D. Zhao

Common-Mode DC-Bus Filter Design for Variable-Speed Drive System via Transfer Ratio Measurements

Filters used in electromagnetic interference suppression are often described in literature on drive systems and have become a standard solution in industry. The effect of the commercial off-the-shelf filter depends significantly on how it is installed. A model that includes the installation parameters is made first and then the parameters of the model are extracted by transfer ratio measurements. One possibility is to include the filter on the dc-bus inside the converter. The differential mode DC-bus filter is well known, but the common-mode DC-bus filter has received little attention. Our model is used to show that the common-mode DC-bus filter can achieve the same or even better suppression of common-mode noise by careful design. The transfer ratio is used to evaluate the performance of filter design.

Investigation of EMI noise transfer characteristic of variable speed drive system

Electromagnetic compatibility is becoming an essential consideration for variable speed drive systems. Many methods are proposed to predict the conducted electromagnetic interference level. They ask to model all components of the drive system including cable and motor. In this paper, it is supposed that the measured noise level is determined in two phases. The first is the main noise source level and the second is the conversion efficiency from main noise source level to measured noise level. The noise transfer characteristic is investigated to understand the conversion mechanism. A transfer ratio is defined afterwards which is independent of the cable and motor. It can be used to evaluate the EMC design of a converter. A simplified model is used to explain this characteristic. Laboratory tests on a 12 kW PWM drive system are carried out to verify this hypothesis. Thorough test results are included in this paper

Common Mode DC-Bus Filter Design for Variable Speed Drive System via Transfer Ratio Measurements

Filters used in EMI suppression are often described in literature on drive system and have become a standard solution in industry. The effect of the commercial off-the-shelf filter depends significantly on how it is installed. A model that includes the installation parameters is made first and then the parameters of the model are extracted by transfer ratio measurements. One possibility is to include the filter on the DC- Bus inside the converter. The differential mode DC-Bus filter is well known, but the common mode DC-Bus filter has received little attention. Our model is used to show that the common mode DC-Bus filter can achieve the same or even better suppression of common mode noise by careful design. The transfer ratio is used to evaluate the performance of filter design.

Noise propagation path identification of variable speed drive in time domain via common mode test mode

Electromagnetic Compatibility (EMC) debugging of power electronics systems depends heavily on the experience of specialists due to the complex mechanisms of electromagnetic noise. In this paper, the time domain approach is used instead of the conventional frequency domain method to identify noise propagation path. The proposed test mode switches the upper or lower transistors of the converter legs simultaneously on and off at a 50% fixed duty ratio. It is called common mode test mode. Because there is no significant functional current flowing, the differential mode noise is minimized and the remaining common mode noise and mixed mode noise are maximized. Therefore, the common mode noise in this test method gives its upper boundary of Electromagnetic Interference (EMI) level when the system is normal operated. A motor drive system is measured to show how this test mode works.

Hierarchical EMC analysis approach for power electronics applications

In this paper, a novel method for EMI (electromagnetic interference) level prediction is proposed. The method is based on the hierarchical structure of the generation of EMI. That is, the determination of EMI level can be divided into three levels, namely the functional level, the transient level and propagation level. The lower level provides parameter values for the higher level. That makes the analysis to be a single direction chain. In functional level, the working points are obtained. Through transient level analysis, the exact noise sources are determined. In propagation level, the high frequency characteristics in the propagation path are expressed including the variation of parasitic parameters. Frequency analysis can be used to get the EMI level measured in the receiver side rapidly. Because this approach is a straight forward method, the impact of any components can be evaluated immediately instead of doing the simulation from begin to end.

New Common Mode EMI filter for motor drive using a fourth leg in the inverter

In this paper, status and recent research trends related to the EMC issues in the variable speed drive system are first reviewed. The existing remedies are discussed in two parts. They are, passive filtering and active filtering. Their merits and demerits are presented. Based on the present solutions, a new common mode suppression approach is proposed. It is called the fourth leg active filter. The principle and benefit are presented. This approach is verified by simulation.