Current transformer

A current transformer is a special transformer used to measure large alternating currents and has only one or a few primary windings, which are energised by the current to be measured, and at least one secondary winding. This current is reduced in reverse proportion to the ratio of primary and secondary windings and can now be processed further using available measuring instruments or electronic circuits. The secondary winding is connected to a current sensor or the current path of an energy counter, for example. The resistive load connected to the secondary winding for the current measurement must not exceed a set value to ensure an accurate measurement result. This is referred to as the burden.

Current transformers are not suitable for measuring direct current. However, current sensors capable of measuring direct current, and based on Hall sensor technology are also regarded as current transformers.