User Guide

3RT1 contactors/ 3RH1 control relays
SIRIUS System Manual
3-8 GWA 4NEB 430 0999-02 DS 01
3.1.2 Positively driven operation
Regulations The regulations for positively driven operation are:
SIRIUS contactors comply with these regulations.
Definition: positively
driven contacts
Positively driven contacts are contacts that are mechanically connected with
one another in such a way that the NC contacts and NO contacts can never
be closed at the same time. This means ensuring that there is a distance
between the contacts of at least 0.5 mm throughout the entire service life
of the contactor, even when there is a defect, such as when the contact has
been wrongly welded (ZH 1/457).
Positively driven opera-
tion in the case of
3RT1/3RH11
Positively driven operation occurs in:
• 3RT101 contactors and 3 RH11 auxiliary contactors in frame size S00 in
both the basic unit and in the auxiliary switch block and also between the
basic unit and the built-on auxiliary switch block
• 3RT1 contactors in frame sizes S0 to S3 between the main contacts and
the normally closed auxiliary contacts. In other words, if the main contact
is welded, the normally closed auxiliary contact will not close.
Positively driven operation does not occur in the case of:
• Electronically optimized auxiliary switch blocks in frame size S00
Positively driven operation is not compulsory for normal controllers. It is,
however, imperative for protective circuits.
3.1.3 Safe isolation
The term "safe isolation" occurs in connection with safety/protective extra-
low voltage (SELV/PELV) and functional extra-low voltage (FELV). Safe isola-
tion reliably prevents voltage that is capable of causing electric shock from
transferring to the safely isolated voltage (e.g. to safety extra-low voltage
that is applied to or switched to the same device).
Safe isolation is also becoming increasingly important due to the more wide-
spread use of electronic systems in high-voltage installations.
Definition Circuits are safely isolated when a single fault does not result in a transfer of
voltage from one circuit to another. Faults to be taken into account are, for
example, a bent or loose conductive part, a bent soldering pin, broken wind-
ing wire, a screw that has fallen out, or a broken partition wall in a device.
• For contactors IEC 60 947-4-1, Appendix H (draft 17B/996/DC)
• For control
relays
IEC 60 947-5-1, Amendment 2, Annex L,
edition 10.1999
• ZH 1/457 Safety rules for controllers on power-operated
presses
•SUVA
Accident prevention guidelines of the Schweizer
Unfallversicherungsanstalt (Swiss institute for acci-
dent insurance)