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Thread: Bldc motor commutation pattern

  1. #1
    New Member New Member sai krishna is on a distinguished road
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    Mar 2017

    Bldc motor commutation pattern

    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?


  2. #2
    New Member New Member
    Infineon Employee
    Infineon Employee
    mbth is on a distinguished road
    Join Date
    Mar 2018
    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.
    The views expressed here are my personal opinions, have not been reviewed or authorized by Infineon and do not necessarily represent the views of Infineon.

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