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Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets of the rotor and the stator slots of a permanent magnet machine. It is also known as detent or no-current torque. This torque is position dependent and its periodicity per revolution depends on the number of magnetic poles and the number of ...
The cogging torque is measured with a torque transducer connected between the test object and the load machine. The cogging torque can be determined in two different ways: Measurement of the cogging torque at slow speed or measurement of the cogging torque with closed-loop position control.
A common example is "cogging torque" due to slight asymmetries in the magnetic field generated by the motor windings, which causes variations in the reluctance depending on the rotor position. This effect can be reduced by careful selection of the winding layout of the motor, or through the use of realtime controls to the power delivery.
The cogging points with no current are caused by reluctant force against a direct magnetic field, rather than retarding the propagation of an alternating magnetic flux, and in practice are the angles where the air volume between the poles of the magnetic rotor and the bulk of the stator is minimised. Movement of the common two step Lavet motor:
The motor speed varies as a non-linear function of load torque and armature current; current is common to both the stator and rotor yielding current squared (I^2) behavior [citation needed]. A series motor has very high starting torque and is commonly used for starting high inertia loads, such as trains, elevators or hoists. [2]
Cogging may refer to: Cogging torque , an undesirable effect in the operation of an electric motor Forge cogging , successive deformation of a metal bar or beam along its length using an open-die drop forge
The typical speed-torque relationship of a standard NEMA Design B polyphase induction motor is as shown in the curve at right. Suitable for most low performance loads such as centrifugal pumps and fans, Design B motors are constrained by the following typical torque ranges: [30] [b] Breakdown torque (peak torque), 175–300% of rated torque
Issues, quality, and performance indicators of direct-drive wheels, and of sim racing wheels in general, include detail and fidelity of force feedback, smooth torque transmission, nearly-zero backlash, rotary encoder resolution, clipping, dynamic range, torque ripple, [2] cogging torque, [10] drivers and digital signal processing with control electronics, [2] [11] signal filtering, [8 ...