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5

DC link voltage high

Danfoss · VLT HVAC Drive FC 102

What does 5 mean?

The intermediate circuit voltage (DC) has risen above the high-voltage warning limit, which is dependent on the frequency converter's voltage rating. The unit is still active, but operating at an elevated voltage could stress internal components or lead to a trip if limits are exceeded.

Common Causes

  • Incoming AC mains supply voltage exceeding the nominal rating of the frequency converter (e.g., >480V for a 400V drive).
  • High regenerative energy feedback from the motor during rapid deceleration, without a braking resistor or dynamic braking module.
  • Malfunctioning or incorrectly sized external braking resistor, preventing sufficient energy dissipation.
  • Deceleration ramp times (e.g., P3-42, P3-43) set too short for the motor's inertia and load dynamics.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Measure the incoming AC mains voltage at terminals L1, L2, L3 to verify it is within the frequency converter's specified operating range.

  2. 2

    Increase the deceleration ramp time in parameter P3-42 (Ramp Down Time 1) or P3-43 (Ramp Down Time 2) to reduce regenerative energy generation.

  3. 3

    Verify the braking resistor connection (terminals 81, 82) and measure its resistance (in Ohms) to ensure it matches the drive's specifications.

  4. 4

    Inspect the braking chopper circuit for proper function; measure voltage across braking resistor terminals (81, 82) during deceleration (power ON).

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Verified technical data. Last updated: April 2026

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Source: Danfoss VLT HVAC Drive FC 102
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