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Electromagnetic interference (EMI) is the unwanted disturbance caused when external currents affect an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. If EMI is high, it can severely impact the working of an electrical system. From impacting the quality of an electrical signal to causing temporary or permanent damage to a component, EMIs can prove to be disruptive.

There are two types of EMI – Conductive EMI and Radiated EMI. Conductive EMI passes through conductive materials such as circuit wires. Radiated EMI does not need conducting material and passes through the air. Both types of EMI can impede the performance of electronic devices in which they occur.

Types of EMI based on the source.

EMI can also be classified on the basis of how it is produced in the below categories:

1. EMI occurring due to natural causes:

Naturally occurring EMI could be due to lightening strokes, snowstorms or dust storms, solar flares, static electricity, cosmic noise, etc. The occurrence of natural EMI is usually sudden and without warning. It can cause damage to an electronic device if the device does not have adequate EMI protection.

Examples of naturally occurring EMI causing disruptions are snowstorms causing static or heavy rains with lightning causing the cell phone signals to be weak. Even the sun can cause EMI in a satellite and impact signal transmissions if the satellite happens to be directly in front of the sun.

2. EMI occurring due to man-made causes:

EMI is also caused by devices that we use in our homes or in industries. EMI from wireless devices is very common even though other electronic devices are also responsible for generating enough EMI to cause disruption in other circuits.

Household appliances can cause EMI. However, usually, the EMI is not high enough to cause severe damage in other devices. The EMI can cause some signal disruption and reduce the performance efficiency of other devices.

Industrial devices can cause EMI of much greater magnitudes. Electrical motors and generators which work at high power in factories can generate EMI that has the potential to impact even a local power grid. EMI from cellular networks can cause signal disruptions in other devices such as even hospital equipment. Similarly, EMI from television transmission can cause disruptions in smaller appliances. Transport systems such as that for the railways operate at high voltages. The EMI they generate can interrupt the working of devices near them, or even in the components of the very same system. Medical equipment such as MRI machines can cause poor performance in the device or any other devices nearby due to EMI.

What is an EMI Filter?

An EMI filter protects a device from EMI. It is fitted into the circuit of the device and helps in suppressing EMI that can enter the circuit through conduction. It inhibits the passage of unwanted currents through the conducting wires while allowing the desired current to flow through the circuit.

EMI filters work by blocking out unwanted currents identified by the frequency of the currents. Since EMI noise is usually at a higher frequency, the filter will block out the EMI noise while allowing the lower-frequency current to pass, thus ensuring normal working of the circuit. EMI filters come with shields to protect the circuits from radiated EMI, too.    

EMI filters for a power supply is made from passive components and has LC circuits. The EMI also take care of safety standards and reduce the chances of an electric shock. A mains EMI filter is placed at the power entry point of a device. This helps the device to be protected from EMI that is generated in the device as well as external EMI.

Bulgin produces Mains EMI Filters with different ratings to take care of different EMI problems.


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