The increase of spring pressure of contact of vacuum circuit breaker will cause the circuit breaker not to close reliably. The four-bar structure will

to a certain extent

affect the output characteristics and mechanical benefits of the mechanism

and thus affect both reliability and stability of circuit breaker in closing operation. In this paper

the operation principle of vacuum circuit breaker is analyzed and the mathematical model of the spring operation mechanism is set up. The cam profile

angle and size of transmission lever

dimension parameters of connecting plate and closing roller in the mechanism are optimized

and the simulation model of spring operating mechanism is set up. The dynamic simulation shows that the pressure of the spring of the contact after optimization is increased by 58% (increase from 1 700 N to 2 686 N)

which can still assure the reliable closing of the operating mechanism of the circuit breaker. The test results show that when the contact spring pressure is 2 500 N

the contact of the circuit breaker can engage reliably

the average closing speed is reduced to 0.68 m/s

and the bouncing time is shortened by 18.4%. The overall scheme after optimization meets the design requirements and has good reliability and stability.