GB168339A - Improvements in or relating to alternating current electrical instruments - Google Patents

Abstract

168,339. Shotter, G. F., and Hill, E. W. March 3, 1920. Induction motor meters; special quantities, registering. - An alternating-current quantity meter has a main shadedp o l e unsaturated electromagn e t 24 driving a metal disc 34, the motion of which is retarded by a perma.nent or continuous-current brake magnet 35. A second shaded pole electromagnet (not shown) connected across the supply mains may be provided to impart a small constant torque to the disc 34 in the same direction a: that due to the main magnet 24. A third electromagnet without shadec poles, connected either in series or ir parallel with the main magnet 24 may be provided to retard the disc further. It is designed so as to become saturated at high loads and thereby increase the range of proportionality of the meter. This electromagnet, or the second shaded-pole electromagnet, or both, may act on the driving- disc 34, or on a second disc 33, which may be mounted on the same spindle 29 as the disc 34, or may be mounted on a second spindle with gearing to add up the rotation of the two discs. A demand indicator having a non-return pointer may be connected to the meter for predetermined intervals of time so as to indicate the average maximum demand. The connection and disconnection of the demand indicator is effected by a motor of which the speed is dependent on the frequency only, consisting of a shaded-pole magnet 17 connected across the supply mains and driving a disc 9.