Innovative blade-structured rotor design for enhanced self-cooling in permanent magnet machines

This paper proposes a novel self-cooling solution for surface-mounted permanent magnet machines, which are widely used in various industry sectors. By properly designing a propeller and integrating it into the rotor structure, leading to a blade-structured rotor design, the self-cooling capability is achieved without the need for rotor wafters or rotor mounted fans. When rotor rotates, the cooling air (coolant) is drawn into the machine through inlets and expelled from the outlets, both inlets and outlets can be in the endplates or in the housing. During this process, air will thoroughly contact various internal components such as end-windings, stator and rotor iron cores along its flow path. As a result, internally generated heat in the windings and in the rotor mounted permanent magnets will be removed effectively. The study focuses particularly on the hot spots (locations with highest temperature) along the air flow path, such as the end-windings and permanent magnets. Different factors that affect the efficacy of this self-cooling solution such as the number of propeller blades, position and size of inlets and outlets, and rotor rotational speeds, are studied and compared. These studies are initially based on 3-dimentional computational fluid dynamic models and later validated through a series of experiments.