Jiafeng Shen

A New Approach to Evaluate Influence of Transverse Edge Effect of a Single-Sided HTS Linear Induction Motor Used for Linear Metro

A new approach has been proposed to evaluate the influence of the transverse edge effect of high-temperature superconducting (HTS) linear induction motor (LIM) in this paper. Taking a 3.5 kW single-sided HTS LIM for an example, the cross-flux density distributions were analyzed by analytical method. Based on results mentioned above, a new transverse coefficient was proposed to evaluate the influence of the transverse edge effect on the cross-flux density distribution. The influences of the motor configurations and parameters on the transverse coefficient were also investigated. The 3-D finite-element method was adopted to verify the accuracy of the presented analytical method.

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.

Influence of magnetic wedge on electromagnetic field distribution of permanent magent traction motor

High-speed train permanent magnet traction motor stator slot installation with magnetic wedge, which can improve the air gap magnetic flux density waveform and reduce the harmonic component. However, in the process of high-speed train running, the motor vibration may cause magnetic wedge fall off, which will increase the air gap flux density harmonics. These harmonics will produce more eddy current losses on the rotor surface, thereby affecting the efficiency of the motor. Thus, this paper takes a 315kW permanent magnet synchronous motor as an example. It has established a mathematical model of two-dimensional transient electro-magnetic field prototype stator with non-magnetic wedge. By using time stepping finite element method for solving 2D electromagnetic field equation, the calculation results of the starting current and starting torque are compared with the experiment results to verify the accuracy of the calculation method. The paper investigates the impact on the motor performance by employing different relative permeability magnetic wedge during starting and normal operation. At the same time, this paper also discusses magnetic wedge falling off number and dropping position on the influence of air gap flux density harmonics, eddy current loss on rotor surface and motor efficiency.

Effect of inverter fault on distribution of electromagnetic field for permanent magnet synchronous motor

Safe and reliable of inverter is directly related to the normal operation of permanent magnet synchronous motor drive system. Therefore, in the paper, taking a 12.5kW Permanent Magnet Synchronous Motor (PMSM) as the research object, two-dimensional transient electromagnetic field calculation model based on vector control strategy is established, and the corresponding assumptions and boundary conditions are also given. By adopting field circuit coupled calculation method, electromagnetic field is theoretically calculated under inverter normal and short circuit fault (SCF) in the upper switch of phase A, respectively. Simultaneously, due to the SCF, DC components are produced in three phase current, and the influence of the magnetic field produced by DC components on air gap magnetic field is analyzed in detail. In order to validate the accuracy of the established calculation model, some relevant experiments have been conducted. The obtained conclusion can provide theoretical basis for drive system fault diagnosis of PMSM.

Numerical calculation of the end region of large air-cooled turbo-generator under the single-phase earth fault

In view of the appearance of asymmetrical operation condition in the air-cooled turbo-generator, the negative sequent current is caused in stator windings, which may endanger the stability of the turbo-generator. With the 2-D and 3-D direct coupled transient electromagnetic field, the end region electromagnetic field distribution with the rated condition and single-phase earth fault condition is studied. Furthermore, the attenuation law of the axial and radial axial leakage magnetic flux distribution on the generator end core under the single-phase earth fault condition is discovered. The no-load calculated result is finally compared with the measured value; the analysis indicates that the error is within the permitted range of engineering application.

Influence of load on discharge performance of high-speed flywheel energy storage system

High-speed and high-capacity flywheel energy storage system with high-performance is a research focus in the energy field. A 200kW, 15000rpm high-speed permanent-magnet machine that used in flywheel energy storage system is investigated in this paper, and its discharge performance is analyzed through establishing a field-circuit coupling model. The relationship between the load and the performance of uncontrolled discharge process of the flywheel system are studied, and the computational results is compared with the experimental ones, which prove the model is correct. On the basis of the above study, the influence of the load and the control circuit on the constant voltage discharge performance of system is analyzed. The results could provide a reference for the design of high performance flywheel energy storage system.

Calculation of motor electromagnetic field for flywheel energy storage system in discharge mode

A Flywheel Energy Storage System (FESS) can solve the problem of randomness and fluctuation of new energy power generation. The flywheel energy storage as a DC power supply, the primary guarantee is to maintain the stability of output voltage in discharge mode, which will cause the variation of motor internal magnetic field. In this paper, taking a flywheel energy storage permanent magnet motor as the study object, constant pressure discharge DC voltage is stabilized at 310v, and then the rotation speed, electromagnetic torque, armature current, and the system output DC voltage are calculated for a FESS in discharge mode. Meanwhile, the change rule of electromagnetic field is given, which can provide reference for FESS design controller.