Torque Analysis and Experimental Testing of Axial Flux Permanent Magnet Couplings Using Analytical Field Calculations Based on Two Polar Coordinate Systems

Axial flux permanent magnet couplings (AFPMCs) are widely used in industrial applications because of their attractive feature that the torque produced by them can be transmitted without any mechanical contact. This paper presents an analysis of the characteristics of AFPMCs with axially magnetized permanent magnets (PMs), based on an approach utilizing space harmonic methods. Analytical field computation is performed by applying a magnetic vector potential and a 2-D analytical model that employs two polar coordinate systems. We thus obtain solutions for the magnetic field distribution produced by PMs that are comparatively easier than using a single polar coordinate system. AFPMC torque is obtained from the analytical solution for magnetic flux density, caused by the PMs, and a Maxwell stress tensor. The analytical results are extensively validated using the 3-D finite element analysis and experimental results.