User Guide

3RT1 contactors/ 3RH1 control relays
SIRIUS System Manual
3-28 GWA 4NEB 430 0999-02 DS 01
Contact reliability of
the auxiliary contacts
The contact areas of the SIRIUS auxiliary contacts display a high degree of
contact reliability. Fault frequency rates of H
F
≤ 10
-8
(i. e. < 1 fault per
100 mill. operating cycles at 17 V, 1 mA) have been registered.
These values apply to auxiliary contacts that are either integrated in the con-
tactor housing or can be snapped on as auxiliary switch blocks.
In the case of built-on auxiliary switch blocks at the side, fault frequency
rates are between 10
-6
and 10
-8
.
The tests are based on the requirements placed on signal generators by
electronic controllers.
This means that with the auxiliary contacts of the SIRIUS contactors or aux-
iliary contactors, the permissible contact resistance is only exceeded once
during a total of 10
8
(100 million) switching operations. During a long period
of operation, therefore, a fault is not expected to occur, irrespective of the
number of switching operations.
A restriction applies in the case of auxiliary switch blocks built on at the
side.
Definition of switch
fault frequency H
F
The fault frequency H
F
is defined as the number of contact faults that occur
during a certain number of switching operations.
3.2.4.3 Electrical service life
Electrical service life of
the main contacts
The service life of the contacts consists of:
• at rated operational current I
e
is defined in acc. with utilization category
AC-4 (switching off 6 times the rated operational current):
200 000 operating cycles
• at mixed modes - in other words, if normal switching mode (the rated
operational current is switched off in acc. with utilization category AC-3) is
mixed with occasional inching mode (several times the rated operational
current is switched in acc. with utilization category AC-4):
the service life can be roughly calculated with the following formula:
Key to the formula:
X Contact service life in mixed mode in operating cycles
A Contact service life in normal operation (I
a
=I
e
) in operating cycles
B Contact service life in inching mode (I
a
= a multiple of I
e
) in operating
cycles
C Percentage of the total number of switching operations accounted for
by inching operations
Characteristic curve:
contact service life of
the main contacts
The following characteristic curves illustrate the contact service life of con-
tactors when switching inductive three-phase loads (AC-1/AC-3), irrespec-
tive of the breaking current and rated operational voltage. The prerequisites
are arbitrary (i.e. not synchronous with the phase relation of the control sta-
tion operating the network).
I
a
= breaking current
I
e
= rated operational current
P
N
= rated output of three-phase induction motors with squirrel cage at 400 V
X
A
1
C
100
-------- -
A
B
--- 1–
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