3RT1/3RH1 contactors
SIRIUS System Manual
3-4
GWA 4NEB 430 0999-02b
Utilization category for
AC voltages
Definition of AC-1 to
AC-4
The definitions of the utilization categories AC-1 to AC-4 for main circuits
can be found in the relevant regulations.
The main areas of application for contactors are:
• AC-3 operation: switching of squirrel-cage motors
• AC-1 operation: switching of resistive loads
• AC-4 operation: plugging, reversing, inching
Test conditions
Test conditions for the various utilization categories:
• In AC-1 operation, the contactor must be able to switch 1.5 times the
rated operational current on and off.
• In AC-3 operation, the starting currents of the motors must be controlled.
In other words, the contactor must be able to switch on 10 times the
rated operational current (I
e
), and switch off 8 times the I
e
.
• In AC-4 operation, the contactor must be able to switch off 12 times the
rated operational current (I
e
) and 10 times the I
e
. This represents extre-
mely high stress for contactors because the high starting currents of the
motors have to be switched off.
The breaking current is decisive in calculating the electrical service life:
• In AC-1 and AC-3 operation, 1 x I
e
must be assumed.
• In AC-4 operation, 6 x I
e
must be assumed because the contactor also has
to switch off the motor during startup.
AC Utilization category for
AC voltages
Switching capacity I/I
e
OnOff
Electrical service life I/I
e
OnOff
AC-1 Not an inductive load or
a slightly inductive load
1. 5 1. 5 1 1
AC-2 Slipring
motors: switch on, switch off
44 2.52.5
AC-3 Squirrel-cage motors:
switch on, switch off
during the run
10 8 6 1
AC-4 Squirrel-cage motors:
switch on, plugging or
reversing, inching
12 10 6 6
Table 3-1: Utilization categories, test conditions for AC voltage
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