GB102335A - Improvements relating to Electric Meters or Relays. - Google Patents

Abstract

102,335. British Westinghouse Electric & Manufacturing Co., (Westing- house Electric & Manufacturing Co.). June 12, 1916. Electro-magnetic current meters.-An electric meter or relay of the induction type is connected with a transformer such that the induced pressure bears a decreasing ratio to the current in the main circuit, and so compensates for the increasing torque of the instrument. The effect in the case of a meter is to give a more even scale, and in the case of a relay to preserve the time-lag under heavy overload, and so enable a series of relays to operate selectively. As shown, the winding 44 of the driving-magnet of the meter is connected in shunt with one coil 39 and in series with an opposing coil 36 on the transformer, the core of which becomes magnetically saturated at a low current-value. An adjustable resistance 41 is inserted between sections of the coil 39, and the current may be supplied from an ordinary transformer 34. The. winding 5 of the relay magnet is similarly connected to coils 22, 24 on a highly magnetized core, and to an ordinary current transformer 19. An additional winding 32 on a third limb of the core may be connected through a resistance 33 to a pressure transformer 29 to cause the relay to operate.with a lower current in one direction than in the reverse direction. The driving-magnets are fitted with shading-rings 4, 49, and the disk armatures are controlled by springs 6, 48 and damping- magnets 9, 52. A piece of soft iron 1<a> on the relay disk is attracted by the magnet 9 as the contact-arm 7 approaches the contact-piece 8.