Measuring Current With An External Current Transformer - Siemens SIMOCODE pro System Manual

13.3.5 Measuring current with an external current transformer (interposing
transformer)
Description
SIMOCODE pro can be operated with external current transformers. The
secondary cables of the current transformer are looped through the three
through-hole openings of the current measuring module, and short-
circuited. The secondary current of the external current transformer is the
primary current of the SIMOCODE pro current measuring module.
Notice
If the main circuit is using rated current, the secondary current of the
current transformer must be within the setting range of the current
measuring module used!
Main circuit
L1 L2 L3
M
3~
Fig. 13-20: Measuring current with an external 3UF18 current transformer
Transformation ratio
The transformation ratio is calculated using the following formula:
Transformation ratio =
In the following examples, the displayed actual current flowing does not
need to be converted, even when an interposing transformer is used, since
SIMOCODE pro only outputs the proportional value, based upon the
parameterized set current I
SIMOCODE pro
GWA 4NEB 631 6050-22 DS 03
Secondary circuit
K1
K2
K3
L
3UF18 current transformer
Primary current (external current transformer)
Secondary current x number of loops n
(ext. current transformer)
.
s
Mounting, wiring, interfaces
Current measuring
Basic unit
module 3UF 71 3UF 70
(current measuring module)
13-33