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3RT1/3RH1 contactors
SIRIUS System Manual
3-16
GWA 4NEB 430 0999-02b
Electrical service life of
the main
contacts
The rated operational current I
e
is defined in acc. with utilization category
AC-4 (switching off 6 times the rated operational current) for a contact ser-
vice life of approximately 200 000 operating cycles.
If mixed modes are used - 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 opera-
tional current is switched in acc. with utilization category AC-4) - the service
life of the contact pieces can be roughly calculated with the following for-
mula:
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
The following characteristic curves illustrate the contact service life of con-
tactors when switching inductive three-phase loads (AC-3), irrespective of
the breaking current and rated operational voltage. The prerequisites are
arbitrary (i.e. not synchronous with the phase relation of the control station
operating the network).
X
A
1
C
100
---------
A
B
---
1
–
⋅
+
-----------------------------------------
=
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