Torque Estimation in Rotating Electrical Machines

Abstract

This contribution introduces a method for torque estimation in rotating electrical machines regardless of their origins. Notoriously, it is not possible to describe with the same interpretation both the synchronous torque and the reluctance torque of e.g. a salient pole synchronous machine or the main torque and the cogging torque of a permanent magnet synchronous machine. Whereas the first is interpreted on the basis of the Lorentz force or alignment of two fields of the stator and rotor, the second term is interpreted as the tendency of the force to minimize the air gap i.e. the reluctance force. Although the total torque (sum of Lorentz and reluctance force) can be derived directly from the formulation of the Maxwell stress tensor or co-energy method (as the finite element programs do), there is still no interpretation capable of calculating all the components of the torque (main torque, oscillating torque, reluctance torque, asynchronous torque, cogging torque, etc.) uniformly.