Testing ensures EMC from the outset

IEC International Standards help prevent interference between systems

By Harry Caul

Electromagnetic interference was widespread a few decades ago. It was most obvious in households when TV screens would suddenly fill with 'snow' or radios crackle when hair dryers or vacuum cleaners were switched on at home or in a neighbouring flat. These incidents have largely become a thing of the past, thanks to IEC work in the domain of EMC (electromagnetic compatibility). New International Standards ensure this remains the case in an environment where more and more electronic and electrical systems are in use.

EMC testing chamber (Photo: Philips) EMC testing chamber (Photo: Philips)

Reliability and safety first

It is essential that electronic and electrical systems or components are capable of operating correctly when they are in close proximity to one another, so meeting EMC requirements. This means that the electromagnetic emissions from each item of equipment are limited and also that each item must offer suitable immunity to disturbances in its immediate environment.

The aim of EMC is to ensure the reliability and safety of all types of systems wherever they are used and exposed to electromagnetic interference. While poor TV and radio reception may be annoying in the home, the effects of electromagnetic interference can be much more serious – and possibly have deadly consequences – on the myriad of systems containing electronic elements that may be affected by it, such as Life Support Systems in hospitals, aircraft and air traffic control systems.

Tackling issues early

As with any design and manufacturing process, the earlier a problem is identified and dealt with, the more cost-effective the course of action is likely to be and the better and safer the end product. IEC TC (Technical Committee) 77: Electromagnetic compatibility, and its SCs (subcommittees) prepare International Standards for EMC to ensure designers and engineers have access to reference material such as standards, specifications and technical reports from the very beginning of the design cycle.

Preventative approach covers all aspects

The IEC’s approach to EMC standardization is based on achieving compatibility between controllable emissions and the immunity of equipment. Standards are prepared with the design stage in mind rather than waiting for the point at which problems arise and need to be solved.

This approach allows manufacturers to identify at an early stage, characteristics such as what emission levels their products should achieve and which immunity tests should be carried out. 
TC 77 prepares the IEC 61000 series of International Standards for EMC. The series is published in several parts. They cover general considerations and definitions; environment; emission and immunity limits; testing and measurement techniques and installation and mitigation guidelines.

The proof is in the testing

Tests are essential to assess the electromagnetic compatibility of equipment. Tests and measurements are covered in the IEC 61000-4 series of standards.

SC 77B: High frequency phenomena, has just published the latest edition of IEC 61000-4-4,Testing and measurement techniques – Electrical fast transient/burst. The object of this standard is to establish a common and reproducible reference in order to evaluate the immunity of electrical and electronic equipment when it is subjected to electrical fast transient/bursts – that is, sequences of a limited number of distinct pulses or an oscillation of limited duration – on supply, signal, control and earth ports. The standard defines the:

  • test voltage waveform • range of test levels
  • test equipment
  • calibration and verification procedures of test equipment
  • test setups
  • test procedure.

It has the status of a basic EMC publication. Basic EMC publications specify the general conditions or rules necessary for protecting devices from electromagnetic interference. They also serve as building blocks for the IEC TCs that develop EMC product standards.

Official and Redline versions

Edition 3 of this International Standard is available as an official publication and in Redline version with track changes, the latter designated S+ IEC 61000-4-4. Redline versions, which were first introduced in 2008 and are available in English only, provide users with a quick and easy way of comparing all the changes between standards and their previous edition. Sixteen Redline versions of International Standards have been published; four of these concern EMC.

When changes introduced in a new International Standard are as extensive as in the case of this latest edition of IEC 61000-4-4, Redline versions are very helpful and highly valued by users.

EMC testing chamber (Photo: Philips) EMC testing chamber (Photo: Philips)
e-bike EMC testing (Photo: TÜV Rheinland) e-bike EMC testing (Photo: TÜV Rheinland)
Mini EMC test chamber (Photo: Vötsch Industrietechnik GmbH) Mini EMC test chamber (Photo: Vötsch Industrietechnik GmbH)