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ErrorLib — Industrial Fault Code Library

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Safety stop

Safety Stop Function Activated

Mitsubishi Electric · FR-D700 Inverter

What does Safety stop mean?

The inverter's safety stop function has been activated, resulting in the immediate shutdown of outputs. This typically indicates that a safety condition has been detected by the system, often an open circuit on the safety input terminals (S1 and SC, S2 and SC), or potentially an internal failure if these inputs are correctly shorted and the drive remains enabled. This is a critical protective action.

Common Causes

  • Activation of a connected safety device (e.g., emergency stop button, safety light curtain, safety interlock) causing an open circuit on the safety input terminals (e.g., STO, SS1).
  • Wiring fault in the safety circuit (e.g., broken wire, loose connection) leading to a loss of signal on the safety input.
  • Misconfiguration of safety parameters or the safety input bypass settings (e.g., if dual-channel safety is required).
  • Internal fault within the inverter's safety monitoring circuit.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Identify and reset all activated external safety devices (e.g., emergency stop button, gate interlock, light curtain).

  2. 2

    Verify the integrity of the wiring to the inverter's safety input terminals (e.g., STOA, STOB terminals for Safe Torque Off) using a multimeter for continuity.

  3. 3

    Inspect the status of the safety relay or safety PLC providing the safety input signal to the inverter.

  4. 4

    Ensure all safety circuit components are restored to their safe operating state and all guard doors are closed.

  5. 5

    Clear the safety stop fault on the inverter and attempt to re-enable the output.

Browse all codes in this manual (78)
Verified technical data. Last updated: April 2026

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Source: Mitsubishi Electric FR-D700 Inverter
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