JP2018163952A - Current transformer - Google Patents

Abstract

Provided is a current transformer which can be miniaturized while sufficiently insulating between a one-turn coil and a multi-layer coil, and has a structure in which a bobbin can be used for general purposes regardless of specifications on the one-turn coil side. A current transformer 1a is formed by laminating a one-turn coil 11a below a multi-layer coil 12 wound around a winding shaft 100 extending in the vertical direction, and the multi-layer coil is wound around a bobbin 10a. The one-turn coil is composed of a wiring 34 formed in an inner layer of a substrate 30 having insulating layers on both upper and lower surfaces, and the substrate is laminated on the lower end surface of the bobbin. [Selection] Figure 4

Description

  The present invention relates to a current transformer.

  The current transformer generates a current that is inversely proportional to the turns ratio, and is used, for example, for detecting a large current flowing on the load side. In general, a coil through which a large current flows is formed by a single-turn coil so that the current transformation ratio is N: 1, and a coil through which a current to be detected flows is an N-turn multilayer coil. The one-turn coil and the multi-layer coil are laminated in the direction of the winding axis while sharing the winding axis.

  FIG. 1 shows a conventional current transformer. FIG. 1A is a perspective view showing the appearance of the current transformer 1, and FIG. 1B is a perspective view when the current transformer 1 shown in FIG. Here, assuming that the direction of the winding axis 100 of the coils (11, 12) is the up-down direction, and that the one-turn coil is laminated below the multilayer-wound coil, and the upper and lower directions are defined, the current transformer 1, as shown in FIG. 1A, a bobbin 10 made of an integrally molded resin is arranged in the magnetic path of the core 20, and the bobbin 10 is wound around a winding 11 of the single-turn coil 11 on the large current side. An area for storing the corresponding wire 111 (hereinafter also referred to as a one-turn coil storage space 13) and an area (hereinafter also referred to as a coil winding space 14) in which the winding 112 serving as the multilayer winding coil 12 is wound. Have. Also, a lead terminal (15, 16) for mounting is connected from the bobbin 10 with one end connected to the end of the wire 111 or the winding 112 of the one-turn coil 11 and the multilayer coil 12 and the other end connected to an external circuit. Has been derived.

  As shown in FIG. 1B, the core 20 attached to the bobbin 10 is an EE type in which an E-type core 21 is faced in the vertical direction, and the bobbin 10 passes through both upper and lower ends. A hole (not shown) into which the middle leg 22 of the E-type core 21 is inserted is formed. The one-turn coil 11 is a round-trip line formed by bending a columnar thick wire 111 into a U-shape. The one-turn coil 11 is mounted in the storage space 13, and the end of the wire 111 of the one-turn coil 11 is the bobbin 10. The lead terminal 15 is also led out. Non-Patent Document 1 below describes the size of a commercially available current transformer.

FDK Corporation, “Current Transformer”, [online], [Search March 2, 2017], Internet <URL: http://www.fdk.co.jp/cyber-j/coil/transformer.html# ct>

  FIG. 2 shows a side view of the current transformer 1 shown in FIG. 1A when viewed from the direction of the arrow in the figure. A problem in the conventional current transformer 1 will be described with reference to FIG. As described above, the current transformer 1 is used for detecting a large current. Therefore, in order to detect a larger current, it is necessary to increase the cross-sectional area by making the wire 111 on the side of the one-turn coil 11 have a thick diameter φ. Moreover, in order to insulate the one-turn coil 11 and the multi-layer coil 12 reliably, it is necessary to widen the space | interval D1 of the one-turn coil storage space 13 and the coil winding space 14. FIG. In addition, it is necessary to secure insulation from an external device by using a large amount of resin for the distance D2 between the one-turn coil 11 and the bobbin 10 to the outside. Therefore, it is particularly difficult to reduce the size of the winding shaft 100.

  Further, if the thickness of the wire 111 on the one-turn coil 11 side is changed according to the detected current, it is necessary to change the shape of the one-turn coil storage space 13, the vertical height, the distance D <b> 1 required for insulation from the multilayer coil 12, and the like. . That is, the conventional current transformer 1 requires different bobbins 10 according to the specifications on the one-turn coil 11 side, and the bobbin 10 cannot be used for general purposes.

  Accordingly, the present invention provides a current transformer having a structure in which a bobbin can be used for general purposes regardless of the specifications on the side of the single-turn coil while being able to be miniaturized while sufficiently insulating the single-turn coil and the multi-layer coil. The purpose is to do.

One aspect of the present invention for achieving the above object is a current transformer in which a one-turn coil is laminated below a multilayer winding coil wound around a winding shaft extending in the vertical direction.
The multilayer coil is wound around a bobbin,
The one-turn coil is composed of wiring formed in an inner layer of a substrate having an insulating layer on both upper and lower surfaces,
The substrate is laminated on the lower end surface of the bobbin,
The current transformer is characterized by this.

The bobbin includes a first lead terminal connected to an end portion of the winding of the multilayer winding coil, and a second lead terminal connected to an end portion of the inner layer wiring constituting the one-turn coil. With
The second lead terminal has a lead terminal portion led out to a predetermined one with respect to the bobbin, and a connection terminal portion led out downward,
The substrate has a through hole through which the connection terminal portion is inserted,
The end of the wiring is in contact with the edge of the through hole,
The connection terminal portion inserted through the through hole is connected to the wiring in the inner layer,
It can also be a current transformer characterized by this.

  The current transformer according to the present invention can be miniaturized while sufficiently insulating the one-turn coil and the multi-layer coil, and the bobbin can be used for general purposes regardless of the specification on the one-turn coil side. Other effects will be clarified in the following description.

It is a figure which shows the structure of the conventional current transformer. It is a figure for demonstrating the problem of the conventional current transformer. It is a perspective view which shows the structure of the current transformer which concerns on the Example of this invention. It is a figure which shows the structure of the single layer winding coil in the current transformer which concerns on the said Example. It is a figure which shows the mounting state of the current transformer which concerns on the said Example.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that in the drawings used for the following description, the same or similar parts may be denoted by the same reference numerals and redundant description may be omitted. In some drawings, unnecessary symbols may be omitted in the description.

=== Example ===
<Structure of current transformer>
FIG. 3 shows a current transformer 1a according to an embodiment of the present invention. FIG. 3A is a perspective view showing the appearance of the current transformer 1a, and FIG. 3B is a perspective view when the current transformer 1a shown in FIG. In this case, the winding axis 100 direction of the coils (11a, 12) is the vertical direction, and the single winding coil 11a is laminated below the multilayer winding coil 12, and the vertical directions are defined. To do.

  As shown in FIG. 3A, the current transformer 1a of the present embodiment, like the conventional current transformer 1, is a one-turn coil (not shown) that is stacked in the vertical direction while sharing the winding shaft 100. ) And the core 20 is disposed so as to form a closed magnetic circuit around the multilayer coil 12. However, in the current transformer 1a of the present embodiment, only the winding 112 of the multilayer winding coil 12 is wound around the bobbin 10a, and a single winding coil is provided below the bobbin 10a around which the multilayer winding coil 12 is wound. It has a structure in which substrates 30 formed by inner layer wiring are stacked. One end is connected to the end of the one-turn coil built in the substrate 30, and the other end is connected to the lead terminal 15 connected to the external circuit and the end of the winding 112 of the multilayer winding coil 12. The lead terminal 16 is led out toward the outside of the bobbin 10a.

  As shown in FIG. 3B, the current transformer 1a includes an EE type core 20 formed by facing two E type cores 21 in the vertical direction, a bobbin 10a around which the multilayer coil 12 is wound, It comprises a substrate (hereinafter also referred to as a coil substrate 30) on which a one-turn coil is formed by the inner layer wiring, and a hole (hereinafter referred to as an intermediate leg insertion hole) through which the middle leg 22 of the core 20 is inserted. 31). In this example, the EE type core 20 is used, but a core having another shape such as an EI type may be used. The bobbin 10a is also formed with a hole (not shown) through which the middle leg 22 is inserted.

  Further, in addition to the middle leg insertion hole 31, a hole (hereinafter referred to as a connection terminal) through which a metal terminal portion (hereinafter also referred to as a connection terminal portion 15a) led out downward from the bobbin 10 is inserted into the coil substrate 30. And a hole (hereinafter also referred to as a positioning hole 33) through which the positioning pin 17 integrally formed with the resin bobbin 10a is inserted.

  FIG. 4 shows a laminated structure of the bobbin 10 a and the coil substrate 30. 4A is a side view of the current transformer 1a seen from the direction of the white arrow shown in FIG. 3A, and FIG. 4B is a view of the current transformer 1a seen from below. It is a top view at the time. In FIG. 4, the core 20 and the multilayer winding coil 12 are omitted.

  As shown in FIG. 4A, the coil substrate 30 has an inner wiring layer for one layer, and the one-turn coil 11 a is formed by the inner wiring 34 of the coil substrate 30. The lead terminal 15 led out from the bobbin 10a and connected to the end of the one-turn coil 11a has a U-shape, and a part 15b is embedded in the bobbin 10a. Then, one end of the U-shape is a terminal portion (hereinafter also referred to as a mounting terminal portion 15c) connected to an external circuit. In this example, after being led out to the side, bent downward. Yes. The other end of the lead terminal 15 is a connection terminal portion 15 a inserted through the connection hole 32 in which the coil substrate 30 is formed. As described above, the connection terminal portion 15a is led out so as to protrude downward from the lower end surface of the bobbin 10a. The coil substrate 30 is formed with a connection hole 32 through which the connection terminal portion 15a is inserted and a positioning hole 33 through which the positioning pin 17 is inserted.

  Further, the lower end surface of the bobbin 10 a is formed with a convex portion 18 that abuts one of the edges 35 of the coil substrate 30 for alignment by engaging the positioning pin 17 and the positioning hole 33. In addition, alignment based on the outer shape of the coil substrate 30 can be performed. As described above, if an appropriate convex shape such as the convex portion 18 or the positioning pin 17 is formed on the lower end surface of the bobbin 10a, the position of the bobbin 10a and the coil substrate 30 can be determined when the current transformer 1a is assembled. Matching becomes easy.

  By the way, the current transformer 1a shown here is a surface mount type, and as shown in FIG. 5, the lead terminals (15, 16) are led out to the side and bent downward or upward. It is mounted by a method such as reflow soldering in a state in which the portion is in contact with the surface 41 of the circuit board 40. Of course, a mounting form in which the lead terminals (15, 16) are inserted into through holes formed in the circuit board 40 is also conceivable. In such a case, the tip of the lead terminal (15, 16) is inserted into the through hole without bending the tip of the lead terminal (15, 16), and the lead terminal (15, 16) is inserted into the through hole. What is necessary is just to solder.

  Thus, according to the current transformer 1a of this embodiment, the one-turn coil 11a is formed by the inner layer wiring 34 of the coil substrate 30. Therefore, a large cross-sectional area can be obtained by increasing the width of the wiring 34. The coil substrate 30 is a printed wiring board having one inner wiring layer. As is well known, the insulating layers disposed on the upper and lower surfaces of the inner layer wiring 34 have sufficient insulating properties. Therefore, as shown in FIG. 4A, it is not necessary to widen the distance D1 between the multilayer coil 12 and the one-turn coil 11a and the distance D2 between the one-turn coil 11a and the outside of the current transformer 1a. Therefore, the size in the vertical direction can be reduced with respect to a conventional current transformer using a wire having a round cross section for a one-turn coil. In addition, the value of the current flowing through the one-turn coil can be freely set according to the thickness and width of the inner layer wiring. That is, current transformers of various specifications can be configured simply by replacing the coil substrate, and the bobbin can be used for general purposes.

  Furthermore, in a current transformer that handles a large current, a current may flow through a single-turn coil through a plurality of lead terminals. In a conventional current transformer, when a lead terminal is added, it is necessary to embed the additional lead terminal in the bobbin and connect the additional lead terminal to the end of the one-turn coil. However, in the current transformer 1a of the present embodiment, since the one-turn coil 11a is formed by the inner layer wiring 34 of the coil substrate 30, a through-hole connected to the end of the one-turn coil 11a is added to the through-hole. An additional lead terminal may be connected or wiring on the circuit side may be connected.

<Coil board structure and current transformer assembly procedure>
As described above, in the current transformer 1 a according to the present embodiment, the one-turn coil 11 a is formed by the inner layer wiring 34 of the coil substrate 30. Hereinafter, a more specific structure and assembly procedure of the current transformer 1a will be described with reference to FIG. In the current transformer 1a according to the present embodiment, the one-turn coil 11a is made of thick copper formed in a U shape by punching press processing or etching processing. And the coil board | substrate 30 is a printed wiring board called a thick copper board | substrate, the circuit wiring is not formed in the upper and lower surfaces of the coil board | substrate 30, and only the inner layer wiring 34 used as the one turn coil 11a is formed. is there. And the connection hole 32 is formed as a through-hole connected to the edge part of the one turn coil 11a. In addition, the coil board | substrate 30 can be obtained if a specification is specified to a board | substrate maker similarly to the general printed wiring board using a thick copper board | substrate.

  When assembling the current transformer 1a, the coil substrate 30 is laminated on the lower end surface of the bobbin 10a around which the multilayer wound coil (12 in FIG. 3) is wound. At this time, the connection terminal portion 15a and the positioning pin 17 protruding from the lower end surface of the bobbin 10a are arranged along the one edge 35 of the coil substrate 30 with the convex portion 18 formed on the lower end surface of the bobbin 10a. The coil substrate 30 is inserted through the corresponding connection hole 32 and positioning hole 33. And if the through hole which is the connection hole 32 and the connection terminal part 15a are soldered, the lead terminal 15 and the one turn coil 11a will be connected.

  Of course, if the value of the current passed through the one-turn coil 11a is small, the one-turn coil 11a may be formed of a metal foil such as a copper foil instead of a thick copper instead of a thick printed circuit board. In any case, in the current transformer according to the embodiment of the present invention, it is not necessary to prepare a dedicated bobbin according to the specification or to change the thickness of the wire for the one-turn coil. If coil substrates having different inner layer wiring cross-sectional areas, particularly different thicknesses, are prepared, current transformers corresponding to various specifications can be manufactured at a lower cost. As for the multilayer winding coil, the thickness and the number of turns of the wire may be changed according to the specifications of a bobbin that can be used for general purposes.

1, 1a current transformer, 10, 10a bobbin, 11, 11a one-turn coil,
12 multilayer coil, 15, 16 lead terminal, 15a connection terminal part,
15c mounting terminal part, 17 positioning pin, 18 convex part, 20 core,
30 coil substrate, 31 middle leg insertion hole, 32 connection hole, 33 positioning hole,
34 Inner layer wiring

Claims (2)

A current transformer in which a single-turn coil is laminated below a multilayer winding coil wound around a winding shaft extending in the vertical direction,
The multilayer coil is wound around a bobbin,
The one-turn coil is composed of wiring formed in an inner layer of a substrate having an insulating layer on both upper and lower surfaces,
The substrate is laminated on the lower end surface of the bobbin,
This is a current transformer. In the current transformer according to claim 1,
The bobbin includes a first lead terminal connected to an end of the winding of the multi-layer winding coil, and a second lead terminal connected to an end of the inner layer wiring constituting the one-turn coil. ,
The second lead terminal has a lead terminal portion led out to a predetermined one with respect to the bobbin, and a connection terminal portion led out downward,
The substrate has a through hole through which the connection terminal portion is inserted,
The end of the wiring is in contact with the edge of the through hole,
The connection terminal portion inserted through the through hole is connected to the wiring in the inner layer,
This is a current transformer.

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