Testing Magnetic Air Circuit Breakers for 5-Cycle Performance

Magnetic air circuit breakers are now rated 8 cycles even though they inherently demonstrate 5-cycle performance. It is therefore the responsibility of the manufacturer to test the circuit breakers so that the duty imposed by the system does not result in misapplications. To assure proper application as 5-cycle breakers the tests should show that: 1. The interrupting time does not exceed 5 cycles. 2. The rated interrupting current shall be symmetrical amperes. 3. An asymmetrical current, whose total rms value is 10% greater than the rated interrupting current, be interrupted. 4. All interrupting tests be made with a recovery voltage equal to the system voltage.