DC under voltage

What does ALARM 8 mean?

The DC-link voltage has dropped below the undervoltage limit. If no 24V DC back-up supply is connected, the frequency converter will trip after a fixed time delay (varying by unit size). This indicates insufficient input power, which can lead to uncontrolled motor shutdown.

• Complete loss of one or more incoming AC mains phases (e.g., L1, L2, L3).
• Severe mains voltage sag or brownout condition below the frequency converter's undervoltage limit.
• Loose or high-resistance connections on the incoming AC mains terminals (L1, L2, L3) causing voltage drop.
• Tripped upstream circuit breaker or blown fuses in the mains supply line.
• Internal fault within the frequency converter's input rectifier or DC-link capacitors.

Click steps to track your progress.

1. 1

   Measure the incoming AC mains voltage (L1-L2, L2-L3, L3-L1) at the frequency converter's input terminals to confirm stable supply.

2. 2

   Check all upstream circuit breakers and fuses for tripped or blown conditions.

3. 3

   Inspect and tighten all mains input wiring connections (L1, L2, L3) at the frequency converter.

4. 4

   Verify the integrity of the 24V DC back-up supply (if installed) and its connection to the control card.

5. 5

   Monitor the DC-link voltage (parameter 16-01 DC Link Voltage) on the display to observe voltage behavior before a trip.