User Guide

3RT1 contactors/ 3RH1 control relays
SIRIUS System Manual
GWA 4NEB 430 0999-02 DS 01
3-27
3.2.4.2 Contact reliability
In industrial control engineering, conventional contactor controls are often
combined with electronic control systems. Combining these systems gives
rise to higher demands than those when using only 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.
Switching with auxil-
iary contacts (≤ 110 V
and ≤ 100 mA)
The following applies to the contactors of the SIRIUS range:
If voltages ≤ 110 V and currents ≤ 100 mA are to be switched, the auxiliary
contacts of the 3RT1 contactors or the 3RH1 auxiliary contactors should be
used instead of the main contacts because of their contact reliability. This
comes from their high contact stability due, in particular, to the shape of the
contact pieces (cross-ribbing).
This ensures that the points of contact remain conductive in spite of surface
contamination.
These auxiliary contacts are suitable for electronic circuits (programmable
controllers) with voltages > 17 V and currents in the milliampere range (test
circuit: 17 V, 5 mA).
Cross-ribbing Surface contamination is the most common cause of control circuit contact
faults. Cross-ribbing the contact areas is an extremely effective way of
increasing contact reliability. All the auxiliary contacts of the SIRIUS contac-
tors have this feature.
The following illustration show you how cross-ribbing is particularly effective
against surface contamination due to the high number of contact areas and
high surface pressure:
Fig. 3-6: Contact areas
Depression
Lip
Isolated contact areas
Here: 13 contact surfaces
Accumulated sur-
face contamination