| In the field of medium and low voltage,vacuum circuit breaker occupies the main position by virtue of its excellent arc extinguishing performance and insulation ability,and the multi break vacuum switch overcomes the saturation problem between contact gap distance and breakdown voltage,so that the vacuum circuit breaker has the ability to develop to a higher voltage level.However,it is found that when the double break vacuum circuit breaker bears the recovery voltage,the voltage distribution at the high and low voltage sides will be uneven,and the larger the capacity of the voltage sharing capacitor will reduce the breaking capacity of the circuit breaker.In order to solve this problem,this paper proposes a method to change the dynamic voltage distribution by adjusting the breaking speed of high and low voltage side fracture,so as to realize the voltage distribution balance between the two fracture vacuum circuit breakers.In this paper,mechanism analysis,simulation calculation and experimental verification are combined to study the influence of breaking speed regulation on dynamic voltage distribution.Firstly,the research status of multi fracture vacuum circuit breaker and its voltage equalization technology at home and abroad is introduced,and the disadvantages of traditional voltage sharing method are obtained.By analyzing the characteristics of vacuum arc and the static and dynamic voltage distribution mechanism of double break vacuum circuit breaker,combined with the influence of breaking speed on the dynamic voltage distribution,a two-stage speed control method of double break vacuum circuit breaker is proposed,which provides theoretical basis for the speed regulation of dynamic voltage distribution.The series model of double fracture vacuum circuit breaker is established in Solid Works software.The voltage distribution of the double fracture vacuum circuit breaker in the process of synchronous breaking,asynchronous breaking and variable speed breaking is calculated by ANSYS electronics desktop.On the one hand,the correctness of the theory of speed control is verified,on the other hand,it lays a foundation for the design and test plan of speed control system.Secondly,a speed control system of double break vacuum circuit breaker is designed,which is composed of charge discharge control module and speed control module.Among them,the charge discharge speed control module has integrated and graded improved the traditional charge discharge control circuit,saving manpower and easy operation.The speed control module is controlled by stm32f103rct6 single chip microcomputer,which captures the optical fiber signal from the delay trigger board,outputs the trigger pulse wave,controls the opening and closing of IGBT to change the breaking speed of the operating mechanism.The breaking speed is obtained by the displacement sensor.At the same time,the control signal of IGBT is designed,which can not only avoid the damage of reverse breakdown voltage to IGBT,but also change the breaking speed.Finally,the speed control test platform is built,and the synchronous breaking,asynchronous breaking and variable speed breaking tests are carried out,and the dynamic voltage distribution in three cases is obtained.Under the condition of synchronous breaking,changing the synchronous breaking speed has little influence on the recovery voltage of the fracture at high and low voltage sides.Under the condition of asynchronous breaking,the breaking speed of the fixed low voltage side is not changed,the breaking speed of the switch on the high voltage side decreases from 1.1m/s to 0.7m/s,and the dynamic voltage non-uniformity coefficient decreases from 29.47% to 10.13%.Under the condition of variable speed breaking,with the further decrease of breaking speed of high voltage side,the voltage distribution percentage of low voltage side increases from 41.5% to 49.0.3%,and the voltage non-uniformity coefficient decreases from 17% to 1.93%.So the switch breaking speed can be matched according to the specific situation,so as to get better dynamic voltage distribution effect.This study provides a reference for solving the dynamic voltage imbalance of multi fracture vacuum switch. |
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