DC under voltage

What does WARNING/ALARM 8 mean?

The DC-link voltage has dropped below the undervoltage limit. This typically indicates an insufficient or fluctuating supply voltage to the frequency converter, leading to a drive trip after a fixed time delay, which varies by unit size. Continued operation with low voltage can cause instability.

• Low or fluctuating incoming AC mains voltage below the drive's specified minimum operating range (e.g., below 340V for a 400V system).
• Temporary complete loss of one or more incoming AC phases, causing a significant dip in the DC link voltage.
• Undersized mains transformer or power supply unable to deliver sufficient current to the drive during motor acceleration or peak load demands.
• High transient loads on the same electrical network causing momentary voltage sags that affect the drive's input.
• Loose connections in the incoming power supply circuit, leading to intermittent voltage drops at the drive terminals.

Click steps to track your progress.

1. 1

   Measure incoming line-to-line voltages (L1-L2, L2-L3, L3-L1) at the drive input terminals (R, S, T) during operation, particularly under load, to verify they remain above minimum threshold.

2. 2

   Inspect all upstream circuit breakers and fuses for trips, loose connections, or signs of wear that could cause intermittent power loss or voltage sag.

3. 3

   Monitor the DC link voltage (e.g., Parameter P0-01 'DC Link Voltage') on the drive display during acceleration or periods of high load.

4. 4

   Verify the drive's mains voltage parameters (e.g., Parameter P8-01 'Mains Voltage', P8-03 'Under Voltage Trip Limit') are correctly configured for the installed power supply.

5. 5

   Consult the facility's electrical engineer to assess the capacity of the mains supply and distribution transformer relative to the connected drive and motor load.