GB228305A - Improvements in or relating to electric relays - Google Patents

Abstract

228,305. Ross, T. W., Ryder, C., and Metropolitan-Vickers Electrical Co., Ltd. Dec. 7, 1923. Induction relays; cut-out arrangements.-A phase-balance relay for a polyphase system comprises a number of induction-type relay elements each provided with a pair of operating coils producing opposed torques upon their respective discs and energized in accordance with the currents in the several phases of the system taken in pairs, so that the compound relay responds to arithmetical values of current differences between the phases of the system. As shown applied to a three-phase system, two similar induction discs 1. 12 with driving magnets 10, 11 and 12, 13 are employed. The magnets 10, 12 are energized in series from the current in one phase of the system from the terminals 21, the magnet 11 from another phase from the terminals 18, and the magnet 13 from the third phase from the terminals 19. Each magnet has associated with it the usual magnet 15 carrying a phase-displaced current derived directly from a secondary winding mounted on the central limb of the main magnet. This magnet may be easily saturable, magnetically, or the secondary winding may feed the magnet 15 through an easily saturable transformer 23, as shown, so as to render the response of the induction elements directly proportional to the currents and avoid the usual square low characteristics. The relays have movable contact-arms 3, 4 connected to one of the terminals 9 and fixed contacts 5 .. 8 connected to the other terminal 9. If the currents in the three phases are equal to one another, the discs will have no resultant torque and the circuit at 9 will remain open.