Auxiliary voltage tests of circuit breakers

Measurement of the outer limits of the operating mechanism is required by international standards such IEEE C37 and as IEC 62271, when certifying a circuit breaker (CB). Some of those tests are valuable to repeat in field tests, obviously to ensure that the CB fulfil its design specification, but those tests and some additional tests in similar spirit can also disclose potential future problems. The most common is to vary the auxiliary voltage but it could also be other energy resources for example hydraulic and pneumatic pressure. This application note will focus of the auxiliary voltage, what the standard requires, sort out the terminology and what tests that are valuable to repeat in field tests.