User manual

Compliance Test System 3.0 User Manual
It should be noted that selecting this “inter harmonics grouping” has little impact on the
measurement results for the vast majority of products. Only products with active power factor
correction AND highly fluctuating power consumption will produce inter harmonic levels that
would add to the level of “C” as given above. Most products do not produce inter harmonics, and
therefore the measured harmonic currents will be the same either way.
2.5 The IEC 61000-3-2 Ed 3.0:2005 Standard
The newer standard allows Class A test to exceed 150% limit and less than or equal to 200% of
the applicable limits under the following conditions, which apply all together:
1) The EUT belongs to Class A for harmonics.
2) The excursion beyond 150% of the applicable limits lasts less then 10% of the test
observation period or in total 10 min (within the test observation period), whichever is
smaller, and
3) The average value of the harmonic current, taken over the entire test observation period,
is less than 90% of the applicable limits.
2.6 IEC 61000-3-3 Flicker
Flicker standards are imposed to limit voltage variations caused by loads connected to the low
voltage supply network that would cause lights connected to the same circuit to flicker. A complex
measurement approach outlined in IEC 868, was devised to correlate voltage fluctuations to a
human perceptibility factor (P). The IEC 61000-3-3 standard sets limits for voltage fluctuations
caused by electrical apparatus with a current level up to 16 Amps per phase. The standard
describes a human flicker perceptibility curve that defines the upper limit for acceptable flicker.
This curve plots the percentage of voltage fluctuation against the amount of voltage fluctuations
per minute.
As is the case for the Harmonics standards, the Flicker standard dates back several years and
was rooted in the IEC 555.3 specification. Today however, the IEC 61000-3-3 standard should be
used to evaluate equipment. Note that low power equipment generally does not cause Flicker
and therefore often can be exempted from this requirement. The standard permits the equipment
manufacturer to prove via analysis that their products are unlikely to cause voltage fluctuations.
This analysis becomes part of a Technical Construction File (TCF) which in turn may be used to
obtain product certification.
2.6.1 IEC 61000-3-3 Flicker Test AC Source Requirements
As is the case with Harmonics testing, the IEC 61000-3-3 standard imposes requirements on the
AC source that is used. Some of these requirements are similar and less severe than those
imposed under IEC 61000-3-2. For example, total harmonic distortion of the voltage can be 3 %
for Flicker testing as opposed to only 1.25% for harmonics testing. The voltage regulation needs
to be better than 2 % which is not a problem for most AC sources. In rare cases, the line voltage
may even be used for this purpose. More often than not, however, the use of an AC source with
well-defined specifications is recommended to obtain repetitive test data and eliminate the
possibility of flicker caused by line fluctuations, not load current fluctuations. California
Instruments offers AC power sources in both single and three phase configurations that meet
these requirements. The same AC power source described under IEC 61000-3-2 (Harmonics)
AC source requirements can be used for Flicker test applications.
To simulate the resistance and inductance of the low voltage distribution systems, the IEC
61000-3-3 requires a specific AC source output impedance to be used. This reference
impedance, as specified in IEC-725, is defined in such a way that it approximates a typical
distribution network impedance. Individual countries may require the use of a different reference
impedance that more closely resembles the actual impedance of that countries’ specific
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