Testing and measurement techniques — IEMI immunity test methods for equipment and systems
IEC 61000-4-36-2020 pdf download.Electromagnetic compatibility (EMC) — Part 4-36: Testing and measurement techniques — IEMI immunity test methods for equipment and systems.
It is essential that testing is conducted in a representative configuration and that careful consideration is given to those aspects of the test set-up that can have a significant impact on test results, for example cable layout. If the requirement is for equipment to be immune to IEMI when in a power-off configuration, then testing with the equipment powered off is applicable. For all other cases, testing with the equipment powered and functioning is essential. Research has shown that transient effects can be significantly enhanced when the equipment is being operated functionally, for example with computer equipment that Is constantly conducting hard drive operations or memory intensive functions.
A summary of test methods that can be used for the assessment of equipment or systems to the effects of IEMI is provided below.
6.2 Derivation of transfer functions
Transfer functions are essential for any equipment or system that is to be tested against the effects of a radiated IEMI source using conducted methods and can also be used to evaluate the protection level of a victim installation.
Transfer functions can either be measured (using techniques such as those discussed in IEC TS 61000-5-9 [7J)or generated analytically using some understanding of relevant geometry.
Transfer functions provide the means of estimating induced currents or voltages on conductors as a result of an EM field illuminating the conductor or from an EM source injected onto external cabling. Transfer functions are generally measured over a broad frequency range (e.g. —1 MHz to —1 GHz) and enable predictions to be computed for any IEMI environment with similar frequency content. Transfer functions can be extended to tens of GHz by measuring internally Induced EM fields and reflecting the change in dominance of the interaction mechanism from cable coupling to aperture coupling.
IEMI simulators are becoming increasingly available as the threat of IEMI is understood and accepted to pose teal risk to the continuing operation of electronic equipment. IEC TR 61000-4-35 [8] contains details on IEMI simulators and their respective parameters. The equipment under test (EUT) shall be set-up in a representative condition of Its intended use for the results to be indicative of the EUT response when fielded. The use of IEMI simulators to assess the protection level of an operational installation is not recommended since it can present a significant interference risk.
For applicable test methods and test set-up of IEMI sources see IEC TR 61000-4-35 [8].
6.4 Radiated tests using a reverberation chamber
IEC TR 61000-4-35 [8] also provides some examples of reverberation chambers. Reverberation chambers can be used to produce the high field levels for equipment level testing and are useful for testing of a material’s shielding effectiveness in accordance with IEC 610004-21 [9).
Care should be taken to understand how the results of measurements made within a
reverberation chamber compare with the realistic case of IEMI interaction which is closer to a
plane wave phenomenon. This difference is discussed in Annex D.
For applicable test methods and test set-up see IEC 61000-4-21 [9].
6.5 Complex waveform injection (CWI)
This method takes the predicted currents from transfer functions and injects them onto conductors one-by-one whilst monitoring for effects. The injected waveforms are a function of the resonances measured by the transfer function and the environment itself and are complex in nature, i.e. they contain many frequencies. Further details on this method can be found in Annex E.
6.6 Damped sinusoidal injection (DSI)
This method uses single frequency damped sinusoidal waveforms and is generally required to be repeated across many frequencies to give an indication of how an EUT can respond to an lEMl environment. For applicable test methods and test set-up see IEC 61000-4-12 [10] and IEC 61000-4-18 [5J.
6.7 Electrostatic discharge (ESD)
Testing to IEC 6 1000-4-2 [11] provides confidence of the continuing operation of the EUT as a result of ESD. ESD is a complex event generally characterised by a fast transient with a risetime of the order of hundreds of picoseconds and a pulse-width of tens of nanoseconds. IEC 61000-4-36-2020 pdf download.