Circuit published here is a dual stage EMI filter. EMI Filters are widely used in applications such as Appliances, Military systems, Aerospace systems , SMPS, VFD drives, AC Servo drives, Energy Management Systems, Computers, Factory Automation Equipment, Industrial Equipment, Medical Equipment, Automotive Battery Charger.
The EMI circuit normally consists of passive components, including capacitors and common mode inductors, connected together to form LC circuits.
The common mode inductor(s) allow DC or low frequency currents to pass through, while blocking the harmful unwanted high frequency currents. The capacitors provide a low impedance path to divert the high frequency noise away from the input of the filter, either back into the device, or into the ground connection. In addition to assisting to meet EMI regulations, the filter also has to meet safety standards.
The inductor temperature rise is measured and for mains operation, the minimum electrical spacing between line, neutral and ground are controlled. This reduces the risk of fire and electrical shock.
Full Project>> Schematic & PCB Layout Available Here