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ErrorLib — Industrial Fault Code Library

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E.OC1

Overcurrent (Control Power Related)

Mitsubishi Electric · A500 Inverter

What does E.OC1 mean?

This error indication occurs if power is supplied only to the R1 and S1 <L11 and L21> terminals (control power) and a start signal is entered, without the main circuit power (R, S, T) <L1, L2, L3> being present. This indicates an incorrect power supply sequence or missing main power when attempting to operate the inverter.

Common Causes

  • Overcurrent detected in control power circuit.
  • Potential short circuit in control wiring.
  • Malfunction of a control component drawing excessive current.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Verify that main circuit power (R, S, T <L1, L2, L3>) is supplied to the inverter before applying a start signal.

  2. 2

    Ensure jumpers across R-R1 and S-S1 <L1-L11 and L2-L21> are removed if using a separate control power supply.

  3. 3

    Confirm that main power is applied to R, S, T terminals *before* attempting to supply control power to R1, S1 or issuing a run command.

Browse all codes in this manual (21)
Verified technical data. Last updated: April 2026

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Source: Mitsubishi Electric A500 Inverter
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