Junquan Chen

Modeling of Temperature Effects on Magnetic Property of Nonoriented Silicon Steel Lamination

This paper proposed a temperature-dependent iron loss model and corresponding dynamic hysteresis model, where temperature coefficient k is introduced to consider the thermal effect on eddy-current loss. The iron loss model is validated by massive experimental measurement of test samples, 1174 combinations of various temperatures, magnetic inductions, and frequencies for nonoriented silicon steel specimen. The relative error of the model is ~11% in a wide range of 50-400 Hz, 26 °C-200 °C, and 0-2 T. The proposed method can be applicable to other types of magnetic materials as long as whose resistivity rate exhibits approximately linear thermal dependence within a temperature range of 26 °C-200 °C.

A Distributed Magnetic Circuit Approach to Analysis of Multiphase Induction Machines With Nonsinusoidal Supply

A 15-phase induction machine supplied by voltages with third-order harmonic injection has nonsinusoidal magnetomotive forces distribution. This paper introduces a distributed magnetic circuit approach to perform magnetic circuit calculations in order to determine the magnetizing inductance for both the fundamental and third-harmonic component. The proposed approach divides the half-pole or one-pole machine model into a large number of fan-shaped sectors. The air-gap flux densities for all sectors are then solved iteratively. The fundamental and third-harmonic inductances are extracted via Fourier analysis of air-gap flux density distribution. Calculated fundamental and third-order harmonic inductances are compared with those obtained from no-load tests of a 15-phase prototype induction machine. The good agreement between calculated and experimental results verifies the accuracy of the presented method.

Influence of magnet shape on torque behavior in surface-mounted permanent magnet motors

This paper discusses influence of magnet shape on torque behavior in surface-mounted permanent magnet (SPM) motors. The effect of pole embrace optimization, magnet-skew and magnet shaping have been analyzed in different 8-pole, 24-slot, three phase SPM motors which having the same stator configuration. Finite-element method (FEM) is used to predict Back-EMF and torque ripple. The result shows magnet-skew can reduce cogging torque efficiently. Magnet sharping with 3rd harmonic increases average torque compared with sine magnet shaping and lower torque ripple compared with magnet-skew with optimized pole embrace.

Development of automatic iron loss measurement system of magnetic material with PWM excitation

With the development of power supply technology, more and more electromagnetic devices are supplied by Pulse Width Modulation (PWM) converter. However, steel manufacturers only provide iron loss curve of silicon steel excited by sinusoidal magnetic flux, which is of limited reference value. In this situation, we developed an automatic iron loss measurement instrument with PWM excitation. After calibration, accuracy of measurement instrument is satisfactory, which can be utilized for experimental study of iron loss excited by PWM supply.

Subdomain Method for Permanent Magnet Biased Homo-Polar Radial Magnetic Bearing

This paper presents an analytical model based on the subdomain method and conformal mapping method for predicting the performance of the permanent magnet (PM) biased homo-polar radial magnetic bearing (HRMB). Due to the homo-polar PM flux field of HRMB, the subdomain method combined with the periodic boundary condition is applied to obtain PM flux field distribution. The saddle winding is treated as a current sheet, while the rotor eccentricity is taken into account with a simple relative permeance model. The conformal mapping method is employed to obtain ending field distribution of HRMB. The developed analytical model is validated by 3-D finite element analysis. It is shown that the coupling effect between two radial freedoms is negligible. Ultimately, the parameters of HRMB are analytically optimized, while the predicted result from proposed analytical model is compared with prototypes experiment results.

Small disturbance stability analysis of multiphase inverter-fed induction motor drive system

The inverter-fed induction motor drive system may become unstable at low frequencies and light load. Taking the inverter-fed five phase induction motor drive system as an example, the small disturbance mathematic model of whole system is deduced, based on small disturbance model of induction motor and switching model of inverter system, the three-dimensional unstable region is presented and discussed by Hurwitz stability criterion of modern control theory, the results of mathematic analysis, simulation and experiments are identical. The effect of variant induction motor parameters, filter-inverter parameters, and operation conditions on system stability is studied in details. The analysis method and the conclusion obtained in the paper may contribute to the design of parameters and stable operation of inverter-fed multiphase induction motor drive system.

DC current carrying characteristics of HTS tapes exposed to external magnetic field at 77K

In order to master DC current carrying characteristics of high-temperature superconducting (HTS) tapes exposed to different external magnetic field and compare the difference of Bi-2223/Ag and YBCO tapes. We chose Bi-2223/Ag and YBCO tapes to experiment. From the experimental results can be analyzed that the diamagnetism of YBCO tapes is stronger than Bi-2223/Ag tape, HTS tapes more easily lose superconductivity in the AC magnetic field than in the DC magnetic field, and the frequency of the AC magnetic field also affects the current-carrying capacity of two kinds of HTS tapes, the critical current and the value of n will reduce with the increase of background AC magnetic field frequency.

Measurement and modeling of temperature effects on magnetic property of non-oriented silicon steel lamination

This paper aims to clearly quantify the thermal effect on magnetization and iron loss component, and propose a temperature-dependent model based on loss separation theory .The model is validated by massive experimental measurement of test samples, combinations of various temperatures, magnetic induction and frequency for non-oriented silicon steel 50DW465 as an example.

Steady state performance analysis of multi-phase induction motor with non-sinusoidal supply

Electromagnetic performance analysis is the very foundation for electric machine design optimization. Thus, the research on performance evaluation methods for multi-phase induction machines with non-sinusoidal supply is of great theoretical value and practical importance, as such process is much more complicated than traditional methods developed for three-phase induction machines. The fundamental and third harmonic equivalent circuits are employed as design tools for induction machines supplied by non-sinusoidal voltages with third harmonic injection. Considering that the air-gap flux density is asymmetrical, extended distributed magnetic circuit approach(EDMCA) is used to calculate the fundamental and third harmonic EMFs. The performance of the induction machine is finally determined by calculating quantities such as the fundamental and third harmonic currents in steady state through 3 layers of iterations. Particularly, the inner-layer iteration that calculates the air-gap magnetic flux and the middle-layer iteration that determines the magnetizing current is quite different from the traditional performance analysis approach for three-phase induction machines. The proposed method is applied to a prototype fifteen-phase induction machine with non-sinusoidal supply. Close agreement between the calculated and experimental results at various working conditions indicates the high accuracy of the proposed method.

Self identification and compensation of position sensor error in interior permanent magnet synchronous machine (IPMSM) drives

This paper presents a nonintrusive and online method to identify and compensate for position sensor error in IPMSM drives. Each IPM motor has a distinct short-circuit current vs. speed characteristic, which is solely defined by its machine design. By controlling the IPM motor to operate at its steady-state short-circuit current during coasting down, all phases of the IPM motor can be safely short circuited using the inverter without introducing any current transients. Then the d-q axes currents measured by the inverter are compared with the known short-circuit characteristic of the IPM motor. Any discrepancy in q-axis current can be used to identify and quantify the position sensor error.