STUDY OF THE WORKING SURFACES OF THE CONTACTS OF ELECTROMAGNETIC STARTERS AND RELAYS USING AN ELECTRON MICROSCOPE

Abstract

It is proposed to replace the serial contact parts based on silver with experimental contact parts based on copper. Climatic tests of the contact parts were carried out to determine the performance and production operation of the experimental contacts. Switching tests of starters and relays were carried out to determine durability. The results of studies of wear resistance and erosion of the contact surface of serial contact parts of PML-1100O4 electromagnetic starters based on silver - СрН-10, СрМ-0.2+М1 and metal-ceramic contact parts based on copper with metal impurities and defined thermodynamically stable compounds. Negative wear is established in stationary and moving contact parts, but moving contact parts wear more intensively, which is typical for alternating current devices. The level of erosive wear increases with a gradual increase in the number of switching cycles and the magnitude of the switching current and reaches its maximum value at the highest current (10 A) with which the starters and relays were tested (4.0 A, 6.3 A, 10 A). The study of the working surfaces of the contacts before, during and after the test was carried out using a scanning electron microscope "Cambridge Stereoscan" S4-10. The metallographic analysis of the contact surfaces contributed to the discovery of patterns of destruction of erosion-rupturing bridging contacts based on Ag and Cu. Contact parts made of experimental contact materials have undergone several years of production tests in real agricultural conditions.