Control Washing machine motor with VFD

  1. 3000alloy

    3000alloy Member

    Messages:
    109
    Location:
    Ireland
    Just wondering from more knowledgeable people than myself. Can a washing machine motor be controlled with a VFD?

    The reason I ask, is I have a belt sander powered by said w/m motor, however the speed is very hard to control. It either wants to take of I to infinity or binds down when pressure is applied to the belt.

    There are no specs on the motor, all I know is it works of single phase.
    IMG_20201017_163907.jpg
     
  2. 3000alloy

    3000alloy Member

    Messages:
    109
    Location:
    Ireland
    I am currently using a basic voltage regulator (SCR) to control the speed.
     
  3. Hopefuldave Intergalactic pot-mender

    Messages:
    1,805
    Location:
    The Shed of Danger, surrey, England
    That looks like a wound-field (no permanent magnets) "universal" motor, if so it'll have a commutator and brushes lurking in one of the end bells (probably the end the wires enter through, There are two ways to wire 'em - "shunt" and "series" - series wound motors have *really* poor speed regulation and without a load can spin up to the point where they self-destruct, why? Under no load, the current in the armature drops and the series winding connection means that so does the field winding current - so there's little back-emf to resist rotation and it accelerates away. In "proper" motor controls the armature and field windings are parallel ("shunt") so there's always enough back-emf to stabilise the motor RPM (and like the series configuration, the field is deliberately weakened to allow high RPM). A simple (but a bit crude) remedy is to connect mains direct to the field winding, SCR-regulated to the armature windings, so there's always enough back-emf to stop the motor running away - or best is a controller designed for the job, which will compensate for load and speed settings, the KB Electronics KBIC series are pretty good but not that cheap and have separate terminals for the field and armature windings if using a wound-field motor, with a permanent magnet motor you use just the armature terminals.

    Dave H. (the other one)
     
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  4. bricol Member

    Messages:
    1,536
    N.Yorks, UK
    I've got a home made linisher running a similar motor. Slowed the belt down, and increased torque at the belt, by using a vee belt drive from motor to belts rollers.
     
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  5. 3000alloy

    3000alloy Member

    Messages:
    109
    Location:
    Ireland
    That's great info.
     
  6. 3000alloy

    3000alloy Member

    Messages:
    109
    Location:
    Ireland
    IMG_20201016_165011.jpg
    This the way I have it wired from the SCR. The earth is attached to the motor out of picture.

    So wire direct mains to field winding and SCR feed to armature. So where would the neutral connect? Leave as is?
     
  7. Hopefuldave Intergalactic pot-mender

    Messages:
    1,805
    Location:
    The Shed of Danger, surrey, England
    OK, this is a guess and needs a meter on Ohms to confirm, but it looks like 2 and 3 are one winding, 4 and 5 the other (as wired, it would go live into 5, through one of 'em, out on 4 and into 2, through the other winding and out on 3 to the neutral) - you could put neutral to 4 and 3, live to 2, SCR-controlled to 5 and if it runs the opposite way to what you want swap live and neutral on ONE of the windings. Don't have a go if it doesn't work! Try it with power applied for a few seconds, if it smokes switch off and have a scratch of your head... You could even test it on DC *very briefly*, if it's an universal motor it'll spin, just tap the battery/similar on in case it's not, don't want to smoke it!

    Dave H. (the other one)
     
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  8. 3000alloy

    3000alloy Member

    Messages:
    109
    Location:
    Ireland

    The way you described the wiring as shown is correct. I'll give it a quick shot 2m. That's great info.
     
  9. Agroshield Member

    Messages:
    1,393
    There's a German guy on YT, the Post Apocalyptic Inventor, who has some videos on using and controlling a washing machine motor. They might give you some insight.
     
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  10. Sammy7

    Sammy7 Member

    Messages:
    367
    Location:
    Sheffield UK
    Just finished my drill conversion yesterday. Managed to get a cheap kB electronics controller off flea bay. And an even cheaper treadmill motor (free). Works like a charm.
     
    • DF46A9E8-8657-4176-865C-5B22C7DBBB75.jpeg
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  11. 3000alloy

    3000alloy Member

    Messages:
    109
    Location:
    Ireland


    I see he uses DC instead of AC power to control the speed, independently through the coil and armature. I think I'll try DC before AC.
     
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  12. 3000alloy

    3000alloy Member

    Messages:
    109
    Location:
    Ireland
    So I have set the 3.3v to the windings and 26v to the Armature. Using my DIY bench DC power supply. Speed is controllable and stable using the voltage potentiometer. So in theory this should work the same with AC as @Hopefuldave has mentioned.

    Quick vid:


    However it has little or no torque.
     
    Last edited: Oct 18, 2020
  13. Hopefuldave Intergalactic pot-mender

    Messages:
    1,805
    Location:
    The Shed of Danger, surrey, England
    Am I readng the meter right in that video? 15v and 0.75A is not a a lot of power! Like 11 watts, an HP is 746 of 'em... What current is going into the field coils, at what voltage? You may beed to bump them both up quite a bit - W/Mc motors are designed to run fairly fast! You may have to do some reduction between motor and drive roller to get it into the speed range you want with enough torque...

    Dave H. (the other one)
     
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  14. 3000alloy

    3000alloy Member

    Messages:
    109
    Location:
    Ireland
    My video above was the test the theory of what the Apocalyptic Inventor said in the YouTube video. My diy power supply is from a old PC power supply with a boost convertor to 26v. It's very basic.

    I have a 48v DC power supply at 12.amp, I could try that and see if the torque is much better?
     
  15. johnser

    johnser Member

    Messages:
    2,132
    Location:
    North Cornwall
    Modern wm motors are indeed 3phase and should be controllable with an inverter. Not a standard universal motor though.
     
  16. 3000alloy

    3000alloy Member

    Messages:
    109
    Location:
    Ireland
    Ok so pin 2 and 3 are the windings. 4 and 5 are the brushes/armature. 6 and 7 tacho.
     
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