It is an electrical circuit or device that suppresses the high-frequency Electromagnetic noise present on the power and signal lines.
The HF noise is generated by different electrical/ electronic devices for ex, motors, electronic controls, power supplies, inverters, clock circuits, microprocessors, appliances, electronic devices, etc.
The frequency range of this noise is 9KHz to 10GHz and it can prevent the signal transmission or the intended performance of electrical/electronic equipment. The lower frequency components of the EM noise can impact the power quality as well.
The EMI is an electromagnetic interference filter which is also called an RFI filter( Radio frequency interference ).
Working of EMI Filter
The EMI filter includes most the electronic device or fixed within a circuit board. The main function is to decrease the high-frequency electronic noise which is generated by the interference of another electronic device.
EMI is mainly generated from electrical current switching and also from electronic power supplies.
There are two differential mode capacitor used C1 and C2,these capacitor is often between 0.01μF and 0.47μF and there are two common mode capacitor used Y1 and Y2 this capacitance should not be large , it is in 10nanofarade if it is too large, it will easily cause leakage.
The inductor L1 is a common-mode choke, which is a pair of coils wound in the same ferrite ring in the same direction.
The inductance is about a few millihenries. For the common-mode interference current, the magnetic fields generated by the two coils are in the same direction, and the common-mode chokes coil exhibits a large impedance to attenuate the interference signal.
For the mode signal, the magnetic field generated by the two coils offsets, so it does not affect the performance of the circuit.
Applications of EMI Filter
EMI Filters are used in applications such as Appliances, Military/Aerospace systems & subsystems, Energy Management Systems, Computers, Factory Automation Equipment, Industrial Equipment, Medical Imaging/Diagnostic/Patient Devices, Exercise Equipment, Automotive Battery Charger, MRI Rooms, Test Chambers/Shielded Rooms, and many others.
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