GB323966A - Improvements in induction type electrical instruments or relays - Google Patents

Abstract

323,966. General Electric Co., Ltd., Turner, H. C., and Hamilton, W. March, 7, 1929. Electromagnetic current meters; power meters. -Analternating-current measuring instrument or relay of the induction type has a moving element in the form of a cylinder or part cylinder arranged round about a magnetic core provided with a winding carrying the current to be measured or a current proportional thereto. An E-shaped laminated core 2 has on its central limb 18 a primary winding 28 adapted to carry the current to be measured or a current proportional thereto. On the yoke 2 between the limbs are two secondarv windings 29, 30 connected in series with one another and with windings 13, 14 on a U-shaped core 5. The movable element comprises an aluminium cylinder 57 arranged to move in the air-gap between the magnet cores 2, 5 and surrounding the E-shaped magnet core 2. Damping is effected bv a permanent magnet 34 and a keeper 39, through the gap between which the cylinder 57 passes. The edge of the cylinder 57 may be shaped as a cam in order to give an even scale, or the core 5 may be arranged to be saturated throughout the range of the instrument or only at the higher values of the current. The cylinder 57 may be tapered axially from one end to the other. The cylinder 57 is mounted on a spindle 55 carrying a pointer (not shown). One end of a spiral spring is secured to the moving system, the other end being attached to a lever for adjusting the zero. The invention is applicable to wattmeters.