Air cored current sensor for digital metering & micro-processor based protection unit

Most of the current sensors use a special core material for sensing the electromagnetic field generated by the current carrying primary conductor. This core especially for current transformer is made out of permeable magnetic materials, which are subjected to iron losses and hence high temperature rise contributed due to both iron & copper loss. At high current the materials gets saturated and hence loose its linearity. This results into increased size, volume, weight and cost of the sensor. The paper discuss about development of 160 Ampere air cored current sensor for metering and micro-processor based release & protection unit, which eliminates the various problem associated with conventional current transformer. It consists of four coil connected in series, wound over an insulated former surrounding the primary conductor. The magnetic field generated by the primary conductor passes through the series coil and there by induces an electromotive force which is proportional to the rate of change of primary current. The voltage output in the secondary coil is further integrated using an integrator circuit to find out the primary current. The integrator circuit is added with adequate filter to take care of the problem associated with the current and phase offset so as to minimize the error between the theoretical & practical results obtained.