The Mechansim Synthesis And Analysis Of New Moulded Case Circuit Breaker

The moulded case circuit breaker(MCCB) is an important electric device in the low voltage power supply and distribution system with the function of breaking and closing the circuit and protects the electrical equipments. With the development of the electric industry for more than one hundred years, the breaking and closing and protection capability has been strengthened, the performance of operating mechanism largely determines the ability of its breaking and closing and protection. A new operating mechanism of moulded case circuit breaker is designed by mean of regeneration motion chain. The main contents are as follows:(1) Determine the performance index for a new moulded case circuit breaker based on the analysis of working principle of the moulded case circuit breaker combined with development status of moulded case circuit breaker in China and abroad.(2) The operating mechanism of the new moulded case circuit breaker based on the original operating mechanism is designed by regeneration motion chain. The closing motion process of moulded case circuit breaker with double toggle mechanism is analyzed by the mean of mechanism sketch, the degree of freedom of the eight states from the closing motion process is calculated and analyzed, and the evolution mechanism of the toggle process is studied.(3) Static analysis of the operating mechanism primarily define the functional relation between design variables and the key parameters. The design variables include the length of link, axis position, spring stiffness and etc, the key parameters include closing force, re-toggle force and etc.According to the vector loop method combined with Lagrange equation formula, the operating mechanism is analyzed by kinematic and dynamic equation. The motion relationship among links are analyzed, also the contact breaking speed is calculated.(4) According to the national design standards of low voltage electrical apparatus combined with the calculating model of static and kinematic and dynamic of the operating mechanism. Some design variables such as the length and quality of link and etc are determined, and the three-dimensional model of the new moulded case circuit breaker is modeled in SolidWorks.The kinematics and dynamics simulation of the operating mechanism are carried out in software Adams, the concept of sensitivity is introduced in this paper. The sensitivity’s values are obtained through iterative calculation of the design variables of the operating mechanism. the main design variables can be chosen by the size of absolute value of sensitivity and the operating mechanism can be optimized by iterative algorithm of Adams.(5) A new measuring device is composed of PLC and rotary encoder, it has been made to measure the closing and breaking time of the operating mechanism, and can be used to compare the measurement results with the simulation results to confirm the operating mechanism correctness or not.Through comparing the experiment results and the simulation, it is found that the designing performance of the operating mechanism can be obtained, the design method and design process for new operating mechanism has a certain reference value, and it provides a theoretical basis for the further development of high-performance moulded case circuit breaker.