare to see a used sewing machine for sale here with a three-phase motor. Factories, of course, have three-phase power for most of their machinery but also use single-phase and for a sewing machine with a clutch motor single-phase power is perfectly adequate. It would be interesting to know how many other manufacturers, besides those in Germany, made three-phase powered sewing machines.

[Digit]

As Hans already referred to, in densely populated Europe, the three-phase power that exits the power plants gets transported all the way to the homes. AC power transmission is three-phase everywhere in the world because using three wires is more efficient than using two to transmit the same amount of power. It’s the last mile from substation to customer that is most expensive and where utility companies need to do the math: is is more cost-effective to put down four or five wires (three phases plus neutral in TT systems or the same plus additional ground in TN systems) or put down two wires?

in densely populated areas it’s more efficient to lay down three phases as it allows for more power to be distributed before you need additional substations. In less densely populated areas, you can get away with two wires at higher than distribution voltage and the occasional transformer (eg a pole pig as I believe it’s called in the USA) that transforms down to distribution voltage in split phase (eg 2x120V, allowing for larger machines to be hooked up to 240V).

[kgg]

On 5/7/2025 at 5:59 PM, Tigweldor said:

Now that is an interesting philosophy - as most people upgrade their shop wiring to 3-phase sooner or later and never look back to regret it.

In Canada a major consideration is that with customer 3 phase service drops is the billing. A lot of companies charge the customer on their 3 phase peak so they pay that demand for the whole year even if their peak is never again reached throughout the year. So for the small or individual customer 3 phase is not a viable option from a cost point of view let along trying to contend with typical 3 phase voltages, 4.16 kv, 12.47 kv and 25 kv.

3 hours ago, Digit said:

AC power transmission is three-phase everywhere in the world because using three wires is more efficient than using two to transmit the same amount of power.

In Canada distribution is similar except that a 3 phase trunk feeder with small 4.16 kv, 12.47 kv and 25 kv will have a ground wire travelling along with the phase conductors from the electrical substation. Single phase taps necessary to feed single phase customers like small business and housing subdivisions a phase and ground are tapped along the 3 phase trunk feeder route. The single phase voltage is then further to reduced to 120v / 240 volts at 60 hz by either pole mounted or pad mounted transformers. Large customers are usually feed at line voltage ( 4.16 kv, 12.47 kv and 25 kv).

kgg

[Northmount]

5 hours ago, kgg said:

In Canada distribution is similar except that a 3 phase trunk feeder with small 4.16 kv, 12.47 kv and 25 kv will have a ground wire traveling along with the phase conductors from the electrical substation.

The 25 kV line down my back lane (Calgary AB) is 3 conductors only.

Drops are made to transformers along the way.  The transformers are connected between 2 phases (resulting in single phase delivery) on the 25 kV line, and deliver 110V - 0 - 110V via 3 conductors.  (The 0V lead is the N (neutral typically white) conductor.)  Overhead drops to houses are via triplex cable.  Connection across the two 110V conductors provides 220V which is typically used for heavier loads like electric stoves, clothes dryers, air conditioners and shop tools like table saws and air compressors.

As the 25 kV line continues down the lane, transformers are connected to the next pair of phases, and onto the next pair, providing a balanced load on the 3 phase system.  It is more economical to use 3 phase transmission as currents flow counter to each other as you look at the actual current flows, reducing the cable diameters versus what would be needed in a single phase system to transmit the same amount of power.

In commercial and industrial applications, utility power (110V lighting, receptacles, small motors, etc.) is often distributed as 208V three phase wye connected.  120V power is available by connecting to one phase and the center tap of the wye connection.

120V and 110V terms are used interchangeably, as is 220V and 240V in many discussions and specifications as they are within design tolerances.  During my electrical education many years ago, what we now call 110V or 120V was simply called nominal 117VAC.