聚微信湖北文理学院
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
扁鹊说病学号2009116140
汽车标志图片
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 increa in the u of speed control of ac induction motor for variable speed drive using pul 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 adverly affect nearby computers, electronic/electrical instruments and give ri 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 discusd. The standard current probe, the standard line impedance stabilization network (LISN)), the electronics interface circuits are ud to measure high frequency common mode current，
bearing current and to minimize the conducted noi from the system. The LISN will prevent the EMI noi 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. drives; bearing current.
bitspirit┊┊┊┊┊┊┊┊┊┊┊┊┊装┊┊┊┊┊订┊┊┊┊┊线┊┊┊┊┊┊┊┊┊┊┊┊┊1.Introduction冯俊熙
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 ri time and fall time of the IGBT are less than 200 nanoconds, the dissipation loss across the device becomes very less and there by increas 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 wit
h parasitic stray capacitance in the system caus 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 ri time (tr i) 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 ca of the IM connected in delta. The reasons for common mode voltage generation are already discusd.
防震减灾法It is noted that the sum of sinusoidal balanced pha voltages in a 3-pha IM at the star point is equal to zero. Therefore,
Vng=(Van+Vbn+Vcn)/3 ⑴Common mode current=Cdν/dt⑵
吴起者
┊┊┊┊┊┊┊┊┊┊┊┊┊装┊┊┊┊┊订┊┊┊┊┊线┊┊┊┊┊┊┊┊┊┊┊┊┊Where ‘C’ is the total capacitance of the system and V an,V bn and V cn are the voltages between the respective phas and the star point in the stator winding
谜语大全及答案100个2.Existing conducted emission, bearing current identification and measurement methods
V arious methods have been propod 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 p
oint 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 inrtion 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 condary should be isolated for its successful operation and this is not possible in many process/engineering industries. An active common noi canceller has been tried to eliminate the conducted emission common mode voltage produced by the PWM inverter. The active common noi canceller superimpos 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 nsor.
Julian propod a filter circuit for reducing the common mode voltage.This filter circuit is bad on current nsing and it operates a fast transistor amplifier for the current compensation. Significant attenuation of the common mode voltage occurs.The method prented in this paper is different from earlier methods. Here,the pha current is nd by the individual current transformer (CT) an
d is suitable for any voltage level. Since the CT is ud for nsing the pha current there is no voltage drop in the nsor 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 ries in each of the phas. Since the circuit us the transformer, there is voltage drop due to the pha current of the IM, hence the terminal voltage applied to the IM gets reduced. The circuit is also ud to reduce the common mode voltage and the common mode current at the star point of the IM. But this circuit is uful for the low voltage and low power applications.In the prent work,the standard LISN,the standard current probes are ud and the results are compared without and with the common mode voltage reduction circuits for the PWM inverter ud for variable speed ac IM drives.
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Julian propod a filter circuit for reducing the common mode voltage.This filter circuit is bad on current nsing and it operates a fast transistor amplifier for the current compensation. Significant attenuation of the common mode voltage occurs.The method prented in this paper is different from earlier methods. Here，the pha current is nd by the individual current transformer (CT) and is suitable for any voltage level. Since the CT is ud for nsing the pha current there is no voltage drop in the nsor 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 ries in each of the phas. Since the circuit us the transformer, there is voltage drop due to the pha current of the IM, hence the terminal voltage applied to the IM gets reduced. The circuit is also ud to reduce the common mode voltage and the common mode current at the star point of the IM. But this circuit is uful for the low voltage and low power applications.In the prent work,the standard LISN,the standard current probes are ud and the results are compared without and with the common mode voltage reduction circuits for the PWM inverter ud for variable speed ac IM drives.
