Torque Density Comparison between Axial-Gap Motors and Radial-Gap Motors Using Simple High-Torque Design Based on Permeance Method

This paper describes comparison of torque density between double axial-gap motors and radial-gap motors, focusing on their flatness ratio (motor shape) on the assumption of small in-vehicle motor applications. The shape and the dimensions of the axial-gap motors are calculated with a simple high-torque design based on a permeance method. The torque density of the axial-gap motors and the radial-gap motors is evaluated, using a finite element method (FEM). Simulation results clarified that the boundary between the two types of the motors is from 0.4 to 0.6 in terms of the flatness ratio, which determines the best approach to maximize the torque density of the motors.