4 Pole motors / esc's

[johnrobholmes]

I am wanting to use a 4 phase brushless motor for my motion control (robot). It seems that it would have much greater low speed power and control as compared to a 3 phase motor (or am i wrong?). There seem to be no ESCs that support this, so my guess is that I will have to build my own. It could control two brushed motors as well, if I could program that well. I am a few years away from this knowledge though- first year EECE student here. It excites me to think that I could do this for myself!!

Is this available for RC use and I have missed it, or is there no real need for it?

I will be turning my own motors soon, as I am in the hunt for a large lathe. This way I could use almost any scrap stator and wind a 4 or 3 phase motor AND have the controller too. I have many years to spend on this, so im not in a rush to get one produced.

In actuality, my end motives are to build a dual hub motor cycle as a "school" project. I think I could build a usable and beautiful machine before it is all over, just for fun.



Dang, my head is running a million miles an hour tonight :rolleyes: Gotta go brush up on trig now.

[Miami Mike]

Never forget the sign of the sine, or you'll go off on a tangent.

[Trevor_G]

You need to be very careful with definitions with brushless motors it can be very confusing. What exactly is the configuration of motor you have?

The term phase is not usually used to describe brushless motors. Rather it is the poles.

The first brushless motors (inriders) used 3 electro-magnetic poles on the stator and two permanent magnet poles on the rotor. These were refered to a three pole motors - refering to the stator.

With the advent of outrider motors people started building motors with many permanent magnet poles. As a result the number of poles now very often refers to the number of permanent magnet poles.

For example the Mega series of inrider motors has six permanent magnet poles on the rotor. In the documentation it is refered to as a six pole motor and references the standard inrider motors are as two pole motors.

This actually makes more sense as all brushless model motors have three electromagnetic poles on the stator.

The important point here is that the ESC is connected the three electromagnets on the stator. So the same speed controller can be used on any motor configuration of the appropriate current rating. The only difference is that the controller runs at differentspeeds.

eg. a six pole Mega running at 20,000rpm will have the speed controller running through the poles at the same rate as a two pole Lehner motor running at 60,000rpm.

I hope the above makes some sort of sense:D

A brushless ESC driving 3 stator coils requires 6 MOSFET switches. Increasing that to 4 would increase the number of switches to 8 without any significant advantage. Given that the MOSFET switches contribute most of the size and cost of ESC why bother?

Which brings me back to the question what is the configuration of your motor?

Trevor

[Miami Mike]

The brushless motors that we use in our models are actually three-phase AC motors. The three-phase alternating current that powers them is synthesized by our brushless ESCs. I see no reason why a four-phase motor couldn't be designed and built as well, although I can't say whether or not it would offer any advantage.

As far as what the configuration of his motor is, I could be wrong, but I gather from his post above that he hasn't built it yet.

[vintage1]

You need to be very careful with definitions with brushless motors it can be very confusing. What exactly is the configuration of motor you have?

The term phase is not usually used to describe brushless motors. Rather it is the poles.


They are 3 phase motors. Tht refers to the signals applied to the three wires coming out.



The first brushless motors (inriders)
[
Inrunners. Inridrers and outriders are the motorcyclists that perform escort duty to presidents and other big cheeses.

used 3 electro-magnetic poles on the stator and two permanent magnet poles on the rotor. These were refered to a three pole motors - refering to the stator.


No those are referred to as 2 pole motors.

With the advent of outrider motors people started building motors with many permanent magnet poles. As a result the number of poles now very often refers to the number of permanent magnet poles.

For example the Mega series of inrider motors has six permanent magnet poles on the rotor. In the documentation it is refered to as a six pole motor and references the standard inrider motors are as two pole motors.

This actually makes more sense as all brushless model motors have three electromagnetic poles on the stator.

The important point here is that the ESC is connected the three electromagnets on the stator. So the same speed controller can be used on any motor configuration of the appropriate current rating. The only difference is that the controller runs at differentspeeds.

eg. a six pole Mega running at 20,000rpm will have the speed controller running through the poles at the same rate as a two pole Lehner motor running at 60,000rpm.

I hope the above makes some sort of sense:D

A brushless ESC driving 3 stator coils requires 6 MOSFET switches. Increasing that to 4 would increase the number of switches to 8 without any significant advantage. Given that the MOSFET switches contribute most of the size and cost of ESC why bother?


He gave the reasons. Possibly better starting torque.

[Miami Mike]

Gotta go brush up on trig now.What famous triangle has three angles that add up to more than 180 degrees? :p

[johnrobholmes]

The motor has not been built yet, and it may never be built (especially if there are no esc's :) )

Configuration is in the air- I dont know enough about motor theory to get my idea into a cad file. Lots of poles, lots of size. I am thinking 4 phase will give a very strong start and holding torque, you can lock the motor down with balanced feilds, giving it a solid hold like a stepper motor.