Siemens SIRIUS 3RW44 Manual page 106

Device Functions
Pre-charge time
Protection against
voltage failure
6-20
The following graphic illustrates the cooling behavior with and without idle time:
Motor
On
Off
Motor
temp. rise
υ
Without
Idle time
υ
With
Idle time
Fig. 6-11: Idle time
The idle time can be set between 1 and 100 s.
Caution
Risk of damage to property.
If the idle time is changed (0 = deactivated), motor protection acc. to IEC 60947
(CLASS 10A, 10, 15, 20, 30) is no longer ensured. I.e. in such cases there will
be no system protection. We recommend protection action to be taken in
parallel.
Caution
Risk of damage to property.
The motor must be designed for such inching operation, otherwise the overload
may cause permanent damage.
When the thermal motor model is tripped, a pre-charge time is started to let the
motor cool down and to prevent the motor from being restarted before the pre-
charge time has elapsed.
If protection against voltage failure is active and the control supply voltage
breaks down while a trip is pending, the current trip condition of the thermal
motor model and the current pre-charge time are stored in the soft starter. When
the control supply voltage returns, the trip condition of the thermal motor model
before voltage failure will be restored.
Idle time
t
Tripping limit
Overload trip
t
Tripping limit
No
Overload trip
t
Idle time
SIRIUS 3RW44 manual
GWA 4NEB 535 2195-02 DS 02