On Calculation of Forces in a Contact Device with Electromagnetic Compensation

Abstract

Compensators of the repulsive electrodynamic forces of electrical contacts provide stable operation of automatic switches during the flow of short-circuit currents. This paper presents a contact device with electrodynamic compensation and its design model. The electrodynamically interacting parts of the compensator structure are the U-shaped bent ends of the current-carrying output tire and slow-moving contacts parallel to each other. The formula for calculating the repulsive electrodynamic force of electrical contacts is given. On the basis of the calculation model, the formulas for the electrodynamic effort of the compensator and expressions for contour coefficient of electrodynamic forces of compensator have been obtained. The condition of complete compensation of the repulsive electrodynamic force of contacts is presented. Calculations of the electrodynamic effort of the compensator of the breaker for a rated current of 630 А with a rated short-time withstand current of 40 kA have been performed. The compensator with the proposed configuration fully compensates for the electrodynamic repulsive force of contacts of circuit breaker, confirming the validity of relations obtained in the work.