Metrological investigation and characterization of current transducer for industrial application

Measurement of Current is a vital task in electrical sector, where the current information is required for monitoring and control purposes. In order to achieve the above-mentioned goals, existing current sensing techniques have to be improved in terms of cost, power loss and size. In this Thesis a new solution of current transducers has been deeply tested, where current signal is converted in a corresponding output voltage of the array of Hall effect sensors, in which the magnetic field produced by the current induces the voltage. The proposed current Transducer, developed in co-operation with an Italian Research Centre of an international Company comprises two arrays of magnetic sensors, the inner array for high-accuracy measurements and the outer array for the measurements oriented to the protection purpose. A dedicated electronics is used in order to properly process the Hall-effect sensor output signals. It is well known that Hall effect-based sensors have some limitations concerning linearity, temperature stability and range of operation. When operated from a constant current source or voltage source, the sensitivity does vary slightly over temperature; they must be accounted for and corrected when a high degree of measurement stability is needed. This thesis validates the offset and sensitivity variation of the current measuring device over a range of temperature from −35 degree Celsius to +125 degree Celsius. Also investigated the thermal drift and linearity with the modification of the voltage supplied to the voltage regulator, which provides the constant offset voltage to the Hall sensor. Finally we have validated the crosstalk effect on the arrays of Hall effect sensor due to currents flowing in parallel conductors. Since in protection systems the current under measurement flows in a conductor that is near and often parallel to other current conductors and the magnetic field that is sensed by magnetic sensors depends on all the currents.