Current transformers and methods for measuring a primary current

Abstract

The invention relates to a measuring current transformer (10) for measuring a primary current (Im) in a primary conductor (11), with a closed ring-shaped magnetic core (12). The ring-shaped magnetic core (12) is designed as a hollow tube, in the interior (13) of which an annular circuit board (14) with a conductor track (15) is arranged, which carries an excitation current (Iexc), wherein the circuit board (14) extends in a partial section (18) of the ring-shaped magnetic core (12) with an outer area (19) outside the ring-shaped magnetic core (12).Furthermore, a method for measuring a primary current (Im) in a primary conductor (11) using a measuring current transformer (10) with a closed ring magnetic core (12) is claimed, comprising the method steps: generating an excitation current (Iexc) which is guided in a conductor track (15) formed on an annular printed circuit board (14), wherein the ring magnetic core (12) is designed as a hollow tube in the interior (13) of which the printed circuit board (14) is arranged and extends in a partial section (18) of the ring magnetic core (12) with an exterior area (19) outside the ring magnetic core (12); controlling and measuring the excitation current (Iexc) using a measuring circuit (16) and determining the primary current (Im) using the measuring circuit (16).