EMI filters for an application with high common mode currents – a Case Study

Inhalt:
In this report, we explore filter design for EMI suppression in an environment with a strong noise source in direct proximity. This induces a high common mode current (3-4 kHz / 400 V / 200–500 mA) into the circuit. In this environment, an attenuation of >50 dB is necessary to protect the application. A common mode choke with very high inductance and big size is necessary to avoid saturation, however, this will exceed the available space. Using an additional capacitor to reduce the choke’s size creates new challenges. To explain how to solve those issues we will describe the system integration process and components design needed using example of these applications.