The Research On Miniature Circuit Breaker Mechanical And Electrical Wear Measurement Methods

Miniature Circuit Breaker is a kind of protective equipment which is widely used on low-voltage line terminal. When severe overload or short circuit fault occurs on the line, the MCB automatically trip to cut off the fault circuit. During the use of MCB, its key electromechanical components produce mechanical wear and electrical wear, which are produced by temperature, radiation, contact collision, mechanical motion and other factors. With the use of MCB, the wear amount continues to accumulate, resulting in reduced breaking reliability, which may cause malfunction or rejection, and the safety of the line will be affected. So it is significant to study the measurement method of mechanical wear and electrical wear. In this paper, test, simulation and theoretical analysis methods are combined to research the issues about electromechanical wear measurement of DZ47-63 type MCB.First, PRO/E is used to establish 3D models of MCB components as bimetallic trip, electromagnetic release, contact system, operating mechanism. Analyze and determine the attribute parameters that can reflect the degradation of MCB. Research the determination method of real-time parameters and their limit value based on the measured data and multi-physics coupling simulation. The evaluation method of fatigue state is put forward for different parts based on different operating characteristics.Then, establish mathematical models for components, including bimetallic trip electric- thermal- structure coupling model, the thrust calculation model of bimetal free end, spring model and motion model of electromagnetic release, energy loss calculation model of electromagnetic release and contact system, motion model for operating mechanism. Build a test system to detect the voltage and current wave of contacts, bimetallic trip, electromagnetic release and the whole apparatus. Calculate the energy loss of MCB components during steady state and breaking process under different operating states based on the test data. And analyze the energy loss proportion of each component to measure the electrical wear amount. Conduct multi-physics coupling simulation on contacts, bimetallic trip, electromagnetic release and operating mechanism based on measured current data. Put forward different mechanical and electrical wear measurement method for different components.Finally, research the typical characteristics of energy proportion and explore the MCB mechanical and electrical wear fusion method at manual closing, manual breaking and fault current automatically breaking modes.