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Power Supply PSS Certification

The PSS certification process, conducted biannually, aims to validate the operation of power supply systems. A recent failure in the ARC1 revealed that the PSS signal remained active, failing to deactivate the main contactor. Investigations indicated that improper screw lengths used for auxiliary contacts on the main contactor led to debris accumulation and sticking issues. As corrective actions, all affected power supplies were checked, cleaned, and tested. Future procedures will include rigorous evaluations for changes to equipment and updates to schematics for enhanced diagnostics.

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Power Supply PSS Certification

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  1. Power Supply PSS Certification

  2. PSS Certification • PSS test conducted twice a year to verify operation of PSS enables and operation • ARC1 Fails PSS certification. Will not turn off when PSS signal is disabled • Power Supply computer indicates that off signal has been sent, but hardwired signal indicates that Main Contactor is not de-energized. PSS will not drop to OFF/Safe status • Main contactor disables after a while, and problem is not easily repeatable.

  3. Power Supply Indicators

  4. Power Supply Failure Indications

  5. Failure Analysis • Main Contactor is sticking and does not decouple when control voltage is disabled. • Investigation finds that Auxiliary contacts have been attached onto Main contactor using screws that were too long • Long screws break through Bakelite material and small pieces onto rails of the armature assembly of the Main Contactor. This may have contributed to some of the “stickiness”, but not conclusive.

  6. Main Contactor Sticking

  7. Recreation of Sticking Contactor

  8. Main Contactor Pictures

  9. Debris

  10. Main Contactor Picture

  11. Corrective Actions • ALL power supplies with Auxiliary contacts have been checked for correct screw lengths. • 9 Additional Supplies found to have incorrect screw length and minute debris in the Main Contactor • All Contactors cleaned, voltage tested and replaced • Additionally, power supply schematics are being revised for quicker diagnostics in the future

  12. Lessons Learned • Changes or additions to existing equipment must be fully analyzed for correct configuration • Non-routine tasks must be evaluated before work is conducted • Test all equipment before installing • Update schematics

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