Contact Reliability - Siemens sirius System Manual

3RT1/3RH1 contactors
Mechanical life
Display of the contactor
function

3.2.3.2 Contact reliability

3-14
A significant criterion for the economical use of contactors is their mechani-
cal endurance. This is expressed in the number of operations that are possi-
ble without placing a load on the conducting path. You cannot expect too
much in terms of mechanical endurance from switches that have to work
with a relatively high contact load, such as isolators and circuit breakers
without neglecting their cost-efficiency. Contactors, on the other hand, are
switching devices designed specifically for very high numbers of operations
and switching frequency.
The following table shows you the mechanical endurance of 3RT1 contac-
tors:
Device
Basic unit, frame size S00
Basic unit, frame size S00 with built-
on auxiliary switch block
Basic unit, frame sizes S0 to S3
Basic units, frame sizes S00 to S3
with built-on, electronically optimized
auxiliary switch block
Table 3-9: Mechanical endurance
The mechanical endurance can be increased if low current is used (for exam-
ple, 17 V 5 mA) but only if there is no arcing during switching.
The 3RT1926 LED indicator block can be connected to the coil connections
of the contactors in frame sizes S00 to S3. It indicates the status of the con-
tactors by means of the yellow LED. The indicator block can be snapped
onto the front in the opening intended for the inscription plate.
The advantage is that the LED indicator block can be used for AC/DC volt-
ages of 24 V to 240 V and that it is protected against polarity reversal.
Increasingly in industrial control engineering, conventional contactor con-
trols are combined with electronic control systems. Working together in this
way gives rise to higher demands than those when used in conventional
contactor controls.
An important requirement is that the signal generators (auxiliary contacts of
contactors, for example) display high contact reliability at low voltages and
currents, while retaining their full switching capacity at high voltages.
Mechanical endurance
30 mill. operating cycles
10 mill. operating cycles
10 mill. operating cycles
5 mill. operating cycles
SIRIUS System Manual
GWA 4NEB 430 0999-02b