There are several tests for circuit breakers. Primary injection is done by injecting the actual current required to energize the circuit breaker. This test makes the circuit breaker interrupt large currents thus shortening its life. A secondary injection test, on the other hand, is done by injecting a current with the contacts closed but with no current flowing on the poles. This is a better way of testing circuit breakers because it uses low voltage signals that are injected to the circuit breaker which prolongs the operating life.
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