Power Supply 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.

PSS Certification

Power Supply Indicators

Power Supply Failure Indications

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.

Failure Analysis

Main Contactor Sticking

Recreation of Sticking Contactor

Main Contactor Pictures

Debris

Main Contactor Picture

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

Corrective Actions

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 installingUpdate schematics

Lessons Learned