JP2867276B2 - Current detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a current detector used for an electronic device, an electric machine, or the like, and more particularly to a current detector provided with a gap in a part of a toroidal ferromagnetic core. The present invention relates to a configuration of a ferromagnetic core of a current detector in which a magnetic sensing element is formed in a gap.

[Prior Art] Conventionally, in a current detector of this kind (FIG. 2), a ferromagnetic core 3 used in a portion forming a magnetic circuit is used.
In particular, a ferromagnetic material A having a high saturation magnetic flux density or a ferromagnetic material B having a small coercive force to reduce a detection error is used for expanding a detection current range. A magnetic gap 1 for inserting such a magnetic sensing element 2 is formed, and the magnetic sensing element 2 is inserted into the magnetic gap 1 and inserted into the magnetic gap 1 in which a magnetic field proportional to a measured current flowing through the through key 5 is generated. Magneto-sensitive element 2
As a result, an output voltage proportional to a large current is obtained.

The output voltage proportional to the current of the through wire 5 detected by the magnetic sensing element 2 is amplified by a signal amplifier circuit to obtain an output voltage proportional to the magnitude of the current, and the magnitude of the through current is detected.

[Problems to be Solved by the Invention] However, in a conventional current detector, the saturation magnetic flux density of a ferromagnetic core used in a portion forming a magnetic circuit directly affects a detection current range. The sensitivity and the range of the detected current are designed to be limited to one target depending on the saturation magnetic flux density of the magnetic material and the shape of the core. Therefore, if the magnetic gap is reduced to obtain high sensitivity in a small current range where resolution is required, the ferromagnetic core is easily saturated, and a sufficient current detection range cannot be obtained. When the magnetic gap is increased to increase the linearity of the large current range, the output of the small current range is small when the magnetic gap is increased. Therefore, separate detection of the large current and the small current is required.

[Means for Solving the Problems] According to the present invention, a gap is provided in a part of the magnetic path of the toroidal ferromagnetic core to eliminate the conventional disadvantage.
In a ferromagnetic core of a current detector having a magneto-sensitive element inserted in the gap, two or more types of ferromagnetic materials having different saturation magnetic flux densities are inserted in series at the center of the ferromagnetic core. A current detector characterized in that the core is constituted by a series connection of the above ferromagnetic materials and has a sensitivity of two or more stages.

[Constitution of the Invention] FIG. 1 shows a ferromagnetic core of a current detector in which a gap is provided in a part of a magnetic path of a toroidal ferromagnetic core and a magneto-sensitive element is inserted into the gap. As described above, a thin plate of a magnetic material B having a low saturation magnetic flux density is inserted into the center of the core of a toroidal ferromagnetic core 3 formed of a ferromagnetic material A having a high saturation magnetic flux density. The core is inserted and two or more magnetic materials are connected in series.

[Operation] current detector using a configuration cores as in the first figure the sensitivity to ferromagnetic material B reaches the magnetic saturation point, the magnetic gap length L _g through wire turns N, the detected current I ( NI /
L _g ). After the magnetic material B is saturated, the magnetic material B
No magnetic flux passes through the portion, and it can be regarded as equivalent to a magnetic gap.
Works the same as. Therefore sensitivity after ferromagnetic material B is saturated it is proportional to _{(NI / L g + L 2} ). A linear output can be obtained until the subsequent ferromagnetic material A reaches saturation. Further, the saturation point of the magnetic material A is extended due to the magnetic gap being enlarged equivalently, and the range of the detection current detector is widened.

[Embodiment] An embodiment will be described with reference to the drawings. FIG. 2 is a configuration front view of a conventional current detector. A through wire 5 for passing a current to be measured is passed through the toroidal ferromagnetic core 23, and a magnetic flux generated by the current of the through wire 5 is focused by the ferromagnetic core 3, and a magnetic gap 1 of the ferromagnetic core 3 is formed. A magnetic flux is generated in the space, and the magnetic flux of the magnetic gap 1 is measured by the magneto-sensitive element 2 to measure the intensity of the magnetic flux. This second
The sensitivity of the current detector in the figure is proportional to (NI / L _g ). Second
The input / output characteristics when a directional silicon steel is used for the ferromagnetic core in the figure are shown by broken lines in FIG.

FIG. 1 shows an embodiment of a ferromagnetic core configuration of the current detector according to the present invention. A ferromagnetic core as shown in FIG. 1 is formed by using directional silicon steel, which is a ferromagnetic material having a high saturation magnetic flux density, as the ferromagnetic material A, and permalloy, which is a ferromagnetic material having a low saturation magnetic flux density, as the ferromagnetic material B. doing. In FIG. 3, the solid line shows the input / output characteristics of the current detector using the core of this embodiment. In FIG. 3, up to point P, the permalloy operates as part of the core, and its sensitivity is proportional to (NI / L _g ).
Permalloy portion in FIG. 3 point P~L becomes magnetic gap equivalent saturated, the sensitivity of the current detector is proportional to _{(NI / L g + L 2} ), the output of this leg is also linear. The sensitivity was reduced by the increase of the magnetic gap, and the current detection range of the current detector composed of only silicon steel was A1 in Fig. 3, but the current detector of the embodiment detected up to A2 in Fig. 3. The current range is wide.

The current detector using the core configured as shown in Fig. 1 has two stages of sensitivity at the point where the permalloy portion saturates (inflection point), thereby achieving high sensitivity characteristics in a small current range where resolution is required. It has become possible to provide a current detector having a wide current detection range for a large current range.

[Effects of the Invention] As described above, the conventional sensitivity is maintained in the small current range where resolution is required, and the detection current range can be linearly expanded by lowering the sensitivity in the large current range. The inflection point and the inclination after the inflection point of the sensitivity of the current detector can be arbitrarily set by selecting the type and thickness (L ₂ ) of the ferromagnetic substance B to be inserted. This two-stage sensitivity current detector combines the characteristics of a small current detector that requires resolution and a large current detector that requires a linear output up to a large current. By winding a through-wire for detecting a large current and a through-wire for detecting a small current, it is possible to detect both a large current and a small current with a single current detector, which is an industrially useful invention.

[Brief description of the drawings]

FIG. 1 (a) shows a ferromagnetic core portion of the current detector of the present invention, FIG. 1 (b) shows a state in which the ferromagnetic material B of FIG. 1 (a) is removed, and FIG. FIG. 3 is a front view showing the configuration of a generally used current detector, and FIG. 3 is a diagram showing input / output characteristics of the current detector. The solid line indicates a current detector using a ferromagnetic core according to one embodiment of the present invention. 1 ... magnetic gap, 2 ... magnetic sensing element, 3 ... ferromagnetic material A
(Oriented silicon steel), 4 ... ferromagnetic material B (permalloy), 5
…… through wire, …… circuit parts, 7 …… circuit board, 8 ……
External terminal.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01R 15/20 G01R 33/06-33/09

Claims (1)

(57) [Claims] 1. A ferromagnetic core of a current detector in which a gap is provided in a part of a magnetic path of a toroidal ferromagnetic core, and a magneto-sensitive element is inserted into the gap. A current detector characterized by having two or more types of ferromagnetic material connected in series by inserting another ferromagnetic material having a different saturation magnetic flux density in series into the core and having two or more levels of sensitivity .