GB350321A - An improved method of compensating the temperature errors caused by the heating up of the current coils in direct current watt-hour electricity meters with shunts - Google Patents

Abstract

350,321. Compensating meters for temperature errors. LANDIS ET GYR SOC. ANON., 1, Hofstrasse, Zug, Switzerland. Aug. 12, 1930, No. 24066. Conven. tion date, Aug. 17, 1929. [Class 37.] In a shunted direct-current energy meter, decrease of current through the current coils due to their heating is compensated for by a resistance of high temperature coefficient, arranged to be heated by the current coil, so connected in the armature circuit as to provide a corresponding increase of armature current. The current coil is in halves 4, 5 and is connected in parallel with a shunt 3 in the main circuit. A compensating resistance 7, consisting of a thin wire of nickel or other material of high temperature cofficient wound on a strip of hard paper, is insulated with oiled paper &c. and arranged preferably between the second and third outermost windings of the half 4 of the current coil. The resistance 7 is in parallel with the armature 6, which consequently receives a higher current as the coils 4, 5 and resistance 7 warm up, thereby compensating for the lower current taken by the coils 4, 5. In order to permit the use of stock resistances 7 of a definite value, complete compensation is effected by means of a potentiometer resistance 8. Alternatively the compensating resistance 7 may have a high negative temperature coefficient and be connected in series with the armature 6, a constantan regulating resistance being connected in parallel with the armature and compensating resistance. Instead of the potentiometer resistance 8 a regulating resistance may be employed, which according to whether there is over or under compensation is connected in series either with the parallel resistance 7 or with the armature 6.