What about electrical tests on breakers?Connect a high current test across the breaker one pole at a time to conduct the following tests:

  • Contact voltage drop. Apply the rated current. If voltage drop exceeds specifications, you may have incorrect contact pressure, loose connections, or damaged contacts.
  • Short circuit protection capability. Pulse the breaker with increasing current, until the breaker trips. Compare to specifications.
  • Overload tripping capability. Apply 300% of the rated current until the breaker trips. Compare how long this takes to the specified time.

Using an insulation resistance tester:

  • Check the contacts. Check open and closed, phase-to-phase, and phase-to-ground.
  • Disconnect any solid-state components and test all control wiring at 1,000VDC.

We'll look at more IR tests in Part 9 of this series.