The Experimental Study Of Miniature Circuit Breaker Protection Characteristics

The current and voltage waveform of the miniature circuit breaker(MCB)in the switching on and breaking process are collected,and the parameters such as breaking time,arcing time and energy are acquired,which is the basic work of MCB's protection characteristics.In order to study the protection characteristics,the design and building of MCB's protection characteristic test system are made and the experimental study is carried out.First of all,the analysis of the MCB's protection characteristic and its degradation is made.MCB failure mode and failure criterion are studied,and the characteristic curve of the protection of overload protection and short-circuit protection characteristics,and the degradation of protection characteristic curve are analyzed.The bimetallic strip of MCB,electromagnetic release,contact and other key components degradation principle are researched and the analysis of its effect on the protective characteristic is conducted.From the point of view of key components property parameters and time,the characteristic of protection are analyzed.Secondly,the test system of the protection characteristics of the MCB is designed and built.The test requirement of protection characteristic of MCB is analyzed,and then the overall scheme design,hardware design and software design of the test system are carried out.In the hardware design,the current generation and control circuit,using the parallel load network,which is independent controlled,connected to different load,by industrial computer via the control board driving the solid state relay,generates different current;The test product,also using the independent control of the parallel structure,of which the power's switching on and breaking state is controlled by the serial solid state relay,depending on the industrial computer and control board,realizes the cyclic access test products;The acquisition circuit is composed of the current and voltage sensor and the data acquisition card,which can achieve high speed data acquisition.The system software is realized in the virtual instrument LabVIEW environment,where the current generation and control circuit,the test products cycle control circuit and the acquisition circuit are coordinated,to complete test mission.In the producer/consumer structure mode,data acquisition and storage procedures realize the efficient synchronization of acquisition andprocessing.Filtering programs eliminate the noises in the collected signals by using digital filter.By dealing with the current and voltage data in the switching on and breaking process of the MCB,the data processing part can obtain the breaking time,arcing time,the energy parameter and etc.Finally,the experimental scheme aimed at protection characteristics is designed,the parameters of the test are analyzed.The energy value and attributed parameters of the key components of the MCB are obtained based on the experimental data,and then a further study of the protective characteristics is made.