Applicable Systems
EFC
FEX
FEI
HNC
Symptoms
Safe stop process timeout. The safety system initiated a safe stop, but the motor did not reach zero speed within the configured time limit. The system escalates to Safe Torque Off.
Possible Causes
- Motor deceleration time too long for the configured safe stop timeout
- Mechanical brake not engaging or worn
- Safe stop monitoring time set too short
- High-inertia load requiring longer decel time than configured
Troubleshooting Steps
- Step 1: Check the safe stop monitoring time parameter in IndraWorks AS
Time setting matches the calculated deceleration time for the load inertia - Step 2: Verify the motor deceleration time matches the safety assessment
Calculated decel time < safe stop monitoring time - Step 3: Test mechanical brake operation if equipped
Brake engages and stops the load within rated time - Step 4: If the safe stop time is too short, recalculate and adjust after safety review
Updated time setting accommodates actual load inertia
How to Reset
1) Check safe stop monitoring time. 2) Verify deceleration time. 3. Test brake. 4) Adjust time if safety assessment permits. Caution: Safe stop monitoring time is safety-critical. Only increase after recalculation per the safety assessment.
Frequently Asked Questions
- Q: How do I calculate the safe stop monitoring time?
Monitoring time = deceleration time + safety margin (typically 1.5x). Deceleration time depends on total inertia (motor + load) and available braking torque.
- Q: What happens if the motor doesn't stop in time?
The safety system escalates from Safe Stop 1 (controlled decel) to Safe Torque Off (immediate torque removal). The motor coasts to a stop without controlled deceleration.
Source: Rexroth IndraDrive Safety Integrated Manual, Bosch Rexroth AG
Category: PLC & VFD