The rated current 1n of the circuit breaker refers to the current that the trip device can pass for a long time, that is, the trip device rated current. For a circuit breaker with an adjustable release, the maximum current that the release can pass through for a long time. The rated current of the trip unit is 1n, which refers to the maximum current that the trip unit can pass for a long time. The operating current setting value of the long-time overload release is Ir. For fixed releases, 1r=In, and for adjustable releases, Ir is a multiple of the rated current of the release 1n, such as 1r=0.4～1×1n. The short-delay electromagnetic release action current setting value Im is a multiple of the overload release action current setting value Ir, the multiple is fixed or adjustable, such as Im=2～10×Ir. For the non-adjustable type, an appropriate setting value can be selected among them. The instantaneous electromagnetic trip unit operating current rating Im' is a multiple of the trip unit's rated current In, the multiple is fixed or adjustable, such as Im'=1.5～11×In. For the non-adjustable type, an appropriate setting value can be selected among them.