Help on single phase motor speed controllers and motor comparability

[Gragson]

I want to be able to slow down a single phase motor on my Pollard drill if possible.
Google fu has thrown up a few things about compatible and non compatible motors to single phase motor speed controllers
Split Phase motor…not suitable for variable speed.
Split Phase Capacitor Start motor…also not suitable.
Shaded Pole motor…This motor is suitable for variable speed but not reversible. Also inefficient.
Split Capacitor motor…This motor is also suitable for variable speed and can be reversible.

I know less than nothing about all that or even if its from a reliable source.

My motor plate is pictured, I don't know if that gives enough info?
3 phase is not an option I want to take in current shed and I would rather not swap the motor.

Are there any single phase motor speed controllers that would work ?

 

[Kram]

There are single phase output frequency converters, I imagine they would work on most.

 

[Gragson]

There are single phase output frequency converters, I imagine they would work on most.

Are there any example links to ones that might work?

 

[Onoff]

Could you go super cheap with a simple, cheap twiddly one? Maybe a kit?

Cebek 1500W AC Motor Speed Controller

Cebek R-10 module is a speed controller for AC electric motors. It will control mains operated electric motors from approximately 33 - 98% of full load with a maximum consumption of 1500W. The R-10 module is also fitted with a minimum speed potentiometer mounted on PCB and interference suppression.

www.esr.co.uk

Do speed indication with a cheap Chinese one:

[£7.62 52% OFF]4 Digital Green LED Tachometer RPM Speed Meter + Proximity Switch Sensor NPN Module Board from Electronic Components & Supplies on banggood
Data sent exceeds limit

 

[eddie49]

Could you go super cheap with a simple, cheap twiddly one? Maybe a kit?

Cebek 1500W AC Motor Speed Controller

Cebek R-10 module is a speed controller for AC electric motors. It will control mains operated electric motors from approximately 33 - 98% of full load with a maximum consumption of 1500W. The R-10 module is also fitted with a minimum speed potentiometer mounted on PCB and interference suppression.

www.esr.co.uk

That would only work on a brush-type AC motor ( a "universal" motor ), not an induction motor.

 

[Kram]

Are there any example links to ones that might work?

Possibly these

Huairdum Variable Frequency Drive, AT2-0750X Inverter Motor Drive 220VAC 5A VFD Rate Controller for Single-phase 0.75kW AC Motor : Amazon.co.uk: Garden & Outdoors

Buy rated Huairdum Variable Frequency Drive, AT2-0750X Inverter Motor Drive 220VAC 5A VFD Rate Controller for Single-phase 0.75kW AC Motor at Amazon UK. Enjoy free delivery on eligible orders.

www.amazon.co.uk

220V 0.75KW 1HP Single To Single Phase Mini Variable Frequency Drive Inverter CNC VFD : Amazon.co.uk: DIY & Tools

220V 0.75KW 1HP Single To Single Phase Mini Variable Frequency Drive Inverter CNC VFD : Amazon.co.uk: DIY & Tools

www.amazon.co.uk

Look for the deacription saying single phase output and google the model number to be sure. Amazon sellers can be lazy with the descriptions, so buying one with prime will allow an easy return if it doesnt work.


However I'd much prefer to swap a 3ph motor and vfd instead. Used motors plus chinese vfd's can be quite cheap.

 

[brightspark]

if you must reduce speed the 3 phase motor with vfd is the way to go if single phase dont bother

 

[Hood]

I looked into this a while ago for a single phase bandsaw, the answers I got back from most places was no go. Normally I would have just shoved a 3 phase motor on and reduced the speed via VFD but this motor is a typical Chinese effort, doesn't conform to any standards so it would require I make up an intermediate bit to reduce flange and shaft size.

 

[daleyd]

I looked into this a while ago for a single phase bandsaw, the answers I got back from most places was no go. Normally I would have just shoved a 3 phase motor on and reduced the speed via VFD but this motor is a typical Chinese effort, doesn't conform to any standards so it would require I make up an intermediate bit to reduce flange and shaft size.

If only you had some means of doing this

 

[Hood]

If only you had some means of doing this

I do but it is not mine and they just decided to keep it running at the normal speed as they mainly cut aluminium.

 

[daleyd]

I do but it is not mine and they just decided to keep it running at the normal speed as they mainly cut aluminium.

Yeah I’d assumed there would be a good reason seeing as you could probably knock one up in the time it takes most of us to make a cuppa

 

[Hood]

Yeah I’d assumed there would be a good reason seeing as you could probably knock one up in the time it takes most of us to make a cuppa

It would have been a bit more complicated as I would have had to make a bobbin shaped section with a top flange bigger than the bottom flange and I would have had to have an adapter shaft which was supported by bearings, so an easy enough job but not dirt cheap.

 

[Gragson]

However I'd much prefer to swap a 3ph motor and vfd instead. Used motors plus chinese vfd's can be quite cheap.

Getting a 3ph motor to mate the cone spindle might take a bit of guessing / searching around, and may need mounting mods, although originally it was a 3ph.
If 1ph converters are sold, that work, what is the downside, just asking?

 

[Hood]

The answers I got back was they needed a very specific type of single phase motor and the usual suspects were not suitable and the one on the bandsaw certainly wasn't. There were Chinese manufacturers saying they had suitable products but I got the impression they were just saying that they would work and I decided to go with the advice from UK and USA manufacturers of such devices.

 

[Kram]

Downside is probably on your own trying to get it to work. However amazon prime returns are very easy so I would call it low risk to try.

Another option is change pulley sizes?

 

[Hood]

Downside is probably on your own trying to get it to work.

Another option is change pulley sizes?

Me or the OP?
If me then pulley swap wasn't an option as it was direct coupled to a gearbox.

 

[Kram]

My reply was to Gragson about the 1ph vfd, not many have used them. If it were a 3ph vfd, most of the forum have one or more

 

[Brad93]

PWM is the only way to do it but that isn't any good for torque as far as I know. I think it's what they use for fans?

VFD & Three Phase Motor

 

[m_c]

Speed controlling single phase motors can be done, but there are issues to overcome.

Single phase squirrel cage motors (aka generic induction motor) speed, is determined by the input frequency.
You can kind of kludge speed control with PWM, but it's not going to give a consistent speed under varying loads, as all PWM is doing is reducing current to the point the motor 'slips' more, but that is fraught with the problem you've reduced torque that much, the motor is just likely to stall as load is increased.

Then there is the problem of how the motor starts. A 3 phase motor always has poles pushing/pulling the motor. A single phase doesn't. They rely on various methods, but most common ones rely on a capacitor to create a lagging phase, which is used to power a secondary coil. If you change the frequency, you change the power and timing of the lagging phase, which could result in either the motor not starting, or the timing/power being such that it's fighting against the main phase, which is likely to result in loss of torque, and overheating.

Finally there is the smoothness issue. Once up to speed, a single phase motor relies on the rotor inertia to smooth out the power pulses. Due to being single phase, you only have power applied 50 times a second. Drop the frequency, you reduce how often those power spikes apply, along with the inertia in the rotor to smooth those spikes, and you can end up with some very noticeable vibration in the system.


And there is the fact the motor shown only has A class insulation, which isn't rated high enough for inverter duty, so could lead to the insulation breaking down due to an inverters switching frequency and transients, unless a suitable sine wave filter is fitted.

 

[Gragson]

Speed controlling single phase motors can be done, but there are issues to overcome.

Single phase squirrel cage motors (aka generic induction motor) speed, is determined by the input frequency.
You can kind of kludge speed control with PWM, but it's not going to give a consistent speed under varying loads, as all PWM is doing is reducing current to the point the motor 'slips' more, but that is fraught with the problem you've reduced torque that much, the motor is just likely to stall as load is increased.

Then there is the problem of how the motor starts. A 3 phase motor always has poles pushing/pulling the motor. A single phase doesn't. They rely on various methods, but most common ones rely on a capacitor to create a lagging phase, which is used to power a secondary coil. If you change the frequency, you change the power and timing of the lagging phase, which could result in either the motor not starting, or the timing/power being such that it's fighting against the main phase, which is likely to result in loss of torque, and overheating.

Finally there is the smoothness issue. Once up to speed, a single phase motor relies on the rotor inertia to smooth out the power pulses. Due to being single phase, you only have power applied 50 times a second. Drop the frequency, you reduce how often those power spikes apply, along with the inertia in the rotor to smooth those spikes, and you can end up with some very noticeable vibration in the system.


And there is the fact the motor shown only has A class insulation, which isn't rated high enough for inverter duty, so could lead to the insulation breaking down due to an inverters switching frequency and transients, unless a suitable sine wave filter is fitted.

Thanks for taking the time to explain it all out. Appreciated.

Given all those variables and potential compatibility issues, I don't think I'll even bother risking a look see, 3PH and VFD it is then..