Applicable Systems
Engel Victus
Symptoms
The servo drive displays Er.971, indicating a DC bus undervoltage warning. The bus voltage has dropped below the warning threshold and is approaching the fault trip level.
Possible Causes
- Incoming power supply voltage too low or unstable
- Power supply wiring gauge too small causing voltage drop under load
- Internal DC bus capacitor degradation reducing bus voltage stability
- Multiple axes drawing current simultaneously causing bus voltage sag
Troubleshooting Steps
- Step 1: Measure three-phase input voltage at drive terminals
All three phases must be within the rated voltage range of the drive - Step 2: Check power cable sizing and length against drive specifications
Cable cross-section must be adequate to prevent voltage drop under full load - Step 3: Inspect DC bus voltage using drive diagnostic menu
Bus voltage should be approximately 1.35x line voltage under normal conditions - Step 4: Verify no excessive loads on the same power circuit
Dedicated power feed recommended for servo drives
How to Reset
To reset: 1) Restore stable power supply. 2) Power cycle the servo drive. Caution: Operating under undervoltage conditions can cause unpredictable motor control and damage the inverter power stage.
Frequently Asked Questions
- Q: What voltage level triggers Er.971?
The warning triggers when the DC bus voltage drops below the warning threshold, typically around 85% of the rated bus voltage.
- Q: Can I ignore Er.971 if it clears on its own?
No. Intermittent undervoltage warnings indicate a power supply or wiring problem that will eventually cause a hard fault and production stoppage.
Source: Engel Servo Drive Controller Manual, Alarm Code Reference Er.971, MXA82A-064-503-00/F
Category: Injection Molding