Study of Understanding Electro-Magnetic Interferences Caused by Power Electronic Equipment and its Mitigation

功率半导体器件的显著进步使得使用igbt的电压源PWM逆变器的载波频率得以提高。这为调速电机驱动系统带来了电压、电流和转矩可控性的显著改善。它还有助于减少噪音。然而，高dv/dt的阶跃共模电压不仅会诱发高频地漏电流，还会诱发电机轴电压和随之而来的轴承电流，从而导致轴承失效。许多关于无源和有源电磁干扰滤波器的技术论文都集中在消除变频器驱动电机的高频漏电流上。然而，就成本和性能而言，还没有人提出实用的EMI滤波器。当用于电绝缘二极管和IGBT模块的普通散热器接地时，高频泄漏电流可能流过二极管和IGBT模块内部存在的散热器和寄生电容器。为了区分两种泄漏电流，将流经电机机架的泄漏电流称为电机机架泄漏电流，将流经散热器的泄漏电流称为散热器泄漏电流。本研究讨论了一种无源EMI滤波器，其目的是消除变频器驱动电机的轴承电流、散热器泄漏电流和电机机架泄漏电流。设计并构建了两套实验系统：一套由载波频率为15 kHz的两电平电压源PWM逆变器和额定电压为200 V 3.7 kW的感应电机组成，另一套由载波频率为8 kHz的三电平电压源PWM逆变器和额定电压为400 V 15 kW的感应电机组成。从没有配备EMI滤波器的200 v 3.7 kW系统中获得的实验波形显示，频率约为3 MHz的不可忽略的泄漏电流流过接地散热器，而不是进入系统接地，而是进入电机机架。这些理解导致示出考虑到存在于二极管和IGBT模块内部的寄生电容的等效共模电路。该等效电路表明，所设计的电磁干扰滤波器不仅能有效地衰减散热器漏电流和地漏电流，而且能有效地衰减电机内部的轴承电流。实验结果验证了该滤波器的有效性和可行性。少

Remarkable progress of power semiconductor devices has enabled an increase in the carrier frequency of a voltage-source PWM inverter using IGBTs. This has brought significant improvements in controllability of voltage, current, and torque to adjustable-speed motor drive systems. It also contributes to reducing acoustic noise. However, a step-wise common-mode voltage with a high value of dv/dt may induce not only high-frequency ground leakage current but also motor shaft voltage and the ensuing bearing current leading to bearing failure.Many technical papers concerning passive and active EMI filters have focused on eliminating high-frequency leakage current from an inverter-driven motor. However, no one has proposed practical EMI filter in terms of cost and performance. When a common heat sink for electrically-insulated diode and IGBT modules is grounded, a high-frequency leakage current may flow through the heat sink and parasitic capacitors existing inside the diode and IGBT modules. … More The leakage current flowing through the motor frame is referred to as the motor-frame leakage current, while the leakage current flowing through the heat sink is referred to as the heat-sink leakage current, in order to distinguish the two leakage currents clearly.This research discusses a passive EMI filter far the purpose of eliminating bearing current, heat-sink leakage current, and motor-frame leakage current from an inverter-driven motor. Two sets of experimental systems was designed and constructed : One consists of a two-level voltage-source PWM inverter operated at a carrier frequency of 15 kHz, and an induction motor rated at 200 V and 3.7 kW, and the other consists of a three-level voltage-source PWM inverter operated at a carrier frequency of 8 kHz, and an induction motor rated at 400 V and 15 kW. Experimental waveforms obtained from the 200-V 3.7 kW system equipped with no EMI filter reveal that a non-negligible amount of leakage current with a frequency of about 3 MHz flows through the grounded heat sink, not into the system ground, but into the motor frame. These understandings lead to illustrating an equivalent common-mode circuit taking into account the parasitic capacitors existing inside the diode and IGBT modules. This equivalent circuit suggests that the EMI filter proposed by the authors is effective in attenuating not only the heat-sink leakage current and the ground leakage current but also the bearing current circulating inside the motor. Experimental results verify the effectiveness and viability of the EMI filter. Less