Grechko A. Improvement of electromagnetic systems for average voltage vacuum circuit-breakers with the purpose of thermal firmness increase on protected equipment

Research object: breaking process of symmetric three-phase short-circuit currents by average voltage vacuum circuit-breaker at the working of electromagnetic drive. Research purpose: improvement of electromagnetic systems for average voltage vacuum circuit-breakers for the equipment's protection efficiency increase from short-circuit currents and improvement of technical and economic indices of vacuum circuit-breakers. Research methods and apparatus: fundamental positions of electric apparatus theory, finite elements method for the magnetic fields calculation, numerical methods for the calculation of nonlinear differential equalizations systems. Theoretical and practical results: unmonotonous dependence of the break-time for average voltage vacuum circuit-breaker on Joule integral in the short-circuit mode for conductive parts, which are on the defensive by these circuit-breakers, is set; the construction of electromagnetic drive, which allows to decrease of vacuum circuit-breaker break-time, is designed; control system for vacuum circuit-breaker with an electromagnetic drive, which provides expansion of functional possibilities of circuit-breakers, is created. Novelty: mathematical model of symmetric three-phase short-circuit breaking by average voltage vacuum circuit-breakers is created. New is that the burning and extinguishing processes of vacuum arc are designed by replacement of circuit-breaker's poles in electric short-circuit scheme to nonlinear resistances, which are determined depending on the values of time moment and current in phase. The range values of contacts break-time for average voltage vacuum circuit-breakers, at which diminishing short-circuit currents thermal action on protected equipment, is first set. Degree of introduction: results and recommendations are used at a production of average voltage vacuum circuit-breakers in series of VB4-E by "AVM AMPER LTD" (Kremenchug). Sphere of the use: electrical engineering industry.