GB564544A - Improvements in or relating to alternating-current measuring instruments - Google Patents

Abstract

564,544. Compensating induction meters for temperature errors. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Sept. 17, 1942, No. 13150. Convention date, Sept. 26, 1941. [Class 37] [Also in Group II] An induction-type watthour meter is compensated for phase-shift between shunt and series fluxes due to temperature-effects in the shunt coil, by providing the latter with a quadrature loop or loops symmetrically -arranged with respect to the pole face of the coil, the loop or loops being disposed in slots which are closed by wedges or keys of magnetic material of negative temperature-coefficient of permeability. In Fig. 1, the potential pole 2 is embraced by a quadrature-loop 13, the sides of which are fitted in slots in the magnetic members 9, .10, and the slots being closed by interlocking wedges or keys 16, 17 of negative temperature-coefficient of permeability providing local magnetic paths for the flux due to current in loop 13. A suitable material is a nickel-iron or nickel-copper alloy of 30 per cent nickel, suitably heat - treated. Additional quadrature-loops 18, 19 surround the auxiliary poles 11, 12 which are positioned to carry part of the current-flux. Adjustment to precise phase-relationship may be effected by sliding the wedges lengthwise, Fig. 8 (not shown), by varying the impedance of the loops, or by adjusting them in the direction of the length of the wedges. For example, the ends of the windings constituting the loops 18, 19 may be brought out and soldered together, the adjustment being effected by lengthening or shortening those ends. A similar arrangement is applicable to a meter having both windings on the same face of the disc, the loops and wedges being on the part of the magnetic structure on the opposite face, Fig. 3 (not shown). In Fig. 4, the voltage-pole is slotted to receive adjacent ends 68, 68a of two loops 69, 69a which may have extensions 70, 70a embracing the auxiliary poles 72, 73, the keys 66, 67 being of small diameter. The current-poles may have an additional phase-adjusting loop 75 of figureeight shape, with its ends 76; 77 soldered and adjustable as to length. In a modification, Fig. 6 (not shown), this additional loop 75 may be placed about the centre pole between the slots and above the loops, the slots having a common opening which is closed by a single wedge. Specification 286,517, [Class 37], is referred to.