Overview of novel magnetically geared machines with partitioned stators

Abstract

This study overviews recent development of a new class of magnetically geared machine topologies, i.e. partitioned stator (PS) machines. They are developed from magnetic gears and magnetically geared machines, as well as stator permanent magnet (PM) machines (switched flux, flux reversal, and doubly saliency PM), wound field, or hybrid PM and field winding machines. Based on the operating principle, i.e. magnetic gearing effect/air-gap field modulation and flux switching by the salient rotor iron poles, various PS machine topologies are developed. All have features of two stators, two air-gaps, and one segmented ferromagnetic rotor identical to a magnetic gear's modulating rotor. Their inherent relationships are revealed, while their electromagnetic performance is compared. Both PM and wound field PS machines are discussed, together with hybrid excited PS-PM machines and Vernier machines. It shows that all of these PS machines share the same torque production principle and the differences are mainly in PM configurations and relative positions of two stators. All PS machines have higher torque density per copper loss compared with their counterparts of single-stator machines. PS switched flux PM machines can produce the highest torque density per copper loss. Note: G r is the gear ratio, n i is the number of iron pieces, p 1 is the low-speed element pole-pairs, p 2 is the high-speed element pole-pairs, ω i is the ferromagnetic pieces' angular velocity, ω 1 is the low-speed element's angular velocity, ω 2 is the high-speed element's angular velocity. The negative sign indicates opposite rotating directions.

General Analytical Magnetic Model for Partitioned-Stator Flux-Reversal Machines With Four Types of Magnetization Patterns

“…The operation principle of PS-FRPM machines is to some extent similar to coaxial magnetic gears [3][4][5] or magnetically geared brushless PM machines [7,16]; their function is based on the modulation of the magnetic field by the iron-poles. Hence, in order to develop the maximum electromagnetic torque, the number of PM pole-pairs (P), the number of rotor iron poles ( r N ) and the number of armature pole-pairs ( s P ) must obey the following relation [4]:…”

“…According to the geometry and materials, the whole problem is divided into six sub-domains as listed in Table I As evident from Fig. 4, relations (5), (7) and (9) can be respectively expressed for the rotor slots, stator slots and slotopenings:…”

“…Therefore, a partitioned stator machine is a high performance electric machine with overload protection and high torque density per copper losses. They can be used in many applications such as power generation and electric propulsion [6,7].…”

“…By separating the armature winding and stationary PMs, the space for the PM and armature winding increases, the motor copper losses decrease, heat is easily dissipated, PMs are kept away from the winding high-temperature zone, and the risk of the PM demagnetization is reduced. Consequently, PS-FRPMM compared with the conventional FRM and conventional PM machines, shows better performance and higher torque density per copper losses [1,2], [6,7], [11][12][13][14][15][16][17]. Thierry Lubin is with the Groupe de Recherche en Electrotechnique et Electronique de Nancy, University of Lorraine, 54506 Nancy, France (e-mail: thierry.lubin@green.uhp-nancy.fr).…”

“…Thierry Lubin is with the Groupe de Recherche en Electrotechnique et Electronique de Nancy, University of Lorraine, 54506 Nancy, France (e-mail: thierry.lubin@green.uhp-nancy.fr). The analyses of the performance of PS machines have been done in [6,7], [11], [16,17]. PS machines are compared with stationary PM machines [7], [11,12] with different magnet topologies [13,14] and different winding configurations [15] based on finite element analyses and prototype.…”