JPH0561764B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current transformer in which the number of turns of the primary winding is one turn, and specifically relates to reducing parasitic inductance in such a current transformer.

[Conventional technology]

Conventionally, in a current transformer in which the number of turns of the primary winding is one turn, as shown in FIG. things were being used. Note that 1d indicates a terminal of the secondary winding 1a.

When using a current transformer with such a structure, for example, in a high-precision measuring instrument, the primary winding 1c
In order to prevent the magnetic field generated by the current transformer from affecting the surrounding area, the current transformer is surrounded by a shield case 1e as shown in FIG. 4.

However, when the current transformer is magnetically shielded with a magnetic material in this way, the shield case 1e
A magnetic flux Φ is generated as shown by the arrow 1f, and this magnetic flux increases the inductance (parasitic inductance) of the primary winding 1c. Further, the magnetic flux Φ causes iron loss in the shield case 1e, which causes heat generation.

[Problem that the invention seeks to solve]

The present invention was made to solve these problems, and aims to reduce the parasitic inductance in the current transformer, as well as reduce the iron loss that occurs when magnetic shielding is used.

[Means for solving problems]

In order to achieve the above object, the present invention comprises a primary winding made of an E-shaped conductor whose middle leg passes through the center of a core and a pair of outer legs located outside the core are short-circuited. It is characterized by this. Examples will be described in detail below.

〔Example〕

FIG. 1 is a configuration diagram of an embodiment of a current transformer according to the present invention. In the figure, 1b is a toroidal core, 1a is a secondary winding wound around the toroidal core 1b, 2 is a primary winding, and 1e is a box-shaped box made of magnetic material arranged to surround a current transformer. case (shield case). A specific configuration of the primary winding 2 is shown in FIG.

In the primary winding 2 shown in FIG. 2, 3 is a T-shaped conductor, and 4 is an E-shaped conductor. E-shaped conductor 4
The middle leg 4a is somewhat shorter in length than the two outer legs 4b and 4c, and a flat conductor 4d is provided at the end of the middle leg 4a in a right angle direction.

In the primary winding 2 having such a configuration, as shown in FIG. 1, the middle leg 4a of the E-shaped conductor 4 passes through the center of the toroidal core 1b, and the outer legs 4b and 4c extend outside the toroidal core 1b. This E-shaped conductor 4 is arranged on the toroidal core 1b so that the E-shaped conductor 4 is located at the same position as the E-shaped conductor 4. T
Both arms 3b and 3c of the E-shaped conductor 3 are attached to the E-shaped conductor 4 so as to short-circuit the outer legs 4b and 4c of the E-shaped conductor 4. In this case, the leg 3a of the T-shaped conductor 3
and the conductor 4d provided on the middle leg 4 of the E-shaped conductor 4 are arranged to face each other with a slight distance between them. The legs 3a and the conductor 4d are used as lead wires for the primary current, and are taken out from the shield case 1e to the outside of the case.

In such a configuration, when a primary current I is supplied from, for example, the legs 3a of the T-shaped core 3, the current I flows through the arms 3b, 3c of the conductor 3→
It flows out from the conductor 4d through the outer legs 4b, 4c of the E-shaped conductor 4→the middle leg 4a. A magnetic field is generated by the current I flowing through the primary winding 2 in this direction, but the arms 3b and 3c of the T-shaped conductor 3 and the E-shaped conductor 4
Since the directions of the magnetic fields within the windows 5a and 5b formed by the legs of the toroidal core 1b are opposite to each other, they are mutually strengthened against the toroidal core 1b.
The direction is to go around b.

On the other hand, the magnetic fields away from the primary winding (conductor) weaken each other because they are in opposite directions. As a result, the shield case 1e and toroidal core 1
The magnetic flux generated in spaces other than b decreases, and the parasitic inductance decreases. Further, heat generation due to iron loss in the shield case 1e is also eliminated.

Note that the current I flowing through the two lead wires 3a and 4d
Since the directions are opposite and the magnitudes are equal, by arranging both lead wires close to each other, the combined magnetic field becomes smaller, which also reduces the parasitic inductance. In this case, it is preferable to make one hole in the shield case 1e and lead out the lead wires 3a and 4d, which are arranged close to each other, to the outside from the hole in order to prevent magnetic flux from being generated in the shield case 1e.

[Effects of the present invention]

As explained above, the present invention has the following effects.

(1) Parasitic inductance of the primary winding is reduced.
In this case, if the parasitic inductance is Ls, the operating frequency is f, and the current is I, the instrument loss is expressed as 2πfLsI ² [VA], so it is possible to reduce the instrument loss at high frequencies and increase the bandwidth. can.

(2) Since the magnetic flux generated in the magnetic shield is reduced, heat generation due to iron loss can be prevented.

(3) Since the magnetomotive force caused by the current is large at two locations on the core 1b, leakage magnetic flux is reduced compared to when the wire is wound at one location as shown in Figure 5, reducing errors. be able to.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the main parts of a current transformer according to the present invention, showing a part of the current transformer in cross section, FIG. 2 is a block diagram of the primary winding used in the transformer of FIG. 1, and FIG. FIG. 4 is a block diagram of the transformer shown in FIG. 3 surrounded by a shield case, and FIG. 5 is a diagram for explaining the characteristics of the current transformer. 1a...Primary winding, 1b...Toroidal core, 2...Secondary winding, 4...E-shaped conductor, 4a
... middle leg, 4b, 4c... outer leg, 3a, 4d...
leader line.

Claims (1)

[Claims] 1. A T-shaped conductor consisting of legs and both arms, and a flat conductor provided at the end of the middle leg in a direction perpendicular to the middle leg, the middle leg being shorter than both outer legs. The arms of the T-shaped conductor are arranged in an E-shape such that the legs of the T-shaped conductor face the flat conductor of the E-shaped conductor with a slight distance between them. A primary winding attached to both outer legs of a conductor, and a secondary winding wound around a toroidal core, the central part of the toroidal core passing through the middle leg of the E-shaped conductor. A current transformer has this toroidal core placed between the outer legs of an E-shaped conductor. 2. The current transformer is arranged in a shield case, and the legs and flat conductor constituting the primary winding, and both ends of the secondary winding are drawn out to the outside through one hole formed in the shield case. A current transformer according to claim 1.