Yunjun Guo

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.

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.

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.

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.

Magnetic circuit calculation of non-salient pole synchronous generator based on distributed magnetic circuit method

Due to low-accuracy of traditional magnetic circuit method with single magnetic loop and some approximate empirical formulas in the magnetic circuit calculation of non-salient pole synchronous generator, the distributed magnetic circuit method (DMCM) is put forward and adopted. The comparison of the results among traditional magnetic circuit method, DMCM and finite-element method (FEM) shows the validity and high-accuracy of DMCM. Furthermore, DMCM is more suitable for some special rotor configuration with subsidiary slots, ventilation slots or the slots for q-axis windings.

A new method for calculating iron loss based on Hilbert Transform

In this paper, a new iron loss model is proposed based on Hilbert Transform, the model requires iron loss curve cluster as its knowledge database. By introducing transient frequency and transient magnitude, it can predict iron loss of arbitrary magnetic flux density waveform through interpolating sinusoidal iron loss curve. Finally, the model is applied to calculating iron loss in stacked silicon steel, and the results are compared with measured data.