EMI Filter Designing Of Convertor Of Adjustable Speed Electrical Power Drive Systems

Variable frequency adjustable speed electrical power drive systems have become the first choice for many adjustable speed drives in industry application. It has many advantages such as saving energy, reducing production cost, industrial automation and product quality, improving human 1iving environment, etc., which makes it more and more widely be applied in all sides of life. However, in recent years, the problem of electromagnetic compatibility(EMC) has become the bottleneck for further popu1 arization, attracting more and more attention to it.In this paper conducted disturbance principle of convertor of variable frequency adjustable speed electrical power drive system is analyzed. Illustrated by the case of a convertor, the coupling paths of differential mode noise and common mode noise are discussed. Based on frequency spectrum of the disturbance signal, the suppress method of conducted disturbance is presented. While designing the EMI filter, separating disturbance signal into common mode(CM) and differential mode(DM) is the problem which is should be solved firstly. The CM spectrum is separated from the disturbance signal which is measured by LISN in the convertor by DM rejection network. The DM spectrum is calculated with the definition of CM and DM. Illustrated by the case of VFD220BH43 E convertor, by the separate results, and the IEC 61800-3, design the CM and DM parameters of the EMI filter.The main reason that affects the filter’s high frequency performance is the coupling between them and the passive device’s parasitic parameter. So that method should be applied to improve the filter. This paper adopts a novel inductance winding structure, using of the negative coupling to suppress the capacitance’s parasitic induction. In order to solve the coupling effect, network analysis method is used to get coupling parameter. Change the shield the capacitance and winding’s structure to reduce the coupling between passive devices. The experimental results verify that after applying the measure to the system, the high frequency performance of EMI filter is greatly improved, and also verify the availability of the adopted measurement.