Applicable Systems
GA700
GA500
A1000
V1000
J1000
Symptoms
The drive trips. The digital operator displays UV1, indicating a DC bus undervoltage. The DC bus voltage has dropped below the minimum operating level.
Possible Causes
- Input power supply voltage dropped below the drive minimum
- Input phase loss (one phase missing)
- Input wiring too thin causing voltage drop
- Internal DC bus capacitor degradation
Troubleshooting Steps
- Step 1: Measure the input voltage at the drive terminals for all three phases
All three phases are present and voltage is within the rated range - Step 2: Check upstream fuses and breakers for blown or tripped elements
All protective devices are closed and fuses are intact - Step 3: Verify the input cable cross-section meets the drive current rating
Cable size meets the drive manual requirements - Step 4: If intermittent, check for loose connections in the supply circuit
All connections are tight and free of corrosion
How to Reset
To reset: 1) Restore the input supply voltage to the rated range. 2) Press the RESET key on the digital operator. Caution: Undervoltage trips can indicate upstream supply problems. Always investigate the power supply quality.
Frequently Asked Questions
- Q: What is the DC bus undervoltage threshold for Yaskawa GA700?
The GA700 trips on UV1 when the DC bus voltage drops below approximately 200V (for 200V class) or 400V (for 400V class drives). The exact threshold depends on the model and parameter settings.
- Q: How does input phase loss cause undervoltage?
A 3-phase drive with one phase missing draws all its power from the remaining two phases, causing increased ripple on the DC bus. When the DC voltage dips below the threshold during the ripple valleys, UV1 trips.
Source: Yaskawa GA700 Technical Manual, 2023
Category: PLC & VFD