In Part I, we introduced you to the concept of testing equipment for immunity to voltage dips and short power interruptions in accordance with IEC 61000-4-111. In addition to specifying the test waveforms, the standard also specifies AC source requirements for full compliance testing.
Most of these requirements are easily met by the California Instruments iX Series AC/DC power sources. Some, however, are not trivial and warrant more attention:
500 A EUT inrush current capability
1 to 5 msec rise and fall time at source output
Current capability at reduced voltage levels
The inrush current requirement of 500 Amps however is not practical, as it would raise the price of the AC source considerably. Since most EUTs don’t draw this kind of inrush current, sizing an AC source for this current level is impractical. Instead, the standard allows the source to measure the peak inrush current to the EUT and verify that it does not exceed the capabilities of the AC source. Our instrument control software provides a “peak inrush current pre-test” option in the IEC 61000-4-11 test window for this purpose. If the peak inrush current of the EUT, as defined in the IEC standard, exceeds the AC source capability, a warning is issued to the operator.
To fully meet the AC source qualification for IEC 61000- 4-11 testing, option -EOS can be added to the iX Series AC/DC power source to ensure output rise and fall times between 1 and 5 micro seconds. This option also ensures the source’s ability to deliver higher rms currents at reduced voltage levels for constant power products. Specifically, 5001iX with -EOS option meets the 23 A at 70% and 40 A at 40 % of Unom requirement called out in the IEC 61000-4-11 standard.
The pass/fail criteria in IEC 6100-4-11 is rather vague. It says,
“The test results shall be classified on the basis of the operating conditions and functional specifications of the equipment under test, as in the following, unless different specifications are given by product committees or product specifications.
a) Normal performance within the specification limits.
b) Temporary degradation or loss of function or performance which is self-recoverable.
c) Temporary degradation or loss of function or performance which requires operator intervention or system reset.
d) Degradation or loss of function which is not recoverable due to damage of equipment (components) or software, or loss of data.
As a general rule, the test result is positive if the equipment shows its immunity, for the duration of the application of the test, and at the end of the test the EUT fulfills the functional requirements established in the technical specification.”
When using the iX Series to perform these tests, you can use the source to measurement measure the load current of the device under test to determine if it is still operating after applying the voltage dips and interruptions. Note, however that this measurement doesn't really determine if the unit is really functioning, only drawing power. For example, if you're testing a microprocessor-controlled device, the processor may have locked up or rebooted during the test. In this case, you may want to run some kind of functional test to determine if the device has passed or failed the test.
For more information on IEC 61000-4-11 testing, contact AMETEK Programmable Power by sending an e-mail to email@example.com or phoning 800-733-5427.
IEC 61000-4-11:2004, Electromagnetic Compatibility (EMC) – Part 4-11: Testing and Measurement Techniques – Voltage Dips, Short Interruptions, and Voltage Variations Immunity Tests. International Electrotechnical Commission. https://webstore.iec.ch/publication/4162.