Method of Turns Arrangement of Non-Circular Rogowski Coil with Rectangular Section

The circular Rogowski coil with a rectangular section is the most common and basic measuring unit of current. However, in some situations, a noncircular Rogowski coil is more suitable because of the limited space to be embedded in and the demand for decreasing the size of the Rogowski coil. Circular Rogowski coil is usually wound uniformly to guarantee the positional accuracy and anti-interference ability considering the very good symmetry. However, for noncircular Rogowski coil, the turns arrangement is usually designed based on experience due to the lack of theoretic direction. This article first proposed a method of turns arrangement of the noncircular Rogowski coil with a rectangular section, which the positional accuracy and anti-interference ability can be achieved at the same time. By establishing the equivalent relation between mutual inductance and electric potential, the turns density of the noncircular Rogowski coil can be acquired by solving the charge density on its equivalent electrodes. The turns density is proven to be unique. For a given turn number, the turns arrangement of the noncircular Rogowski coil can be obtained by discretizing the turns density. As an example of the method, a square Rogowski coil, which can be used in chip current measurement in Press Pack insulated gate bipolar transistors (IGBTs), is particularly designed and contrasted with the traditional square Rogowski coil with turns equidistantly arranged to verify the great positional accuracy and anti-interference ability. The results of the calculation and experiment show that this method is very effective.