Help with a washing machine motor. - Page 1
Forum section: electronics / projects

author: avitsur
author_rank: Contributor
timestamp: July 11, 2021, 08:27:13 am
content: 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.

author: Benta
author_rank: Super Contributor
timestamp: July 11, 2021, 09:07:39 am
content: 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.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 11, 2021, 09:55:45 am
content: 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 everyvacuum cleanerin 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).

author: Benta
author_rank: Super Contributor
timestamp: July 11, 2021, 10:19:58 am
content: 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.

author: avitsur
author_rank: Contributor
timestamp: July 11, 2021, 10:43:53 am
content: Quote from: Siwastaja on July 11, 2021, 09:55:45 am

author: avitsur
author_rank: Contributor
timestamp: July 11, 2021, 10:58:42 am
content: 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.

author: Benta
author_rank: Super Contributor
timestamp: July 11, 2021, 11:38:51 am
content: Seeing the photo of the tacho generator, that machine must have been pretty dampAnyway, I see 8 terminals plus protective earth, total 9.This makes sense:Field low speed (washing)Field high speed (spinning)ArmatureTacho generatorSiwastaja is not saying it's a DC motor. It's auniversalmotor, meaning it will run on both AC and DC. He just suggested a method for testing it.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 11, 2021, 12:24:11 pm
content: 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.

author: richard.cs
author_rank: Super Contributor
timestamp: July 11, 2021, 01:15:22 pm
content: Quote from: Siwastaja on July 11, 2021, 12:24:11 pmYes, 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.

author: avitsur
author_rank: Contributor
timestamp: July 11, 2021, 01:26:14 pm
content: 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.

author: eblc1388
author_rank: Frequent Contributor
timestamp: July 11, 2021, 04:10:36 pm
content: 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.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 11, 2021, 04:21:43 pm
content: Quote from: avitsur on July 11, 2021, 01:26:14 pmStart 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.

author: Miyuki
author_rank: Frequent Contributor
timestamp: July 11, 2021, 04:27:34 pm
content: Quote from: eblc1388 on July 11, 2021, 04:10:36 pmIs this a reason they made a different sound in reverse?

author: eblc1388
author_rank: Frequent Contributor
timestamp: July 11, 2021, 05:10:30 pm
content: 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.

author: Benta
author_rank: Super Contributor
timestamp: July 11, 2021, 05:50:46 pm
content: Again, don't forget the tacho feedback. It's necessary.

author: eblc1388
author_rank: Frequent Contributor
timestamp: July 11, 2021, 06:13:12 pm
content: Thanks for the reminder, Benta.Connection diagram updated to include tacho feedback.

author: Benta
author_rank: Super Contributor
timestamp: July 11, 2021, 07:01:59 pm
content: 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).

author: amyk
author_rank: Super Contributor
timestamp: July 11, 2021, 07:35:26 pm
content: 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...

author: Benta
author_rank: Super Contributor
timestamp: July 11, 2021, 07:50:26 pm
content: 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.

author: eblc1388
author_rank: Frequent Contributor
timestamp: July 11, 2021, 07:55:33 pm
content: Quote from: Benta on July 11, 2021, 07:01:59 pmVery 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.

author: Benta
author_rank: Super Contributor
timestamp: July 11, 2021, 08:37:07 pm
content: Quote from: amyk on July 11, 2021, 07:35:26 pmNo 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.

author: amyk
author_rank: Super Contributor
timestamp: July 12, 2021, 12:28:54 am
content: Quote from: Benta on July 11, 2021, 07:50:26 pmAmerica. I've never seen (or heard!) a washing machine with a brushed motor.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 12, 2021, 12:48:40 am
content: The Post Apocalyptic Inventor had made a few videos on reusing washing machine motors:Quote from: Benta on July 11, 2021, 08:37:07 pmMust be quite a small machine for one day of clothes to fill it.

author: avitsur
author_rank: Contributor
timestamp: July 12, 2021, 04:24:01 am
content: 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?

author: Benta
author_rank: Super Contributor
timestamp: July 12, 2021, 11:12:13 am
content: Quote from: avitsur on July 12, 2021, 04:24:01 amNot 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.

author: richard.cs
author_rank: Super Contributor
timestamp: July 12, 2021, 11:24:47 am
content: When you say 1400 rpm, do you mean on the motor (not the washing machine drum)?That's quite a low speed. You could achieve that in shunt connected mode and not need to use feedback (in shunt mode the motor will tend to run at constant-speed like a permanent-magnet motor, in series mode it tends to run at constant-power and overspeeds at low loads).In the shunt arrangement the field winding is put in parallel with the brushes, possibly with a resistor or some electronics to limit the field current. I would be inclined to connect a 100 W tungsten lamp in series with the field, and then connect that to the mains input, and the brushes also to the mains input. Then wind it up slowly on a variac (or a large light dimmer if you don't have a variac) and see what speed you get. Find the size lightbulb that gives you the speed you want, and then you can replace it with some simple electronics to regulate the field winding.Of course if you really want constant 1400 rpm, then you would be better off with a 4-pole induction motor. The main advantage of a universal motor is that they can spin faster than synchronous speed, and thereby achieve high power in a small space. If you don't want to go fast then it's a relatively poor choice.

author: Zero999
author_rank: Super Contributor
timestamp: July 12, 2021, 11:31:19 am
content: Quote from: richard.cs on July 12, 2021, 11:24:47 amConsider, using a belt or gears, to reduce the speed.A small transformer, around 24V to 50V, could be used, to run the motor in shunt mode. Something, like a current monitoring relay, is a good idea, to cut the power to the armature and prevent overheating/speeding, if the field winding/transformer/wiring fails, for whatever reason.

author: amyk
author_rank: Super Contributor
timestamp: July 12, 2021, 01:38:33 pm
content: Quote from: richard.cs on July 12, 2021, 11:24:47 amNote that reducing the field current willincreasethe speed of a shunt-wound motor.Also, field windings for shunt operation will have finer wire and more turns than for series; attempting to use the latter in the former configuration can lead to the release of magic smoke...

author: Benta
author_rank: Super Contributor
timestamp: July 12, 2021, 01:59:51 pm
content: It's possible, but risky to try shunt mode. A couple of points to be aware of:- the windings on universal motors have very low resistance. You'll need some kind of current limiting for the fiels coils, and decrease the voltage to the armature (the brushes).- the motor will no longer run on AC, but only DC.

author: richard.cs
author_rank: Super Contributor
timestamp: July 12, 2021, 03:37:04 pm
content: My understanding is that shunt operation is an intended and supported mode in at least some washing machines, but probably not without some current limiting on the field winding. I have certainly used the motors in shunt on lower voltage DC, though it of course makes sense to measure winding impedances and/or bring it up slowly whilst watching current if trying to do this from full mains voltage.It will remain an AC/DC motor in shunt mode so long as your method of limiting the field winding current keeps the correct phase relationship. A resistive ballast will do this (hence the tungsten lamp suggestion), as will a PWM-based electronic solution.

author: Miyuki
author_rank: Frequent Contributor
timestamp: July 12, 2021, 06:13:47 pm
content: Quote from: NiHaoMike on July 12, 2021, 12:48:40 amI never realized how insanely fast this thing must run to reach 1000+RPM on the drumThat gearing ratio is huge

author: Benta
author_rank: Super Contributor
timestamp: July 12, 2021, 06:43:37 pm
content: Quote from: richard.cs on July 12, 2021, 03:37:04 pmI've never seen shunt operation, but there may be some rare washing machines that use it. Normally, if there are two field windings they are either serial or parallel for speed or torque, but still wired in series with the armature.Concerning shunt operation on AC: yes it can be done but power and torque will not be good. The problem is, that field and armature timing will be different to universal mode, where timing is "forced" by the series connection.The video posted by NiHaoMike is really good, by the way, and touches on all the points raised in this thread.

author: amyk
author_rank: Super Contributor
timestamp: July 13, 2021, 01:14:33 am
content: Quote from: Miyuki on July 12, 2021, 06:13:47 pmThat motor is insanely loud too, sounds more like a vacuum cleaner than a washing machine to me... are universal motors and the additional circuitry needed to control their speed going to cost less or more than an induction motor?

author: avitsur
author_rank: Contributor
timestamp: July 13, 2021, 03:54:59 am
content: Hi to all,I'm amazed by the amount of info given here and I would like to thank each and every one of you. now to work.

author: james_s
author_rank: Super Contributor
timestamp: July 13, 2021, 05:35:28 am
content: Quote from: Benta on July 11, 2021, 05:50:46 pmWhy? I have loads of devices powered by universal motors, none of them have tacho feedback. It's needed by the washing machine to regulate the speed under widely varying loads but it shouldn't be necessary to run the motor.

author: james_s
author_rank: Super Contributor
timestamp: July 13, 2021, 05:39:32 am
content: Quote from: amyk on July 13, 2021, 01:14:33 amThey're not really all that loud when installed inside the washer. Universal motors have been pretty standard on European washing machines for decades, they're used because it's easy to control the speed and the washers are front loaders and don't have a transmission like American washers have. It's really only in North America that induction motors are the norm, in top load washers with an agitator. Most modern washers I've seen have switched reluctance motors, I'm pretty sure some have BLDC and I suspect that will eventually be used in pretty much everything.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 13, 2021, 05:54:51 am
content: Quote from: Benta on July 11, 2021, 07:50:26 pmI have seen one, in an apartment building I lived in while studying, it was an old "industrial" machine, with three-phase supply. Likely has two windings, high-speed (likely 2 poles per phase) and low-speed (more poles). The obvious downsides of the induction motor, despite dual windings, is large size and lowish spinning speed, because the speed choices (for 50Hz) would be, for example, 600 and 3000 rpm. There was a separate machine for spinning the laundry afterwards, also used an induction motor but now geared for high RPM. That did a great job.People often forget mains frequency driven induction motors are very crappy, practically useless for all other purposes except constant-speed near the rated speed. This feature also makes "starting" them awkward.A VFD (inverter) fixes this fundamental problem. But a brushed motor does the same in a simple way (it's a mechanical "variable frequency drive"), and brushed motors can actually be very good if constructed well.So being able to generate acceptable torque with acceptable efficiencyat any RPMis one reason to use brushed motors (against fixed frequency AC motors), but another one is miniaturization, they can run with higher internal frequency, higher RPM, and thus, less iron. This is specifically why they are used in vacuum cleaners, compare the 1kW vacuum cleaner universal motor with an 1kW induction motor, the weight difference is like 0.5kg vs. 5kg! The exact same thing why 400Hz AC motors are much smaller for the power than 50 or 60Hz motors.

author: james_s
author_rank: Super Contributor
timestamp: July 13, 2021, 06:17:36 am
content: American washing machines always had induction motors, the only time I ever saw anything else was a couple of different European washing machines people had imported, the cute little front loaders that are common there were totally foreign here, no stores ever sold them and most considered them to be far too small.There were only 2 or 3 different companies that actually built them and they didn't really change at all on the inside from the 1950s up into at least the early 2000's when front loaders like the Maytag Neptune started to gain traction. The only real difference between a 1960 washer and a 1990 washer is the cosmetic skin, a nice thing about this is you can still buy most of the parts for even the very old ones. The induction motors are very reliable, I've never seen a washing machine motor fail. They have a mechanical transmission that is used to select between back and forth agitation and the high speed spin cycle. Shifting is accomplished by the oscillating mechanism referred to as a wigwag, it oscillates whenever the motor is running and carries a pair of solenoids that pull or push on a pair of sliding shift levers depending on which solenoid is engaged. About the only thing that ever goes wrong with these things is the seal on the agitator shaft and occasionally a wire breaks to the wigwag.

author: Benta
author_rank: Super Contributor
timestamp: July 13, 2021, 06:32:56 pm
content: Quote from: james_s on July 13, 2021, 05:35:28 amDid you even bother watching the video posted by NiHaoMike? Apparently not. It shows the issue perfectly, including the runaway behaviour of the motor. But OK, 17 minutes is a strain on attention span.No worries, the interesting part is between 1:00 and 9:30.

author: james_s
author_rank: Super Contributor
timestamp: July 13, 2021, 08:23:27 pm
content: No, I don't like watching videos, I'm busy and usually multitasking. It isn't a matter of attention span, it's simply not wanting to spend 17 minutes on something that could be conveyed in 10 seconds. Either way I've run lots of universal motors without tach feedback. If it runs away then run it at a lower voltage or make sure you keep a load on it.

author: Benta
author_rank: Super Contributor
timestamp: July 13, 2021, 08:59:13 pm
content: Didn't you just post two videos? 44 minutes and 30 minutes.Keep riding your hobby horse, but you're NOT helping the OP here.US washing machines are not relevant, sorry.The only thing we can probably agree on is, that US appliances are significantly different to European ones. That's fine. Let's leave it at that.Cheers.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 15, 2021, 09:25:10 am
content: Quote from: james_s on July 13, 2021, 08:23:27 pmI explained the speed runaway issue and the two possible solutions (feedback or asuitable(not any) mechanical load) also in my first post in this thread, it takes maybe 1 minute to read.

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2021, 06:03:24 am
content: Quote from: Benta on July 13, 2021, 08:59:13 pmSomebody said they had never seen an induction motor in a washing machine so after looking for a diagram and not finding one I found a couple of videos. You don't have to sit there and watch the entire cycle for 44 minutes, glancing at it for a few seconds shows you everything necessary to understand how the machines work. If you don't think it's relevant then ignore it.

author: amyk
author_rank: Super Contributor
timestamp: July 17, 2021, 03:45:40 am
content: I guess some people are just a little too eager to show how their country's appliances are better.Quote from: Siwastaja on July 15, 2021, 09:25:10 amThe washing machines that use them have a really huge ratio between the drum and the motor, 10:1 or more, and spins are >1000RPM, so >10kRPM is normal and not at all stressful for these relatively small motors. The guy in that video was just scared of turning it up all the way, he didn't even let it reach 10k!It doesn't look like it's easy to damage one by overspeed anyway; here's a video of one running full speed and theneven faster(!) by field weakening (which is definitely very hard on the brushes and commutator):

author: eblc1388
author_rank: Frequent Contributor
timestamp: July 18, 2021, 10:18:35 am
content: Checking my circuits collection I have found the following universal motor control circuit with speed feedback. The source is, unfortunately not known.

author: avitsur
author_rank: Contributor
timestamp: July 19, 2021, 04:21:40 am
content: eblc1388, thanx for the circuit diagram. I would like to ask two questions - 1. is it for 230Vac mains supply? 2. how do you control the direction of the rotation?

author: Zero999
author_rank: Super Contributor
timestamp: July 19, 2021, 09:51:05 am
content: Quote from: avitsur on July 19, 2021, 04:21:40 am1) The supply voltage will depend on the motor's rating.2) Reverse the connections to the brushes, to change the rotation.3) This is not a beginner friendly circuit.