Research On Permanent Magnet Linear Motor Operating Mechanism For Vacuum Circuit Breaker

As protection and control equipment for power system network,vacuum circuit breaker(VCB)is one of the basic components of smart grid.The driving force of VCB is derived from operating mechanism during opening and closing.Its performance directly determines operation characteristics and reliability of VCB system.The traditional operating mechanism and the rotary motor operating mechanim have the problems of complex structure,low reliability and large dispersion.The detent force of slot linear motor operating mechanism brings thrust pulsation,motor vibration and degradation of speed control.These factors lead to imprecise opening and closing for 12 kV VCB.In order to solve these problems,the slotless tubular permanent magnet linear synchronous motor(TPMLSM)operation mechanism is proposed.Take it as research object,the structure and electromagnetic characteristics of this operating mechanism are designed and determined.Its structural parameters are globally optimized by using multi-population genetic algorithm.This algorithm can maintain the diversity of the population and speed up convergence of the algorithm.After optimization,the TPMLM detent force which affects opening and closing of VCB are restrained.At last,the static and dynamic characteristics and quantitative characterization of TPMLM operating mechanism with different voltage levels VCB are analyzed by using finite element method.Performances of VCB TPMLM operating mechanism are analysed.According to the actual needs and operating conditions of 12 kV VCB,the working performances of linear motors with different structural forms are contrasted.Aim at providing larger linear motion kinetic energy in short time and short distance,the slotless TPMLM is used for operating mechanism of 12 kV VCB.The body structure and electromagnetic parameters are designed by numerical analysis method.Particular requirements of high thrust density and low thrust pulsation are integrant during opening and closing process.Therefore,permanent magnet thickness,polar pitch and width of ring winding are optimization variables.And electromagnetic thrust,thrust aberration rate and motor constant(ratio of electromagnetic thrust and square root of copper loss)are optimization objectives.The optimal structure parameters of slotless TPMLM are obtained.Traditional operating mechanism(such as spring actuating mechanism,electromagnetic mechanism and permanent magnetic mechanism)and the rotary motor operating mechanism have the problems of complex structure,low reliability,large dispersion thrust pulsation,motor vibration and degradation of speed control.These factors lead to imprecise opening and closing of VCB.According to generation mechanism of detent force for PMLM,the thrust pulsation is restrained from the sides of slot and slotless structure,slot-poles number,permanent magnet width,length of primary iron core and primary iron core end with special size ring iron on the basis of analytic method.Based on above research,structure schemes of 40.5kV and 126 kV VCB operating mechanism with slotless TPMLM are put forward.Parameters of operating mechanism body are designed and optimized to suppress thrust pulsation.Physical and mathematical models of slotless TPMLM operating mechanism are established.Static and dynamic characteristics of 12 kV,40.5kV and 126 kV VCB slotless TPMLM operating mechanism are numerically simulated and analysed by using finite element method.The 12 kV,40.5kV and 126 k V VCB slotless TPMLM operating mechanisms which are designed and determined in the paper can well satisfy their national standard requirements when opening and closing.