ot1 Over-torque 1 Fault in Delta MS300 Drive

ot1 Over-torque 1 in the Delta MS300 Drive indicates that the motor torque has exceeded the configured Over-torque 1 detection level. The drive continuously monitors the motor torque to protect the motor and driven machine from excessive mechanical stress. When the actual torque exceeds the threshold defined by the over-torque protection parameters, the drive generates Warning/Fault ot1 and responds according to the configured protection mode.

ot1 Over-torque 1 Fault in Delta MS300 Drive


This condition generally indicates a problem with the mechanical load, motor sizing, drive parameter settings, or application configuration, rather than a hardware fault in the drive.

Possible Causes

  • Incorrect Over-torque 1 parameter settings.
  • Incorrect Pr.06-07 Over-torque detection level.
  • Incorrect Pr.06-08 Over-torque detection time.
  • Mechanical lock or jam.
  • Excessive machine load.
  • Motor capacity too small for the application.
  • Acceleration or deceleration time too short.
  • Excessive V/F voltage setting.
  • Incorrect V/F curve configuration.
  • Excessive load during low-speed operation.
  • Torque compensation gain set too high.
  • Improper speed tracking parameter settings.
  • Restart after momentary power loss causing high torque.
  • Restart after fault causing excessive current.
  • Incorrect maximum current setting for speed tracking.
  • Poor application tuning.

Solutions

  • Reconfigure Pr.06-07 and Pr.06-08.
  • Remove any mechanical obstruction or machine jam.
  • Reduce the machine load.
  • Replace the motor with a larger capacity if necessary.
  • Increase the acceleration and deceleration times (Pr.01-12 to Pr.01-19).
  • Adjust the Motor 1 V/F Curve (Pr.01-01 to Pr.01-08).
  • Correct the midpoint voltage setting if necessary.
  • Reduce the load during low-speed operation.
  • Increase motor capacity for heavy-duty applications.
  • Adjust Pr.07-26 Torque Compensation Gain until the output current decreases without causing motor stall.
  • Correct the speed tracking parameter settings.
  • Enable and properly configure the speed tracking function.
  • Adjust Pr.07-09 Speed Tracking Maximum Current.
  • Verify Pr.06-06 Over-torque Detection Selection is configured for the required operating mode.

Additional Information

The Delta MS300 continuously monitors motor torque during operation.

ot1 Over-torque 1 is generated when the motor torque exceeds the configured protection threshold.

According to Delta, the first items to verify are:

  • Pr.06-07 – Over-torque Detection Level
  • Pr.06-08 – Over-torque Detection Time
  • Mechanical load conditions
  • Motor sizing
  • V/F configuration
  • Torque compensation settings

The drive response is determined by Pr.06-06 – Over-torque Detection Selection:

Pr.06-06 ValueDrive Response
0No function
1Continue operation after over-torque detection during constant speed
2Stop after over-torque detection during constant speed
3Continue operation after over-torque detection during RUN
4Stop after over-torque detection during RUN

Unlike an Overcurrent Fault, ot1 Over-torque 1 is based on the calculated motor torque rather than instantaneous output current.

Common Symptoms

  • Drive displays ot1 Over-torque 1.
  • Warning occurs during heavy load.
  • Motor slows under load.
  • Drive trips if configured to stop.
  • High output current is observed.
  • Machine stalls during startup.
  • Warning appears during low-speed operation.
  • Alarm occurs after restart following a power failure.
  • Torque compensation causes excessive current.
  • Warning clears after reducing the load or correcting parameters.

Recommended Troubleshooting Sequence

  1. Verify that the warning/fault is ot1 Over-torque 1.
  2. Check Pr.06-07 – Over-torque Detection Level.
  3. Check Pr.06-08 – Over-torque Detection Time.
  4. Verify Pr.06-06 – Over-torque Detection Selection.
  5. Inspect the machine for mechanical binding or overload.
  6. Reduce the machine load if necessary.
  7. Increase Pr.01-12 to Pr.01-19 (acceleration/deceleration times).
  8. Review the Motor 1 V/F Curve (Pr.01-01 to Pr.01-08) and adjust the midpoint voltage if required.
  9. Reduce the load during low-speed operation.
  10. Adjust Pr.07-26 – Torque Compensation Gain.
  11. Verify speed tracking parameters and Pr.07-09 – Speed Tracking Maximum Current.
  12. Confirm the motor is correctly sized for the application.
  13. Reset the warning or fault if required.
  14. Test the drive under normal operating conditions.
  15. Contact Delta technical support if the warning or fault persists.

ot1 Over-torque 1 Check Table

Check PointAction
Pr.06-07Verify Over-torque Detection Level
Pr.06-08Verify Over-torque Detection Time
Pr.06-06Confirm Over-torque Detection Selection
Mechanical loadRemove jams or excessive load
Motor capacityVerify suitability for the application
Pr.01-12 to Pr.01-19Increase acceleration/deceleration times if necessary
Motor 1 V/F CurveAdjust Pr.01-01 to Pr.01-08, especially midpoint voltage
Pr.07-26Reduce Torque Compensation Gain if excessive
Pr.07-09Verify Speed Tracking Maximum Current
Delta technical supportContact if the warning or fault remains after inspection

Preventive Maintenance Tips

  • Properly configure Pr.06-06, Pr.06-07, and Pr.06-08 during commissioning.
  • Avoid operating the machine above its rated load.
  • Periodically inspect the driven equipment for mechanical binding.
  • Use appropriate acceleration and deceleration times.
  • Verify V/F curve settings whenever the motor or application changes.
  • Tune torque compensation carefully to avoid excessive current.
  • Verify speed tracking parameters after firmware or application changes.
  • Ensure the motor is correctly sized for the application.
  • Monitor motor current and torque trends during routine maintenance.
  • Record recurring ot1 Over-torque 1 warnings to assist long-term diagnostics.

Proper configuration of Pr.06-06 (Over-torque Detection Selection), Pr.06-07 (Over-torque Detection Level), Pr.06-08 (Over-torque Detection Time), Pr.01-12 to Pr.01-19 (Acceleration/Deceleration Time), Pr.07-26 (Torque Compensation Gain), and Pr.07-09 (Speed Tracking Maximum Current), together with inspection of the mechanical load, motor sizing, and V/F curve settings, will help prevent recurring ot1 Over-torque 1 warnings in Delta MS300 drives, ensuring reliable motor operation, effective overload protection, and dependable long-term performance of the drive system.

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