GB318857A - Improvements in or relating to the speed regulation of alternating current induction meters - Google Patents

Abstract

318,857. Blathy, O. T. Sept. 10, 1928, [Convention date]. Void [Published under Sect. 91 of the Acts]. Induction motor meters.-An adjustable magnetic bridging- member is inserted in or adjacent to the air gap of the magnetic shunt of the voltage magnet so that the reluctance of the air gap can be varied. As shown the magnetic shunt f for the voltage magnet b surrounds the magnet in the form of a casing, so that an air gap is formed between the polepiece c and the casing f. A screw h, of magnetic material, is screwed into the wall e of the shunt casing f so that its disc-shaped head i extends into the air gap g between the pole-piece c and the wall e. By adjusting the screw h the magnetic reluctance of the gap g, and consequently the speed of the meter for a given load, may be varied. In a modification, the head i is omitted and the free end of a spring finger extends into the airgap g and is adjusted by the screw h. In another form, a non-circular disc is rotatably adjustable on a pin secured to the wall e, so that a greater or. smaller part extends into the airgap. In another construction a magnetic member is rotatably adjustable about a screw on the front of the pole shoe c, and has a portion bent over at right angles forming a pole face which can be moved nearer to or further from the wall e. In a modification for a two-limbed voltage magnet having horns with an airgap between them forming the magnetic shunt, a brass screw with an iron head is screwed between the ends of the horns.