Permanent magnet excited electric motor with improved torque ripple
AssigneePapst Licensing GmbH & Co. KG
InventorsMartin Burgbacher, Michael Hermann
Life of this patent
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Abstract
A brushless direct current motor has a substantially cylindrical, external permanent magnet rotor having a plurality of north poles and south poles. The rotor surrounds a substantially cylindrical stator provided with a plurality of main poles between which auxiliary poles are interspersed. An annular gap is defined between the rotor and the stator. To reduce magnetic or reluctance caused fluctuation of the motor torque, each main pole of the stator has an angular extent which substantially corresponds to that of a rotor pole. Furthermore, the stator periphery is provided with protuberances arranged such that permanently magnetically caused components of torque ripple are reduced.
Claims16
A multi-phase brushless d.c. electric motor comprising a stator and a magnetic rotor, one of the rotor and stator being hollow and having a substantially cylindrical internal surface, and the other of the stator and rotor having a substantially cylindrical external surface and being received within said internal surface such that a substantially cylindrical air gap is defined between said internal and external surfaces, wherein the stator is arranged to have a number of main poles and a number of auxiliary poles interspersed among the main poles with stator slots having orifices separating all poles around its substantially cylindrical surface, and the rotor has a plurality of magnetic rotor poles around its substantially cylindrical surface, the interaction of the rotor poles and the main and auxiliary poles being arranged to effect rotation of the magnetic rotor, and wherein the substantially cylindrical surface of the stator is provided with protuberances which are generally parallel with respect to the motor axis, and wherein the angular extent of each said main pole of the stat or substantially corresponds to the angular extent of a rotor pole.
A multi-phase brushless d.c. electric motor comprising a stator and a magnetic rotor, one of the rotor and stator being hollow and having a substantially cylindrical internal surface, and the other of the stator and rotor having a substantially cylindrical external surface and being received within said internal surface such that a substantially cylindrical air gap is defined between said internal and external air gap is defined between said internal and external surfaces, wherein the stator is arranged to have a number of main poles and a number of auxiliary poles around its substantially cylindrical surface, and the rotor has a plurality of magnetic rotor poles around its substantially cylindrical surface, the interaction of the rotor poles and the main and auxiliary poles being arranged to effect rotation of the magnetic rotor, and wherein the stator has substantially planar end faces, and at least one of said end faces is greater in dimension than an intermediate cross-section of the stator taken between the end faces, wherein the stator end faces are magnetically influenced by one or both end faces of the rotor magnet.
Dependencies are inferred from the claim text.