What is the Use of EMI Filter

http://www.engineersedge.com/instrumentation/components/emi_filter.htm

The power supply is a different system and the need to remove the problem at it's source.

EMI (Electro magnetic Interference) filters are the nothing but capacitors between line and neutral. power supply Lines acts as intenna for high frequency signals and pick up these signals as receiving antenna. These signal rides over DC signals and modulate it. By putting capacitors across dc line we short circuit these EMI signals and feed pure DC to the desired system.

EMI filter is normally installed before Inverter's and It work as by-directional Trap .

1) for suppression of interference on the inlet of the Inverter ( very usefully if are other Inverters on the same line)

2) For trap the interference created from the Inverter it self to the main line.

Hi Poster, EMI filters are installed to protect circuits from electro magnetic interference, the best place to protect a single item from such interference from a practical perspective is close to the unit that you are trying to protect, from such EM interference's.

Cheers

Joe

The EMI filter in the power supply line is to prevent conducted noise from the load and it's switching circuit being fed back into the power supply. If you had a computer or sensitive electronics running off the same power phase the noise could affect it's operation. Typically a solid state relay will put 80db of noise onto the line.

This is why electrical equipment has to be tested for EMC compliance in Europe. With major electrical installations the EMC tests should be carried out on site and suitable EMI filters added to the lines as necessary.

There are two aspects to EMI :-

1. Susceptibility - when the equipment malfunctions due to noise delivered to it by the power line (or any other connection or radio wave pick-up).
2. Emissions - of noise onto the power line (or any other connection or by electromagnetic wave), which can interfere with proper operation of other equipment.

In practice, it is necessary to address both keeping emissions down and having adequate immunity. A filter in the power line may be there to serve both functions. Filters are often necessary in connections other than power. EMI will go in/out by any available route!