S.M. Karabanov, V.A. Korotchenko, V.I. Solovyev, Je.I. Sokolovskij, Zh.V. Solotenkova

A computer model, which is determined by using a small (about 20 ns) step in time the most important parameters of the opening of magnetically operated contacts has been developed: coordinate (grid points) and velocity of the contact part, elastic, magnetic and electrostatic forces, interelectrode voltage, current of autoelectronic emission and the resulting value of the energy released at the positive electrode. One of the basic features of the developed model is calculation of changes of voltage between contacts as a result of a charge of intercontact capacity from the power supply with its simultaneous category an autoelectronic current. Changes of capacity in the course of a divergence or rapprochement of contacts are considered. The model offers several other innovative solutions: introduced by the boundary value of a contact gap, which corresponds to the excess of the actual opening of the contacts and an increase in voltage across the gap; approximate estimate of the surface roughness of contacts or non-parallelism by providing a zone of contact at the time of opening in the form of microsalient with the set sizes; the introduction of elastic reflection of the contact part of a specific time delay after impact under the influence of electrostatic and magnetic forces; determination of the total magnetic resistance of air and contact part of the experimental value of MMF is released. The model was tested in application to the reed switch MKA-14108 in the opening of direct current 20 mA for the power supply voltage 100 V. It is shown that in the course of deenergizing reed switch the electric force (together with magnetic force decreasing in time) leads to occurrence of a series of repeated short circuits of contacts to corresponding throws of pressure and a current. Duration of a series before full disconnection - nearby 100 µs, the number of closures - up to 10, moving of the ends of contact part ? (0,2 - 0,8) µm, impulses of a current of autoelectronic issue - to 20 мА, the total energy allocated on the anode at the expense of electronic bombardment, - 7 µJ. The simulation results are confirmed by experimental oscillograms of voltage changes at the reed switch rupture of an electric current in a circuit with resistive load.