Applicable Systems
GA700
GA500
A1000
V1000
J1000
Symptoms
The drive trips. The digital operator displays UV2, indicating a control power undervoltage. The internal control circuit power supply voltage has dropped below the minimum.
Possible Causes
- Control circuit power supply failure
- Internal power supply component degradation
- Momentary power interruption that was too long for the ride-through capacity
- Control power transformer or converter fault
Troubleshooting Steps
- Step 1: Check if there was a momentary power interruption in the facility
Confirm with facility whether any power blips or dips occurred - Step 2: Verify the input power is stable and within the drive rating
Input voltage is stable and continuous - Step 3: Power cycle the drive to see if the fault clears on reboot
Drive powers up normally after a complete power cycle - Step 4: If the fault recurs, the internal control power supply may need service
Drive operates without UV2 after internal service
How to Reset
To reset: 1) Power cycle the drive completely (remove and restore input power). 2) If the fault recurs, contact Yaskawa service. Caution: UV2 faults may indicate internal power supply degradation. Schedule service if the fault recurs after power cycling.
Frequently Asked Questions
- Q: What is the difference between UV1 and UV2?
UV1 indicates the main DC bus (power section) is undervoltage, typically caused by input supply issues. UV2 indicates the control circuit power supply is undervoltage, which may be an internal drive issue.
- Q: What is power ride-through on a Yaskawa drive?
Ride-through is the ability of the drive to maintain operation during brief power interruptions (typically a few cycles). The DC bus capacitors provide energy during the interruption. If the interruption exceeds the ride-through time, UV1 or UV2 trips.
Source: Yaskawa GA700 Technical Manual, 2023
Category: PLC & VFD