GB645668A - Improvements in or relating to electrical indicating instruments - Google Patents

Abstract

645,668. Power-factor measurements ; power meters. GENERAL ELECTRIC CO., Ltd., RUDGE, T. R., and TURNER, H. C. Oct. 13, 1948, No. 26663. [Class 37] An instrument for measuring the resultant of two or more vector quantities, such as a power-factor meter, alternating current wattmeter, or synchroscope, includes an electromagnet comprising a pair of opposing polepieces 6 united by a yoke 4, a portion of which is movable to admit a conductor 8, and a part situated between the polepieces 6 comprising one or more fixed coils 13 adapted to magnetize one or more vanes 14, 15 mounted on a shaft 10 which carries a pointer 3. One half of the yoke 4 is hinged and attached to a spring-loaded lever 7 which can be moved to a position 71 to pivot the movable portion of the yoke to a new position 4<SP>1</SP> so that the yoke can be passed over a conductor 8 and the magnetic circuit again completed by releasing the lever 7 to allow the movable portion of the yoke to return to its original position. In the power-factor meter shown, the moving system comprises two quadrant-shaped iron vanes 14, 15 in parallel planes fixed to the shaft 10, their centre lines being at right angles to one another. Two fixed coils 13 are arranged so that one is just beneath each of the vanes 14, 15. These coils are connected in parallel through a resistance and a condenser respectively between a pair of leads 19 terminating in a plug 20 by which they are connected between the mains, so that the currents in the oils 13 are proportional to the voltage and substantially in phase and in quadrature therewith. A flux is produced between the polepieces 6 proportional to the current in the conductor 8 and in a predetermined phase relation therewith. The deflection of the pointer 3 is proportional to the power-factor and the scale 2 may be calibrated to give a direct reading of power factor.