How many Pole Pairs does a GM3506 actually have?

I am using the GM3506 from iPower.

Unfortunately the motor does not specify its number of pole pairs anywhere on the website, but motors of the same name are listed as 12N14P on Amazon and Aliexpress

Given that the motor (supposedly) has 14 magnets I would expect it to have 7 pole pairs (like mentioned here).

However, running the motor with the find_pole_pairs utility function returns 11 pole pairs and all the posts I’ve seen on this forum run this motor with 11 pole pairs in the config.

Does anyone know why there is this disconnect? Is this a case of bad datasheets, false advertisement, simpleFOC not finding the correct number of poles, or is my understanding of pole-pairs incorrect?

Much thanks in advance!

Hi @InfiniteArray , welcome to SimpleFOC!

No, I think you understand it correctly. 14 permanent magnets means 7 pole pairs.

I think this is likely the case - the iFlight website doesn’t list the motor’s configuration, unfortunately, but one apparent difference between the AliExpress and Amazon listings is the winding resistance - given as 5.6Ω on iFlight but 14.3Ω on AliExpress.

So perhaps this is also a case of the producer changing the product internally, but keeping the same product exterior.

Note also the AliExpress motor is a “GM3506-130T”, while the iFlight store lists it as just “GM3506”, so perhaps they aren’t quite the same model.

Of course its possible the pole pairs utility is getting it wrong, but if it is reliably returning 11 PP, and the motor works well with this setting in closed loop, then its likely to be correct.

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Adding another comment for posterity, in case anyone is googling it:
The GM3506 with 11 pole pairs is in a WYE configuration. You can initialize its phase resistance via:

BLDCMotor motor = BLDCMotor(11, 5.50f/2.0);

see the Phase resistance chapter in the wiki (Phase resistance | Arduino-FOC) for why you must divide the phase resistance by 2.