Analysis Of Electromagnetic Field And Temperature Field Of Low Speed High Torque Permanent Magnet Motor

Low speed high torque permanent magnet motor, which can drive loader directly without reducer, has the advantages of low torque fluctuation and good adjustment characteristics. Therefore, it is widely applied in the production of various departments, especially in the areas of oil field pumping units, numerical control machine and automation equipment. However, with high torque motors widely applications in various industrial fields, kinds of faults emerge repeatedly. In those faults, locked-rotor phenomenon always occurs in oil field. Therefore, it is necessary to do deeply research in the electromagnetic field and the temperature field distribution of the motor. Motor-electric power is sent out in the form of heat, which will cause the temperature of the motor components rising rapidly. Eventually, motor can not work. Motor temperature rise is important factor which affects motor life and operation reliability, so the accurate analysis of the temperature field has the vital significance.Taking a 5kW,10-pole surface type low speed high torque permanent magnet motor for example, the electromagnetic field and the temperature field of this prototype under locked-rotor fault are analyzed in this paper. First of all, according to the electromagnetic field theory, using field-circuit coupled finite element method,2-D motor field, circuit and motion coupling is analyzed. Under no-load operation, no-load operation and locked-rotor operation the electromagnetic field distribution can be obtained. So the magnetic flux density of the motor parts can be determined. Eventually, according to iron loss characteristics table, the core iron loss values of stator and rotor can be obtained. The copper loss values of the motor windings are calculated by formula. Based on the electromagnetic field calculation, according to the heat transfer and fluid mechanics theory, the 3-D finite element model of the motor is established. Analysis of the temperature field is conducted. Finally, the temperature distribution under locked-rotor operation can be obtained. The temperature distribution trend is consistent with the actual project results. In this paper, using finite element software,2-D and 3-D finite element model of low speed high torque permanent magnet motor are established. Motor losses, thermal conductivity and convection coefficient calculation methods are given. Under locked-rotor operation temperature changes of motor stator windings and permanent magnet of rotor are analyzed. This has important engineering significance for design and optimization of low speed high torque permanent magnet motor.