Novel DC Current Transformer by the Reed Relay’s Release MMF

F. Castelli, M. Faifer

Abstract

Accurate dc current transformers (DCCTs) are required for high current precision power supplies- Three basic categories of devices are available: devices which uses Ohms law (V=RI) called current shunts, devices which use Amperes law ( ∫ Hdl =ΣI ), called magnetic current sensors, and devices which uses both, called direct current transformers, DCCT’s The novel DCCT (NDCCT) uses Amperes law, and a reed relay (RR) as magnetic current sensor to detect when the primary and secondary ampere-turns would exactly be equal in magnitude and opposite. RR detects the zero flux condition occurring at the outlined balance condition. NDCCT is a clamp-on current probe. Two versions of NDCCT are illustrated, the one as dc current comparator and the other DCCT. By test results on an experimental NDCCT an uncertainty of 1.410-7 on the ratio error at 1 kA of the primary current is achieved.

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IMEKO TC

TC4 - Measurement of Electrical Quantities

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