Notes On Configuration; Figure 6-2: Basic Circuit Diagram, Line Capacitance - Siemens sirius System Manual

3RH, 3TX, LZX coupling links
Connection

6.2.7 Notes on configuration

Contact microwelding
Switching inductive
loads
Max. line length in AC
operation
6-8
Screw-type terminals
The two-tier coupling links are fitted with slotted screws for a maximum
screwdriver blade width of 4 mm.
Plug-in relay couplers have plus-minus POZIDRIV 2 screw-type terminals.
Cage Clamp terminals
The two-tier coupling links described in Section 6.2.1 are available with
Cage Clamp terminals as well as screw-type terminals.
When capacitive loads are switched, a short-circuit current briefly occurs
(for a period lasting only microseconds) if the capacitor is not connected in
series with a resistor. This can result in contact microwelding and the con-
tact being unable to open after the control supply voltage is removed. To
prevent this from happening, a resistor can be connected in series, or a cou-
pling link with a semiconductor output and short-circuit protection can be
used.
The contacts are tested in acc. with EN 60947-5-1, utilization category AC-
15 and DC-13. Going beyond the requirements of the standard, a continuous
test was carried out on the contacts with an AC-15 load for 100,000 operat-
ing cycles. The electrical service life of the contacts was thus tested over
100,000 operating cycles at the specified current under normal conditions. A
lower load on the contacts or a protective circuit for the inductive load
increases the service life of the contacts. If this service life is insufficient, a
semiconductor coupler with an unlimited service life must be used.
Each wire has a line capacitance that works like a capacitor connected in
series to the coupling link. The effect of this in operation with alternating
current is that so much current may flow due to the line capacitance that the
coupling link does not fall in spite of a switch being open. To remedy this, a
parallel resistor can be fitted to A1/A2 of the coupling link, or an RC combi-
nation can be used. Both of these measures change the performance and
switching times of the coupling link.
The following basic circuit diagram shows the line capacitance:
C = line capacitance
L
Button/
switch
~

Figure 6-2: Basic circuit diagram, line capacitance

The line lengths specified in the NSK catalog were calculated for a line
capacitance of 0.3 nF/m. This depends on the wire used.
A1
Relay coupling link
A2
SIRIUS System Manual
GWA 4NEB 430 0999-02b