Energy conversion by nonlinear permanentmagnetmachines

Stored energy and coenergy are defined for a permanent magnet system. It is shown that either stored energy or coenergy may be used to determine permanent magnet reluctance torque where the magnetisation characteristics of regions within the system are arbitrary. It is shown how residual magnetism may be incorporated into classical electromechanical coupling theory. It is, therefore, shown how general equations for torque can be derived for nonlinear permanent magnet systems from classical electromechanical coupling theory. The approximation made in deriving a simplified equation for torque in a linear system is described. Finally, the validity of the first quadrant representation of the rate of change of coenergy within a permanent magnet material, relevant to CAD systems on electromagnetics, is demonstrated.