Study On Suppression Of Loss And Temperature Rise Of High-speed Permanent Magnet Motor

The rotor heat dissipation condition of high-speed permanent magnet motor is poor,it is easy to lead to high temperature rise of permanent magnet and even irreversible demagnetization.In order to make the motor operate reliably,it is of great significance to reduce the rotor eddy current loss and temperature rise of high-speed permanent magnet motor.Therefore,the methods of restraining rotor eddy current loss and temperature rise of high-speed permanent magnet motor are studied in this paper.For surface mounted high-speed permanent magnet motor,the influence of a layered composite sleeve structure on rotor eddy current loss and temperature rise is studied.The outer layer of the sleeve structure is made of carbon fiber material and the inner layer is made of titanium alloy material.Firstly,the stress of layered composite sleeve structure is calculated and analyzed,and different sleeve schemes meeting the strength requirements of rotor are obtained.Then the motor loss under different sleeve schemes is calculated based on the two-dimensional time-step finite element method.Finally,the most effective sleeve scheme to restrain the temperature rise of permanent magnet is obtained through the calculation and analysis of temperature rise.The suppression method of rotor eddy current loss of interior high-speed permanent magnet motor is analyzed.The influence of the increase of the equivalent air gap on the electromagnetic performance of the interior high-speed permanent magnet motor after adding the copper shielding layer structure is considered,and the measures to ensure the electromagnetic performance unchanged are given.Through the calculation and analysis of loss and temperature rise,the reasonable thickness of shielding layer is given.The eddy current circuit resistance can be increased and the eddy current loss can be reduced by using the permanent magnet segmentation method.The changes of eddy current loss and temperature rise of the permanent magnet are calculated when each permanent magnet of the motor is divided into 2-6 pieces.In order to improve the heat dissipation capacity of the motor,an axial air cooling structure with air duct on the outer surface of the casing is designed to cool the rotor of high-speed permanent magnet motor on the premise of ensuring the unchanged water-cooling structure of the original machine.Taking the surface mounted motor as an example,the cooling structure is introduced in detail,and then based on the calculation method of fluid-solid coupling,the effects of water velocity,flow path of cooling air and different cross-sectional area of air duct on the temperature rise of motor permanent magnet are analyzed.