Weiming Ma

A novel stand-alone dual stator-winding induction generator with static excitation regulation

On the basis of the new idea of electric power integration, a novel stand-alone dual stator-winding induction generator (DWIG) system is built. In this generator, there are two sets of windings to be embedded in the stator slots. One, referred to as the 12-phase power winding, supplies power to the dc load via a 12-phase bridge rectifier, and the other, called the 3-phase excitation winding, is connected to a pulsewidth modulation (PWM) voltage source static excitation regulator (SER). A solid iron squirrel cage rotor is suitable for high speed generation. Experiments and simulations show the ac capacitors can reduce the inductance of rectifier loads and help to reduce the capacitance of the SER. A simple control methodology based on stator voltage orientation (SVO) is presented to regulate the output voltage of the 12-phase bridge rectifier in this paper. Moreover, the electric energy quality and the relative influence factors are studied by detailed experiments and analyses. The proposed system is especially suitable for self contained electrical systems, such as those found on electric vehicles, ships, and aircraft, where high performance and compact size are essential.

A New Approach to Research the Transverse Edge Effect in Linear Induction Motor Considering the Edge Fringing Flux

In this paper, we propose a new approach to analyze the transverse edge effect using the vector electric potential. The edge fringing flux is considered by separating the air-gap magnetic density created by stator current and secondary eddy current, respectively. The variations of the total thrust force, the magnetization inductance and the secondary resistance varying with the air gaps, the stator widths and the end portion widths were studied.

Modeling of a Double-stator Linear Induction Motor

In this paper, the coupling effect of a double-stator linear induction motor (LIM) is studied with the 3-D finite-element method (3-D FEM). The thrust force of the double-stator LIM with in-phase current is compared with the forces with inversed current and single stator excited. According to the 3-D FEM results, two coupling models of the double-stator LIM are built and validated by a thrust force test.

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.

The transient thermal characteristics of periodic pulse-type linear induction motor

This paper focuses on the temperature attenuation of the periodic pulse-type linear induction motor stator. A simplified 1-D transient temperature field model of the stator was built first. The main factors that impact the stator temperature decay rate are studied. A stator transient thermal network model was built to predict the temperature quickly. Using the 1-D transient temperature field analysis results, the number of nodes of the transient thermal network model was determined. The effect of the coil loss with temperature is also considered in the thermal network model.

Modeling and parameter measurement scheme for double primaries coupling Linear Induction Motors

In order to improve the redundancy performance, Linear Induction Motor (LIM) could be designed to have m primaries (m is an integer and m≥2) and just one secondary. When anyone of the primaries runs in failure model, other remanent primaries could accomplish the scheduled target. The paper represents equivalent circuit of double primaries coupling (m=2) LIM based on the research of mathematic model. Test data of no load and locked mover for single primary excited and double primaries excited with the same current are used for parameter measurement. Calculation results of the machine performance (e.g., terminal voltage and force) based on the motor model are presented and compared to test data from a prototype LIM. Result of compare shows that motor model and parameter measurement scheme for double primaries coupling LIM is efficient and accurate. Result of calculation and test indicates that when excited with the same current, efficiency and thrust density of double primaries coupling LIM are improved.

Application of feed forward control in the excitation system of pulse rectified generator

Conventional excitation control system of the generator keeps the terminal voltage stable using terminal voltage feedback, which cant meet the fast response requirement for the rectified generator with pulse loads due to the lag characteristics of feed back control strategy and the inertia influence of generator. A feed forward control strategy is proposed and a digital excitation control system based on Digital Signal Processing (DSP) controller is built for the rectified generator. The principle of the feed forward control strategy is introduced. Experimental results show that with pulse loads, dc-link voltage drops deeply only with feed back control, however by adding the feed forward control into the excitation control system, the dc-link voltage drops slightly (less than about 2%), in the mean time, the dynamic response speed and voltage adjustment precision are improved greatly.

Analysis of magnetic field distribution and parameter calculation of linear induction motor with novel winding construction

The two-dimension magnetic-field distribution of a slotless double-sided long-stator linear induction motor is analyzed in detail. Based on this, the computation formulae of relevant inductance parameters and electromagnetic thrust force of motor are derived. Finally, the results of analytic calculation and finite element calculation are compared and analyzed. The comparison results verify the validity and superiority of the proposed analysis methods, which also proposes theoretical basis for the accurate calculation of electromagnetic performance of this novel linear induction motor.

Research of zero-crossing detection technology in linear induction motor

It is useful to adopt sub-power supply in linear motor for high efficiency. Zero-crossing detection technology is usually used in phase and frequency measurement. In this paper, zero-crossing detection technology is firstly applied to track transportation for sub-power supply. The performance of traditional zero-crossing detection technology in existence is compared particularly in this paper, and shortages of traditional methods are also pointed out. A new zero-crossing detection method is proposed in this paper. Simulation and experiment are executed about the new method; the correctness and the feasibility of the new method are validated.

Dynamic characteristics of a linear permanent magnet brushless DC launcher by finite-element analysis

This paper is concerned with the analysis of a linear permanent magnet brushless DC launcher composed of an armature and a permanent magnet stator. An efficient analysis method using time-stepping finite-element method (FEM) is employed in order to analyze the dynamic characteristics of this kind of motor, and a prototype machine is fabricated on the basis of the results. Measured value shows a good agreement with the result of the calculation by using time-stepping FEM. It verifies the validity of the method and provides a new way for the practical design.