JPH02275367A - Ammeter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current measuring device, that is, a current measuring device for measuring the current flowing through a primary conductor.

[Prior Art] Figure 6 shows a partial cross section of a Rogowski coil, which is a conventional current measuring device, as shown in, for example, Electrical Engineering Handbook 1 (published by the Institute of Electrical Engineers of Japan, October 30, 1982), page 585. Fig. 7 is a cross-sectional view taken along the line ■-■ in Fig. 6, and in the figure, symbol (1) is the primary conductor, and (2) is the primary conductor (1) provided so as to pass through it. The annular insulator (3) is a winding wire wound around the insulator (2) as shown in FIG.

In the conventional current measuring device configured as above,
The current ■ flowing through the primary conductor (1) generates a magnetic field H in the winding (3). The relationship between the magnetic field H and the current I is expressed by the following equation (1) based on Ampere's circuit integral theorem.

I=SHd1・・・・・・・・・・・・(1) This magnetic field H
is calculated from the winding (3) using the following formula (2) % formula % However, B is the magnetic flux density, S is the magnetic flux linkage area of the winding (3),
μ. is the vacuum permeability, e is the winding per unit length (3)
is the voltage induced in

Assuming that both S and e are constant, the following formula % formula % Here, ■ is the terminal voltage of the winding (3).

As can be seen from the above equation (3), the current I flowing through the primary conductor (1) can be measured by integrating the terminal voltage of the winding (3).

[Problem to be solved by the invention] In the conventional current measuring device configured as described above,
When the winding (3) is wound in many layers, it is difficult to manufacture the magnetic flux linkage plane 1s to be constant at any position, and therefore the induced voltage e per unit length is also constant. It's gone. As a result, there is a problem in that an induced voltage is generated in the winding (3) due to the external magnetic field, resulting in a large measurement error, and there is a problem in reducing such measurement errors. .

This invention was made to solve the above problems, and can prevent the generation of induced voltage due to external magnetic fields.
The purpose of this invention is to obtain a current measuring device that can prevent measurement errors from occurring due to the influence of external magnetic fields.

[Means for Solving the Problems] A current measuring device according to the present invention is provided with an iron core so as to interlink with a primary conductor to form a magnetic path, and a first winding and a second winding are wound around the iron core. and the first winding is short-circuited.

[Operations] In this invention, the current in the primary conductor is measured from the voltage induced in the second winding. At this time, the magnetic flux caused by the primary conductor of the iron core is concentrated to prevent the influence of external magnetic fields, and the first winding prevents magnetic saturation of the iron core.

[Example] Hereinafter, the present invention will be described based on figures showing examples thereof.

FIG. 1 is a partially sectional front view showing the essential parts of a current measuring device according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. 1 is a schematic configuration diagram showing the state of the winding shown in FIG. 1, and the same or equivalent parts as in FIG. 6 are denoted by the same reference numerals, and the explanation thereof will be omitted.

In the figure, the code (4) is an annular core that passes through the primary conductor (1);
interlink with each other to form a magnetic path. (5) is a first winding wound around the iron core (4), and both ends of the first winding 5) are electrically connected to each other, thereby short-circuiting. (
6) is a second winding wound around the iron core (4) so as to be above the first winding (5), and both terminals of this second winding (6) are connected to a measuring part (not shown). be done.

In the current measuring device configured as described above, when a primary current flows through the primary conductor (1), the first
A secondary current flows in the winding (5) such that the ampere turns are the same. However, since the first winding (5) is short-circuited, its resistance is only that of the winding resistance, and therefore its voltage, that is, the secondary voltage, becomes low. Also, the shorted first
Since an electromotive force is generated in the winding (5) so that the primary conductor (1) generates a magnetic flux that cancels the magnetic flux generated in the iron core (4), the magnetic flux generated in the iron core (4) is also small.

On the other hand, since the second winding (6) is also wound around the iron core (4), a voltage corresponding to the secondary voltage is induced by the magnetic flux of the iron core (4). The primary current can be measured by integrating the voltage of the second winding (6) using a measuring section such as an integrator, as in the conventional Rogowski coil.

In reality, if you adjust the number of turns of the second winding (6) so that, for example, when the primary current is 100 OA, the voltage of the second winding (6) is 1, the voltage can be measured. You can easily find the primary current by simply doing this.

As mentioned above, the main magnetic flux due to the primary conductor (1) is caused by the iron core (
4), the main magnetic flux passing through the first winding (5) becomes large. On the other hand, since the external magnetic field enters the iron core (4) from the space, the magnetic resistance is large and the influence of the external magnetic field is small. For this reason, the second winding (
Even if the magnetic flux linkage surface 1s is non-uniform due to the density and density of 6), there is almost no influence from the external magnetic field, and the occurrence of measurement errors due to this can be prevented.

In addition, the short-circuited first winding (5) has a primary conductor (1>
Since an electromotive force is generated to generate a magnetic flux that cancels the magnetic flux generated in the iron core (4), magnetic saturation of the iron core (4) is prevented, and the cross-sectional area of the iron core (4) can be reduced, making it practical. It can be made to any desired size.

In the above embodiment, both ends of the first winding (5) were simply connected and short-circuited, but as shown in FIG. Good too.

FIG. 4 is a configuration diagram showing the main parts of a current measuring device according to a second embodiment of the present invention. The second winding is omitted in the one in FIG. 4, but the second winding is shown in FIG. It is similar to

In this case, the first winding (5) due to the electrical resistance (7)
Since the voltage of the second winding (6) increases, the voltage of the second winding (6) also increases, and the voltage of the second winding (6) with respect to the primary current becomes
This is effective for adjusting to a predetermined value.

Further, in the above embodiment, the first winding (5) is wound in the lower layer and the second winding (6) is wound in the upper layer around the entire circumference of the iron core (4), but for example, the upper layer and the lower layer may be reversed. The winding positions and winding methods of the first winding and the second winding are not limited to the above embodiments.

FIG. 5 is a configuration diagram showing the main parts of a current measuring device according to a third embodiment of the present invention. Although the second winding is omitted in FIG. 5, the second winding is the same as that in FIG. 3. be.

In this current measuring device, the first winding (5) is connected to the winding A (5a
) and winding B (5b), which are connected in parallel via an electric resistor (7).

In this case, each of the windings A, B (5a) and (5b) carries a current of 1/2 ampere turn with respect to the -transmission conductor (1). Therefore, the resistance of the first winding (5) as seen from the primary side becomes small, and thereby the voltage of the first winding (5) becomes low.

Therefore, the cross-sectional area of the iron core (4) can be made smaller.

Further, in the above embodiment, the iron core (4) is an annular core with a square cross section, but it may also have a circular cross section, a polygonal cross section, a polygonal annular core, etc. It may be something that is possible.

[Effects of the Invention] As explained above, the current measuring device of the present invention uses an iron core that interlinks with the transmission conductor to form a magnetic path, so this iron core concentrates the magnetic flux caused by the primary conductor. This has the effect of preventing the generation of induced voltage due to an external magnetic field and preventing the generation of measurement errors due to the influence of the external magnetic field. Furthermore, since the first winding wound around the iron core is short-circuited, magnetic saturation of the iron core is prevented, and the cross-sectional area of the iron core can be reduced.

[Brief explanation of drawings]

FIG. 1 is a partially sectional front view showing the essential parts of a current measuring device according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. 1 is a schematic configuration diagram showing the state of the winding wire in FIG. 6th block diagram showing the main parts of the current measuring device according to the embodiment
The figure is a partially cross-sectional front view of a Rogowski coil as an example of a conventional current measuring device, Figure 7 is a cross-sectional view taken along the line ■-■ in Figure 6, and Figure 8 is the winding shown in Figure 6. FIG. 2 is a schematic configuration diagram showing the state of FIG. In the figure, 1) is the - transmission conductor, (4) is the iron core, and (5)
is the first winding, and (6) is the second winding. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] an iron core interlinked with a primary conductor to form a magnetic path; a first winding wound around the iron core and short-circuited; and a second winding wound around the iron core; A current measuring device characterized in that the current in the primary conductor is measured from the voltage induced in the winding.