what is the difference between a 2 pole and 4 pole brushless motor ? - RC Groups
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Dec 29, 2009, 08:31 PM
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what is the difference between a 2 pole and 4 pole brushless motor ?

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Dec 30, 2009, 08:00 PM
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MarcRacer18's Avatar
Two pole has two electromagnets, 1 north, 1 south.
Four pole has four electromagnets, 2 north, 2 south.
Four pole motors have a north-south-north-south configuration.

Standard brushed motors have 3 poles, some up to 9 poles. Brushless motors go from 2 poles all the way up to 8 poles.
Dec 30, 2009, 08:55 PM
NeverAgainVolunteerYourse lf
nick_75au's Avatar

"Poles are the number of sets of three-way electromagnetic windings that a motor has.

In the simplest three-phase motor, there are 3 separate electromagnets formed by the single set of three-way windings. Thus, there is a set of North-South electromagnetic poles formed. This motor is said to have "2 poles" (although strictly speaking, the motor has 6 electromagnetic poles).

As the three voltage phases, each 120 degrees off from one another, gradually rise and fall, the strength of each electromagnetic winding set rises and falls in relation to the frequency of the voltage changes. This causes the rotor to rotate once per voltage cycle. In a 60 Hertz system, this results in a base speed of 60 Hertz, or 3600 rpm. A 50 Hertz system has a base speed of 3000 rpm.

The next most complex motor has two sets of three phase windings, and is called a "4-pole motor". It is the most common motor produced, and has a 60 Hertz base speed of 1800 rpm (the 50 Hertz speed is 1500 rpm).

6-pole motors operate at 1200 rpm (1000 rpm at 50 Hertz). 8-pole motors operate at 900 rpm (750 rpm at 50 Hertz). "

OK I copied this from somewhere else but its in simple terms, discusses AC motors and brushless motors operate on a similar principle.
The hi lighted section is relevant because brushless ESCs are variable frequency and along with PWM are able to vary the speed of the motor.
As can be seen more poles means slower motor given voltage and frequency remain the same.
As brushless motors are Permanent magnet machines some of the quoted material doesn't apply so its possible to have a 2 pole motor faster than a 4 pole motor due to different winding configuration {more turns}

Dec 31, 2009, 12:02 PM
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which is better for an rc speedboat ?
Dec 31, 2009, 05:11 PM
NeverAgainVolunteerYourse lf
nick_75au's Avatar
Number of poles is probably only a minor consideration, better to look at Kv and torque needed (determined by size of boat).
I'm not an FE guy but I believe most of the motors used are 2 pole motors, they calculate on spinning the prop at 30 000 to 35 000 Rpm and match voltage to Kv to achieve that figure.
If you post details/ pic's of the boat in the Fast Electric boats section you will get some knowledgeable guys helping you out

Oct 17, 2014, 06:08 PM
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some motor says like this Number of Poles: 12/14 and some 22 pole so the higher pole is better ? what does the poling do like left more r stronger ????
Oct 18, 2014, 01:03 AM
Registered User
Given that a 2 pole and a 4 pole inrunner brushless motor have the same number of windings, diameter can and rotor magnetic and are running on the same voltage, the 4 pole motor will produce more torque at a more constant thrust per revolution of the rotor.

They will also perform better at lower PRM speeds due to the number of pulses on each revolution.

Out runner motors run better at the lower PPM’s due to the number of increased poles around the fixed magnetic and also produce higher torque values at lower RPM’s.
Oct 19, 2014, 11:42 AM
Registered User
You must be forewarned that most ESC for brushless motors are set up for 2 pole motors from the factory and must be reprogrammed for 4 pole motor use. I some cases the speed control will not function with a 4 pole motor unless reprogrammed.

Also when first setting up a motor in a new boat and prop combination, set the timing of the motor to zero to start with and then test run the boat as you increase the timing in steps.

Your best torque and speed combination will be at zereo timing.

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