新能源电动汽车英文翻译.doc

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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湖北文理学院 毕业设计（论文）报告纸
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 μ V，common mode voltage in dB μ V and the bearing current in dBμA without and with minimizing circuits.
Keywords. EMI;a.c.drives; bearing current.

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, Voltage 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 ⑴
Common mode current=Cdν/dt ⑵

Where ‘C’ is the total capacitance of the system and Van,Vbn and Vcn are the voltages between the respective phases and the star point in the stator winding

2.Existing conducted emission, bearing current identification and measurement methods
Various methods have been proposed to reduce the conducted emission common mode voltage and the measurement of bearing current. An output reactor connected to the inverter out put reduces the dv/dt of the inverter output voltage, which in turn reduces the common mode voltage at the star point of the IM and the flow of bearing current. Wious configurations of L-C filter have been reported. The inductance ‘L，and capacitance ‘C’ are designed according to the permitted insertion loss for the given power rating of the inverter. The draw back of the filter method is the voltage drop across the filter.
In the passive filter method, the transformer secondary should be isolated for its successful operation and this is not possible in many process/engineering industries. An active common noise canceller has been tried to eliminate the conducted emission common mode voltage produced by the PWM inverter. The active common noise canceller superimposes a compensating voltage applied at the star point. This has the same amplitude as the common mode voltage produced by the PWM inverter but has opposite polarity; hence the common mode voltage applied to the load is cancelled completely. However, this method is suitable only for low voltage/power applications due to the resistive current sensor.
Julian proposed a filter circuit for reducing the common mode voltage.This filter circuit is based on current sensing and it operates a fast transistor amplifier for the current compensation. Significant attenuation of the common mode voltage occurs.The method presented in this paper is different from earlier methods. Here,the phase current is sensed by the individual current transformer (CT) and is suitable for any voltage level. Since the CT is used for sensing the phase current there is no voltage drop in the sensor there by there is no reduction of terminal voltage applied to the IM.
In tiidr circuit, the primary winding of the transformer is connected in series in each of the phases. Since the circuit uses the transformer, there is voltage drop due to the phase current of the IM, hence the terminal voltage applied to the IM gets reduced. The circuit is also used to reduce the common mode voltage and the common mode current at the star point of the IM. But this circuit is useful for the low voltage and low power applications.In the present work,the standard LISN,the standard current probes are used and the results are compared without and with the common mode voltage reduction circuits for the PWM inverter used for variable speed ac IM drives.

Julian proposed a filter circuit for reducing the common mode voltage.This filter circuit is based on current sensing and it operates a fast transistor amplifier for the current compensation. Significant attenuation of the common mode voltage occurs.The method presented in this paper is different from earlier methods. Here， the phase current is sensed by the individual current transformer (CT) and is suitable for any voltage level. Since the CT is used for sensing the phase current there is no voltage drop in the sensor there by there is no reduction of terminal voltage applied to the IM.
In tiidr circuit，the primary winding of the transformer is connected in series in each of the phases. Since the circuit uses the transformer, there is voltage drop due to the phase current of the IM, hence the terminal voltage applied to the IM gets reduced. The circuit is also used to reduce the common mode voltage and the common mode current at the star point of the IM. But this circuit is useful for the low voltage and low power applications.In the present work,the standard LISN,the standard current probes are used and the results are compared without and with the common mode voltage reduction circuits for the PWM inverter used for variable speed ac IM drives.

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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
摘要
由于现代电力电子器件的出现和微处理器的采用，交流异步电机的速度控制被广泛应用了,这种使用用于使用PWM逆变器的变速驱动器中。使用交流感应电机，将速度 控制运用在工艺和航空航天工业上有很多优点，但由于现代电力电子器件具有快速开关 性，寄生耦合产生了不良影响，这些不良影响包括辐射性的和传导性的电磁干扰，这些电磁干扰对附近的计算机，电力、电仪器产生不利影响，还是感应电机里的轴承电流发 生流动。由于感应电机里的轴承电流发生流动，在轴承的内圈会发生放电现象，这样会 降低轴承的内圈寿命。在高功率转换器和逆变器中，辐射性的和传导性的排放成为主要 的关注。在这篇文章里，由于传导性的排放，讨论了轴承电流的鉴定，在修改后的感应 电机的轴承电流的测量，轴承电流的减少，标准电流探测仪，标准线阻抗稳定网络，电子接口电路，这些被用于测量高频共模电流，轴承电流和减少来自系统的传导性的噪声。标准线阻抗稳定网络通过传导方式将减少从供给源进入系统的电磁干扰噪声，如果人意与PWM系统中的快速开关性有关的，将不被允许进入供应线，那么就同时阻止电磁干扰的产生。在与联邦通讯委员会和特别电台干扰标准委员会标准比较后，在有最小化电路和无最小化电路的两种情况下，改图以频率比绘制，以dBμV作为线电压，dBμV作 为共模电压，dBμA作为轴承电流。
关键词：电磁干扰，交流驱动器，轴承电流
1.介绍
在电力电子器件的发展下，如绝缘栅双极晶体管，电力MOS场效应晶体管和在微处 理器的进步下，交流感应电机在使用PWM逆变电路的变速驱动器中变得受欢迎了。由 于绝缘栅双极晶体管的上升时间和下降时间不比200纳秒少，整个设备的散热损失变得 小了，从而提高了电路的性能。然而由于设备的快速开关动作，逆变器输出的dv/dt变大 了，这种高dv/dt的电压转换与系统中的寄生杂散电容耦合高频率的接地线电流或者共模 电流，因此成为轴承电流，在系统中引入大量的电磁干扰。
在图1中，I/g(接地电流的大小)取决于电缆电容，机器电容设备的寄生电容，输出电压的上升时间和系统电压，由于感应电机的快速开关性，在感应电机的转子轴上产生了电压，这种感应电压引起了循环电流，通过轴承入大地，导致在轴承内圈发电装置动作。由于发电装置，轴承的寿命降低，共模电压Vng（图1）可以从感应电机定子绕组的星点上测量，如果感应电机是三角形接法，还可以从3个1MΩ的电阻对地接法的连接点上测量。共模电压产生的原因也被讨论了。据指出，三相感应电机的正弦平衡相电压在星点上的各为0.因此，
Vng=(Van+Vbn+Vcn)/3 ⑴
共模电流=Cdν/dt ⑵
其中，C是系统的总电容，Van，Vbn，Vcn是在定子绕组各自的相与星点间的电压。

2.传导性的排放，轴承电流的鉴别和测量方法
为了减少传导性的共模电压，轴承电流的测量，己提出各种方法。连接到输出逆变 器的输出电抗器减少了逆变器输出电压的dv/dt,逆变器输出电压的dv/dt反过来减少感 应电机星点的共模电压和轴承电流的流动，已经公布了各种配置的LC滤波器，电感L 和电容C是根据逆变器额定功率的允许插入损耗设计的，滤波方法的缺点是滤波器的电压较低。
在无源滤波法中，变压器的次级线圈因其成功运作应被隔离，然而在许多工序/工程 行业中，这种做法是不可能实现的。一种起作用的常见噪声消除器被用于试图消除由 PWM逆变器产生的传导性排放共模电压。这种起作用的常见噪声消除器将应用于在性点 上的补偿点呀叠加起来，这与由由PWM逆变器产生的传导性排放共模电压具有相同的 振幅，但具有相反的极性。因此，加载负载上的共模电压被完全取消，然而，由于电阻电流传感器，这种方法仅适应于低压/功率设备。
朱利安等人提出一种降低共模电压的滤波电路，该滤波电路基于电流感应的，而且它只用快速晶体管放大器来作为电流补偿，结果是共模电压由明显的降低。本文提出的 方法于以前的方法不同，在这里，相电流是由单独的电流互感器检测出来的。另外，相 电流还适合于任意数值的电压。由于电流互感器被用于检测相电流，在传感器中没有压 降，因此运用于感应电机的端电压没有减少。在他们设计的电路中，变压器的初级绕组 与每一相相连，由于电路试用了变压器，由于感应电机的相电流的存在，变压器没有压 降，因此应用到感应电机的端电压得到了降低。他们所设计的电路也被用于降低，在感 应电机星点上的共模电压和共模电流，但是这个电路也适用于低压和低功耗应用设备。 在目前的工作下，使用了标准电流探测仪和标准线阻抗稳定网络，并在由共模电压下降 电路的没有这个电路的两种情况下，比较了结果，这些电路被用于交流感应电机驱动器调速的PWM逆变器。