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Write error during operation

Write Error During Operation

Mitsubishi Electric · FR-D700 Inverter

What does Write error during operation mean?

Parameter writing has been attempted while the inverter is actively operating (STF/STR signal is ON) and Pr. 77 Parameter write selection is not set to '2'. This error prevents parameter changes from being applied while the motor is running, which could cause instability, unsafe conditions, or unexpected behavior if allowed.

Common Causes

  • Attempting to modify parameters while the inverter is running (STF/STR signals active) and Pr. 77 (Parameter write selection) is set to '0' or '1'.
  • An automation sequence or operator command tried to change a parameter without first sending a stop command to the inverter.
  • An external communication device (e.g., HMI, PLC) issued a parameter write command while the inverter was actively controlling a motor.
  • A faulty input signal (e.g., STF or STR stuck ON) erroneously indicating operation.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Send a stop command to the inverter (e.g., turn OFF STF/STR signals) to bring the motor to a complete stop.

  2. 2

    Access Pr. 77 (Parameter write selection) and set it to '2' (Write enabled from any source) if frequent on-the-fly parameter changes are required.

  3. 3

    Verify the status of the forward (STF) and reverse (STR) command terminals using a multimeter to confirm they are OFF before attempting parameter writes.

  4. 4

    Ensure the external control system (e.g., PLC) sequence includes a stop command before initiating any parameter write operations.

  5. 5

    Re-attempt the parameter write operation after the inverter has stopped and Pr. 77 is correctly configured.

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Verified technical data. Last updated: April 2026

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Source: Mitsubishi Electric FR-D700 Inverter
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