A current transformer includes a closed magnetic circuit and a secondary winding. A first part of the closed magnetic circuit completely surrounds a primary conductor, and a second part of the closed magnetic circuit forms the secondary winding. The second part of the closed magnetic circuit serves as a magnetic core of the secondary winding. The closed magnetic circuit forms a plurality of branch magnetic circuits at the second part, and a secondary winding is formed on each branch magnetic circuit. Each branch magnetic circuit serves as a magnetic core of a corresponding secondary winding. Each secondary winding is staggered with each other in at least one of the length, the height and the thickness.

Electrical current transducer (2) of a closed-loop type for measuring a primary current (I.sub.p) flowing in a primary conductor (1), comprising a fluxgate measuring head (7) and an electronic circuit (16) including a microprocessor (18) for digital signal processing. The measuring head includes a secondary coil (6) and a fluxgate detector (4) comprising an excitation coil and a magnetic material core. The electronic circuit comprises an excitation coil drive circuit (14) configured to generate an alternating excitation voltage to supply the excitation coil with an alternating excitation current (I.sub.fx), the secondary coil (6) connected in a feedback loop (12) of the electronic circuit to the excitation coil drive circuit (14), the electronic circuit further comprising a ripple compensation circuit (26, 28) configured to compensate for a ripple signal generated by the alternating excitation voltage.

Electrical current transducer including a housing (5), a magnetic field detector device (3) comprising a magnetic field sensing element (11), and a magnetic circuit comprising a magnetic core (4) with a gap (6) and a bridging device (8) mounted on the magnetic core and spanning across the gap. The bridging device comprises a gap-width setting portion (26) made of a non-magnetic material inserted in the gap configured to determine a minimum width of the gap. The bridging device comprises at least two parts (8a, 8b), a first part mounted against a first lateral side (14a) of the magnetic core and a second part mounted (8b) mounted against a second lateral side (14b) of the magnetic core opposite the first lateral side, at least one of the first and second parts comprising fixing extensions (30) cooperating with the other of the first and second parts configured for clamping together the first and second parts around a portion of the magnetic core comprising the gap.

Electrical current transducer including a housing (5), a magnetic field detector device (3) comprising a magnetic field sensing element (11), and a magnetic circuit comprising a magnetic core (4) with a gap (6) and a bridging device (8) mounted on the magnetic core and spanning across the gap. The bridging device comprises a gap-width setting portion (26) made of a non-magnetic material inserted in the gap configured to determine a minimum width of the gap. The bridging device comprises at least two parts (8a, 8b), a first part mounted against a first lateral side (14a) of the magnetic core and a second part mounted (8b) mounted against a second lateral side (14b) of the magnetic core opposite the first lateral side, at least one of the first and second parts comprising fixing extensions (30) cooperating with the other of the first and second parts configured for clamping together the first and second parts around a portion of the magnetic core comprising the gap.

There is provided a neutral pole transformer module for a circuit breaker capable of minimizing an influence of external noise, detecting a neutral pole current at low manufacturing cost, and detecting a neutral pole current without modifying a configuration of an existing overcurrent relay or without installing an additional component in the existing overcurrent relay. The neutral pole transformer module for a circuit breaker comprises a ZCT configured to allow a transmission line of a neutral pole detection current output from the current transformer to pass therethrough and to provide a secondary output current signal obtained by reducing the neutral pole detection current in a predetermined ratio; a printed circuit board configured to convert the secondary output current signal into a voltage signal, and to differentiate the converted voltage signal and output the same; and an enclosure formed of an electrical insulator and enclosing the ZCT and the PCB.

There is provided a neutral pole transformer module for a circuit breaker capable of minimizing an influence of external noise, detecting a neutral pole current at low manufacturing cost, and detecting a neutral pole current without modifying a configuration of an existing overcurrent relay or without installing an additional component in the existing overcurrent relay. The neutral pole transformer module for a circuit breaker comprises a ZCT configured to allow a transmission line of a neutral pole detection current output from the current transformer to pass therethrough and to provide a secondary output current signal obtained by reducing the neutral pole detection current in a predetermined ratio; a printed circuit board configured to convert the secondary output current signal into a voltage signal, and to differentiate the converted voltage signal and output the same; and an enclosure formed of an electrical insulator and enclosing the ZCT and the PCB.

A current transformer according to the present invention may comprise a magnetic core, a secondary coil, and a magnetic flux compensation member. A main circuit of an air circuit breaker penetrates the magnetic core. In addition, the secondary coil is arranged to be adjacent to the magnetic core, and a secondary current is induced through a current flowing in the main circuit. In addition, the secondary coil supplies the induced secondary current to a relay. The magnetic flux compensation member may be coupled to the magnetic core so as to correct magnetic flux of the secondary coil.

A current transformer according to the present invention may comprise a magnetic core, a secondary coil, and a magnetic flux compensation member. A main circuit of an air circuit breaker penetrates the magnetic core. In addition, the secondary coil is arranged to be adjacent to the magnetic core, and a secondary current is induced through a current flowing in the main circuit. In addition, the secondary coil supplies the induced secondary current to a relay. The magnetic flux compensation member may be coupled to the magnetic core so as to correct magnetic flux of the secondary coil.

An inductive current transformer for transforming a primary current into a secondary current, has a secondary winding with two terminals, an electronic device for transmitting information to an external measuring device, a first inductive coupling device connected to the secondary winding, and a power supply device which is coupled to the secondary winding via the first inductive coupling device and which is adapted to generate a supply voltage for the electronic device from the secondary electric current of the secondary winding.

An inductive current transformer for transforming a primary current into a secondary current, has a secondary winding with two terminals, an electronic device for transmitting information to an external measuring device, a first inductive coupling device connected to the secondary winding, and a power supply device which is coupled to the secondary winding via the first inductive coupling device and which is adapted to generate a supply voltage for the electronic device from the secondary electric current of the secondary winding.