Preselected Or Synchronous Frequency Responsive Patents (Class 335/101)
  • Patent number: 4968960
    Abstract: A rotating disc electromagnetic relay has an operating element which applies a torque to the disc tending to close the main contacts and a restraint element generating a torque which together with a spring tends to open the relay contacts. The operating and restraint elements each have an E-shaped core defining two magnetic circuits with a common center leg. Two voltages to be compared are applied to two input coils on the center leg of each element in the same sense to generate a flux representative of the sum of the voltages in the operating element and in the opposite sense to produce a flux representative of the difference between the two voltages in the restraint element. The flux in the common leg of each element divides between the two magnetic circuits. The flux in one magnetic circuit of each element is shifted in phase by a first lag coil on an outer leg of the core to generate the opening and closing torque, respectively.
    Type: Grant
    Filed: December 20, 1989
    Date of Patent: November 6, 1990
    Assignee: ABB Power T & D Company Inc.
    Inventors: Redjem Bouhenguel, Shan C. Sun