Determining motor pole count
If magnetic pole count of permanent magnet AC/BLDC motor is unknown, there is an easy way to determine it experimentally.
Needed items:
- 3 phase AC/BLDC motors
- Adjustable lab DC power supply
Procedure:
- Wire DC power supply + and - wires between any of two leads of the motor. I.e. + to A and - to B while C is not connected.
- Use the PSU to drive some DC current to the windings. Don't exceed motor's current rating. A good starting value may be 20-30% of motor continuous current. Now motor should start holding position as the rotor's magnets snap to the driven windings.
- Rotate motor shaft by hand or tool and count the distinct snapping positions per one revolution.
- Motor pole count is twice as much as the number of snapping positions found in the previous step. I.e. if motor snaps 2 times per revolution, it means that motor has 4 magnetic poles.
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