Study on Performance Changes of EV Traction Motor Applying CFRP Sleeve to IPMSM

Abstract

In general, the interior permanent magnet synchronous motor (IPMSM) is mainly used as the traction motor of electric vehicles. IPMSM uses a rib and bridge structure to prevent permanent magnets (PMs) from being separated by centrifugal force when the motor rotates. Increasing the thickness of the ribs and bridges to satisfy rigidity at high speeds acts as a cause of increased leakage flux, thereby reducing motor performance. In this article, to improve the performance of IPMSM, we benchmark existing products to derive a proto analysis model and verify it through testing. In addition, the rib and bridge shapes that cause leakage flux are removed from the proto model and a carbon fiber-reinforced plastic (CFRP) sleeve is applied. Next, stress analysis is performed to confirm whether the safety factor is met at the required maximum speed. Also, as a result of comparing the no-load characteristics, it was confirmed that the leakage flux decreased and the back electromotive force (Back EMF) increased. However, in the case of the CFRP model with increased Back EMF, the current for field weakening control increases, making it difficult to drive at high speed. Therefore, an improvement design was performed to bring the field weakening current to the same level as the proto model. As a result, the CFRP model had a similar performance to the proto model and improved efficiency.