Fig. 1 DC and AC EMI Filter
This paper presents a highly compact multi-turn integrated Differential Mode (DM) and Common Mode (CM) DC and AC EMI filter (per Fig. 1) for a high-power inverter (200 kW, 300 A) used in aerospace applications. Design challenges pertaining to high current, high altitude and strict weight requirement are tackled. Key aspects such as impact of load and converter multi-loop resonances, E-field and form factor on the design are discussed. Consequently, a PCB based multi-turn solution featuring ultra low EPC and low E-field was adopted. The design is based on masked impedance approach wherein the AC CM Filter is used to damp/control resonance due to motor CM impedance seen on the DC side. While the DC CM filter provides additional attenu-ation for mid and high frequency CM noise. The DM filter design follows conventional design process, while considering commutation loop RLC parameters for three level structure (derived from FEA simulations).
Additional feature includes an embedded AMR current sensor for DC side current sensing, useful for inverter prognostics. The specific weight of the proposed filters is 58.8 kW/kg while for the converter (shown in Fig. 2) is approximately 20 kW/kg. A 3-LType inverter is used for demonstration of the filter performance (with DO-160 standard as the EMI constraint).
Fig. 2. 3L-Ttype inverter with integrated filters (Illustration of RC damper mounted next to module on the coldplate