新能源电动汽车英文翻译

湖北文理学院

毕业设计(论文)英文翻译

题目在采用PWM逆变器下的变速感应电机驱动器中的传导性排放轴承电流的减少和鉴定

专业机械设计制造及其自动化

班级机制0911

姓名杨成杰

学号2009116140

指导教师

职称周立文（学校）冯南（企业）

2013年5月10日

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Minimization and identification of conducted emission bearing current in variable speed induction motor drives using PWM inverter

Abstract. The recent increase in the use of speed control of ac induction motor for variable speed drive using pulse width modulation (PWM) inverter is due to the advent of modern power electronic devices and introduction of microprocessors. There are many advantages of using ac induction motor for speed control applications in process and aerospace industries, but due to fast switching of the modem power electronic devices，the parasitic coupling produces undesirable effects. The undesirable effects include radiated and conducted electromagnetic interference (EMI) which adversely affect nearby computers, electronic/electrical instruments and give rise to the flow of bearing current in the induction motor. Due to the flow of bearing current in the induction motor，electrical discharge machining takes place in the inner race of the bearing which reduces the life of the bearing. In high power converters and inverters, the conducted and radiated emissions become a major concern. In this paper, identification of bearing current due to conducted emission, the measurement of bearing current in a modified induction motor and to minimize the bearing current are discussed. The standard current probe, the standard line impedance stabilization network (LISN)), the electronics interface circuits are used to measure high frequency common mode current，bearing current and to minimize the conducted noise from the system. The LISN will prevent the EMI noise entering the system from the supply source by conductive methods, at the same time prevents the EMI generated if any due to PWM, fast switching in the system, will not be allowed to enter the supply line. For comparing the results with Federal Communications Commission (FCC) and Special Committee on Radio Interference (CISPR) standards, the graphs are plotted with frequency Vs，line voltage in dB μV，common mode voltage in dB μV and the bearing current in dBμA without and with minimizing circuits.

Keywords. EMI;a.c.drives; bearing current.

┊┊┊┊┊┊┊┊┊┊┊┊┊装┊┊┊┊┊订┊┊┊┊┊线┊┊┊┊┊┊┊┊┊┊┊┊┊1.Introduction

With the development of power electronic devices like the insulated gate bi-polar transistor (IGBT), the power MOSFET and the advances in microprocessors, the ac induction motor is becoming popular in variable speed drives with PWM inverter circuits. Since the rise time and fall time of the IGBT are less than 200 nanoseconds, the dissipation loss across the device becomes very less and there by increases the performance of the circuit. However, due to the fast switching action of the device the dw/dt of the inverter output becomes large. This high dw/dX voltage transition coupled with parasitic stray capacitance in the system causes high frequency line to ground current or common mode current and hence bearing current; introducing large EMI in the system.

In figure 1，Ilg (the magnitude of ground current) depends on the cable capacitance, machine capacitance，parasitic capacitance of the devices, the output voltage rise time (tr ise) and the system voltage, V oltage gets induced in the rotor shaft of the induction motor due to fast switching. This induced voltage generates circulating current and flows to the ground through the bearing resulting in an electrical discharge machining (EDM) action at the inner race of the bearing.

Due to the EDM, the life of the bearing reduces. The common mode voltage Vng (figure 1) can be measured from the star point of the stator winding of the induction motor (IM) or connected node of three 1MO resistors to the ground in case of the IM connected in delta. The reasons for common mode voltage generation are already discussed.

It is noted that the sum of sinusoidal balanced phase voltages in a 3-phase IM at the star point is equal to zero. Therefore,

Vng=(Van+Vbn+Vcn)/3 ⑴Common mode current=Cdν/dt⑵