Electromagnetic interference or EMI is a magnetic interference caused by an electronic device. This interference degrades or damages the integrity of a component or signal and alters the functionality of electronic equipment. Electromagnetic interference that encompasses radio frequency interference or RFI is divided into two categories:
Narrowband emission: These are man-made emissions and are restricted to a limited area of radio spectrum. The hum made by power lines present the perfect example of narrowband emission, and it may be present as continuous or sporadic.
Broadband emissions: These are natural as well as man-made in origin. Such emissions are likely to affect a large area of electromagnetic spectrum. They can be one time event; random, sporadic or continuous.
There are several factors that lead to the production of EMI or electromagnetic interference. The interference with which EMI EMC filters deal with is generated inside an electrical device by opposition to current, impedance in an interconnected circuit. Voltage variance in conductors also lead to generation of electromagnetic interference in any electrical device. However, such interference is also produced externally by cosmic energy. For instance; power or telephone lines, solar flares, power cord and other appliances.
In most of the cases, power lines are responsible for generation of a significant proportion of electromagnetic interference that are carried through them to equipment.
On general basis, EMI EMC filters are used to diminish the ill effects of these interferences. These filters are either internal modules or devices with sophisticated yet planned designs to reduce these components causing hurdles.
EMI EMC filters don't involve hard science but has two basic type of components i.e. capacitors and inductors that work in close association to surpass these unwanted signals. The fundamental of using capacitors lies in the fact that it inhibits direct current (which acts as the carrier of electromagnetic interference into the device being used) while allowing the alternating current to pass through easily.
On the other hand, inductors basically are tiny electromagnets with the power to hold energy in a magnetic field while the current is passing through it. It thereby reduces total voltage. Capacitors or the shunting capacitors (called so when used in EMI EMC filters), direct current in a particular range & high frequency away from any component or circuit. Then the capacitors feed the high frequency interference or current into inductors, which are arranged in a series, and as the current passes through inductors, overall voltage is reduced protecting the equipment from damages.
