Design and Analysis of Cooling System for High Speed PM Synchronous Motor with Magnetic Bearings

Abstract

Due to the high loss density and thermal dissipation difficulty of high speed permanent magnet synchronous motor (HSPMSM), permanent magnet is prone to irreversible demagnetization at high temperature. Furthermore, overheating of the rotor will lead to the decrease of the strength and stiffness of shaft, elongation of shaft, etc, affecting the bearings suspension accuracy and stability, especially for the motor with magnetic bearings. To solve these problems, an improved radial and axial hybrid cooling system, greatly simplifying the ventilation cooling structure, is presented for a 70kW, 30000 rpm HSPMSM with magnetic bearings in this paper. The fluid field and temperature field calculation model are established by finite element software, and the fluid flow distribution in cooling system and the temperature distribution of the motor are both analyzed in detail. Finally, experiments with the prototype show that the improved hybrid cooling system has excellent cooling effect, and also show that the motor with rated speed can run stably for a long time under no-load and load conditions, whose efficiency is over 97%.