Design and Analysis of Multiphase Dual-Rotor BLDC Motor for its Application in Electric Vehicles /

Abstract

The objective of this thesis is to design and analyze performance of novel dual rotor multiphase brushless DC (BLDC) motors for electric vehicle application. The proposed motor combines the positive characteristics of multiphase BLDC motor and dual rotor BLDC motor thus achieving better fault tolerance capability, high power density and less per phase stator current. Finite element method is used to design three dual rotor BLDC motors such as 3-phase, 5-phase, and 7-phase. The design parameters and operating conditions are kept same for fair comparison. The stator current and torque performance of the proposed motors are obtained using finite element method (FEM) simulation and compared with traditional 3-phase dual rotor BLDC motor. It is possible to use low power rating power electronics switches for the proposed motor. Simulation results also validate low torque ripples and high-power density in the proposed motors. Finally, the fault analysis of the designed motors shows that the fault tolerance capability increases as the phase number increases. In the second part of this thesis, a dual-rotor (DR) topology is introduced into traditional brushless dc motor to achieve high efficiency and improved output torque. For this purpose, the design parameters of the rotor and stator for the proposed dual-rotor BLDC motor are optimized. The motor size and permanent magnet volume for the motor are kept constant. Magnetic equivalent circuit (MEC) method and genetic algorithm (GA) are selected to perform the required optimization tasks. In addition to this, a finite element analysis (FEA) tool such as JMAG-Designer is utilized to optimize the motor design and then validate its results with the magnetic equivalent circuit method and genetic algorithm. Finally, an optimized design of the stator of the motor is achieved that results into reduced torque ripples.