DC Under Voltage

What does 400 mean?

This fault indicates that the DC link voltage within the drive has dropped below a safe operating threshold. This can be caused by an unstable or lost input power supply, severe voltage sags, or an internal fault in the drive's rectifier section. The drive cannot operate reliably with insufficient DC link voltage and will trip to protect itself.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Verify that the supply transformer (if used) is correctly sized and wired.

2. 4

   Measure the DC link voltage directly (if safely accessible) to confirm the drive's reading and check for ripple.

3. 5

   If the incoming power is stable, the fault might point to an internal issue with the drive's rectifier or DC link capacitors.