Electric Contact Complation On Line Analysis And Optimization Design Of Circuit Breaker

Great capability transmitting and distributing electricity equipments bring powerful electrodynamic force under short circuit conditions during power transmission. The high repulsive force value between contact members due to current path shrink arising mostly at contact closure and/or in transient under short circuit conditions is particularly onerous for power switch applications. It results in the contact force value between contact members dropping obviously and either contact floating or bouncing which are associated with an electric arc and following contact welding, which affect the transporting and distributing electricity equipments normal running. Higher is the current value higher is probability of a contact repulsive. Therefore, this problem is of great importance for any circuit breaker especially for vacuum circuit breakers of a low voltage which are of a compact structure.To avoid the contact floating or bouncing at closure and during any inrush current under short circuit conditions, a special compensation system flexibly combined with the contact itself has been developed, which employs an electromagnetic effect of the contact load itself based on electromagnetic force mechanism. However the electromagnetic force is generated by electromegnetic field with a certain form and distributing characteristic. It is necessary to analyse and calculate the electromegnetic field of the electric contact compensation system on line of circuit breaker.The content of this thesis is about the electromegnetic force analysis and optimization design of the electric contact compensation system on line of circuit breaker.In this thesis, electromagnetic field differential equation is derived from the basic electromagnetic field principle-Maxwell equation group. The electromegnetic force analysis of the electric contact compensation system on line of circuit breaker is carried out using Finite Element Method (FEM), and comparing with the analytic method results. The different shape and different geometrical parameter compensation system effecting on electromagnetic force value and distributing are analyzed. Curve-fitting and Equations of electromagnetic force as the function of shape, geometrical parameter and load of the compensation system are given according to the calculating results, the optimization designing of compensation unit is based on it.Besides, Potential-temperature theory, Wiedemann-Franz law in metal conduction theory, Newton formula and thermal balance Equation are used respectively for thermal calculating of the electric contact and compensation system on line of circuit breaker under steady and transient state. Favourable thermal steady performances of them are proved.Another part of this thesis is that the visualized finite element simulation software was developed based on VB programming platform using ANSYS-APDL module. Furthermore, parameter optimization design of the compensation system was carried through based on thermal and electromagnetic force analysis. A visualized parametic model is established under certain constraints, which provide the engineers with new track and method to design and analyze structures in future.The circuit breaker performance can be improved significantly by theory analysis, calculation and experiment investigation for on-line contact compensation. The contact rebounds under closure are suppressed and the dynamic resistance of the closed contacts under short circuit conditions is found even to be decreased. Due to the reverse threshold of the compensator under operation the speed of contacts at opening is increased what increases the breaking ability of the switch.