Bayda E. Multiphysical Models of High Voltage Vacuum Circuit Breakers with Bistable Polarized Actuators in Dynamic Modes.

In the dissertation work the problems of creation of multiphysical models used in the research and designing of medium voltage vacuum switching devices are considered. The object of the study is transient lectromagnetic processes in a heterogeneous, nonlinear, moving medium conducting electric current and including high-coercive per-manent magnets; processes related to the theory of elasticity, solid state mechanics, phe-nomena in non-stationary thermal fields, and the theory of continuum mechanics. Subject of research – vacuum switching devices with bistable polarized actuators; dy-namics of actuators; static and dynamic deformation of the contact system of the circuit breaker and the mechanism under the influence of the actuator; the ability of the circuit breaker to switch on and the thermal stability of the circuit breaker under the influence of emergency overvoltage's; liquid dampers; electromagnetic actuator’s control circuit. Research methods – the investigations of electromagnetic, mechanical, thermal proc-esses and fluid flow processes are based on analytical and numerical mathematical models that take into account the most significant linear and nonlinear interconnections between phenomena. Numerical solutions of partial differential equations are carried out using spe-cial application software packages, the reliability of which is repeatedly confirmed and does not cause doubts, as well as codes written by the applicant. The following scientific results have been obtained in the work. For the first time a model of dynamics of a polarized bistable actuator with permanent magnets has been developed based on calculations of transient electromagnetic field in a nonlinear non-uniform medium conducting electric current and containing permanent magnets taking into account the motion of parts of the actuator in conjunction with nonlin-ear equations of electric circuit and motion. The parameters of forced switching on of ac-tuators are calculated and recommendations on the design and parameters of actuators are given. The multiphysical models of studying the influence of actuator parameters on static and dynamic mechanical stresses in a vacuum chamber bellows have been developed, rec-ommendations have been obtained for choosing the optimal structure of a bellows and its durability, its fatigue endurance is calculated. A model of the influence of actuator pa-rameters on dynamic mechanical stresses in the contact system and the switching mecha-nism based on the theory of elasticity was developed, due to which the geometry of the drive shaft was calculated and its material was chosen. For the first time, multiphysical models have been developed to determine the effect of the actuator's dynamic characteristics on the ability of the circuit breaker to activate the emergency overloads: shock dynamics and contact vibration time are defined; the Stefan thermal problem solved, the heat of phase transitions is taken into account, and the possi-ble strength of contact welding is determined; recommendations for reducing the contact collision rate due to the use of a liquid damper based on the Navies Stokes equation and dynamics of the actuator are given; the model of heating and deformation of the contact surface was developed and on its basis recommendations were given regarding calcula-tions of the required force of contact pressure and the geometry of the contacts in the con-ditions of thermal stability. The original models of circuits connecting actuator coils to different sources of elec-tric energy have been investigated and analyzed, and recommendations on their practical implementation have been given. The results of the study were checked on layouts, prototypes and used in the devel-opment of vacuum circuit breakers, tests of which models were confirmed by the obtained recommendations and conclusions. Implementation of the main scientific and practical results of the dissertation work was reflected: in agreement with «ABM Ampere», Kremenchk agreement No. 33/98-12 between NTU «KhPI» and «ABM Ampere» LLC «Influence of the parameters of a bista-ble polarized vacuum actuator of the circuit breaker on its ability to switch on», research and development work performed by order of Ukrenergokompleks-2 LLC, Kharkov «Bistable actuators in control plants and distribution of liquid flows», the acts of imple-mentation are added.