Industrial Engineer · phase 14 of 16
DC Bus Undervoltage
Trip or warning caused when DC-link voltage falls below the level needed for reliable operation.
The Explain card
- Plain English
- A bus undervoltage warning or trip means the DC link has dropped below what the drive needs to run the motor properly. The line sagged, a phase went missing, or the supply was switched off.
- Example
- A large motor starts across the line on the same feeder. The voltage dips for half a second, the drive's bus falls below its limit, and the drive trips or rides through depending on its settings.
- Why it matters
- Undervoltage tells you about the supply rather than the drive. Ride through settings, a kinetic buffering function that uses the load's inertia to hold the bus up, and a stiffer feeder are the answers, and none of them is a new drive.
- Hook
- The drive noticing that the lights flickered.
Where it sits in the deck
Phase 14: VFD Safety, Faults, and Diagnostics
What a drive does when it trips, what the fault codes are telling you, and how safe torque off stops the motor without killing the panel.
