Vacuum, SF6 and Air-Break Contactors for Medium Voltage Controllers

Vacuum, SF6 and air-break contactors are compared with emphasis on items of interest to users. Interruption of short- circuits over the full range of prospective currents is discussed and the advantage of high interrupting capability in a contactor is emphasized. The possibility of high peak voltages and high rates of rise of voltage with vacuum contactors is treated together with the means to reduce and control such transients. Comparisons are made among contactor types on size, weight, endurance, losses and maintenance. A summary is given of the advantages of each type of contactor.