Current Transformer - Beckhoff KS3403 Installation Manual

2.5

Current transformer

In principle, the choice of current transformer for the KL3403 is not critical. The internal resistance within the
current circuit of the KL3403 is so small that it is negligible for the calculation of the total resistances of the
current loop. The transformers should be able to produce a secondary rated current of 1 A. The primary
rated current I can be selected arbitrarily. The common permissible overload of 1.2 x I
pn
the KL3403, but may lead to small measuring inaccuracies.
Accuracy
Please note that the overall accuracy of the set-up consisting of KL3403 and current transformers to a large
degree depends on the accuracy class of the transformers.
Approval and certification
A set-up with a class 0.5 current transformer cannot be approved or authenticated. The KL3403 is
not an approved billing meter according to the electricity meter standard (DIN 43 856).
Current types
The KL3403 can measure any current type up to a limiting proportion of 2 kHz. Since such currents are
frequently created by inverters and may contain frequencies of less than 50 Hz or even a DC component,
electronic transformers should be used for such applications. The KL3403 is also available as a special
version with an interface for ±20 mA.
Overcurrent limiting factor FS
The overcurrent limiting factor FS of a current transformer indicates at what multiple of its primary rated
current the current transformer changes to saturation mode, in order to protect the connected measuring
instruments.
Please note the rated current!
The KL3403 must not be subjected to more than 5 A for a prolonged period of time! For systems in which
the over-current limiting factors of the transformers allow secondary currents of more than 5 A, additional
intermediate transformers with a ratio of 5A/1A or 1A/5A should be used!
Protection against dangerous touch voltages
During appropriate operation of the KL3403 with associated current transformers, no dangerous voltages
occur. The secondary voltage is in the range of a few Volts. However, the following faults may lead to
excessive voltages:
• Open current circuit of one or several transformers
• Neutral conductor cut on the voltage measurement side of the KL3403
• General insulation fault
Ensure accidental-contact protection!
The complete wiring of the KL3403 must be protected against accidental contact and equipped with associ-
ated warnings! The insulation should be designed for the maximum conductor voltage of the system to be
measured!
The KL3403 allows a maximum voltage of 500 V for normal operating conditions. The conductor voltage on
the current side must not exceed 500 V! For higher voltages, an intermediate transformer stage should be
used!
KL3403/KS3403
NOTE
WARNING
Version: 3.2.0
Product overview
is no problem for
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