GB335971A - Improvements in or relating to electrical measuring and protective apparatus for alternating current circuits - Google Patents

Abstract

335,971. Nalder Bros. & Thompson, Ltd., and Lipman, C. L. July 2, 1929. Current, pressure, a n d phase meters; reactance and resistance measurements.-A quotient, differential measuring instrument (usually of the induction type) comprises an electromagnet structure with a main core portion, for example A<1>, Fig. 5, and an auxiliary core portion C magnetically in parallel therewith, a current winding on the yoke A producing a divided flux. The main flux, in combination with supplementary fluxes due to windings on the external cores A<1>, C (or as shown in Fig. 5 a voltage winding V on the pole B' of an internal core B) produces a torque on the induction disc D constituting the main rotor. The auxiliary flux in the auxiliary core, by itself or in conjunction with windings (short circuited windings C<1> which may be adjustable are shown) produces a control torque on an induction disc D on the main rotor spindle d which assists or opposes the main torque. The main and the auxiliary control devices may be of the moving coil or moving iron type. Shortcircuited coils f, which may be adjustable, serve for the phase adjustment of the magnetic fluxes produced by the coils P, V. By suitable adjustment of the control torque, the instruments so designed will operate correctly over the full range of possible current and voltage variations to which they are subjected, and, in a quotient instrument, any law associating voltage, current and phaseangle may be followed to give, for example, a rising, drooping or level characteristic of impedance with increase of load. Various dispositions of the coils in relation to the magnetic circuit are described whereby various characteristics may be obtained. Specifications 321,686 and 324,056 [both in Class 38 (v), Electric switches &c.] are referred to.