Analysis On Breaking Effect Of A New Low-voltage Binary-Fluid Circuit Breaker

Low-voltage circuit breaker is important electrical apparatus which makes sure the safe operation of power grid.Traditional circuit breaker has many shortcomings,such as easily arcing,easily fusion welding with electric contacts by solid contacts.Binary-fluid circuit breaker is based on the difference on magnetic properties,density of magnetic fluid and conductive fluid.The electrode of binary-fluid circuit breaker adopt solid-liquid contact which has small contact resistance and no fusion problem.In order to optimize the designing parameters of binary-fluid circuit breaker,the numerical simulation of the electromagnetic field,flow field and temperature field of the circuit breaker is realized by Ansoft Maxwell,Fluent and Ansys Mechanical software with physical model which can work under 630 A.Optimum design parameters of binary-fluid circuit breaker is obtained by analyzing the influence of different factors on breaking effect.(1)By analyzing magnetic field,the magnetic field distributions is obtained in all the regions of binary-fluid circuit breaker.It is found that magnetic induction in magnetic fluid is much higher than that in conductive fluid.The magnetic induction increases at firstly,then decreases in x direction.It also decreases gradually in y direction and changes little in z direction.The current density of binary-fluid circuit breaker is obtained by analyzing electric field.The distribution of Lorentz force and magnetization force is also calculated.With the increase of the ampere turns of electromagnet and the electrode current,the magnetic induction increases accordingly.(2)The flow field in xy section of fluid is simulated,putting magnetic field into flow field using MHD model and putting the distribution of magnetization force into flow field using UDF.It is found that breaking time is 0.37s and the closing time is 0.1s by analyzing the fluid field of interrupting and closing process of binary-fluid circuit-breaker.The numerical simulation is consistent with the experimental results by contrasting the result of numerical simulation and experiments.The optimum design parameters of binary-fluid circuit breaker is obtained by analyzing the effect of air,fluid volume and magnetic field on breaking time,closing time,distance of open contacts and wave.The optimum design parameters is without air in cavity,15mm of conductive fluid height,10mm of magnetic fluid height and 11000 ampere turns of electromagnet.(3)It was also found that temperature of all the parts of binary-fluid circuit breaker is in the range of normal operation by analyzing temperature field,which verified circuit breaker could work steadily and chronically.The change of temperature in different electrode current and width of fluid is analyzed for providing reference to choose appropriate sectional area of fluid in different currents.