摘要
Abstract
Miniature circuit breakers(MCBs)are essential protective apparatuses in the low-voltage distribution network.They are designed to interrupt fault circuits promptly and function as control switches for opening and closing normal circuits.During circuit interruption,an electric arc occurs between the moving and stationary contacts,ablating the contact material and leading to electrical life degradation.However,existing evaluation methods often overlook factors such as arc root transfer and breaking current,resulting in inaccurate electrical life evaluation and poor robustness.This paper proposes a novel electrical life evaluation method that incorporates the arc root transfer phenomenon during the breaking process and accounts for the impact of varying current levels on contact erosion.
First,an electrical life testing platform consisting of an experimental circuit,a signal acquisition module,an automated contact opening and closing mechanism,an arcing phase angle judgment module,an electromagnet driving module,and a host computer was developed.The mechanism precisely controls the handle to perform closing operations,and the host computer synchronously activates the signal acquisition module for real-time data collection.The arcing phase angle judgment module continuously monitors current phase characteristics and triggers the electromagnet driving module at predefined phase angles to execute controlled opening operations.Electrical life tests were conducted on six prototype devices under different current levels and arcing phase angles.The signal acquisition module automatically captured arc voltage and current waveforms during each breaking operation,while contact thickness measurements were manually recorded at intervals of every 1000 operations.
Second,the arc motion process under different arcing phase angles and currents was observed using a high-speed camera.The influence of arcing phase angle and breaking current on arc root transfer was analyzed.Experimental results demonstrate that smaller arcing phase angles and higher breaking currents significantly increase the probability of arc root transfer.This phenomenon reduces the energy transferred to the contact material during the breaking process,thereby impacting the accuracy of electrical life evaluation models.
Third,the moment of arc root transfer was precisely identified through characteristic analysis of arc voltage variations during the transfer process.The time and arc charge associated with contact ablation were extracted by synchronizing arc voltage and current waveforms.This step effectively quantifies the arc energy injected into the contact material,providing a foundation for constructing a more accurate electrical life evaluation model.The relationship between accumulated arc charge and contact thickness loss was established using the contact erosion factor,which exhibits an inverse proportionality to breaking current magnitude.Experimental data fit the relationship between the breaking current and the contact erosion factor.
Finally,a method for evaluating the electrical life of MCBs is proposed,which uses arc charge and contact erosion factor as input variables and contact thickness loss as the output variable.Experimental verification under random arcing phase angle shows that the prediction error of the proposed method is 8.14%.The proposed method demonstrates low prediction error,robustness,and reduced computational complexity.This work provides a valuable reference for the development of intelligent MCBs.关键词
微型断路器/电寿命评估/弧根转移/开断电流/触头烧蚀Key words
Miniature circuit breaker(MCB)/electrical life evaluation/arc root transfer/breaking current/contact erosion分类
动力与电气工程
