In this paper

based on the analysis of the traditional reliability design method has its instinct limitations in mechanical reliability design and application of vacuum circuit breaker

the mechanical reliability design method of a vacuum circuit breaker（VCB）and its components is proposed based on the physics of failure and reliability physics（PoF/RP） theory

the impulse fatigue life calculation method of the inner transmission parts of the operating mechanism is analyzed theoretically. The fatigue life of vulnerable components of three kinds of operating mechanism

spring-type operating mechanism

separated magnetic circuit type bistable-state permanent magnetic actuator

and high-speed repulsion operating mechanism

used in a 126 kV VCB are analyzed

respectively. Calculated results show that

the impulse fatigue life of the opening and closing inter-locking pawl is 1 654 operations

under the impact of impulse stress during the operation of the spring-type operating mechanism. The impulse fatigue life of the dynamic core and stationary core is calculated to be both 17 710 operations

when the permanent magnetic actuator operates with an opening velocity of 2.5 m/s and a closing velocity of 1.5 m/s. The impulse fatigue life of the supporting part

used as a dynamic transmission part for the contact spring

the impulse fatigue life is 302 operations

when the high-speed repulsion mechanism operates with an opening velocity of 5.5 m/s and a closing velocity of 1.3 m/s. The calculated results are verified to be approximate accordance with the onsite mechanical endurance test results.