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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 photo labelled FIG. 8 is from a patent application. It shows two rotors assembled into a single unit, with eight permanent magnets attached to the outer surface of the inner rotor, and eight to the inner surface of the outer rotor. [5] Vendors are working on both axial [6] and radial flux configurations. [7]
Most motors exhibit positional torque ripple known as cogging torque. In high-speed motors, this effect is usually negligible, as the frequency at which it occurs is too high to significantly affect system performance; direct-drive units will suffer more from this phenomenon unless additional inertia is added (i.e. by a flywheel ) or the system ...
The rotor is made of permanent magnet. Small synchronous motor with integral stepdown gear from a microwave oven A synchronous electric motor is an AC electric motor in which, at steady state , [ 1 ] the rotation of the shaft is synchronized with the frequency of the supply current ; the rotation period is exactly equal to an integer number of ...
Schematic of a permanent magnet motor using brushes and magnets in the stator. A permanent magnet motor is a type of electric motor that uses permanent magnets for the field excitation and a wound armature. The permanent magnets can either be stationary or rotating; interior or exterior to the armature for a radial flux machine or layered with ...
However torque ripple (also called cogging torque for permanent magnet synchronous machines in open circuit), which represents the harmonic variations of electromagnetic torque, is a dynamic force creating torsional vibrations of both rotor and stator.
A permanent magnet (PM) motor does not have a field winding on the stator frame, instead relying on PMs to provide the magnetic field against which the rotor field interacts to produce torque. Compensation windings in series with the armature may be used on large motors to improve commutation under load. Because this field is fixed, it cannot ...
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.