Study On Permanent Magnetic Actuator And Intelligent Control Of Middle-voltage Circuit Breaker

As a kind of new Actuator of Circuit Breaker, Permanent Magnetic Actuator (PMA) has the advantage of less parts, higher reliability and maintenance-free and so on, so it has been paid more and more attention by people all over the world.In the paper, the mostly work is the study on Middle-voltage Circuit Breaker PMA ,its principle, the static characteristic, the dynamic characteristic and the control system. In the calculation of static magnetic field, the Finite Element Method (FEM) is used. The force characteristic of PMA with exciting current and without exciting current are calculated and analyzed. Because the dynamic character of PMA is affected by permanent magnet and exciting current, in this paper, new mathematic model and equation are established and the calculation result is analyzed. The data of exciting current, magnetic force, Moving-core velocity, Moving-core displacement and capacitance voltage at any time during opening and closeing operation and every factor's effect on dynamic character are obtained.In the paper ,the intelligent control unit based on single-chip microprocessor for intelligent breaker integreates many functions such as protection, control,and measurement. The signals of currents, voltages,active power and reactive power are monitored in real time. The control unit can not only control opening/closing operation of circuit breaker, but also has the functions of over-current/under-voltage trip,closing/opening interlock for mal-operation and diagnosis and warning for the failure of the operation system.In the final part,the paper focuses on the intelligent control and Synchronous Closing Technique of vacuum circuit breaker.