Junci Cao

Thermal Optimization for a HSPMG Used for Distributed Generation Systems

High-speed permanent-magnet generators (HSPMGs) are common and important power generation equipment used in distributed generation systems. A 100-kW-level HSPMG is investigated in this paper, and its cooling system is optimized through electromagnetic-fluid-thermal analysis. First, the 2-D electromagnetic field of the machine is calculated by using the time-stepping finite element method, and the electromagnetic performance and loss distributions (heat sources) are determined, particularly the eddy loss of the rotor sleeve. Then, a thermal analysis model of the fluid for the HSPMG is established. Through numerical calculating, the whole region 3-D temperature distribution in the HSPMG is obtained, in which the influence of temperature on material properties is considered. Considering the variations of heat transfer abilities of the cooling medium, the temperatures in machines with different cooling structures are comparatively analyzed, and new cooling grooves with variable cross sections are proposed, which make the temperatures in the machine lower and more evenly distributed. The obtained conclusions may provide useful reference for the optimal design and research of HSPMGs.

Analyses on Electromagnetic and Temperature Fields of Superhigh-Speed Permanent-Magnet Generator With Different Sleeve Materials

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.

Electrothermal Combined Optimization on Notch in Air-Cooled High-Speed Permanent-Magnet Generator

A 30 kVA, 96000 r/min, air-cooled high-speed permanent-magnet generator (HSPMG) is investigated in this paper. Considering effects on both the magnetic circuit and heat transfer paths comprehensively, the stator slot notch in this HSPMG is optimized. First, using the time-stepping finite-element method, the transient electromagnetic fields of HSPMG are numerically calculated, and the electromagnetic losses in different components are obtained. Then, after the determination of other mechanical losses in such a machine, a 3-D fluid-thermal coupling calculation model is established, and the working temperature distribution in the HSPMG is studied. Thus, the electromagnetic-fluid-thermal coupling analysis method on the HSPMG is proposed, and the use of the influences of machine notch height on machine magnetic circuit and cooling air flowing path are investigated. Meanwhile, both the electromagnetic performance and the temperature distribution in HSPMG with different stator notch height are studied, and a series of analytical equations is deduced to describe the variations of machine performances with stator notch. Using the proposed unbalance relative weighting method, the notch height is optimized to enhance the performance of HSPMG. The obtained conclusion could provide reference for HSPMG electromagnetic calculation, cooling system design, and optimization design.

Influence of Rotor-Sleeve Electromagnetic Characteristics on High-Speed Permanent-Magnet Generator

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.

Performance Evaluation of a Low-Speed Single-Side HTS Linear Induction Motor Used for Subway System

Due to the critical characteristics and the magnetic flux pinning phenomenon of the high-temperature superconducting (HTS) material, the electromagnetic calculation for the HTS motor is more complicated than for conventional motors. In this paper, the equivalent electrical conductivity and the equivalent magnetic permeability are proposed to represent the critical characteristics and the magnetic flux pinning phenomenon, respectively. Considering the low-speed single-sided HTS linear induction motor as an example, the 2-D mathematical model is established and its boundary conditions are given. The model is solved using the time-step finite-element method. The flux density distributions and the performance parameters, such as thrust, vertical force, eddy-current loss, efficiency, power factor, and so on, are obtained. In addition, the magnetic flux density around the HTS windings is also calculated to evaluate the influence of the leakage magnetic flux on the critical current. Finally, the experiment is carried out to validate the accuracy of the established model.

Influence of material electromagnetic properties on HTS Linear Induction Motor used in rail transit

Secondary Eddy loss accounts for over 80% of the total loss of High-Temperature Superconducting (HTS) Linear Induction Motor (LIM) used in rail transit system, it is therefore of great significance to investigate the influence of the material electromagnetic properties on HTS LIM. In the paper, a newly proposed copper-iron (Cu-Fe) alloy is utilized to develop the secondary of HTS LIM. The four schemes of material electromagnetic properties are set up to comparatively analyze the electromagnetic distribution and performances of HTS LIM. The four schemes are aluminum reaction sheet-iron back iron, aluminum reaction sheet-steel No. 45 back iron, 16% Cu-Fe alloy (16% copper in weight) secondary, and 20% Cu-Fe alloy (20% copper in weight) secondary, respectively. Firstly, the electrical and magnetic properties of the main materials used in HTS LIM are investigated by experiments, respectively. And then three-dimensional transient (3-D) time-stepping finite element model of HTS LIM is established and the boundary conditions are given. The experimental results, carried out on the developed 3.5kW HTS LIM prototype, are shown to validate the accuracy of the established 3-D finite element model. The electromagnetic field and eddy current field distributions are studied by the established 3-D finite element model. The flux density around the HTS coils is also studied. On the basis of the field analysis, performances such as RMS phase current, thrust, power factor, etc. of the machine with the four secondary material schemes under different slips are investigated.

CQICO and Multi-objective Thermal Optimization for High Speed PM Generator

This paper proposes a novel Continuous Quantum Immune Clonal Optimization algorithm for thermal optimization on a 117 kW high-speed permanent-magnet generator (HSPMG). The proposed algorithm mixes the Quantum-Computation into the Immune-Cloning-Algorithm and causes better population diversity, higher global searching ability, and faster convergence which is approved by simulation results. Then, the improved algorithm is applied to seek an optimized slot groove and improve HSPMG thermal performance, where the 3-D fluid-thermal coupling analyses are processed with a multiobjective optimal group composed of the highest temperature and temperature difference. Both the proposed algorithm and the obtained conclusions are of significances in the design and optimization of the cooling system in electric machines.

Influence of Magnetic slot Wedge Defect on Starting Performance of high voltage line-start permanent magnet synchronous motor

In the actual operation, the stator magnetic slot wedge is vibrated by the large alternating electromagnetic force, which causes the stator magnetic slot wedge to defect and then affect the starting performance and efficiency of motor.

PMSM Low Speed Position Detection on Carrier Phase-Shifted PWM Technology

This paper reports a novel position detection method for permanent magnet synchronous motors (PMSM) operating at standstill and low speed via the application of carrier phase-shifted PWM technology. And also a polarity identification method for PMSM in a rotary frame along with the position detection by using the neutral voltage is proposed. The new technique identifies PMSM motor position from simple measurements on the neutral point voltage which affected by the variation of inductances in responding to rotor position. Then, along with the current vector control, the developed methods are applied in driving a PMSM start at standstill and low speed. The theoretical analysis results are verified by the experimental data obtained from tests at different rotor positions within one electrical cycle during operating of both standstill and low speed.

CQICO and multi-objective thermal optimization for high speed PM generator

This paper proposes a novel Continuous Quantum Immune Clonal Optimization (CQICO) algorithm for thermal optimization on an 117kW high speed permanent magnet generator (HSPMG). Via mixing the Quantum Computation into the Immune Cloning Algorithm, the new algorithm is benefited with better population diversity, higher global searching ability, and faster convergence which approved by simulation results. Then, the improved algorithm is applied to seek an optimized slot groove can improve HSPMG thermal performance, in which the 3-D fluid-thermal coupling analyses are processed with a multi-objective optimal group composed of the highest temperature and the temperature difference. Both the proposed algorithm and the obtained conclusions are of significances in the design and optimization of the cooling system in electric machines.