The magnitude of the resistance R of the RC
member is determined according to the fol‐
lowing equation:
R=U/I
L
(Where U= Voltage across the load and I
L
=
current through the load)
The magnitude of the capacitor is determined
using the following equation:
C=k * I
L
k=0,1...2 (dependent on the application).
Only use capacitors of class X2.
Units: R = Ohm; U = Volt; I
L
= Ampere; C =
µF
If consumers are connected which have
a high starting current (e.g. plug-in,
switched mains power supplies), then a
means of limiting the starting current
must be provided.
The switching-off process can be investigated
and documented using an oscilloscope. The
voltage peak at the switch contact depends on
the selected RC combination.
Fig. 25: Switching-off process shown on the
oscillogram.
Fig. 26: RC protective circuit for the relay con‐
tacts
Typical AC current application with an inductive
load:
n 1) Load (e.g. alpha motor-driven pump)
n 2) RC-protective circuit
– Typical RC protective circuit at 230 V
AC:
– Capacitor
[0.22µF/X2]
– Resistance
[100 Ohm / 1 W]
(metal
oxide (pulse resistant))
n 3) Relay contact (XR1, XR2, XR3)
7.3.6 Connect the sensors electri‐
cally to the controller
User qualification, electrical installation: Elec‐
trical technician, see
Ä Chapter 3.4 ‘User quali‐
fication’ on page 24
Ready-made coaxial cable
If possible use only pre-assembled
coaxial cables, which you can select
from the product catalogue.
–
Coaxial cable 0.8 m, pre-assem‐
bled.
–
Coaxial cable 2 m-SN6, pre-
assembled.
–
Coaxial cable 5 m-SN6, pre-
assembled.
Assembly and installation
58
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