Study Of Electromagnetic And Thermal Characteristics Of IMCCR

As the development of science and technology rapidly, requests for motor performance is higher and higher, and the tendency of motor turn to high power density, because of the intersect research among various disciplines. At present, in some special occasions starting with heavy load, like the oil beam pumping unit and electrical vehicles, ordinary induction motor are used as the driver. However, the rated power of used motor is much higher than real needed in such situation to satisfy the high starting request, and the efficiency and power factor of motor are much lower than rated value while normal operating, which would cause energy waste. Solid rotor induction motor, although can be competent the starting request in above situation, the efficiency and the power factor are even lower than that of ordinary motor while operating, moreover eddy current in rotor is lager and would cause heat seriously. It is meaningful both in scientific and practical significance to research new high performance electric material, design new style motor, enhance motor performance and reduce the temperature rise.A new type induction motor with compound cage rotor(IMCCR) is developed, whose design concept and construction is different from normal induction and solid rotor induction motor. Special shape rotor slot is designed, and alloy(magnetic and electric conductive) bars and cast aluminum bars are inserted in it, which made this kind of motor to have good starting performance and similar operating performance to that of normal induction motor. Based on the finite element method(FEM) numerical analysis, the electromagnetic and thermal characteristics of IMCCR are studied.The calculation model for FEM numerical analysis about IMCCR electromagnetic field is established, and the distributions of magnetic field in motor and eddy current in alloy are researched. Then, starting and operating performance of the new motor are determined, by comparing with same power ordinary induction motor, advantages of IMCCR could be seen clearly. To study the influence of rotor slot shapes and bar material on motor performance, the relationships between IMCCR starting and operating characteristics and motor rotor slot shapes and bar material combinations are determined. Magnetic shunt phenomenon caused by alloy bars, which is both the conductor of magnetic and electric, has been analyzed, also the relationship between magnetic shunt and rotor slot shape. At the same time, the variation of motor operating performance with alloy geometry size also calculated. All of these analysis would be supply theoretical references for the optimization of IMCCR.Aiming at the increasing of heat density cause by magnetic and electric conductive alloy bars, the two dimensional mathematical model for IMCCR whole region temperature field is developed. Correlation ship between motor slip and heat transfer or conductivity coefficient in solve region, and distribution of eddy loss are determined. By using the unidirectional electro-thermal analysis method is researched, distributions of steady temperature field in whole cross section of motor could be obtained, also the variation of motor temperature with load. Further more, influence of rotor bar material heat conductivity coefficient on motor temperature distribution is studied, and the comprehensive effect of rotor bar material electrical conductivity, magnetic conductivity and heat conductivity on motor electromagnetic field and temperature field are analyzed.Considering the complex distribution of rotor eddy current while motor locked, equivalent layered physical model of compound cage for transient temperature field analysis is established. Distribution characteristic of temperature in each part at different moment in locked process are studied, and thermodiffusion process in stator equivalent windings and bidirectional heat transfer between stator and rotor are researched. In addition, the radial transient heat transfer processes of rotor while motor locked working and natural cooling are analyzed. Effects of stator material on temperature distribution in air gap layer near the stator inner surface are studied. This work is very important to determine the temperature rise at motor different parts in the process of locked.Some experiment works have been done for prototype of IMCCR, including starting and operating performance under different load and temperature rise test, and temperature at some key moment in motor locked working process is also measured, all of which are compared with the calculated results.