A solenoid assembly for a circuit breaker having a clapper with an increased mass is provided. The mass, preferably at least one non-ferrous slug, increases the mass of the clapper so that the solenoid response time is slowed. That is, the added mass creates an inertial delay that slows the solenoid clapper as the clapper moves between the first position and the second position. Preferably, the delay is between 48 ms and 60 ms, and more preferably 50 ms. The clapper having a non-ferrous slug may also be incorporated into existing circuit breakers by, for example, coupling the non-ferrous slug to the preexisting clapper, or replacing the clapper with a clapper assembly having at least one non-ferrous slug thereon.