The Research And Optimization Of Bus-Bar Emi Filter Based On Its Multi-Physical Characteristics

Integrated EMI filters based on the magnetic integration technology are getting more and more attention due to their advantages in power density and high frequency performance. Unlike traditional discrete EMI filters and other integrated EMI filters, bus-bar EMI filter can attenuate noise current by both “reflection” and “dissipation”, which can assure that bus-bar EMI filter will have a good performance in high frequency. The present research on bus-bar EMI filter is very limited, which mainly focus on the characteristics of materials and basic elements in bus-bar filter, while the multi-physical characteristics of bus-bar EMI filter are still unclear, such as the design of dissipation layer and the power loss as well as the temperature rise of filter under different working current. Therefore, the research in this thesis is constituted of following parts:Based on the structure and principle of bus-bar EMI filter, the principle for material selection is stated, the procedure of ceramic fabrication is given, a new method for metallizing the ceramic surface is applied. The dissipation layer is designed systematically, including its structure and thickness.The multi-physical fields model of bus-bar EMI filter is established, based on which the harmonic magnetic characteristics of filter is analyzed and the power loss of filter is derived. Under the condition of natural convection heat dissipation, the temperature rise of the filter is calculated by “heat-fluid” analyze. The corresponding experiment is carried out to test the temperature rise of bus-bar EMI filter and to verify the theoretical calculation.Two 3D finite element models for bus-bar EMI filter with a core and a CM choke outside are established separately, based on which their “magnet-heat-fluid” characteristics are analyzed and their temperature rise are calculated. The temperature rise experiment is carried out to verify the accuracy of theoretical calculation.A new CM choke with the function of noise dissipation is proposed which is the idea expansion of bus-bar EMI filter. The voltage-transfer characteristic of a single stage EMI filter using the new choke is tested based on S parameter. The bus-bar EMI filter using the new choke is applied to suppress the noise in a converter; the effectiveness of the optimal design for choke and bus-bar EMI filter is verified.