Overview

Safety relays with relay enabling circuits – safety with floating contacts

SIRIUS safety relays with relay enabling circuits are not only extremely space-saving thanks to their compact design, they also offer extra safety with positively driven NO and feedback contacts in pairs. If one of the contact welds, the other assumes the disconnection of the circuit. A positively driven feedback contact (NC) then performs the fault detection of the damaged work contact (NO).

3SK121 expansion units are available for increasing the number of enabling circuits.

3TK2826 safety relays

The 3TK2826 is a parameterizable safety relay. It is used as an evaluation unit for typical safety chains (identify, evaluate, realize). A number of functions can be set using the DIP switches on the front. The 3TK2826 is therefore universally applicable.

Safety sensors (e. g. EMERGENCY-STOP command devices) are connected to the input, contactors or valves for switching off the "dangerous function" are connected to the output. The 3TK2826 performs monitoring of the sensor and actuator functions as well as the safe disconnection of the outputs (enabling circuits).

3TK2826 with DIP switch

DIP switch No.	OFF	ON	Circuit diagram
1	Without cross-circuit monitoring	Switching mat operation
2	NC/NO evaluation	NC/NC evaluation
3	2 x 1-channel	1 X 2-channel
4	Debounce time for sensor inputs ?50 ms	Debounce time for sensor inputs ?10 ms
5	Autostart sensor input	Monitored start sensor input
6	Cascading input autostart	Monitored start cascading input
7	With start test	Without start test
8	Automatic start after mains failure (not permitted in connection with a start test)	Without automatic start after mains failure

For an overview table of the selection and ordering data, see the following PDF.