Bldc motor commutation pattern

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cross mob
Not applicable
Hello all,

Will the commutation output pattern be differed for various pole pairs?

For example;
when we use 1 pole pair: mech revolution(360°)/1 pole pair= 360°, that means rotor travelled one full rotation. To activate six MOSFET's the six step commutation pattern: 360°/6=60°,that means for every 60° every hall sensor changes its state.

when we use 5 pole pair: mech revolution(360°)/5 pole pairs=72°, that means rotor travelled only 72°. To activate six MOSFET's the six step commutation pattern: 72°/6=12°,that means for every 12° the hall sensors changes their state.

In both scenarios will the commutation output pattern be same or different?

Thanks
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mbth
Employee
Employee
The pattern produced by the HALL sensors is dependent on the number of sensors, its positions and the number of poles of the rotor magnet. Every sensor has 2 states (e.g. hi and low) according to a detected north or south pole of the rotor magnet. Normally 3 120 degree phase shifted sensors are required to detect the correct commutation pattern. As you mentioned correct in your example if the number or stator matches to the rotor pole pairs the produced pattern will remain the same. Remark that the rotor speed calculated out of the HALL signals needs to be devided by the number of pole pairs.
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