Description of the individual safety relays
3.7 3TK28 safety relays with solid-state enabling circuits
3TK28 safety relays
Manual, 07/2016, NEB926157502000/RS-AB/003
127
3.7.3
3TK2842 safety relay
3.7.3.1
Applications
Applications of the 3TK2842 safety relay
You can use the 3TK2842 safety relay in EMERGENCY STOP devices according to
DIN EN / IEC 60947-5-5 and in safety circuits according to DIN EN / IEC 60204-1, e.g. with
movable guards and protective doors or with contactless protective equipment according to
DIN EN / IEC 61496-1, electrical equipment of furnaces according to DIN EN 50156-1 and
automatic gas burner control systems for gas burners according to DIN EN 298.
Depending on the external circuitry, a max. performance level PL
e
/ Cat. 4 per
DIN EN ISO 13849-1 or SIL 3 per DIN EN / IEC 62061 can be achieved with this device.
The device can monitor safety shutdown mats with evaluation according to the cross-circuit
principle (see Figure 3-62 Safety shutdown mat, autostart (2-channel) (Page 135))
3.7.3.2
Description of function and connection information
The solid-state 3TK2842 safety relay has a safe solid-state output and a time-delayed safe
solid-state output.
The operating state and functioning are indicated by three LEDs.
On startup, the device runs a self-test in which the internal electronics are checked for
correct functioning. All internal parts of the circuit are cyclically monitored for faults during
operation.
Connect the EMERGENCY STOP button or the position switches or light array to terminals
Y11, Y12, and Y21, Y22. Connect the ON button in series with the NC contacts of the
external actuators to the supply voltage L+ (24 V DC) and to terminal Y34. The cascade
input 1 must either be routed via a safe output or directly to supply voltage L+ (24 V DC).
External actuators or loads can be connected to safe outputs 14, 28. Make sure that the
actuators or loads and the 3TK2842 solid-state safety relay have the same ground potential.
If solid-state sensors are used (light array monitoring, etc.) and in single-channel operation,
Y35 must be connected to L+ (24 V DC). For autostart operation, Y32 must be routed
directly and Y34 via NC contacts of the external actuators to L+ (24 V DC).
Correct functioning of the sensor circuits is checked by means of a clocked signal.
OFF-delay times
The table below provides an overview of the OFF-delay times t
v
Table 3- 5
3TK2842
Rated control supply voltage
U
S
[V]
Start type
OFF delay t
V
[s]
Article No. Screw-type Article No.
Spring-type
24 V DC
Auto/
monitored
0,05 ... 3
3TK2842-1BB41
3TK2842-2BB41
0,05 ... 30
3TK2842-1BB42
3TK2842-2BB42
5 ... 300
3TK2842-1BB44
3TK2842-2BB44
