PEMI2STD/LK,115 Filters

EMI/RFI filters are electronic devices mainly employed for the purpose of blocking the passage of high frequency noise (either electromagnetic interference [EMI] or radio frequency interference [RFI]) caused due to the presence of certain electrical equipment, which can interfere with other systems and can also cause damage to their electrical and electronic parts. The most commonly used types of EMI/RFI filters are LC-type (inductor-capacitor) and RC-type (resistor-capacitor) networks. Both of these filters have their own differences in terms of their application fields and working principles.

The LC-type or inductor-capacitor network of EMI/RFI filter is primarily used to suppress higher frequency noises. This filter is formed by a combination of both inductors and capacitors, which forms a series-resonant circuit that can block the passage of high-frequency signals. In this network, the inductors oppose the passage of high frequencies, whereas the capacitors impede the passage of low frequencies. The inductance and capacitance values should always be selected in such a way so as to produce the maximum amount of performance of the filter. Typically, LC-type filters are employed in applications such as nuclear plants, where there is a need to suppress higher frequency interference.

The RC-type or resistor-capacitor network of EMI/RFI filter is usually utilized in applications like the attenuation of higher frequency electromagnetic interference, as the properties of the resistor and the capacitor are such that they block the signal in a simpler manner. The filter is formed by connecting a resistor and a capacitor in series or in parallel, in such a way so that the resistor forms an electrical resistance to the passage of a signal, and the capacitor acts as an inductor, to impede the passage of low-frequency signals. This network is relatively easier to construct with the help of a few resistors and capacitors. This type of filter is typically used in vehicles, as well as in substantial industrial applications.

The EMI/RFI filters formed by LC and RC networks are ideal for different types of applications. Generally, they are available in various standard configurations, according to the size of their components, and are also available as surface-mount devices in different combinations of inductance and capacitance. In either of the cases, the important factor to consider while designing the filter is to adequately select the values for the individual components, ensuring that they will produce the maximum amount of efficiency for the filter in the respective application.

To conclude, the EMI/RFI filters formed by LC or RC networks are extremely useful when it comes to suppressing higher frequency noises in various applications. Depending on the type of application, the user can decide which network will suit their needs better, and also which combination of inductance and capacitance will provide the most performance from the filter.