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Modern multiphase electric machines take advantage of additional degrees of freedom for various purposes, including harmonic current injection to increase torque per ampere. This new approach introduces a non-sinusoidal air gap flux density distribution causing additional technical problems and so the conventional assumptions need to be revised. The paper presents a methodology for synthesis of air gap magnetic field generated by a symmetrically distributed multiphase windings including the rotor field reaction due to the machine’s load. The proposed method is suitable either for single-layer or double layer windings and can be adopted either for full-pitched or chorded winding including slots effects. The article analyses the air gap flux density harmonic content and formulates conclusions important to multiphase induction motors. It also discusses effects of time harmonic currents and illustrates the principle of changing number of pole-pairs typical for harmonic currents being injected to increase torque.

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In this paper the design and the magneto-static simulation of axial-flux permanent- magnet stepper motor with the disc type rotor is presented. Disk motors are particularly suitable for electrical vehicles, robots, valve control, pumps, centrifuges, fans, machine tools and manufacturing. The brushless machine with axial flux and permanent magnets, also called the disc-type machine, is an interesting alternative to its cylindrical radial flux counterpart due to the disk shape, compact construction and high torque density. This paper describes a design of four phase microstepping motor with the disc type rotor. The FEM modeling and the 3D magneto-static simulation of the disk stepper motor with permanent magnets is being subject of the article, too. Disc rotor type permanent magnet stepper motor for high torque to inertia ratio is ideal for robotics and CNC machines.

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