IEC 61000-4-4: Testing and Measurement Techniques - Electrical Fast Transient / Burst Immunity Test. Basic EMC Publication.

EFT Background

Electrical Fast Transients (EFT) are caused anytime a gaseous discharge occurs (a spark in air or other gas), the most common being the opening of a switch through which current is flowing. As the switch is opened, arcing occurs between the contacts; first at a low voltage and high frequency while contacts are close together, and later at a higher voltage and lower frequency as the contacts become separated. Coupling of the EFT into electronic products occurs when power cables handling high currents are run in close proximity to power, data, and/or I/O cables.

Electronic products are tested for EFT immunity to insure their continued reliable operation if subjected to realistic levels of fast transients. The European Union’s EMC Directive mandates EFT testing for virtually all electrical and electronic products as a condition for obtaining the CE Mark before shipping to a member state of the European Union.

Applicable Standards

Generic Immunity, Product and Product Family Standards require that EFT tests be performed in accordance with Basic EMC Standards: IEC 801-4, IEC 61000-4-4 or EN 61000-4-4. Thermo KeyTek’s Application Note, “EMC Standards Overview,” provides an overview of European Standards for electromagnetic compatibility, describes how the Standards relate to one another, and lists sources for procuring copyrighted documents.
1 IEC 801-4, IEC 61000-4-4, and EN 61000-4-4 are essentially the same for test voltages and levels.

Basic EMC Standard

The Basic EMC Standards for EFT define methods of generating consistently reproducible fast transients for test purposes. They specify generator and coupler/decoupler design and performance in an attempt to produce correlation results between test sites. The Basic EMC Standard specifies how to perform EFT testing, the Generic, Product and Product Family Standards specify the test levels and pass/fail performance criteria.

Test Levels
 

Test Set-Up

Coupling Methods

Waveforms

Waveform Verification

One problem noted with IEC 61000-4-4 is that simulator designs can be quite different and although each has a 50 ohm source impedance and provides the specified pulse into a 50 ohm termination, some simulators provide significantly more or less energy than others into loads that are not 50 ohms - the AC power input of most electronic products is something other than 50 ohms. To deal with the problems, changes to the standard were proposed to require waveforms be verified into a 1000 ohm load. Unfortunately, these changes were not accepted; however, this and other proposed improvements to IEC 61000-4-4 will be included in a forthcoming Annex.

Test Execution

EUT Performance Criteria

EFT Simulators

Information Retrieved from Thermo Scientific.