Current transformer for electronic meters - uses negative feedback amplifier connected to transformer secondary to compensate for losses due to leakage current

摘要

A current transformer is for electronic meters, especially electronic electricity meters. It is designed for circuit and constructional simplicity with resultant savings in production, costs. The proposed current transformer enables the electronic meter to be used over a large range of measurement, and to these ends an iron or ferrite core piece with a large air gap is used for the transformer. More specif. the primary working consists of a single wire while the secondary consists of several windings of thin wire. An amplifier with capacitive negative feedback is connected to the secondary winding of the current transformer to compensate for the lag and frequency dependency of the secondary voltage (Us) the lag being -90 deg. relative to the magnetizing current and is caused by the leakage current.