Method for forming a capacitor module circuit in an inverter using impedance matching

A method for forming a capacitor module circuit including a Y-capacitor to suppress switching noise in an inverter for driving a drive motor of an electric vehicle, the method comprising the steps of:

• (a) forming a capacitor module by predetermining the capacitance of the Y-capacitor and measuring actual voltage or current waveforms from the Y-capacitor;
• (b) extracting and separating independent and detailed frequency components by filtering the voltage or current waveforms with respect to frequency bands and forming a parallel equivalent circuit including an impedance resistor, an inductor, and a capacitor at each of the separated frequency components;
• (c) determining a value of each element by comparing simulation waveforms obtained by sequentially changing the value of each element as resistance, inductance, and capacitance in the parallel equivalent circuit with the actually measured voltage or current waveforms;
• and
• (d) forming the capacitor module circuit using the Y-capacitor having the determined capacitance when a parallel impedance equivalent circuit including the elements having the determined values is finally completed.