Stator theory 101

[buzbybixby]

Can someone tell me why stators are put together using several thin metal stator pieces glued together? Would it make any difference if you machined a 5mm thick stator for instance insted of using (5) 1mm thick metal stators?

Buz

[hansel]

Can someone tell me why stators are put together using several thin metal stator pieces glued together? Would it make any difference if you machined a 5mm thick stator for instance insted of using (5) 1mm thick metal stators?

If you use one big chunk of metal, as the metal moves through a magnetic field, electrons swirl around in the metal, like water in a stream swirling around a rock. These are called eddie currents. These currents causes heat in the stator which is wasted energy and actually make it harder for the motor to turn. Making the stator out of thin plates prevents the eddie currents.

[Q]

The eddie currents are also the reason why the plates should be insulated from each other. This part is often overlooked.

[buzbybixby]

Thanks guys, I've got it now

[3DMomo]

I was talking to my physics Prof. about the discussion here and I asked him what would possibly happen if we were to wind our motors using sectioned pieces of coil such that the magnetic field produced would result in lesser Eddie currents much like the sectioned stator. He said it was an interesting idea and that doing so would also result in smaller mechanical displacement when high currents are passed through the coils. This is particularly interesting to those making larger motors where such factors are a problem. Anyone know how this would affect the motor? Would there possibly be an increase in efficiency?..

[Jay C]

Could you draw up a sectioned winding? I can't picture it.

Jay

[3DMomo]

So basically you make Coil (A) 9T (Or however many you need) then Coil (B) 9T as well followed by (C) and (D)...Your left with 4 starts and 4 ends. Put all the starts together as one. Once your done your other two arms (9 arm stator), you put all the ends of the 4 coils together. This is phase one so in an ABCABCABC wind A would be done. Once you’re done the other 2 phases the rest is just like normal, wye or delta it's up to you. Altogether this motor would have 36 9T coils in 3 phases.


Hope this helps.
Mo

[hansel]

This looks very similar to winding 3 or 4 wires at a time except that the 4 wires are usually just wound together so you don't end up with different sections of coil for each wire. It lets you use smaller wire, so you can get tighter coils and the 4 wires are combined in parallel to cut the total resistance. It's a substitute for using one thick wire.

I don't think it has any effect on eddie currents though. Does it?

[Jay C]

Like hansel said this is parallel windings. It is used when you would rather use (or don't have any other wire) thin wire. Thinner wire is easier to wrap but multiple strands are hard to manage. I see no advantage to what you are trying to address as the frequencies we are at are well below any skin effect frequencies.

My 2 cents,
Jay

[3DMomo]

Yeah no doubt that this is "like" winding multiple strands, but it's actually not. The magnetic field produced by the sectioned coils must certainly somehow be different in a separated coil rather then using multiple strands. Parallel strands wound over one another will not give you the same field.

[Jay C]

Why not? The flux is determined by the amps times the number of turns and the saturation of the iron. Do you have some formula that show the flux lines produced by four coils is any different than that produced by 1 larger one?

[hansel]

In practice I don't think you would see a difference. If you really get into the details, then the 4 parallel windings have 4x the slope as they twsit along the stator as compared to the seperate windings and that will give you a SLIGHTLY different field.

[Jay C]

Different better (ie stronger) or different worse (weaker)? Our main concern is the amount of flux.

[hansel]

Different better (ie stronger) or different worse (weaker)? Our main concern is the amount of flux.

Using a wire gauge (not sure the number) that would allow that many turns on a stator, and some crude approximations, I get that 3DMomo's wind would be 0.5% better. I'm sure there are other factors that will change the motor more than that.

[3DMomo]

Me.. I'm actually not too sure exactly what winding like this does. All I know is that doing so would be much like sectioning a stator, which is the topic. My physics Prof. did however say that the greatest influence winding like this would have on a motor, would be the mechanical displacement which would occur in the coil when higher currents are applied. On my behalf, this is just a thought.



Mo

[hansel]

My physics Prof. did however say that the greatest influence winding like this would have on a motor, would be the mechanical displacement which would occur in the coil when higher currents are applied.

By mechanical displacement, do you mean the wires actually moving on the stator? It seems like a varish or some other material to bind the wire down could be applied to stop that.