AC Motor speed & direction control

[zacky]

Please, could some one explain how the Wash Machine's AC Motor ( with capacitor on it )speed and direction controlled ?
During the wash cycle, the motor rotates back an forth at low speed, while at spin cycle rotates at very high speed.
My question is how during the wash cycle the motor's speed is reduced and the rotation direction is reversed?

 

[waross]

During the wash cycle, the motor in most machines runs in one direction and the gearbox generates the back and forth movement.
The speed is controlled by reconnecting the windings to provide more or less poles.
The direction is controlled by reversing the polarity of the starting winding.
yours

 

[jraef]

While that is true of older machines, the new (expensive) energy efficient ones are using either small AC dives and 3 phase motors, or apparently some use BLDC dives, as witnessed by our friend itsmoked in a tangent started on Dec. 5th in this thread;

thread237-172357

JRaef.com
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For the best use of Eng-Tips, please click here -> faq731-376

 

[itsmoked]

Thanks jraef.

Zacky didn't specify really which style. In the top loaders the back and forth is created in a transmission (Agitation). And just as waross sez it is a fixed AC motor that turns one way to to agitate and pump water(which is valved to recirculate thru a strainer) and then turns the other way to spin and pump water(which is valved to drain). This style uses an AC motor and they just hook up the start part of the winding differently before starting to reverse it.

All front loaders use BLDC and they actually control the motor speed and direction via PWM. The speeds are profiled with acceleration curves etc..

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[zacky]

Thanks for your great help.
Also I noticed in the machine schematic a coil named " BRAKE/CLUTCH" what that coil for ?

 

[itsmoked]

Then you are talking a top loader.

The clutch/brake is to stop the 120lbs of rotating metal/wet clothes at the end of spins. Partly for safety and partly because there will be resonances in the area between wash speeds and reaching spin speed that will send a washing machine around the room like a super-ball. They want to force a rapid transition thru those regions.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[zacky]

well itsmoked,so could you please how that cluch/brake works ? is it mechanical system ?

 

[itsmoked]

Yes! Friction applied thru a clutch. In some cases I think they use the clutch to engage the motor to the gear train. Not sure. They'd do this because it would be hard to start a rinky-dink motor - agitator wrapped with clothes. I believe I have seen them start the motor and about 1/2 second into the start engage the transmission but this is speculation.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

You can usually hear the "clunk" when the clutch engages, especially as the washer gets older and the parts get sloppier.

BTW folks, this is hardly a professional engineering issue, be prepared for the inevitable red flag. I won't do it, but there are those more intent on keeping this forum clear of homeowner related postings.

 

[waross]

I have seen some washers with a centrifugal clutch to bring the spin up to speed.
respectfully

 

[zacky]

Sorry for the delay.I noticed that during the spin cycle the"BRAKE/CLUCH" solenoid is energized and pulling the arm of brake and preventing the motor from spinning.
Now I disconected one of the wires going to "BRAKE/CLUTCH" solenoid and now it is de-energized and the machine spins BUT AT LOW SPEED.
Is the problem the electronic control unit?

 

[waross]

The brake may be braking the ring gear of a planetary drive. There are a lot of different methods of driving the spin and the wash cycle and you will probably get several other guesses. Until you supply more information that is all you will get. Guesses.
yours

 

[stardelta]

Washing machine motors can be a law unto themselves. There are many many types and variations. My suggestion is you post the question in a Domestic appliance repair forum, remember to include the make and model of your machine. Here is a couple of good ones.

http://fixitnow.com/faq.htm

http://www.washerhelp.co.uk/diy-repair-help.html

 

[itsmoked]

I actually have good luck googling for appliance stuff. I would think somewhere someone will describe how the tranny on your model works or even years of your brand... They never change stuff.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com