Cogging torque

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Cogging or pole sensitivity ( English cogging torque ) denotes a characteristic of electric motors, the permanent magnets in the stator and a slotted armature from magnetic steel sheets or vice versa a grooved stator and an armature with permanent magnets possess. In motors that are grooved both in the stator and in the armature, cogging torques also occur during operation.

By changing the air gap when changing from armature tooth to armature groove compared to the permanent magnet, the magnetic resistance and thus the force on the armature varies.

The effect is undesirable in most electrical machines, but is specifically exploited in reluctance motors or stepper motors .

Cogging torques lead to fluctuating torques (uneven running, especially at low speeds). The rotor stops only in certain positions by switching off the machine.

Motors with ironless armatures or ironless stator windings have no cogging torques.

Individual evidence

  1. M. Flankl, A. Tüysüz and JW Kolar: Cogging Torque Shape Optimization of an Integrated Generator for Electromechanical Energy Harvesting . In: IEEE Transactions on Industrial Electronics . December 2017. doi : 10.1109 / TIE.2017.2733441 .

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