外文翻译--变频调速交流牵引电机绝缘电老化机理的研究.doc

Investigation on Insulation Electrical Aging Mechanism of Inverter- Fed AC Traction MotorsInverter - fed traction motors used in motor train unit are regarded as the research object for insulation electric aging mechanism, based on re-search productions of insulation technique of inverter-fed motors . High frequency equivalent circuit model s of cable and stator winding are established to simulate over-voltage of motor terminal sand uneven voltage distribution of windings. A novel high frequency high voltage test system has been developed to carry out life time tests of traction motor windings. Change tendency of dielectric loss , partial discharge and thermally stimulated current (TSC) are used to deduce insulation electric breakage mechanism.High frequency equivalent circuit models of cable and stator winding are established to simulate over voltage of motor terminals and uneven voltage distribution of windings. The simulation results show that the over-voltage is the function of rise time , cable length and reflection ratio on motor terminals. Critical length and critical rise time is corresponding one to one. The over-voltage is up to the maximum value as long as the cable length is reater than the critical lengthA novel high frequency high voltage test system has been developed in place of inverters to carry out insulation aging test. Pulse square waves are generated by IGBT and are enlarged by high frequency and high voltage transformers in the device. The maximum value of high frequency and high voltage square waves is up to 10 kV. The results of life tests of motor windings indicate that he relationship of insulation lifetime and the amplitude of pulses is the inverse power law model , the relationship of insulation lifetime and the frequency of pulses is exponential model under continuous pulses condition. When the test ambient temperature is below 200，the temperature has little influence on insulation lifetime of magnet wire with corona resistant film insulation.A novel partial discharge detection device was developed by impulse current sensor , hand computer. According to the character is tics of the tested signals , a new algorithm based on wave let- envelope detection technique is proposed to filter EMI from the test system and space electromagnetic waves. Because of the influence of very large dV/dt and high frequency plus - minus voltage discharges under continuous square waves condition are different from those under sine voltage condition. On the one hand , larger dV/dt leads to higher breakdown voltage.On the other hand, high frequency plus-minus voltage conversion causes a lot of space charge cumulated on the insulation surface. Large break down space charge result in discharge pulses with short rise time and large magnitude . The number, magnitude and power of partial discharges increase with the temperature , frequency and voltage change of square waves. The number of partial discharge become large with the frequency of square wave increase in the unit time , but it becomes small in one period of square wave. Contrast tests are carried out under AC and 10kHz square wave pulse conditions. The differences between AC aging and square wave pulse aging are studied based on change curves of dielectric loss, partial discharge pattern and TSC. These curves prove that square wave pulses bring more defects than AC voltage to the insulation materials. Under qua re wave pulse condition , the two key factors which to insulation aging are discharge ad space charge. Damage actions of partial discharges and space charges are intensified with voltage , frequency and temperature increasing. Due to the destruction of discharges under the square wave condition , the weaknesses of insulation structure will break down rapidly if partial discharges occur. Discharge channel comes into being as a result of the cooperation of partial discharges and space charges. Insulation surfaces are destroyed by partial discharges. Injection and draw - off of electric charges generating by charges result in molecular chain fracture inside insulation structure. Subsequently, discharge channels are expanded along the breaking point in the insulation. Finally, the process leads to insulation is the use of power semiconductor devices will be the role of on-off frequency to another frequency power conversion power control devices. We are now mainly used in cross-frequency converter - direct - way to pay (VVVF inverter or variable frequency vector control), before the adoption of power-frequency AC power into DC power rectifier and then converted to DC power supply frequency and voltage can be controlled AC power to supply the motor. Inverter circuit in general by the rectifier, intermediate DC link, inverter and control of four parts. Part of three-phase bridge rectifier is not controlled rectifier, inverter part of three-phase bridge inverter IGBT and PWM output waveform, the middle of DC link for the filtering, storage and buffer DC reactive power. Inverter Selection, Selection converter to determine the following: The purpose of the use of variable frequency; constant voltage control or constant current control. Inverter type of load; such as the vane pump or pumps, such as volume, with particular attention to the performance of the load curve, the performance curve determines the ways and means of application. Inverter and load matching problem; voltage matching; Inverter rated voltage and load in line with the rated voltage. Current matching; ordinary centrifugal pump, rated current of the inverter and the motor rated current line. For a special deep-water pumps, etc. If the load is necessary to refer to the electrical performance parameters to determine the maximum current inverter current and. Torque matching; this situation in the constant torque load or deceleration device that may occur from time to time. In the use of high-speed motor drive inverter, due to anti-high-speed electric motor small, high-order harmonic generation to increase value resulting in increased output current. Therefore the inverter for high-speed motor selection, and its capacity to be slightly larger than the selection of general motors. If you want a long cable converter running at this time to take measures to curb a long cable on the impact of coupling capacitance to avoid shortage of inverter output, so in such circumstances, the frequency converter to enlarge the capacity of a file or in the inverter output installed reactor output. For some special applications, such as high temperature, high altitude, at this time will cause lower capacity inverter, inverter capacity to enlarge a block. Internal high-power inverter is the electronic components, extremely vulnerable to the effects of temperature, products are generally called for 0 55 , but the work in order to ensure safe, reliable, should be taken into account the use of room, it is best controlled at 40 under . In the control box, the converter should normally be installed in the upper box, and strictly comply with the product specification of the installation requirements, absolutely does not allow easy heat heating elements or components close to the bottom of the installation of inverter. II. The ambient temperature. High temperature and large temperature changes, the inverter internal condensation prone to the phenomenon of performance of the insulation will greatly reduce and may even lead to short-circuit accident. When necessary, the need to increase the desiccant in the box and heater. In water treatment, the generally heavier than water, if the temperature variation, then the problem would be more prominent. III. Corrosive gases. The use of the environment if the concentration of corrosive gas, and not only the corrosion of lead components, such as printed circuit boards, but also accelerate the aging of plastic devices to reduce the insulation performance. IV. Vibration and shock. Equipped with inverter control cabinet by the mechanical vibration and shock will cause bad electrical. Thermoelectric. At this time, apart from improving the mechanical strength of the control cabinet, away from the vibration source and the impact of the source but also the use of anti-seismic rubber pad fixed outside and inside the control cabinet of the type of electromagnetic switch components generated vibration. Equipment for some time, should carry out inspection and maintenance. V. electromagnetic interference. Inverter in the work of rectification and frequency as a result, has created a lot of the surrounding electromagnetic interference, these high-frequency electromagnetic waves in the vicinity of the instrument, apparatus, a certain degree of interference. Accordingly, instrumentation and electronic systems inside should be optional metal case, shielding of the instrument transducer interference. All the components should be grounded and reliable, in addition, all electrical components, apparatus and instruments should be used to connect between the control cable shielding and shield should be grounded. Electromagnetic interference, if not handled properly, often the entire system will not work, resulting in failure of or damage to the control unit.变频调速交流牵引电机绝缘电老化机理的研究 在变频电机绝缘技术研究成果基础上，以动车组变频牵引电机为研究对象，建立电缆和定子绕组高频等效电路模型，研究电机端过电压以及匝间电压分布特性;研制一套基于高压方波脉冲的绝缘老化试验系统，进行牵引电机绕组的绝缘寿命实验，依据介质损耗、局部放电等参量的变化，分析绝缘材料的破坏机理。构建电缆和电机定子绕组的高频等效电路模型， 计算分析电机端电压及定子绕组内部电压分布.结果表明，变频牵引电机端过电压波形呈一种振荡衰减的波形，其峰值是电机端反射系数、电缆长度和上升沿时间的函数。临界电缆长度和临界上升沿时间是一一对应的，当电缆长度超过临界电缆长度时，电机端电压峰值达到最大值。研制一套基于高压方波脉冲的绝缘老化试验装置，通过模拟逆变器对绝缘材料进行老化试验。装置采用电力电子技术产生方波脉冲，经高频变压器升压，输出高压方波脉冲，其峰值最高可达10k V 。电机绕组寿命试验表明: 在连续方波脉冲下，绝缘寿命与脉冲方波幅值的关系符合反幂模型，与频率的关系成指数模型。在200以下，用耐电晕聚酞亚胺薄膜制作的电机绕组绝缘的寿命受温度影响较小。采用脉冲电流传感器、示波器和计算机建立一套高压方波脉冲下局部放电测量装置。根据实际测量信号的特征，提出一种小波包一包络算法，对传感器输出信号进行处理，滤除来自高压方波脉冲和空间电磁波的干扰，提取出放电信号。与传统正弦交流下的放电不同，方波脉冲下的局部放电，受到高电压变化率、正负电压高频转换的作用。一方面d V / d t 增大使得气隙击穿动态电压增加，另一方面正负电压转换频率高、速度快，大量空间电荷累积在气隙表面。电压变化率越大、频率越高， 放电脉冲上升沿时间越短，放电幅值越大.基于方波脉冲的局部放电发生次数随电压幅值、环境温度的升高而增强。随着频率的增加，放电量和放电功率增加，同一时间内放电次数增加，而单个周期内的放电次数减少。分别在工频交流和10 k Hz 高压方波脉冲下进行电机绕组绝缘老化试验。介质损耗、局部放电、热刺激电流等绝缘老化表征参量的变化趋势表明，高压方波脉冲对电机绕组绝缘的老化作用远大于工频交流电压。方波脉冲下导致变频牵引电机绝缘老化的主要因素是局部放电和空间电荷，方波脉冲幅值、频率以及环境温度的提高都会增强局部放电和空间电荷对聚合物的破坏。由于方波脉冲下局部放电的破坏作用远大于工频交流，所以在方波脉冲电压下，绝缘结构对局部放电更加敏感，局部放电在绝缘薄弱位置的放电通道发展迅速，容易造成绝缘材料击穿。放电通道是由局部放电和空间电荷协同作用形成的，一方面局部放电造成从表面向内腐蚀绝缘介质，而另一方面空间电荷注人与抽出造成绝缘介质内部分子链断裂，放电通道迅速扩展，最后导致绝缘材料击穿。变频器是利用电力半导体器件的通断作用将工频电源变换为另一频率的电能控制装置。我们现在使用的变频器主要采用交直交方式（VVVF变频或矢量控制变频），先把工频交流电源通过整流器转换成直流电源，然后再把直流电源转换成频率、电压均可控制的交流电源以供给电动机。变频器的电