Applicable Systems
EFC
FEX
FEI
HNC
Symptoms
Maximum safe speed exceeded. The safety system has detected that the actual motor speed has exceeded the configured maximum safe speed limit. The safe stop function is immediately activated.
Possible Causes
- Motor speed exceeded the configured safe speed limit (S-0-0053)
- Encoder feedback error causing false speed reading
- Safe speed limit set too low for the application
- Mechanical overhauling load driving the motor beyond safe speed
Troubleshooting Steps
- Step 1: Check the safe speed limit parameter (S-0-0053) in IndraWorks AS
Parameter value matches the application safety assessment - Step 2: Verify encoder feedback is accurate by comparing with a tachometer
Speed reading from encoder matches independent tachometer - Step 3: Review the application to determine if the safe speed limit needs adjustment
If the safety assessment allows, increase the safe speed limit - Step 4: If speed genuinely exceeded the limit, investigate the mechanical cause
Address overhauling load or controller tuning issues
How to Reset
1) Investigate speed feedback accuracy. 2) Review safe speed limit setting. 3) Address mechanical causes. 4) If safety assessment permits, adjust the limit. 5) Reset requires safety function acknowledgment. Caution: Safe speed parameters are safety-critical. Only modify after a proper safety assessment per EN ISO 13849-1.
Frequently Asked Questions
- Q: What is a 'safe speed'?
Safe speed is a safety-relevant parameter that defines the maximum allowable motor speed under all conditions, including fault scenarios. It is set during the machine safety assessment.
- Q: Who can change the safe speed limit?
Only qualified safety personnel after conducting or reviewing the machine risk assessment. The parameter is typically protected by a safety password.
Source: Rexroth IndraDrive Safety Integrated Manual, Bosch Rexroth AG
Category: PLC & VFD