Case Studies

Where we excel

Intermittent ‘turn-on/off’ faults repeatedly resulting in isolation.

The Problem

  • In 2010 equipment was showing intermittent ‘turn-on/off’ faults repeatedly resulting in isolation. This had become a long standing problem.
  • Equipment was being returned to the OEM, only to be returned ‘NFF’, despite the fault continuing to be present when returned to service
  • Issue was compounded by 12 week lead time for repair, resulting in sets running without a full complement of working inverters


  • 2 weeks of intensive reverse engineering and tests led to discovery of the root cause:
  • Degrading internal connection within IGBT, leading to false error detection


  • Custom test devised to detect the issue at an early stage
  • Failing IGBTs replaced with alternative batch
  • SET took over repair from OEM


  • NFF rate dropped to near zero. The problem was being found and corrected
  • Lead times reduced to typically 2 weeks
  • Sets were running with full compliment of working inverters
  • This and other work contributed to the Silver Spanner Award for most improved fleet

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