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

[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.

[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: