Help with a washing machine motor.

[avitsur]

Hi,
I have a washing machine that we have replaced with a new one. it's motor is in good condition and I would like to make use of it. in order to determine the function of the wires connected to it - I've addressed the manufacturer of the motor "Nidec" in Italy. I found it very disappointing that they didn't even bother to reply. I wonder if a member of the forum have experience with a motor like this and shed some light. attached a pic of the motor's label.
Thanx.

[Benta]

Universal motor, very common in older washing machines. Controlling it is not easy. It should have a tacho generator on one end for speed feedback, without that it's uncontrollable.

The most used controller IC was the Motorola TDA1085C, search for a datasheet to see what you need to do.

[Siwastaja]

Universal motor works with DC supply fine so it's very easy to get spinning. Try it with a few 12V batteries in series or something, just don't go nowhere near the nominal voltage (maybe max 50V) without substantial mechanical load.

What Benta says about controllability is correct in the sense that in a series wound motor, the field and armature current are the same (in series) which makes it spin to almost unlimited RPM given even near the nominal voltage, possibly self-destructing in the process.

Careful feedback is indeed one way of dealing with it, other, most commonly seen in almost every vacuum cleaner in existence, is just having a mechanical load that has a characteristic of extorting increased torque per increased RPM, like a fan does. So it would work fine as a motor driving a large fan, water pump, etc. for example.

Basically it's a brushed DC motor where the direction of rotation is always the same regardless of polarity, hence making it also work with AC (since the different polarity semicycles both drive it in the same direction, only causing pulsating torque, not nice but acceptable). If direction change is needed, internal connections need modification (i.e., with armature and field windings in series, the polarity of either one, but not both, needs to be swapped).

[Benta]

Concerning reversal, my guess is that the armature and field windings have separate terminals on this motor. A washing machine needs to go in both directions.
All in all, probably 6 terminals coming out:
Armature (2)
Field (2)
Tacho generator (2)

Cheers.

[avitsur]

Universal motor works with DC supply fine so it's very easy to get spinning. Try it with a few 12V batteries in series or something, just don't go nowhere near the nominal voltage (maybe max 50V) without substantial mechanical load.

I'm confused a bit. you are saying that the motor is a dc motor, but on the label (upper right corner) it's stated "230-240v 50-60Hz" which I think indicates that it's an ac motor. I wish that Nidec would have been more polite.

[avitsur]

I hope that it will help. attached three pics- one of the tacho at the rear end, pic of the wiring harness leading to the motor (is there a convention in the wires colors or any manufacturer to himself?) and a pic describing one of the two brushes.
Thanx.

[Benta]

Seeing the photo of the tacho generator, that machine must have been pretty damp

Anyway, I see 8 terminals plus protective earth, total 9.

This makes sense:
Field low speed (washing)
Field high speed (spinning)
Armature
Tacho generator

Siwastaja is not saying it's a DC motor. It's a universal motor, meaning it will run on both AC and DC. He just suggested a method for testing it.

[Siwastaja]

Universal motor is one that spins in the same direction regardless of the polarity of applied voltage. So it makes no sense to call it either DC or AC motor.

It runs smoother on DC. Slightly better efficiency as well. With AC, the torque ripples because the thing turns on and off sinusoidally 100 or 120 times a second.

But AC is what comes out from the socket so that's why it has AC ratings printed on it. It's the simplest and cheapest use case, it makes no sense to rectify and smooth the voltage with capacitors just to give a bit smoother motor operation, besides you could use a different type of motor then.

Seeing it has separate field windings with all connections exposed, you can use it more like a SepEx motor, that's probably how it was originally used anyway.

In any case, the key idea is that both Field and Armature needs to have voltage applied. Either from separate power supplies, or wiring them in series. Direction of rotation is defined by the difference of the polarities. If both polarities swap at the same time, like when driving them in series from mains, rotational direction does not change.

[richard.cs]

Seeing it has separate field windings with all connections exposed, you can use it more like a SepEx motor, that's probably how it was originally used anyway.

Yes, often they are connected series (with tacho feedback) for fast spinning and shunt for slow tumble.

If run on DC you can get full power at less than the rated AC voltage because the winding impedance is lower, often something around half. They will turn on 12V DC in both shunt and series modes, though power output will be very low.

[avitsur]

Siwastaja - sorry, I didn't understood right your previous response. it much clearer now. I would like however to ask, if it's not too much a trouble for you - if you can draw a free hand sketch how to wire the motor preferably using the two speeds if possible and reversing it's rotation direction.
Thanx.

[eblc1388]

It seems that you can have choices of two speeds and two directions of rotation. In reality, you don't. Most high speed universal motors are constructed in such a way that their brushes are shifted from the electrical axis to reduce sparking caused by armature reaction. So they can be operated in one direction only. If one try to operate it in high speed in the other direction, it would result in severe sparking at the brushes. At very low speed, this brush shifting does not cause any problem.

So you can really have three choices. Low speed rotation in both directions and high speed in a particular direction.

To change motor direction, a double pole double throw(DPDT) switch can do the job by changing the direction of current flowing in the armature.

To change motor speed, a SPDT switch can be used. If the full portion of stator winding is place in circuit, the motor rotational speed is relatively lower than only part of the winding is used.

[Siwastaja]

Siwastaja - sorry, I didn't understood right your previous response. it much clearer now. I would like however to ask, if it's not too much a trouble for you - if you can draw a free hand sketch how to wire the motor preferably using the two speeds if possible and reversing it's rotation direction.
Thanx.

Start by connecting battery + to either of the Armature terminals. Another Armature terminal to either one of the Low speed Field terminals. The remaining Low speed Field terminal back to battery -. See what happens.

[Miyuki]

It seems that you can have choices of two speeds and two directions of rotation. In reality, you don't. Most high speed universal motors are constructed in such a way that their brushes are shifted from the electrical axis to reduce sparking caused by armature reaction. So they can be operated in one direction only. If one try to operate it in high speed in the other direction, it would result in severe sparking at the brushes. At very low speed, this brush shifting does not cause any problem.

Is this a reason they made a different sound in reverse?

[eblc1388]

Possibly. Usually the brushes are mounted at an angle to the commutator segments so friction is different in rotation directions. Or maybe the different sound you have heard is due to heavy sparking at the brushes.

@avitsur: the connection diagram you asked for.

[Benta]

Again, don't forget the tacho feedback. It's necessary.

[eblc1388]

Thanks for the reminder, Benta.

Connection diagram updated to include tacho feedback.

[Benta]

Almost there (I'm not trying to annoying, honestly).
Now S2 just needs to be changed to a DPDT switch. The second pole being necessary to tell the controller if the motor is wired for high- or low speed (by scaling the tacho signal accordingly).

[amyk]

How long do the brushes usually last on those?

Here, washing machines commonly use induction motors and the motor is almost never the first part to fail.

Also, Nidec is Japanese, not Italian...

[Benta]

Where's "here"?
Must be an interesting place. Personally, I've never seen a washing machine with an induction motor. Today, it's mainly BLDC, but cheap machines still use universals.

[eblc1388]

Almost there (I'm not trying to annoying, honestly).
Now S2 just needs to be changed to a DPDT switch. The second pole being necessary to tell the controller if the motor is wired for high- or low speed (by scaling the tacho signal accordingly).

Very true. 

In fact, I would rather S1 and S2 be SPDT signal switches going to the speed controller and the original S1 & S2 replaced by relays directly controlled by the speed controller instead.

The speed controller can then coach down the motor speed before reversing rotation direction and possibly prevent wrong rotation in high speed mode.

[Benta]

How long do the brushes usually last on those?

No idea. These are consumer machines.
In our two-person household, the washing machine ran almost once a day, each wash taking around one hour. It ran for 20 years before the program timer gave up and we got a new machine.

Say, 300 days/year x 1 hour x 20 years = 6,000 hours. Might have run to 10,000 hours.

Not bad, actually.

[amyk]

Where's "here"?
Must be an interesting place. Personally, I've never seen a washing machine with an induction motor. Today, it's mainly BLDC, but cheap machines still use universals.

America. I've never seen (or heard!) a washing machine with a brushed motor.

[NiHaoMike]

The Post Apocalyptic Inventor had made a few videos on reusing washing machine motors:

In our two-person household, the washing machine ran almost once a day, each wash taking around one hour. It ran for 20 years before the program timer gave up and we got a new machine.

Must be quite a small machine for one day of clothes to fill it.

[avitsur]

Hi,
Thanx for the drawing. I intend to use it with ac (mains) supply. at the beginning of the post, I was offered by Benta to use TDA1085C for the speed control circuit. since I need a fixed speed of ~1400rpm, I would like to ask if there is a simpler option?

[Benta]

Hi,
Thanx for the drawing. I intend to use it with ac (mains) supply. at the beginning of the post, I was offered by Benta to use TDA1085C for the speed control circuit. since I need a fixed speed of ~1400rpm, I would like to ask if there is a simpler option?

Not really. Regardless of whether you need fixed speed or variable, you still need a controller. That's just the way it is with universal motors. Unless you can define your mechanical load so that it fits exactly to the speed/torque characteristics of the motor.
I'd say building a controller is easier.