Aging Impact of Permanent Magnets in Synchronous Machines for Traction Applications

With the continuous electrification of the industrial and transportation systems, higher demanding specifications are being imposed on electrical motors, leading to higher degradation due to the aging of their components. This thesis focuses its attention on the study of the effect that the degradation of the magnetic properties of permanent magnets, as a result of exposure to elevated temperatures, has on the performance of the electrical machines in which they are applied. A comprehensive study was conducted, including an experimental part of data collection and a simulation part. Initially, a method for measuring magnetic flux density was designed, implemented, and validated. This exploits the induction law to obtain the average value of flux produced by permanent magnets from a voltage measurement. After that, aging tests at 140°C till 186 hours were performed on three samples of NdFeB magnets to observe changes in their magnetic properties, particularly the decay of magnetic flux density. The measurements showed no appreciable decay, so a fourth sample of another magnet grade was tested but again no aging was found. For this reason, it was decided to consider previously obtained data from a colleague to develop the simulation part. The experimental results were supplemented by a detailed finite element analysis to simulate the impact of the observed degradations on machine performance. The results show a decrease in magnetic flux density for prolonged periods. This is reflected in the torque produced by the motor in a negative way. In addition, effects, albeit marginal, were found on machine efficiency.