GB882169A - Improvements in or relating to regulated electrical power supply equipment - Google Patents

Abstract

882,169. Current measuring. STANDARD TELEPHONES & CABLES Ltd. Dec. 6, 1957 [Dec. 13, 1956], No. 38092/56. Class 37. In a balanced to ground electrical power supply equipment, separate power supply units PSUA, PSUB feed respective supply lines with direct current of substantially the same value, each unit having one earthed terminal; and magnetically controlled thermionic diodes, each having a controlling winding connected to a respective supply line, actuate current indicating devices in the discharge paths thereof in dependence on current fluctuations in the supply lines. The constant current source PSUA is monitored by magnetic diode VI having a control winding CC1 energized by the source current, and a bias winding CC2 connected in parallel with the diode discharge path between a 150-volt stabilized supply line L1 and earth. The diode current varies inversely with the source current, and centre-zero relays B, C in the cathode circuit of 071 are adapted to indicate absolute deviations of Π1% and Π5% from norm of the source current. An identical arrangement monitors the current from a second source PSUB; the two sources constituting a balanced-to-ground direct-current supply system, the negative and positive sides of PSUA and PSUB respectively being earthed. A centrezero differential relay A connected between the cathode circuits of diodes V1 and VI1 is adapted to indicate mutual deviations in the currents from the two sources. Rectifier bridges may be inserted in the source current lines and the control windings CCl, CCl1 fed therefrom, Fig. 2 (not shown), for monitoring alternating-current supply lines. The relays B, C, B<SP>1</SP>, C<SP>1</SP> may be double wound, the second windings being polarized by the stabilized supply L1. In another embodiment, Fig. 4 (not shown), each diode has a second bias winding CC3, CC3<SP>1</SP> connected in series with the control winding CCl<SP>1</SP>, CC1 of the other diode. In a further embodiment, Fig. 5 (not shown), each diode has a second bias winding CC4, CC4<SP>1</SP> inserted into the cathode circuit of the other diode. Specifications 629,542, 642,375, 768,029 and 776,550 are referred to.