High-Speed Coreless Axial-Flux Permanent-Magnet Motor With Printed Circuit Board Winding

Gearless and compact motors operating at high speeds (above 10 000 r/min) are increasingly being used in many fields. This paper presents the design and analysis of a coreless axial-flux permanent-magnet motor for high-speed, low-power applications. The proposed motor is designed to rotate at a speed of 30 000 r/min. To ensure the reliability of the motor at high speeds, it is essential to minimize torque ripple and the magnetic attraction between the stator and the rotor in the axial direction. Therefore, in this paper, a novel coreless stator design using multilayer printed circuit board (PCB) is proposed. The PCB stator ensures uniform distribution of the phase windings, which minimizes harmonics in the back EMF of the motor. The multilayer PCB stator makes the motor highly compact, efficient, and reliable. To improve the air-gap flux density in the coreless design, a lightweight Halbach-array based rotor is used and the Halbach magnets are covered with a high-strength nonmagnetic material to achieve high rotor integrity. MagNet 3-D and COMSOL Multiphysics are used for the finite element analysis and optimization of the motor and the simulation results are presented. A prototype of the motor is fabricated and tested with sensorless field oriented control to validate the simulation results. The back EMF obtained for the prototype is sinusoidal and its performance characteristics ensure efficient and reliable performance at high speeds.