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Product overview
Fig. 3: Principle coil current transformer
Dangerous voltages with secondary side not connected
The secondary winding must be connected to a current measuring device or short-circuited, otherwise high
core losses or dangerous voltages may occur on the secondary side. Before replacing the measuring elec-
tronics in the secondary circuit, the current transformer must therefore be short-circuited at its secondary
terminals.
Grounding of secondary terminals
According to DIN VDE 0141 (01/2000) paragraph 5.3.4, current and voltage transformers for nomi-
nal voltages from U
(U
≤ 1.2 kV), grounding is not required if the transformer housings do not have any metal surfaces
m
with large contact areas.
Characteristic values and calculation
In principle, the construction, and thus also the calculation, correspond to a normal transformer. The basic
relationship between input and output current is determined by the ratio of the number of turns N of the
primary and secondary sides. An important characteristic value in the design of a current transformer is
therefore the transformer ratio.
I
= N
/N
* I
Out
1
2
In
10
WARNING
= 3.6 kV must be grounded on the secondary side. For low voltages
m
Version: 1.0
SCT5xxx
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