Loss analysis of an asynchronous multiphase motor-generator for avionics applications

This paper aims at analyzing electric motor-generators specifically designed for the avionic application in More Electric Aircraft, where the machine is included inside the main gas turbine. Because of the harsh environment the problem of evaluating and reducing the losses produced in these machines becomes crucial. For such a purpose, this paper presents an accurate estimate of the magnetic and Joule losses produced inside the machine, when operating as generator in a range of frequencies from 200 Hz up to 400 Hz. Particular attention is paid to the investigation of the effects introduced by the use of a high number (6 and 12) of phases, due to fault tolerance reasons. The analysis is developed on a small (10 kW) prototype, consisting of a four-pole twelve-phase induction machine. The numerical computations are performed through a validated 2-D finite element code, based on a step-by-step procedure and on the sliding mesh technique. A sophisticated laminated dynamic Preisach model, whose parameters are identified from a large set of measurements, provides an accurate estimate of the iron losses and their separation into the three fundamental components also under skin effect regime. The results show that six and twelve phase configurations produce significant loss decrease.