【正文】 Lm is mutual inductance between stator and rotor. The corresponding impedance Z(ω) can be readily derived from the equivalent circuit. Even though the equivalent circuit describes the steadystate electric characteristics of a balanced induction motor at low frequencies well, it fails to express the steadystate electric and dielectric properties of the motor at stator winding insulation of a PWM inverterfed induction motor will be much . In order to disclose the reason for motor winding premature deterioration, we analyzed the parameter changes of the motor equivalent circuit at would be presented, which is based on the theoretical and simulation research of the voltage stressed on windings and the voltage distributed in coils. Because of the rotor confine the flux to the air gap and through the airgap. Therefore, the motor by power frequency voltage. Numerous investigations on motors were recently reported. Those the purposes of the analysis .First, the models based on Finite Element， Analysis were proposed to examine the motor at a per turn level. These kinds of models are plex and are primarily used for motor design. The second categories are used to examine application specific problems with founding particular simulation model. These motor models are relatively simple and easily interfaced with the simulation software. The paper establishes a model of the stator winding at of turntoturn voltage using the equivalent model established in Matlab. Motivation for the simulation arises from a need to probe into the reasonof stator winding premature deterioration . Equivalent circuit of singlephase stator winding at power frequencyA single phase stator winding at power frequency can be modeled as an equivalent circuit as shown in . In this circuit, there is no capacitance which dominants the impedance at toturn mutual inductance all increase. Their bined effects could be represented by an inductance in series with the winding resistance. It is denoted as Lh, shown in . Equivalent circuit of singlephase stator winding at order to proving that there are distributed capacitances in motor winding at the motor terminal box. Use triangular wave signal generator and sine wave generator to produce a series of feed these pulses into any two phases of the motor. We find out that the line current is a series of pulse, which frequency is identical to that of voltage pulses, by observing the motor winding current with an oscilloscope. And there is a current pulse corresponding to each of the rising and falling edges of the voltage pulses. This experiment proves that there are capacitances in motor windings. The PWM voltage pulses and the stator current are shown in . The experimental result of moto。外文文獻Design and Research on VariableFrequency SpeedRegulatingAbstractThis paper covers the design of variablefrequency speedregulating Measurement System, which is a new topic in 1980s’. It discusses the affection of variable frequency power supply on Asynchronous motor, which is one of the key ponents of the Asynchronous Motor system. Also, according to the design characters of this kind of motor which are introduced. And Designed by Computer Aided As basis, Finally Design a new motor ，Based on the validity and correctness of the principles, the design of test data was been proved. Keywords： Variablefrequency； speedregulation ； Dynamometer CAD1 INTRODUCTIONVoltage source pulse width modulation (PWM) inverters widely used in the adjustable speed systems due to their favorable performance. The recent advancements in power electronic switching devices ,reduced the switching time and improved the performance of the PWM inverters for driving induction motors. The switching frequency of up to 20 kHz is mon with the insulated gate bipolar transistors (IGBT) for inverters. PWM inverter volume was reduced as well as the output the induction motors leading to premature aging of the insulation materials. Insulation failure was found in some motors when they used for 12 years. The winding insulation of some motors was destroyed even in the test （1）. Especially, in many industrial applications the PWM inverter and the motor must be at separate locations, and long cables are required. Because characteristic impedance of the motor is much more than that of the cable, the PWM voltage is reflected at motor terminal, which results in a . This can be well explained by transmission lines theory. It proved by our experiments （2）. Meanwhile, some experiments and research reports deterioration frequently takes place on the first turn of lineend coil. Then, the research on the voltage distribution in the coil is very important and significant to probing into the mechanism of motor insulation deterioration, to the development of variable frequency technology and to the design, manufacturing and application of induction motors. In this paper, we will focus on the motors used largely in industry and powered by acdcac voltage source PWMIGBT inverters. We will analyze PWM voltage distribution in motor windings and investigate the premature aging mechanism of winding insulation.2 HIGH FREQUENCY MODEL OF THE MOTORAs is known well, an induction motor at power frequency can be represented by an equivalent circuit depicted in , which affords an easy way was to analyze the motor performance. In the equivalent circuit of Fig. 1,Rs and Ls are stator winding resistance and leakage inductance。同時，在本科學習期間，我得到了同學們的熱心幫助和鼓勵。王老師所給予我的，不僅是學業(yè)上的直接指導和關心，更重要的是為我樹立了學習的榜樣。參考文獻[1] 陳伯時．電力拖動自動控制系統(tǒng)[M]．北京：機械工業(yè)出版社，2003．[2] 李永東．交流電機數(shù)字控制系統(tǒng)[M]．北京：機械工業(yè)出版社，2002．[3] 王兆安，黃?。娏﹄娮蛹夹g[M]．北京：機械工業(yè)出版社，2000．[4] 洪乃剛．電力電子和電力拖動控制系統(tǒng)的MATLAB仿真[M]．北京：機械工業(yè)出社，2006.[5] 周淵深．交直流調(diào)速系統(tǒng)與MATLAB仿真[M]．北京：中國電力出版社，2004．[6] 劉英．異步電動機調(diào)速系統(tǒng)的仿真研究：[D]河北：華北電