Electromagnetic compatibility

Electromagnetic emissions, whether man-made or natural, have the potential to disturb a vulnerable device, by either causing it to malfunction or to stop operating
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EMC

Not that long ago, passengers on airplanes were asked to shut off their mobile phones during take-off and landing. In hospitals, certain areas are still off-limits to mobile phones since they could cause medical equipment to malfunction. The reason is that devices such as mobile phones can generate electromagnetic interference that disturbs the proper functioning of vulnerable equipment.

Electrical currents create electromagnetic (EM) waves. The term electromagnetic interference (EMI) recognizes that these waves can cause disturbances at any frequency range (Hz to GHz). 

Successful avoidance of these interferences is known as electromagnetic compatibility (EMC). EMC is the process in which such electromagnetic interferences are contained so that all surrounding equipment can operate safely and reliably.

IEC International Standards specify the general conditions and rules necessary for achieving electromagnetic compatibility. They specify emission measurement methods, set emission limits, detail immunity testing techniques and test levels, and recommend mitigation methods.

The need for IEC publications on EMC continues to grow, influenced by new technologies, miniaturization, and electronics that can operate on a wide range of frequencies.

Understanding EMC

Every electrical and electronic device produces a certain level of so-called electromagnetic interference (EMI) that can adversely affect the performance of similar equipment located nearby.

Electromagnetic compatibility (EMC) provides methods that help contain EMI so that electrical and electronic systems or components are able to work correctly even when they are close together.  In essence, EMC is about protecting sensitive equipment such as radio receivers, domestic appliances or electronic circuits from electromagnetic interference, and containing the electromagnetic emissions for example from large scale batteries, power lines or electric motors so that they can't interfere with more sensitive devices. 

Multiple sources of electromagnetic disturbances can have a cumulative effect on a device. For example, the emissions from several laptop computers combined with those from mobile phones could disrupt systems in an aircraft.

The electromagnetic disturbances from each item of equipment must be limited and, simultaneously, each item must have an adequate level of immunity to the disturbances in its environment.

Several techniques can be used to achieve EMC. Avoidance techniques call for the removal of the source of disturbance or the reduction of its level of emissions. Alternatively, mitigation techniques, such as filtering or shielding, can limit the effect of the disturbance.

EMC safety

In situations where electromagnetic interference (EMI) could lead to a safety hazard, special design and testing procedures need to be applied. For functional safety applications, the safety integrity levels of the device or system must be considered.

Achieving functional safety requires a careful evaluation of the product design for failure modes in the presence of EMI. There is also a need to consider life cycle design, the performance of a device as well as to test the product to ensure that its safety function is maintained.

 

EMC publications

IEC publications on EMC are used by manufacturers from the design stage. They help contain EMI from the start and facilitate later immunity testing.

IEC basic publications on EMC cover the general aspects of electromagnetic interference and specify the general conditions and rules necessary for achieving electromagnetic compatibility. They apply to a wide range of products and systems.  

Other categories of EMC publications address specific products operating in environments such as lighting, industrial manufacturing, power stations or substations where high currents, magnetic fields, or electromagnetic pulses can be found.