Calculation of thermal transient behavior of a 9-phase permanent magnet synchronous motor for flight traction applications

Nowadays internal combustion engines are being replaced with electrical drives in various traction applications in order to reach ecological goals. In case of the flight traction application, the main difficulties are connected with the high-fault tolerant demand and with necessity to have the system with the smallest possible weight. Additionally, the limited energy storage makes it necessary to use the electrical drive system with the highest possible efficiency. Due to high power density and efficiency, the most common type of electrical machine that can be used in such applications is the permanent magnet synchronous motor (PSM). Moreover, the use of a multiphase machine is one of the possibilities to reach the abovementioned high fault tolerance. Since a high temperature is the main reason of failure during operation and, at the same time, there is a trend to decrease of the machine size and increase power density, the calculation of the thermal behavior becomes the important aspect of the whole machine design. In this work, the approach for the thermal behavior calculation of multiphase PSM using Finite Element Analysis (FEA) is introduced. The transient thermal behavior calculation of a totally enclosed PSM is implemented. Additionally, the influence of the Open-Circuit Fault (OCF) on the thermal behavior of the PSM is estimated. This paper provides also the thermal basics for the transition from natural convection to effective conduction in the air gap of the totally enclosed electrical machine during calculation of the thermal FEA. The whole approach can be used further for thermal behavior analysis of the electrical machine for other types of traction application such as road vehicle application.