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Li W.,Beijing Jiaotong University | Qiu H.,Harbin University of Science and Technology | Zhang X.,Beijing Jiaotong University | Cao J.,Beijing Jiaotong University | Yi R.,Beijing Jingyi Jingye Electrical Technology Co.
IEEE Transactions on Industrial Electronics | Year: 2014

In this paper, a superhigh-speed permanent-magnet generator (SHSPMG) which has an alloy sleeve on the rotor outer surface is investigated. The purpose of the sleeve is to fix the permanent magnets and protect them from being destroyed by the large centrifugal force. However, the sleeve material characteristics have much influence on the superhigh-speed machine, and therewith, most of rotor eddy-current losses are generated in the alloy rotor sleeve, which could increase the device temperature. Taking a 117-kW 60 000-r/min SHSPMG as an example, the influence of the sleeve on the generator output performance is analyzed when the generator sleeve is made of stainless steel, carbon fiber, copper-iron alloy, and copper. In addition, the eddy-current loss distributions could be gotten, and therewith, the variations of the eddy-current losses in different kinds of sleeves are analyzed. Based on the 3-D coupling field between the fluid and temperature, the temperature distributions were obtained when the sleeve adopts different materials. Moreover, the temperature variations of the permanent magnets are further analyzed. The obtained conclusions may provide some references for the design and analyses of the SHSPMG. © 1982-2012 IEEE. Source


Liu R.,Beijing Jiaotong University | Ma J.,Beijing Jiaotong University | Ma J.,Beijing Jingyi Jingye Electrical Technology Co.
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2014

In superconducting electric equipment, the current lead connects the room-temperature power supply and the low-temperature superconducting magnet. It is the main source of thermal leakage in the system. In order to decrease the thermal leakage, it is necessary to analyze the thermal loss of current lead. The heat leakage analysis and optimization design of 35 kV/2 kA current lead are presented in this paper. Based on initial range of current lead acquired from traditional methods, the electric-thermal coupling analysis will be executed based on finite element method. The length and cross sectional area ratio of the current lead at minimum heat leakage condition will be obtained. Under the nitrogen forced cooling flow condition, the heat transfer problem of the current lead and the nitrogen is analyzed. The temperature distribution of copper wire and nitrogen flow, heat transfer coefficient and pressure will be calculated. The results are helpful to determine the operating parameters of the vacuum pump. Source


Li W.,Harbin University of Science and Technology | Qiu H.,Harbin University of Science and Technology | Yi R.,Beijing Jingyi Jingye Electrical Technology Co. | Zhang X.,Harbin Institute of Technology | Li L.,Harbin Institute of Technology
IEEE Transactions on Applied Superconductivity | Year: 2013

With the development of the higherature superconducting material, the higherature superconducting machine becomes the very important research direction in the electrical machine domain. It integrates the advantages of highpower density, small machine size, and zero resistance of the superconducting windings. In this paper, taking an axial-radial flux-type higherature superconducting permanent-magnet synchronous motor (ARFTHTSPMSM) as an example, based on the investigations about the configuration characteristics and the operation principles of such machine, the mathematical model for the 3-D transient electromagnetic field was established. The magnetic field in this motor was analyzed by using the time-stepping finite-element method. In addition, the distribution characteristics of the magnetic flux in the air gap and ferromagnetic bridge were discussed, and then, the variations of the air-gap flux density, ferromagnetic bridge flux density, and non-load back electromotive force were analyzed when the motor is operating at different axial magnetic motive force. Both the theoretical analysis results and the experimental data indicate the notable advantage of adjustable excitation in such machine. Finally, based on the aforementioned analysis, the rotor eddy current losses were calculated, and their distribution characteristics were studied when the motor is operating at the starting process and the steady state, respectively. The obtained conclusions may provide useful reference for the design and research on the ARFTHTSPMSM. © 2013 IEEE. Source


Li W.,Beijing Jiaotong University | Qiu H.,Harbin University of Science and Technology | Zhang X.,Beijing Jiaotong University | Cao J.,Beijing Jiaotong University | And 2 more authors.
IEEE Transactions on Industrial Electronics | Year: 2014

Alloy rotor sleeves are used extensively in high-speed permanent-magnet machines since they could fasten the permanent magnets availably. However, it is inevitable that eddy-current losses will be generated in the sleeve, which may make the permanent magnets overheated. In order to reduce the rotor eddy-current losses, this paper focuses on the influence of the rotor-sleeve electromagnetic characteristics. Taking a high-speed permanent-magnet generator (HSPMG) as an example, the variations of output performance and rotor eddy-current losses were analyzed when the generator adopts the steel sleeve and the copper-iron alloy sleeve, respectively, and therewith, the principles of the variations were exposed. Then, the rotor eddy-current losses were further analyzed when the generator sleeve conductivity was changed. The worst range of the sleeve conductivity was also given, in which the rotor eddy-current losses were the largest. Additionally, the increase of the sleeve permeability could reduce the main magnetic circuit reluctance and improve the operating point of permanent magnets. On the other hand, it can increase the pole-to-pole flux leakage dramatically. So, the generator performance should be analyzed by considering the two factors when the rotor-sleeve permeability was different. © 1982-2012 IEEE. Source

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