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.

• Momentary or sustained loss of one or more input phases to the drive.
• Input supply voltage sag below the drive's minimum operating threshold (e.g., below 340VDC for a 400V drive).
• Faulty input rectifier section within the drive, preventing proper DC bus charging.
• Loose or corroded connections at the drive's input terminals (L1, L2, L3) or upstream breaker.
• Excessive transient load on the supply line shared with other equipment causing voltage dips.

Click steps to track your progress.

1. 1

   Measure the incoming AC supply voltage (L1-L2, L2-L3, L3-L1) at the drive's input terminals with a multimeter (Expected: within drive's rated range).

2. 2

   Check for loose connections or corrosion at the drive's input power terminals (L1, L2, L3) and the upstream circuit breaker.

3. 3

   Monitor the DC link voltage (e.g., Display P0-03) during operation to observe its stability and compare to drive specifications.

4. 4

   Verify the capacity of the upstream power source and circuit breaker to handle the drive's inrush and running current.

5. 5

   Inspect the drive's input rectifier bridge for signs of damage (e.g., burn marks, bulging components) if input voltage is stable but DC link is low.