Papers by Author: Wei Li Li

Abstract: For the complex status of fluid flow in stator radial ventilation ducts of large turbo-generator, the temperature distribution of stator is dramatically affected by the flow status of cooling medium in stator ventilating ducts. In this paper, a new ventilating ducts structure in stator is investigated. According to fixing a wind deflector on the stator teeth adjacent to the ventilation ducts, the fluid flow status of cooling air is changed flowing in stator ventilation ducts. For this reason, the effect of heat transfer in stator is changed. Taking an air-cooled turbo-generator as an example, considering the characteristics of fluid flow and heat transfer in turbo-generator ventilation system, the three-dimensional fluid flow and heat transfer coupling model is established. Using finite volume method, three-dimensional fluid field and temperature field control equations are coupling solved. Based on this, the velocity distribution in ventilating ducts is obtained. Besides that, the velocity distribution is studied with the cooling air flows into radial ventilation ducts at different incident angles. The influences of wind deflector and incident angles on the fluid velocity and temperature distribution are analyzed. Based on that, some useful conclusions are obtained.

Abstract: Taking a 315kW, 6kV permanent magnet synchronous motor (PMSM) with solid rotor as an example, the physical and mathematical models of PMSM three dimensional temperature fields analysis are established according to the heat transfer principles. The basic hypothesis and boundary value problems of the solving region in the motor are also presented. The 3-D temperature field in stator of PMSM was calculated, and the influences of heat transfer coefficients with consideration of the axial wind or not on stator temperature were analyzed. By comparing the test results with the calculated results, the influences of axial wind on motor temperature were investigated. These conclusions provide a reference for thermal design of the motor with co-axial fan and enclosure cooling fan.

Abstract: The eddy current loss of stator strands in the in-phase slot and out-phase slot was calculated by the finite element method (FEM). 3D static heat transfer equations and equivalent variation equations of large turbo-generator under the Cartesian coordinates system were given. The stator temperature field of large turbo-generator was calculated by using 3D FEM, and the influence of thermal conductivity reduced due to main insulation aging both in in-phase slot and out-phase slot on the stator was analyzed. The obtained conclusions will provide theoretical basis for fault prediction and fault diagnosis.

Abstract: Permanent magnet synchronous motor (PMSM) used for driving hybrid electric vehicle (HEV) have the characteristics of high power density, high efficiency, high reliability and good dynamic performance. However, it’s a very complex process for PMSM pulling into synchronization and it is difficult to analyze and calculate the starting and operating performance exactly, which would be very important for HEV application. So based on the requirement of HEV, a 30kw PMSM is studied. The 2D transient electromagnetic fields of this motor were calculated by using an improved finite element method. Starting performance was analyzed, and some parameters such as stator current and time-speed characteristic could be obtained. From the study on performance of machine with different ratio of spacing of damping bar (Lb) / stator pitch (Ls) in solid rotor and different number of damping bars in laminated rotor, that influence of rotor structure on starting process were studied. The calculated results show good agreement with the experimental data. Some reasonable conclusions were obtained, which could provide some help for the design of this kind of PMSM and the application of it in HEV.

Abstract: New type Fe-Cu alloy is used in the bar of induction motor with compound cage rotor(IMCCR). In this paper, the preparation of three kinds of Fe-Cu alloy is introduced. The influence of its microstructures, hardness and impact toughness is studied by using metalloscope and scanning electron microscope. Meanwhile, physical propertie such as resistivity, and B-H curve is tested by using magnetic testing device and bridge circuit. The influence of carbon content changing on microstructure and performance of Fe-Cu alloy is analysised, which has positive significance to the new type material using in motor.

Abstract: 3kW two poles induction motor with compound cage rotor is illustrated in this paper, and 2-D thermal stress field of induction motor rotor is calculated and analyzed by finite element. Contrasting with common induction motor, induction motor with compound cage rotor has specific rotor shot shape and the bar is comprised of the upper compound material and the lower cast aluminium, which cause distribution of thermal stress is special. The motor with the rotor shot of compound material laid at single site is chosen to analyzing. The maximum thermal stress in the bar is calculated at different load, and the distribution of thermal stress in the bar is analyzed at rate load. The law of distribution of thermal stress in the bar has same reference value for designing new type of induction motor.

Abstract: A new kind of alloy (conductor for electric and magnetic), is proposed in this paper, which applied in induction motor rotor bars, and a kind of induction motor with compound cage rotor(IMCCR) is obtained. By using the electromagnetic-thermal coupling analysis method, the transient temperature field of an IMCCR is numerically analyzed, and the transient thermal process of motor operating with blocked rotor for 10s and then stopped for 10min natural cooling is calculated. The heat diffusion of stator equivalent windings and the double-directions heat transmission processes in stator are analyzed. Based on which, the influences of rotor material permeability and conductivity on motor performance are studied. Comparing with the normal nonmagnetic material, the alloy could improve motor performance significantly while ensure motor thermal performance, which indicates the wide application of such alloy in electrical machines.