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9

Inverter overload

Danfoss · VLT HVAC Drive FC 102

What does 9 mean?

The frequency converter is operating with an excessively high current for too long, nearing its thermal protection limit. The electronic thermal inverter protection counter issues a warning at 98% and an alarm trip at 100%. The unit cannot be reset until the counter drops below 90%, indicating a significant risk of damage to the inverter if prolonged.

Common Causes

  • Output current to the motor exceeding the frequency converter's rated current for an extended period.
  • Frequency converter is undersized for the motor and application's continuous load requirements.
  • Mechanical binding, obstruction, or excessive friction in the driven machinery causing increased motor torque demand.
  • Acceleration or deceleration ramp profiles (P3-41, P3-42) set too short for the load's inertia and drive capacity.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Measure the actual output current to the motor using a clamp meter on one of the output phases (U, V, W) and compare it against the drive's rated current.

  2. 2

    Verify parameter P1-02 (Motor Current) and P1-03 (Motor Speed) are correctly set according to the motor's nameplate data.

  3. 3

    Mechanically inspect the driven load for obstructions, excessive friction, or misalignment that could increase torque requirements.

  4. 4

    Increase acceleration and deceleration ramp times in parameters P3-41 (Ramp Up Time 1) and P3-42 (Ramp Down Time 1) to reduce peak currents.

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Verified technical data. Last updated: April 2026

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110 Volts low10Motor overload temperature11Motor thermistor over temp
Source: Danfoss VLT HVAC Drive FC 102
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