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## A.74 Definition
Yaskawa Sigma-7 alarm A.74 is overload — the motor has been running above rated torque for too long. The drive calculates a thermal model and triggers A.74 when the model reaches 100%.
## Check the Overload Level
In SigmaWin+, monitor Un009 (overload level %). Normal operation should stay below 50%. If Un009 is consistently above 70%, overload alarm is likely.
## Common Causes on Servo Press
### 1. Forming Force Exceeds Motor Rating
The press is being used beyond its rated tonnage. Check:
- Actual tonnage monitor reading vs press rated tonnage
- Material thickness and grade vs die design spec
### 2. Motion Profile Too Aggressive
High acceleration + high forming speed = high peak torque. The thermal model accumulates even if each individual stroke is within limits.
Fix: Reduce forming speed from e.g. 100mm/s to 70mm/s. Reduce acceleration. Add rest time between strokes.
### 3. Gib Friction
Excessive gib friction adds constant load to the motor. Check gib clearance — if below 0.005mm, the gib is too tight.
### 4. Counterbalance Pressure Wrong
If pneumatic counterbalance pressure is too low, the motor must lift the full slide weight on the return stroke. Check counterbalance pressure per press manual.
## Parameter Pn521
Pn521 sets the overload warning level (default 20% before alarm). Do not increase this to avoid the alarm — fix the root cause instead.
## Reset
A.74 requires the motor to cool down. Wait until Un009 drops below 20% before resetting.