EMC stands for Electro Magnetic Compatibility.  It’s basically a standard that determines that an electronic or electrical product shall not generate electromagnetic disturbances, which may influence other products, equipment radio signals etc. So in other words, EMC addresses the problems of noise emission as well as noise immunity of electronic and electrical products and systems. Electromagnetic disturbances occur as conducted interference as well as radiated emissions and immunity problems. Generally EMC, Electro Magnetic Compatibility, can be spilt down into two areas

Conducted Emissions

So what are conducted emissions? The term conducted emissions refers to the mechanism that enables electromagnetic energy to be created in an electronic and coupled to an AC power cord. The allowable conductive emissions from electronic devices are controlled by regulatory test bodies. If a product passes a radiated emission test for example but fails a conducted emissions test, the product cannot be legally sold.
The primary reason that conductive emissions are regulated is that electromagnetic energy that is coupled to a product’s power cord can find its way to the entire distribution network. This causes problems with power factor and the reactive power caused by the summation of lots of devices connected to the network can cause transforms at energy supply sub-stations to overheat and fail.

Controlling conducted emissions is an inherent problem that requires planning in the design phase. Selecting the appropriate control and test measures within the design and implementing them in an effective manner is critical to success.  The EMC design measures selected must not conflict with operational requirements yet satisfy EMC product compliance testing.

Radiated Emissions

Within the field of EMC, the term Radiated Emissions refers to the unintentional release of electromagnetic energy from an electronic device or apparatus. Any electronic device may generate Electromagnetic fields that unintentionally propagate away from the device’s structure. In general, Radiated Emissions are usually associated with non-intentional radiators, but intentional radiators can also have unwanted emissions at frequencies outside their intended transmission frequency band.
No electrical product or installation can be designed seriously unless all aspects of EMC are taken into account. This is not only important for common products such as radios, television sets, computers, telephones, washing machines, etc., but it is also especially important for complex products such as vehicles, aircraft, ships and large industrial installations. These are very sensitive to EMC problems and no one wants to accept serious disturbances within a big chemical plant. So it is important to employ a test strategy!
Every country requires all electronic products to be compliant with conducted and radiated emissions EMC standards, we would strongly recommend that compliance should be checked as an iterative test process, i.e. don’t wait until a product is launched before starting testing, as change at this stage could be extremely costly and could also result in long shipment delays and lost orders.