JP2015135239A - Curent sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor capable of heightening the accuracy of detection where a current value is close to zero at a low cost.SOLUTION: A current sensor 1 is configured so that, when current flows in a bus bar 2, a core 3 enclosing the bus bar 2 gathers magnetic fluxes around the bus bar and a flux density occurring in a gap part 4 of the core 3 is read by a hall element 5, and thereby a current value is read. Two divided bodies 7 and 8 are combined to form the core 3 that defines the length of a magnetic path around the bus bar, the core 3 having formed therein two gap parts (a gap part 4 and a gap part 6) for defining a positive clearance between the two divided bodies 7 and 8 adjacent to each other along the periphery of the bus bar. The hall element 5 is disposed in the gap part 4 of the two gap parts.

Description

  The present invention relates to a current sensor that measures a current flowing through a measurement object using a magnetoelectric conversion element.

  In Patent Document 1, when a current flows through a bus bar to be measured, a core surrounding the bus bar collects magnetic flux around the bus bar, reads a magnetic flux density generated in a gap portion of the core with a magnetoelectric conversion element, and calculates a current value. A current sensor having a reading structure is disclosed.

JP 2009-58451 A

  When an electromagnetic steel sheet is used for the core, since it has a larger magnetic hysteresis characteristic than that of Permalloy or the like, a weak magnetic flux remains in the gap even when the current applied to the bus bar is zero. As a result, the detection accuracy near zero current value is degraded.

  The present invention has been made paying attention to such problems, and an object of the present invention is to provide a current sensor capable of increasing detection accuracy near a current value of zero at low cost.

  A current sensor that solves the above problem is a current sensor that measures a current flowing through a measurement target using a magnetoelectric transducer, and when a current flows through the bus bar that is the measurement target, the core surrounding the bus bar generates a magnetic flux around the bus bar. In a current sensor configured to collect magnetic flux and generate a current value by reading a magnetic flux density generated in a gap portion of the core with a magnetoelectric transducer, a core that defines a magnetic path length around a bus bar by combining a plurality of divided bodies In the core, two or more gap portions that define a positive separation distance are formed in two divided bodies adjacent to each other along the periphery of the bus bar, and a magnetoelectric conversion element is disposed in any gap portion. Is the gist.

  According to this configuration, the ratio of the gap portion to the magnetic path length and the demagnetizing field coefficient defined are increased, thereby reducing the influence of the magnetic hysteresis characteristics. That is, the hysteresis can be improved without using a high-cost, low-hysteresis material such as permalloy for the core. Therefore, the detection accuracy near the current value of zero can be increased at low cost.

About the said current sensor, it is good also as a core being formed including the several division body which makes a mutually symmetrical shape.
According to this structure, it leads to the improvement of the material yield at the time of core manufacture.

About the said current sensor, the core by a some division body is prescribed | regulated along the plane orthogonal to the direction of the electric current which flows into a bus-bar.
According to this configuration, the magnetic flux that is orthogonal to the direction of the current can be easily captured by the core, and magnetic collection is preferable.

  In the current sensor, two divided bodies that define the gap portion where the magnetoelectric conversion element is disposed as the first gap portion, define the other gap portion as the second gap portion, and form the second gap portion. The separation distance may be set to be equal to or less than the separation distance between the two divided bodies forming the first gap portion.

  If the separation distance between two adjacent parts along the periphery of the bus bar is too large, the magnetic flux collecting ability is lowered and it becomes difficult to fulfill the role of the core. In this respect, according to this configuration, it is possible to achieve both improvement of hysteresis and securing of the magnetic flux collecting ability.

  In the current sensor, the core is formed in a C shape along the periphery of the bus bar, the magnetoelectric conversion element is arranged in the gap between one end and the other end, and the core is equally divided into two along the periphery of the bus bar. Another gap portion that defines a positive separation distance may be formed at the position to be.

  According to this configuration, a core is formed by combining two divided bodies having the same shape. Therefore, it leads to the improvement of the material yield at the time of core manufacture.

  According to the present invention, it is possible to improve the detection accuracy near the current value zero at low cost.

The figure which shows the shape of a division | segmentation core. The figure which shows the magnetic path length around a bus-bar. The characteristic view which shows a hysteresis curve. The figure which shows the modification of the shape of a division | segmentation core.

Hereinafter, an embodiment of the current sensor will be described.
As shown in FIG. 1, the current sensor 1 includes a core 3 that surrounds a bus bar 2 to be measured. As the material of the core 3, an electromagnetic steel sheet obtained by magnetically improving iron, which is advantageous in terms of cost among ferromagnetic materials, is used. The core 3 is formed in a C shape along the periphery of the bus bar 2, and a hall element 5, which is a magnetoelectric conversion element, is disposed in the gap portion 4 between one end and the other end of the core 3. Thus, another gap portion 6 that defines a positive separation distance is formed at a position that equally bisects the core 3. That is, the core 3 includes two divided bodies 7 and 8 that are symmetrical to each other. The separation distance between the divided bodies 7 and 8 by the gap portion 6 is set shorter than the separation distance between the divided bodies 7 and 8 by the gap portion 4. A current flows through the bus bar 2 in a direction orthogonal to the paper surface, and the core 3 is defined by the divided bodies 7 and 8 along a plane orthogonal to the current direction (a plane parallel to the paper surface).

  As shown in FIG. 2, the magnetic path length L around the bus bar is defined by the core 3. The magnetic path length L is the length of the magnetic path along the periphery of the bus bar 2. The magnetic path length L 1 by the divided body 7, the magnetic path length L 2 by the divided body 8, and the magnetic field by the gap portion 4. It is represented by the sum of the path length Lg1 and the magnetic path length Lg2 by the gap 6. When the demagnetizing factor is expressed by (Lg1 + Lg2) / L, the demagnetizing factor increases as the width of the gaps 4 and 6 increases.

  As shown in FIG. 3, the relationship between the current flowing through the bus bar 2 and the magnetic flux density read by the Hall element 5 is represented by a hysteresis curve. Here, the hysteresis width indicating the difference between the positive residual magnetic flux and the negative residual magnetic flux when the current flowing through the bus bar 2 is zero decreases as the demagnetizing field coefficient increases.

Next, the operation of the current sensor 1 will be described.
When a current flows through the bus bar 2, the core 3 collects the magnetic flux around the bus bar, and the magnetic flux density generated in the gap portion 4 is read by the Hall element 5. At this time, a potential difference V defined by V = R × I × B / d is generated in the Hall element 5 (R: Hall coefficient specific to the electromagnetic steel sheet that is the material of the core 3, I: current flowing through the bus bar 2. , B: magnetic flux density, d: thickness of the core 3). Therefore, the current value flowing through the bus bar 2 can be read by reading the magnetic flux density with the Hall element 5.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The core 3 includes a gap portion 6 in addition to the gap portion 4 in which the hall element 5 is disposed. According to this configuration, the ratio of the gap portion (Lg1 + Lg2) to the magnetic path length (L) and the demagnetizing factor are increased, thereby reducing the influence of the magnetic hysteresis characteristics. That is, the hysteresis can be improved without using a high-cost, low-hysteresis material such as permalloy for the core. Therefore, the detection accuracy near the current value of zero can be increased at low cost.

(2) The core 3 is formed including the two divided bodies 7 and 8 that are symmetrical to each other. According to this structure, it leads to the improvement of the material yield at the time of core manufacture.
(3) The core 3 by the two divided bodies 7 and 8 is defined along a plane orthogonal to the direction of the current flowing through the bus bar 2. According to this configuration, the magnetic flux that is orthogonal to the direction of the current can be easily captured by the core 3, and magnetic collection is preferable.

  (4) The gap part 4 in which the Hall element 5 is disposed is defined as a first gap part, and the other gap part 6 is defined as a second gap part. On this assumption, the separation distance (Lg2) between the two divided bodies 7 and 8 forming the second gap part (gap part 6) is the two divided bodies forming the first gap part (gap part 4). 7 and 8 are set shorter than the separation distance (Lg1). Here, if the separation distance between two divided bodies that are adjacent along the periphery of the bus bar is too large, the magnetic flux collecting ability is lowered and it becomes difficult to fulfill the role of the core. In this respect, according to this configuration, it is possible to achieve both improvement of hysteresis and securing of the magnetic flux collecting ability.

  (5) The core 3 is formed in a C shape along the periphery of the bus bar, the hall element 5 is disposed in the gap portion 4 between one end and the other end thereof, and the core 3 is evenly distributed along the periphery of the bus bar. Another gap portion 6 that defines a positive separation distance is formed at a position that bisects. According to this configuration, the core 3 is formed by combining the two divided bodies 7 and 8 having the same shape. Therefore, it leads to the improvement of the material yield at the time of core manufacture.

  (6) For the core 3, if the width of the gap portion 4 is increased instead of providing the gap portion 6, the hysteresis characteristics equivalent to this example can be obtained with one gap portion 4. However, in this case, the core 3 increases in size as the width of the gap portion 4 increases. In this regard, according to the present configuration, it is not necessary to increase the width of the gap portion 4, and thus the core 3 can be reduced in size.

In addition, the said embodiment can also be changed and actualized as follows.
As shown in FIG. 4, the core 3 </ b> A may be formed including four divided bodies 11 to 14 that are symmetrical to each other. In this case, four gap portions that define a positive separation distance are formed in two divided bodies adjacent along the periphery of the bus bar 2. Specifically, a gap portion 21 is formed between the divided body 11 and the divided body 12, a gap portion 22 is formed between the divided body 12 and the divided body 13, and a gap is formed between the divided body 13 and the divided body 14. A portion 23 is formed, and a gap portion 24 is formed between the divided body 14 and the divided body 11. Here, the widths of the gap part 21 and the gap part 23 are equal, the widths of the gap part 22 and the gap part 24 are equal, and the former is shorter than the latter. The Hall element 5 is disposed in the gap portion 24.

  The magnetic path length LA around the bus bar by the core 3A is represented by LA = L11 + L12 + L13 + L14 + Lg11 + Lg12 + Lg13 + Lg14. L11 is the length of the magnetic path by the divided body 11, L12 is the length of the magnetic path by the divided body 12, L13 is the length of the magnetic path by the divided body 13, and L14 is the magnetic path by the divided body 14. Is the length of Lg11 is the length of the magnetic path by the gap part 21, Lg12 is the length of the magnetic path by the gap part 22, Lg13 is the length of the magnetic path by the gap part 23, and Lg14 is by the gap part 24 The length of the magnetic path. The demagnetizing factor is represented by (Lg11 + Lg12 + Lg13 + Lg14) / LA.

  -It is not limited to using the core from which all the division bodies make mutually symmetrical shape. As long as at least two divided bodies are symmetrical with each other, the material yield at the time of core fabrication is improved. However, it is allowed to use cores in which all the divided bodies are not symmetrical with each other.

  -When two adjacent divided bodies along the periphery of the bus bar are brought into close contact with each other, the separation distance becomes zero, and therefore a gap portion that defines a positive separation distance is not formed at that location. Therefore, it can be applied to the current sensor of the present invention on the premise that a core having two or more gap portions that define a positive separation distance is used in addition to the contacted portion. In this respect, the gist differs from a current sensor that simply uses a split core.

  DESCRIPTION OF SYMBOLS 1 ... Current sensor, 2 ... Bus bar (measurement object), 3 ... Core, 3A ... Core, 4 ... Gap part (1st gap part), 5 ... Hall element (magnetoelectric conversion element), 6 ... Gap part (2nd ), 7 ... divided bodies, 8 ... divided bodies, 11-14 ... divided bodies, 21-24 ... gap portions.

Claims (5)

A current sensor that uses a magnetoelectric transducer to measure the current flowing through the measurement target.When a current flows through the bus bar that is the measurement target, the core surrounding the bus bar collects the magnetic flux around the bus bar and creates a gap in the core. In a current sensor that has a structure that reads the current value by reading the generated magnetic flux density with a magnetoelectric transducer,
A plurality of divided bodies are combined to form a core that defines the magnetic path length around the bus bar, and the core includes two gap portions that define a positive separation distance between two adjacent divided bodies along the bus bar circumference. One or more current sensors, wherein a magnetoelectric conversion element is disposed in any gap portion. The current sensor according to claim 1, wherein the core is formed including a plurality of divided bodies that are symmetrical to each other. The current sensor according to claim 1, wherein a core is defined by a plurality of divided bodies along a plane orthogonal to the direction of current flowing through the bus bar. The gap portion where the magnetoelectric transducer is disposed is defined as the first gap portion, the other gap portion is defined as the second gap portion, and the separation distance between the two divided bodies forming the second gap portion is: The current sensor according to any one of claims 1 to 3, wherein the current sensor is set to be equal to or less than a separation distance between two divided bodies forming the first gap portion. A core is formed in a C shape along the periphery of the bus bar, and a magnetoelectric conversion element is disposed in a gap portion between one end and the other end of the core, and the core is equally divided into two along the periphery of the bus bar. The current sensor according to claim 1, wherein another gap portion that defines a separation distance is formed.