DC overvoltage

What does ALARM 7 mean?

The DC-link voltage has exceeded its limit, causing the frequency converter to trip after a certain time. This often occurs due to regenerative braking or excessive mains voltage, which can damage the inverter section if not mitigated.

• Excessively high incoming AC mains voltage, consistently above the frequency converter's maximum input voltage.
• Rapid deceleration of a high inertia load, causing significant regenerative energy feedback to the DC link.
• Braking resistor failure (open circuit) or incorrect sizing (too high resistance) if installed.
• Deceleration ramp time (P3-42, P3-44) set too short for the application, generating excessive regenerative voltage.
• Fault in the frequency converter's DC-link measurement or protection circuitry.

Click steps to track your progress.

1. 1

   Measure the incoming AC mains voltage (L1-L2, L2-L3, L3-L1) and confirm it is within the frequency converter's specified operating range.

2. 2

   Increase the deceleration ramp time (P3-42 for ramp 1, P3-44 for ramp 2) to allow for slower energy dissipation.

3. 3

   Verify the connection and resistance of the external braking resistor (if present) and ensure it matches the value specified in P2-11 (Brake Resistor Ohms).

4. 4

   Consider implementing a brake chopper and resistor combination or a regenerative front end for high inertia applications.

5. 5

   Review the application for external forces causing motor regeneration, such as overhauling loads or rapid changes in load direction.