Description of the individual safety relays
3.6 3TK28 safety relays with relay enabling circuits
3TK28 safety relays
72
Manual, 07/2016, NEB926157502000/RS-AB/003
3.6.6
3TK2825 safety relay
3.6.6.1
Applications
Applications of the 3TK2825 safety relay
You can use the 3TK2825 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. for
movable guards and protective doors.
Depending on the external circuitry, a maximum performance level PL
e
/Cat. 4 in accordance
with DIN EN ISO 13849-1 or SILCL 3 in accordance with DIN EN/IEC 62061 can be
achieved with this device.
3.6.6.2
Description of function and connection information
The 3TK2825 safety relays have three instantaneous redundant enabling circuits with NO
functions and two instantaneous one-channel signaling circuits. The enabling circuits are
used for safety-related shutdown of actuators; the signaling contacts are used for a non-
safety-related signaling function.
Diagnostics is performed using three LEDs.
The 3TK2825 is suitable for monitoring actuator and sensor circuits according to
DIN EN / IEC 60204-1 in "Autostart" or "Monitored start" mode.
When the EMERGENCY STOP buttons are released or position switches operated and the
ON button is pressed, the redundant safety relays, the electronics, and the external
contactors are monitored to ensure that they are functioning correctly.
If monitoring results in a fault-free state, it is possible to start the device using the ON button
(in "monitored start" mode). This closes the enabling circuits. In autostart mode, starting and
therefore closing the enabling circuits is initiated directly after closure of the sensor contacts
on detection of the fault-free state.
With 3TK2825, the ON circuit Y33/34 is checked for short-circuit. That means it is identified
as a fault if Y33/34 is closed before the EMERGENCY STOP button is reset.
The device also monitors the sensor circuits for cross-circuits. This is done based on various
potentials in the sensor circuits.
3.6.6.3
Commissioning
After the supply voltage is applied to terminals A1 and A2, the 3TK2825 safety relay is ready
for operation. The internal parts of the circuit are constantly monitored for faults during
operation.
If any sensor is operated, or a fault is detected, the safety relay disconnects without delay.
