Atec Pacific-Power-M6204 - Manual (Page 2)

IEC Flicker Impedance
Applications
The M6204 IEC Flicker Impedance provides the required lumped impedance to create a Flicker test system consisting of
a Programmable AC Power Source, an IEC compliant Flicker Meter or Power Analyzer with Flicker measurement mode
and the required lumped impedance between the AC Source and the UUT. The IEC Flicker standard is based on analyzing
voltage fluctuations caused by changes in UUT load current working against a reference impedance (Z
ref
). Z
ref
was cho-
sen to simulate the typical public utility impedance found in Europe. An incorrect or out of tolerance Flicker Impedance
can lead to significant errors in Flicker measurement results.
Flicker Testing
For single phase applications, the Phase A and Neutral impedance combine to provide the required single phase Z
ref
of
Z = 0.40 + j0.25 Ω so the same M6204 Impedance can be used for either single or three phase Flicker testing.
Phase Impedances: Z
L
= 0.24 + j0.15 Ω each phase
Neutral Impedance: Z
N
= 0.16 + j0.10 Ω
Other IEC Test Standards
The same IEC Flicker impedance is also called out to be used during other IEC Tests. Examples of some of these IEC Test
Standards are shown in the table below.
The M6204 Impedance is compatible with these IEC 61000-4 Immunity test standards.
IEC Reference Descritption
IEC 61000-4-13 Harmonics and Inter Harmonics Immunity Test
IEC 61000-4-27 Unbalance, immunity test for equipment with input current not exceeding 16 A per phase
High Quality
Benefits
• The M6204 IEC Flicker Impedance is constructed of high quality resistive and inductive components sized to handle
load currents up to 16Arms with ease. Proper heat sinking and forced airflow ensure stable operation over a wide
temperature range, even under full load conditions that can persist for many hours. The same impedance module
can be used for either Single phase or Three phase UUT Flicker testing without the need to rewire or re-configure.
Lumped Impedance
• Compared to “synthesized or electronic” impedance solutions as employed by some manufacturers, the M6204 pro-
vides the required separate Neutral Impedance which is not available on AC Sources with synthesized impedance.
This ensures accurate Flicker measurement results under all circumstances, including unbalanced three phase load
conditions caused by the UUT.
• Furthermore, synthesized impedance circuits often have a limited frequency range and may closely approximate
the required impedance at 50Hz but will not accurately simulate the effect of higher current harmonic frequency
components present in UUT current for non-linear loads. A lumped impedance like the M6204 does not have such
a frequency dependency and will correctly respond to current harmonics.
AC Source Matching
• Since most AC Power Sources have a non-zero output impedance, adding the lumped impedance to an AC Source
will have a cumulative effect resulting in an overall combined output impedance to the UUT that will exceed the ac-
tual Z
ref
value. This will result in overstated Flicker measurement results that may lead to an UUT not passing Flicker
test where it otherwise would have.
• By obtaining both the AC Power Source and the IEC Flicker Impedance from the same manufacturer, you can be
sure both are matched. This means the lumped impedance as well as the AC Source output impedance is adjusted
to ensure the combined impedance is within Z
ref
tolerances.
Requirements for the IEC Flicker Impedance when testing UUT’s with Currents up to 75 Arms per phase are covered by
IEC Standard 60725, currently at revision 3.0. For UUT’s with phase currents of 16 Arms per phase or less (either single
or three phase UUT’s), the required Z
ref
is defined as a combination of resistive and inductive components with the fol-
lowing nominal values: