XT2640 Operating Manual
13 July 2016
Page 90 of 187
The XT2640 provides you with assistance in choosing the classification of a EUT by giving the range of Watts
measurements encountered during the assessment; this along with other details available to you regarding the EUT can
then be used to allow you to select the classification to use.
According to EN61000‐3‐2, Class C(spcl) only applies to a EUT having a specific current waveform which has a specific
shape and has a specific phase relationship to the voltage waveform (see figure 2 and clause 7.3b in EN61000‐3‐2). The
XT2640 does not check that the current waveform meets this requirement and so this is your responsibility, it is
recommended that you capture the current waveform in some fashion and check its shape and phase relationship and
report those findings in your final assessment report to support selecting class C(spcl). In general, selection of class C(spcl)
is not recommended and selection of class C(tbl3) is recommended for such a EUT if possible.
18.1.4.2
EN61000
‐
3
‐
12
LIMITS
TABLE
SELECTION
The XT2640 performs assessments according to EN61000‐3‐12 using the tables 2, 3, 4 and 5 as defined in that standard. It is your
responsibility to choose the table to apply.
Note:
The XT2640 provides you with assistance in choosing the classification of a EUT by giving the range of current
measurements encountered during the assessment for each phase which then allows you to decide if the EUT is a “balanced
load”. The definition of balanced load requires knowledge of whether the EUT was designed to have identical phase
loading, and if measurements are used then the word “identical” is probably too narrow as no two measurements are ever
“identical”.
The XT2640 also provides you with assistance in choosing tables 4 and 5 as these rely on the EUT meeting certain
conditions during assessment, entitled ‘a’, ‘b’, ‘c’, ‘d’, ‘e’ and ‘f’ in EN61000‐3‐12 clause 5.2, by reporting whether conditions
‘a’, ‘c’, ‘d’ and/or ‘f’ are met. The XT2640 cannot assist with whether conditions ‘b’ or ‘e’ are met (which are actually both
the same condition) as these depend on knowledge which cannot be obtained from measurements but are dependent on
“
the
design
of
the
piece
of
equipment
”.
The XT2640 also provides you with assistance in choosing which table to use for a “hybrid” EUT by detecting if
circumstance ‘a’ applies as defined in EN610000‐3‐12 clause 5.2. The XT2640 cannot assist with circumstance ‘b’ for
“hybrid” equipment as that is dependent on “
the
construction
of
hybrid
equipment
”.
18.1.4.3
EN61000
‐
3
‐
12
RSCE
VALUE
SELECTION
Assessment of a EUT to EN61000‐3‐12 requires a reference value entitled “Rsce” in EN61000‐3‐12. For all table selections, the
selection of a Rsce value is critical to the pass/fail result of the assessment and EN61000‐3‐12 contains the methods for you to use to
derive its value and also to ensure that the test wiring, current measurement resistance, and supply source resistance are applicable
for a given Rsce value.
Generally, a Rsce value of 33 may be applied (which is then generally acceptable for the EUT to be used on all supplies), but often a
EUT will not meet this requirement so a higher Rsce must be selected by you which allows the EUT to meet the requirements but
restricts the final use of the EUT only to certain supplies.
The XT2640 assists with this by allowing you to either‐
a)
Configure a zero value for Rsce, in that case the XT2640 automatically provides the lowest value for Rsce for which the
assessment results in a passing status for all supply phases (if possible)
b)
Change the configured Rsce value manually and reassess the measurements without actually repeating the assessment
itself.
Reassessing the previous assessment measurements in this manner may not be definitive as a changed Rsce value may affect the
requirements for supply source and the wiring used to perform the assessment, so it may be necessary to actually repeat the
entire assessment to resolve a final Rsce value which is acceptable if the initial assessment was run with wiring etc. assuming a
lower Rsce value.
18.1.5
RANGE
OF
XT2640
MEASUREMENTS
FOR
COMPLIANCE
It is often accepted without question that an EN61000‐4‐7 Class 1 compliant measurement device such as the XT2640 meets the
measurement requirements of EN61000‐3‐2 and ‐12. This is not actually the case in practice; the repeatability and reproducibility
requirements contained in EN61000‐3‐2 and ‐12 far exceed the accuracy requirements for a Class 1 device defined by EN61000‐4‐7,
and the Class 1 accuracy requirement in EN16000‐4‐7 does not guarantee that the measurement equipment even has sufficient
accuracy to assess a EUT to within the limits stated in EN61000‐3‐2 or ‐12.
The range of measurements specified below for the XT2640 include the requirements for Class 1 of EN61000‐4‐7, the repeatability
and reproducibility requirements of EN61000‐3‐2, and the repeatability requirements of EN61000‐3‐12, all with a minimum of a 4:1
margin which is the industry norm for measurement uncertainty, and are valid throughout the operating environment range
specified in section 25.2 of this manual when the XT2640 is using its internal current shunts. If using external current shunts then
see section 18.1.5.1 for further details, depending on the specifications of the external current device the range of currents, power
and power factor specified may be different when using external current devices.
When configured for EN61000‐3‐2 or ‐12 measurements, the XT2640 is guaranteed to exceed the requirements of the above listed
standards within the following ranges of measurements (this specification replaces all other relevant accuracy specifications
contained in section 26 of this manual for assessment results purposes only)‐
Frequency
: Any frequency in the range 45‐54Hz or 56‐65Hz (assessment using frequencies in the range 54‐56Hz is possible
but not recommended).
Voltage
: Any phase voltage in the following range for each channel type (the current option does not affect the ranges
allowed)‐
A or S channel type: 75‐700Vrms.
