Cogging torque is the torque created by the magnetic attractive force between magnets on the rotor and the iron teeth of the stator. There are multiple rotor positions within a revolution where the cogging torque is high which results in an ununiform torque output. This irregular torque is especially evident in applications with low inertia and speed. Cogging torque can be minimized by adjusting the pole and slot count of the motor, by skewing the magnets on the rotor, or by skewing the lamination stack. By design, slotless motors have zero cogging torque as they have no iron teeth in the stator.
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