Troubleshooting of Siemens SIRIUS 3SK2 Safety Relay

The maximum read back time for dark testing of tFB secure output is 3 ms (fixed) or 3~400 ms (F output delayed)

TQ output terminal response time<5 ms (semiconductor output)

TA actuator response time refer to the contactor/motor starter manual

5.3 Fault response time (including flag) under single channel actuator wiring

If a flag is used in the logic, each flag will add a tCYCL.

Formula:

tFR1=tS+tIN+2tCYCL+tTIMER1+tDELAY+tCYCL+tTIMER2+tFB+tQ+tA

t FR1=t S+t IN+2t CYCL+t TIMER1+t DELAY+t CYCL+t TIMER2+t FB+t Q+t 

5.4 Fault response time under dual channel actuator wiring (without flag)

tFR2=tS+tIN+2tCYCL+tTIMER1+tDELAY+tQ+tA

t FR2=t S+t IN+2t CYCL+t TIMER1+t DELAY+t Q+t A

Note: Under dual channel wiring, the dark test readback time tFB is not included in the fault response time, as the dual channel structure can tolerate brief pulses during single channel dark testing.

5.5 Calculation Example: Emergency stop with dual channel shutdown through two contactors

Sensor: SIRIUS 3SB3 emergency stop button, tS=10 ms (assumed)

tCYCL = 15 ms

No timer in logic, no input delay

TQ<5 ms (take 5 ms)

TA: The response time of RT20 contactor is about 20 ms

Motor inertia ignored

tFR2=10+15+2×15+0+0+5+20=80ms

t FR2=10+15+2×15+0+0+5+20=80 ms

This is the longest time from pressing the emergency stop button to the motor being powered off. When calculating the safe distance, the inertia stop time of the motor after the contactor is disconnected should also be added.

Remote diagnosis achieved through PROFIBUS

After configuring the 3RK35 DP interface module on 3SK2, the upper controller (such as SIMATIC S7) can read diagnostic data through PROFIBUS DPV1.

6.1 Available data sets

Content of access methods for devices belonging to the data group

DS0 basic unit (slot 1) reads device status, group faults, configuration errors, and operating modes

DS0 DP interface (slot 0) reads DP interface status and communication failure

DS1 basic unit reads the same as DS0 plus channel diagnostic information

DS92 Basic Unit Read Detailed Device Message List (Up to 1000 entries)

6.2 Diagnostic Frame Structure

PROFIBUS standard diagnostic section (6 bytes)+device related diagnostics (6 bytes)+status messages (12 bytes)+channel diagnostics (up to 18 bytes). The channel diagnosis carries an error number from DS92.

6.3 Common DP Error Numbers

Number Description Explanation

7. Exceeding the upper limit. Memory module is too small, reducing configuration

Too many components below the lower limit, insufficient memory, and cycle time exceeding the limit

9. Incorrect output wiring and device self-test errors

16 Parameterization Error Configuration CRC Error, Invalid Parameter Values

19 Communication error PROFIBUS or system interface error

24 actuator shutdown configuration error, handshake error, wiring/logic error

25 Logical errors in security related shutdown user programs

26 External wiring error, memory module not inserted

The upper PLC can read the data group through SFB 52 "RDREC" and trigger an alarm or automatic reset process based on the error number.

6.4 PROFIBUS bus fault handling

When the DP interface detects a bus interrupt, it will replace the PROFIBUS logic input with 0, but the safe mode will not exit. The LED BF is constantly on in red, and the display screen shows "BF".

After the bus is restored, the device automatically uses the actual value without manual intervention.

Factory reset and device replacement

7.1 Factory reset steps (applicable to all 3SK2)

Turn off the 24V DC power supply.

Press and hold the RESET button on the front panel without releasing it.

Power on again and continue holding down RESET.

Observe the DEVICE LED: first flash yellow, release RESET; If it turns red and flashes, press and hold again; Release RESET within 10 seconds when the DEVICE LED is off.

The LED starts flashing yellow, indicating that it is recovering. After completion, the device will automatically restart and enter configuration mode.

effect:

All configuration information in the internal memory has been deleted.

If an external memory module (45mm model) is inserted, the module data will also be cleared.

The DP address is restored to 126.

7.2 Replacement of defective equipment

Replace safety relay (22.5mm):

Use Safety ES to backup the configuration, or save the configuration through the diagnostic display screen.

Disconnect all terminals (removable terminals can be pulled out as a whole while keeping the wiring intact).

Dismantle the equipment.

Install new equipment of the same model.

Insert the terminal back and load the backup configuration.

Replace safety relay (45mm):

Pay attention to external memory modules: they can only be plugged in and unplugged after power failure. If the old memory module inserted into the new device contains configurations from other device families (such as MSS 3RK3), a configuration error will be returned, and the release needs to be canceled and downloaded again first.

After replacement, a complete functional test (configuration test+system test) must be performed.

Replace DP interface or diagnostic display screen:

Directly replace with the same model without the need for reconfiguration. The system automatically matches hardware after power on.