The IEC 61000-4-11 is an EMC standard by the International Electrotechnical Commission for testing and measurement techniques for voltage dips, short interruptions, and voltage variations. This standard specifies the tests, procedures, and limits for voltage dips, dropouts interruptions, and variations of electrical and electronic equipment working on an AC supply having a rated input current not exceeding 16 A per phase with 50 to 60 Hz. 

Fig: Voltage dips

Voltage dips and interruptions are sudden reductions of the supply voltage. These sudden reductions can affect the operation of the equipment. These dips are caused by load switching, faults in the main supply, etc. Voltage dropouts are dips that are 95 to 100% deep and may last up to 1 minute. If these voltage dips and dropouts occur in high-resolution imaging systems used for medical purposes such as MRI scans and CT scans even for one minute, then the systems would lose critical data over that period thus affecting their efficiency and reliability. Similarly, a momentary voltage drop in an amplifier or a receiver can cause transient glitches (noise) which could affect the load it is driving. 

Even the digital circuits are affected by the voltage dips. The clock cycles of a digital circuit get affected by the voltage dips resulting in a glitch on the other end. Illegal functioning, late response, and memory corruption are some of the after-effects of voltage interruptions and dropouts in a digital circuit. 

IEC 61000-4-11 specifies the test environment and test procedures also. Some of them are: 

• The type designation of the Equipment under test (EUT).
• Information on possible connections, corresponding cables, and connectors. 
• Representative operational modes of the EUT for the test. 
• Performance criteria are used and defined in the technical specifications. 
• Operational modes of EUT
• Description of the test setup.

Several other directions like the EUT will be tested for three dips with an interval of a minimum of 10 secs, EUTs with more than one power cord would have to test each power cord individually, use test generators, etc. 

The first edition of the standard was released in 1994. Over the years several amendments and new editions were released replacing the old ones. The Latest and most valid edition is the IEC 61000-4-11:2020 with its two amendments. The latest edition is a technical revision of its predecessors. This edition defined the rise time and fall time of the transients and the origin of voltage dips and short interruptions. 

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