Find number of pole pairs in Direct Drive hub motor easily.

[BareKuda]

This is mainly for direct drive hub motors.

1. Disconnect battery and charger to reduce chance of shorting something out while messing with phase wires. Ensure motor is free to rotate safely (wheel of the gound).
2. Disconnect any 2 phase wires.
3 Using a power source that gives about 5 amps, such as a 50 watt laptop power supply, connect one phase to negative and have a means to momentarily connect the other phase to positive.
4. Plug in the power supply and and momentarily connect the 2nd phase wire. The motor will jump to a pair.
5. Using a good reference, mark the tire with chalk or some suitable marker.
6. Rotate the motor a bit forward. Repeat step 4. If motor jumps back to the first mark, rotate motor forward twice as far as last time and repeat until it jumps to a new pole pair.
7. Continue around until you get back to start. You should see all marks are equally spaced.
8. Count the marks. In my case i have 26 pole pairs, or 52 magnets.

 

[spinningmagnets]

Very clever!

 

[BareKuda]

This also works with inrunner motors. Here is a surface mount 4 pole pair motor and a V-Type 5 pole pair motor. Some controllers need to know how the magnets are arranged because of flux weakening settings.

At first i was wondering how a QS3000 motor can have:
Magnets:Height 70mm, 40pcs, 5 pole pairs
But then see they put 2x 70mm magnets end to end to be 20x 140mm long magnets. Then they arrange those in a V shape so there are 10x V-type poles, which makes 5x V-Type pole pairs.

 

[Nixunen]

Or you can just short two phase wire together and start to spin wheel / motor. You "feel" each polepairs. So just spin wheel one full revolution / circle and count polepairs.

 

[BareKuda]

Or you can just short two phase wire together and start to spin wheel / motor. You "feel" each polepairs. So just spin wheel one full revolution / circle and count polepairs.

You cant feel the pole pairs by shorting two phases in a 26 pole pair hub motor. I already did that to test each phase for problems. All you feel is drag, not cogging.

 

[rew]

FYI, a lot less current is usually necessary.
Some powersupplies don't like being effectively shorted out. A current limited powersupply e.g an NiMh charger might be preferable.