GA500 Uv1 fault on a conveyor, what to check first?
My GA500 drive on a conveyor system keeps tripping with a Uv1 fault while running, especially when under load. What should I check first to troubleshoot this?
A Uv1 fault on a Yaskawa GA500 drive indicates a DC Bus Undervoltage, meaning the DC bus voltage dropped below the level set in L2-05 while the drive was operating. This typically occurs when the input power supply is unstable, dips, or loses a phase, or due to issues with the drive's input wiring or components. The fault triggers a shutdown if the power loss is not restored within 15 ms, causing the motor to coast to a stop.
Likely causes and checks
1Input phase loss
- Points to it
- The drive is losing one or more phases of its input power supply, leading to an insufficient DC bus voltage, especially under load. This can also be indicated by a PF (Input Phase Loss) alarm.
- Check
- Isolate the drive, then inspect the main circuit input wiring and fuses. Measure all three input phases under load to confirm stable voltage.
2Loose input terminals
- Points to it
- Poor connections at the input terminals can cause intermittent power loss or voltage drops, leading to undervoltage faults. This may also manifest as heat marks on the terminals.
- Check
- Tighten all input terminal screws to the manufacturer's specified torque.
3Supply dip, loss, or unstable voltage
- Points to it
- External power supply issues, such as voltage dips, complete power loss, or general instability, can cause the DC bus voltage to drop below the detection level.
- Check
- Log the input voltage over time to identify any correlation with plant power events or the starting of large loads. If the supply is confirmed stable, check the main circuit magnetic contactor.
4Worn main circuit capacitors
- Points to it
- Over time, the main circuit capacitors can degrade, reducing their ability to maintain stable DC bus voltage, particularly in older drives, even with a healthy power supply.
- Check
- Read parameter U4-05 [CapacitorMaintenance]. If the value is above 90%, the manual recommends replacing the board or the entire drive.
Next check: After checking the input wiring, fuses, and terminal tightness, monitor the input voltage to the drive to rule out external power supply issues. If the problem persists, investigate the drive's internal components like capacitors.
Related questions
Describe the fault or upload a photo, and InduQT checks it against the manufacturer manuals. Share the result here when it helps someone else.