what is the difference between a 2 pole, 4pole or whatever pole?

[crazyjr]

I don't know if its been dealt with here before, But i was wondering what the difference between the various pole designs. I am getting into the design aspects ( reading) and figured i'd start with the basics. If this has been dealt with, Can i get a link?

[Maxxman]

the more poles the more torque.

sorry i can't be any more helpful.

[Serum]

It are the amount of N-S poles the magnetic rotor has. A 4 poler has got two N and two S poles. (put like NSNS)

[zeropointbug]

Don't forget coils as well, a 2 poler has 2 coils per 'phase' (motor wire), so 6 coils total. Likewise a 4 poler has 4 poles per phase, so 12 coils total.

[Serum]

I don't think that's the case.

[zeropointbug]

Unless brushless DC is different than multi-phase AC motors, I am pretty sure that is what it is, # of coils.

[Serum]

It might be, but it's not necessarily made that way. My bigmaxx had 12 coils though.

This has some interesting theories, not only about 2 and 4 poles.

http://www.allaboutcircuits.com/vol_2/chpt_13/6.html

[zeropointbug]

That's interesting, I am not familiar with the way it terms a few things though, for instance # of poles. In the industry, when someone refers to a motor having 4 poles, I have always known it being 4 poles per phase, times the # of phases you are driving.

It also says a brushless DC motor has square back EMF waves, how can that be? It's a natural movement and a natural wave would follow.

[crazyjr]

that would explain the Neus being so expensive, double magnets AND double coils;)

edit: I was reading the above link and am wondering, how Novak got away with three sensor wires, the pic on link shows 4 sensors

[zeropointbug]

Well it doesn't really make them more expensive having more coils, as it's generally the same amount of copper inside the stator as a 2 pole. I am just a little confused right now with the 'terms' various manufacturers are using, and the article Serum posted... we know how these motors work, it's just kinda lost in translation right now. :032:

IMO, I am pretty sure the Neu's have double the coils as a 2 pole motor, otherwise why would the turn count be so low. We should get to the bottom of this kind of stuff and make a sticky thread, Serum?

[BrianG]

Originally Posted by zeropointbug

It also says a brushless DC motor has square back EMF waves, how can that be? It's a natural movement and a natural wave would follow.

lol, it seems I was having this exact discussion with someone else recently. Actually, I believe the back EMF pulses will be an odd-shaped square wave with a larger pulse on the front end and taper down. You have to remember we are not feeding sine waves to the motor. When using sine waves, the field does not collapse as hard since you aren't totally removing voltage at once. You're probably thinking of variable frequency drives?

[zeropointbug]

Yes, I guess I am more accustomed multi-phase induction motors, I know the back-EMF for these are pure sine wave.

I can't remember what thread it was but you were saying the same thing, that it would not be sine wave.

Oooh how I long for induction motors for R/C! :027:

[BrianG]

Well then, get designing and release some motors and ESCs already! :)

[zeropointbug]

Maybe Brian, just maybe, someday. That will need an electronics degree of course. :p

[BrianG]

Naw! You have the vision, you just need to find someone with the skill. You think Bill Gates actually programmed Windows?