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difference between 2 Inverter Washing machine motors

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I have 2 washing machines at the moment a Samsung series 5 9kg and a 10 years old Hotpoint 8Kg and both have brushless induction motors.

The hotpoint machine is ultra quiet when washing, you just hear the clothes sloshing round in the drum . - its been like that from new , so its not the fact that the motor has 'worn in' and got quieter over time.

The Samsung one sort of like 'whirrs' as its revolving  and no water in the drum . the Samsung washing machine has a feature that weighs the clothes at the beginning of every wash , with no water in the drum just clothes going around dry in the drum for about 10 seconds or so , and weight the clothes and adjusts the time of the wash and (I presume measures the dose of liquid because its an auto dose machine) - now the hotpoint  washing machine does not do this , it just fills up the drum with water and as the drum is filling up with water (and detergent/powder from the soap drawer) and revolves ultra quiet. 

so I observed as well this whirr that takes place also takes place when the Samsung washing machine is spinning as well ... or rather when it is slowing down from spinning .  and i also notice that the drum (seems) to slow down quicker from spin that the hotpoint does. - This is leading me to come to a conclusion that maybe its not an issue of the actual motor (as all induction motors should work in the same way I would imagine?) - its got me thinking now if the actual motor control board maybe has components in it to operate in a way of synchronous  or some kind of electronically 'braking the drum' after spinning to make the drum slow down after a fast spin and that maybe this 'electronic way' of braking the drum / reducing its spin speed after it has spun is making this whirring noise that I dont get with the Hotpoint washing machine? 

What do you reckon, could I be right? - have you heard of washing machines using components on the motor control board to 'brake' the drum to make it slow down quicker after a spin? 

 

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Hi Andy. Yes you can slow an induction motor down rapidly. I think they just give it a burst of reverse power, so it tries to run the opposite way. 
 

I wouldn’t have thought it would be good for a motor to try to run when it’s already spinning in the opposite direction. I also can’t think of the point of it. 

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4 minutes ago, Whitegoodshelp (Andy) said:

Hi Andy. Yes you can slow an induction motor down rapidly. I think they just give it a burst of reverse power, so it tries to run the opposite way. 
 

I wouldn’t have thought it would be good for a motor to try to run when it’s already spinning in the opposite direction. I also can’t think of the point of it. 

Thanks Andy for the reply , oh well at least that is one explanation. That sounds exactly what it is doing. Only thing I can think of why they are doing that then is to shave off (a very miniscule but none the less) time off the wash before it gets to its next stage so :

When spinning in the Rinse cycles , slow it down so the drum can start filling up quicker, rather than having the rinse water enter the drum while the drum is still spinning fast..

and 

In end spin cycle slow down the drum quickly so that the wash cycle can finish quickly so door can open to get washing out. 

In any case if thats what its doing it is causing the machine to whirr as it slows down / reverses the motor as its slowing down on an (which should be nice quiet and smooth) induction motor (which it would be if it didnt have the reverse applied to it as its slowing down) 

Don't get me wrong , its not a 'shrill' like you would get with a carbon brush motor, no-where near it, but it still makes a whirr , whereason the Hotpoint where it does not sound like its got any electronic means of braking  when the drum is slowing down after a spin / when power is cut to the motor, then it slows down nice and quietly and smoothly. 

I suppose to most users they would not give a second thought to it , I am most probably only noticing it because I have got the slightly more quieter Hotpoint washer even though both have brushless induction motors - if I had just the Samsung (and was coming straight from carbon brush type washing machine) I would most probably be saying how fantastically the Samsung washing machine is compared to our last one 😄




 

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Now that sounds pretty noisy Andy, what have you got in there? What is that thumping noise? It seems to me that it is only half-heartedly trying to spin, or just energising spin for a second. Possibly because the load seems a little bit unbalanced, and it's not confident enough to go into full spin?

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2 hours ago, Whitegoodshelp (Andy) said:

Now that sounds pretty noisy Andy, what have you got in there? What is that thumping noise? It seems to me that it is only half-heartedly trying to spin, or just energising spin for a second. Possibly because the load seems a little bit unbalanced, and it's not confident enough to go into full spin?

I did amplify the sound through audacity because the phone's camcorder did not pick up the whirring hardly at all - but I wanted to relay that noise. 

The thumping is the clothes as they brush past the little lip top of the door gasket , because the washing machine 'weighs' the clothes dry ... if they were wet, or rather when they are wet you dont really hear them rubbing past that lip. I am presuming the lip is there to stop garments from getting caught between the door gasket and the door glass bowl. So if something did get stuck between the rubber door gasket and the glass door the lip would just push the clothes into the drum instead of getting stuck. I think thats what the lip on the rubber door gasket is there for anyway?
And in fairness on that video I had 'overloaded' the drum as well that cycle before recording it so thats also a reason why it knocked on that lip. So if I load the drum correctly you dont get that thump/knock ... but the whirr noise is the one I am surprised about especially with an invertor motor - but cannot yet make out if the whirr is from the motor itself or the electronics of the motor driver board sending the noise down through the motor.
 

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21 hours ago, andyr12345 said:

in fairness on that video I had 'overloaded' the drum

It's very difficult to overload such a big drum Andy. If the laundry was wet, they'd have possibly settled down a bit more.

 

It's always difficult to judge noises on recording and videos because they all use automatic level control, which essentially compresses the sound. It makes some noises that are fairly quiet in the room seem much louder on the recording.

My impression is that the motor is trying to spin, so the motor gets spin power, but instantly the sensors sense that it's not very well balanced and cuts power to the motor. It keeps trying over and over with same results. So the whirring noise is just the motor spinning for half a second and then losing power.

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