Modeling and analysis of the influence of air gap structure size on the churning loss in wet-type permanent magnet synchronous motors

Wet-type permanent magnet synchronous motors (WTPMSM) are extensively utilized to meet the power density requirements of electro-hydrostatic actuators (EHA), which are widely used in modern aircraft control systems. These motors are valued for their superior thermal performance and compact design. However, WTPMSM face a key challenge in the form of oil churning loss, especially within narrow air gaps. This churning loss can significantly impact the motor's performance and efficiency. In this paper, an analytical model has been established and computational fluid dynamics (CFD) has been employed to simulate the internal flow of the motor, thereby predicting the churning loss. The paper also investigates churning loss caused by the thread air gap in the wet motor, examining the effects of thread geometry, size, and motor speed on churning loss. Strategies such as optimizing thread design and adjusting operational parameters are proposed to mitigate churning losses. In summary, churning loss of WTPMSM is significantly influenced by the thickness of the air gap and the depth of the threads. These findings provide guidance for the design of electric motors. Future research should delve deeper into the specific impacts of various design parameters on churning losses and explore methods to reduce churning losses through enhanced motor design.