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EP-4102525-B1 - CURRENT TRANSFORMER MODULE

EP4102525B1EP 4102525 B1EP4102525 B1EP 4102525B1EP-4102525-B1

Inventors

  • IMAZATO, YUICHI
  • KASATANI, KAZUHIRO
  • MORI, KAZUSA

Dates

Publication Date
20260513
Application Date
20210127

Claims (4)

  1. A current transformer module comprising: a current transformer (10) comprising a resin-made bobbin (20) and a core (50) mounted on the bobbin (20), wherein the bobbin (20) is formed with a primary coil hole (40) of through-hole, and has a U-shaped primary coil (30) disposed through the primary coil hole (40) and a wire-wound secondary coil (27); and a casing (80) for housing the current transformer (10); the primary coil (30) being a U-shaped pin having a pair of legs (32, 32) and a U-shaped bent portion (31) connecting the legs (32, 32); and the casing (80) having a contact area (82) positioned opposite the U-shaped bent portion (31) of the primary coil (30), wherein the contact area (82) has a concaved surface to prevent the primary coil (30) from falling out, wherein the legs (32, 32) of the primary coil (30) have distal ends passing through the primary coil hole (40) of the bobbin (20), and the legs (32, 32) extending out of the primary coil hole (40) are provided with a retaining portion (33) larger than the primary coil hole (40).
  2. The current transformer module according to claim 1 wherein the casing (80) comprises an upper case (81) and a lower case (85), and the contact area (82) is formed on the inner side of the upper surface of the upper case (81).
  3. The current transformer module according to claim 1 or 2 wherein the primary coil hole (40) includes a main hollow section (41) having a diameter equal to or larger than the retaining portion (33), and a reduced diameter section (42) formed at the forward end of the main hollow section (41) and having a diameter smaller than the retaining portion (33).
  4. The current transformer module according to any one of claims 1 to 3 wherein the retaining portion (33) is formed by subjecting the legs (32, 32) to a crushing process.

Description

TECHNICAL FIELD This invention relates to a current transformer module used in various AC equipment and adapted to detect electric currents flowing through the equipment to provide output control and overcurrent protection operation of the equipment. More specifically, the invention relates to a current transformer module wherein a U-shaped pin is employed for a primary coil. BACKGROUND ART A current transformer is used to detect electric currents in high-power electric instruments such as air conditioners and IH devices that operate on household power supplies. A current transformer comprises a primary coil, a secondary coil, and a core for forming a magnetic path common to these coils (see, for example, Patent Document 1). In the current transformer, a current-sensing resistor is connected to the secondary coil, and the power supply commercial frequency of the instruments is energized to the primary coil. When the current in the primary coil changes, the magnetic field in the secondary coil changes through a magnetic circuit, creating a potential difference at both ends of the current-sensing resistor in the secondary coil. The difference is detected as a voltage at the current-sensing termination resistor. The instrument inputs the voltage into the microcomputer to control the inverter circuit, etc., to thereby controlling the input to or output from the instrument. The primary coil uses a so-called U-shaped pin with the conductive wire bent in a U-shape, as shown in Patent Document 1. A current transformer comprises a core component and a core mounted on the core component. In general, the core component is made by inserting a U-shaped pin, which serves as the primary coil, into a primary coil hole formed in a resin-made cc, and then winding the secondary coil. The current transformer is housed in a resin-made casing to produce a current transformer module. JP H03 227004 is a further example of a current transformer having a core mounted on a bobbin as well as a wire-wound winding and a U-shaped pin winding both mounted on the bobbin. JP2002064020 discloses a current transformer with a U-shaped coil having a retaining portion formed after the insertion of the U-shaped coil's legs through the bobbin. The document EP4006929 belongs to the prior art according to Art. 54(3) EPC and discloses an example of a current transformer which provides a current transformer having an E-type core formed of an electromagnetic steel sheet and having three legs extending substantially parallel to each other and a connecting part connected at each end of the legs and an I-type core formed of an electromagnetic steel sheet and having the same length as the connecting portion, the I-type core being placed on and bonded to the connecting part of the E-type core to form a single-piece core component. PRIOR ART DOCUMENT (s) PATENT DOCUMENT Patent Document 1: Japanese Utility Model Application Publication SHO.63-18824 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION When a current transformer module with a U-shaped pin for the primary coil is mounted on a printed circuit board, the terminal portion at the end of the U-shaped pin is pushed by the printed circuit board, sometimes causing the primary coil to lift up. In addition, if a U-shaped pin is inaccurately shaped, it's is not easy to insert such a U-shaped pin (i.e., primary coil) into the bobbin, and the bobbin sometimes breaks if the pin is inserted forcibly. To produce a current transformer module, the core component is produced by inserting the U-shaped pin, i.e., the primary coil, into the bobbin and then winding the secondary coil around the bobbin. In the subsequent process, a core is mounted on the core component. The assembly of the core component and core is then inserted into the casing whereby the current transformer module is produced. However, the U-shaped pin sometimes dropped out after the U-shaped pin was inserted into the bobbin and before the current transformer is housed in the casing. An object of the present invention is to provide a current transformer module that can prevent the primary coil from being lifted or dropped, and prevent the bobbin from being cracked when the primary coil is inserted into the bobbin. MEANS TO SOLVE THE PROBLEMS A current transformer module of the present invention comprises: a current transformer comprising a resin-made bobbin and a core mounted on the bobbin, wherein the bobbin is formed with a primary coil hole of through-hole, and has a U-shaped primary coil disposed through the primary coil hole and a wire-wound secondary coil; anda casing for housing the current transformer;the primary coil being a U-shaped pin having a pair of legs and a U-shaped bent portion connecting the legs; and the casing having a contact area positioned opposite the U-shaped bent portion of the primary coil, wherein the contact area has a concaved surface to prevent the primary coil from falling out, whereinthe legs of the prima