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Effect of Motor Design Parameters on Cogging Torque – Part 2

Reduction of cogging torque helps in reducing the motor noise generated due to electromagnetic causes.

Shape of Magnet

  • Magnet shaping will change the airgap flux profile and hence the harmonics.
  • Elimination or reduction of certain harmonics will lead to lower cogging torque.
Uniform Ring Vs Shaped Ring
Cogging torque in 10-Slot / 4-Pole motor

Size of Slot Opening

  • Smaller slot opening offers lower change in magnetic circuit reluctance and hence reduce the cogging torque.

Cogging torque in 6-Slot / 4-Pole motor

Number of Pseudo Slots

  • Pseudo slots increase the effective number of teeth as seen by airgap flux.
  • Number of pseudo slots per tooth resulting in fractional slot/pole system help to lower the cogging torque.
  • Mechanical stability and production feasibility need to be considered while deciding the number of pseudo slots and its dimensions.

Cogging torque in 10-Slot / 4-Pole motor