WO2007110943A1

WO2007110943A1 - Magnetostrictive modulation current sensor and method for measuring current using that sensor

Info

Publication number: WO2007110943A1
Application number: PCT/JP2006/306454
Authority: WO
Inventors: Takashi Tadatsu
Original assignee: Loyal Port Company Limited
Priority date: 2006-03-29
Filing date: 2006-03-29
Publication date: 2007-10-04

Abstract

[PROBLEMS] To provide a non-contact magnetostrictive modulation current sensor featuring small size, rigid and simple structure, high precision, and large current measurement capability, and capable of measuring even a DC current. [MEANS FOR SOLVING PROBLEMS] The magnetostrictive modulation current sensor comprises a piezoelectric element (1) provided with an electrode to exhibit piezoelectric effect, a magnetostrictive material (2) coupled mechanically with the piezoelectric element (1), and a coil (3) wound around the magnetostrictive material (2), wherein the magnetic flux of a current (4) measured passes trough the magnetostrictive material (2) and crosses the coil (3).

Description

Specification

Magnetostrictive modulation type current sensor and current measurement method using this sensor

[0001] The present invention relates to a current sensor that measures current in an insulated state without being connected to a conductor to be measured in the same way as a known CT (Current Transformer) in alternating current, and in particular, regarding frequency characteristics. It relates to a current sensor that can measure direct current and can measure current values up to a large current in the 1000A range.

Background art

[0002] The well-known CT has the advantage that it can be measured while insulated from the measurement lead, but it is used for direct current and alternating current of the frequency in the vicinity, and pulsating current in which direct current and alternating current are superimposed. Can not do it. Therefore, a hall element type, a magnetic modulation type, a magnetic bridge type, and the like have been proposed as insulating DC current sensors that replace CT.

In addition, as a current sensor combining a magnetostrictive material and a piezoelectric element, “a magnetic field sensor and a current detector using the same” (see Patent Document 1) and “a current measuring transformer based on a mechanical wave” ( (See Patent Document 2), but these all transmit the distortion of the magnetostrictive material due to the magnetic field of the current to be measured to the piezoelectric element, and measure the value of the current to be measured by measuring the voltage generated by the piezoelectric element. To do.

[0004] A force that generates a voltage when a piezoelectric element is distorted. A static distortion (a steady distortion that remains distorted and does not change in distortion) does not generate a voltage. Therefore, it is appropriate to use the dynamic distortion caused by the magnetic field that fluctuates due to the AC current, as in “Current measurement transformer based on mechanical waves” (see Patent Document 2). As mentioned in this section, it is limited to AC current and cannot measure DC current.

[0005] On the other hand, in the specification of "magnetic field sensor and current detector using the same" (see Patent Document 1), it is described that direct current can be measured as an effect of the invention. There is no explanation of what is possible, but rather, in view of the function of the piezoelectric element and the structure of the invention of Document 1, it is impossible to measure a direct current by the invention of Document 1. [0006] Recently, as a device that requires a DC current sensor, development of a so-called hybrid car, a fuel cell vehicle in which a motor and an internal combustion engine are combined, or a fuel cell for cogeneration, etc., has become active. There is a need for highly reliable DC current sensors. In particular, there is a need for an inexpensive direct current sensor that is robust and compact and can accurately measure a large current in the automotive field.

Patent Document 1: Japanese Patent Laid-Open No. 2000-88937

Patent Document 2: Japanese Patent Laid-Open No. 2001-116774

However, none of the conventional DC sensors as described above satisfy the above requirements.

That is, for example, the Hall element type has a narrow temperature range that can be used due to the use of a semiconductor, and is not suitable for harsh environments because it is vulnerable to radiation.

The magnetic modulation type requires multiple cores and multiple coils, so it is inferior in robustness and price. In addition, the electric power for driving the sensor is large at large currents, so it is in the field aiming for so-called energy saving. This is a major drawback. In addition, self-heating due to iron loss due to excitation is large, and cooling may be required depending on the application. Incidentally, the magnetic modulation type requires a magnetomotive force larger than the current to be measured.

DC sensors developed for micro currents such as magnetic bridges are not suitable for measuring large currents.

Disclosure of the invention

Problems to be solved by the invention

[0008] In view of the technical current state of such a DC sensor, the present invention is small, “robust” and simple. • High accuracy • Non-contact type magnetostriction modulation type capable of measuring DC current with the feature of being able to measure a large current. An object of the present invention is to provide a current sensor.

Means for solving the problem

[0009] The configuration of the magnetostrictive modulation type current sensor of the present invention (hereinafter referred to as the current sensor of the present invention) for the purpose of solving the above problems includes a piezoelectric element provided with electrodes so as to exhibit a piezoelectric effect, A magnetostrictive material mechanically coupled to the piezoelectric element (a magnetic material having magnetostrictive characteristics, the same applies hereinafter) and a coil wound with the magnetostrictive material are provided, and the magnetic flux of the current to be measured is It is characterized by crossing the coil through the material.

In other words, in the current sensor of the present invention, the magnetic current to be measured is guided to the magnetostrictive material, and a voltage that varies is applied to the piezoelectric element, thereby causing a variation in the distortion of the piezoelectric element. The fluctuating strain of the magnetostrictive material is caused by the fluctuating strain of the magnetostrictive material, and the magnetic permeability of the magnetostrictive material is fluctuated by the fluctuating strain of the magnetostrictive material. The measured current is measured by generating an electromotive force in the coil crossed with and detecting the electromotive force.

The invention's effect

[0011] Since the current sensor of the present invention operates according to the above-described operation principle, even when the current to be measured is a direct current and the magnetic flux does not fluctuate, a fluctuating voltage is applied to the piezoelectric element and crosses the coil. Since the magnetic flux fluctuates, the direct current can be measured.

In addition, frequency components whose fluctuation of current to be measured is relatively lower than the fluctuation frequency of the voltage applied to the piezoelectric element can be measured by the above operating principle, and higher frequency components should be measured by the operating principle of conventional AC CT. DC power can be measured up to high frequencies.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the current sensor of the present invention will be described with reference to the drawings. 1 and 2 show a piezoelectric element 1 provided with electrodes so as to exhibit a piezoelectric effect, a magnetostrictive material 2 mechanically coupled to the piezoelectric element 1, and a coil 3 wound around the magnetostrictive material 2. The magnetic field sensor which consists of is shown typically, and is the foundation of the current sensor of the present invention

[0013] FIG. 1 shows a piezoelectric magnetoresistive element 1 on one end face or both end faces in the length direction of a rod-shaped magnetostrictive material 2 having a square cross section (hereinafter, “end face” is used in this sense, but in FIG. 1, one end face). This is the basic structure of the magnetic field sensor that is provided and the coil 3 is wound around the magnetostrictive material 2. Practically, an AC voltage having a frequency at which the magnetostrictive material 2 resonates is applied to the piezoelectric element 1. Due to this resonance, the magnetostrictive material 2 is greatly distorted, the magnetic permeability is also greatly changed, and the magnetic flux in the magnetostrictive material 2 is similarly changed. As a result, an electromotive force is generated in the coil 3 wound with the magnetostrictive material 2. The same applies when piezoelectric elements are provided on both end faces of the magnetostrictive material 2. This electromotive force is proportional to the strength of the magnetic field, so measure the strength of the magnetic field. it can.

[0014] This magnetic field sensor is easy to use if the AC voltage for driving the piezoelectric element 1 is stable, but can be used even if it is unstable, such as when the amplitude fluctuates or DC is superimposed. wear. If the driving voltage of the piezoelectric element is unstable, it can be corrected by processing means such as an electronic circuit that processes the detected electromotive force. In addition, as described above, when the frequency is the frequency at which the magnetostrictive material is resonated, the driving efficiency is high, but it is not necessarily required to resonate.

[0015] FIG. 2 shows one side surface or both side surfaces along the length direction of the magnetostrictive material 2 similar to the magnetostrictive material 2 in FIG. 1 (hereinafter, “side surface” is used in this sense, but in FIG. 2, one side surface) This is a magnetic field sensor when the piezoelectric element 1 is provided in Fig. 2, but in the case of Fig. 2, there is a distortion mode as shown in Figs. Even when the piezoelectric element 1 is provided on either surface, an electromotive force is generated in the coil 3 due to the distortion of the magnetostrictive material 2 as in the description of FIG. In Fig. 2, the coil 3 winds the piezoelectric element 1 and the magnetostrictive material 2 together.

[0016] FIG. 5, FIG. 6, FIG. 8, and FIG. 9 are all examples of embodiments of the current sensor MSM-cs of the present invention.

In these current sensors MSM-cs of the present invention, at least one element of the magnetic field sensor described in FIG. 1 or FIG.

That is, the current sensor MSM-cs of the present invention can measure the current that is the source of the magnetic field by detecting the magnetic field generated by the current to be measured based on the operating principle of the magnetic field sensor.

In addition, the electromotive force of the coil 3 in the current sensor MSM-cs of the present invention is proportional to the current to be measured, and the amount of change in the magnetic permeability of the magnetostrictive material 2, that is, the voltage applied to the piezoelectric element 1. Is also proportional to Therefore, the AC voltage is modulated and applied to the piezoelectric element 1 with a voltage proportional to the voltage applied to an arbitrary power load, or when the proportional voltage is an AC voltage, it is directly applied to the piezoelectric element 1. Furthermore, if the current flowing through the power load is the measured current, the electromotive force of coil 3 is proportional to both the voltage and current of the power load and is proportional to the power consumption of the power load. Become. Therefore, the configuration of the current sensor MSM-cs of the present invention depends on the configuration of the piezoelectric element driving circuit to be connected. (See FIGS. 13 and 14).

Example

A specific example of the current sensor MSM-cs of the present invention will be described with reference to FIG. 5 and FIG.

In FIG. 5, the magnetostrictive material 2 and the piezoelectric element 1 are both cylindrical. In this embodiment, the magnetostrictive material 2 and the piezoelectric element 1 are bonded together by epoxy resin, and are integrated together. However, if the magnetostrictive material 2 and the piezoelectric element 1 are mechanically coupled, The means is not limited to adhesion, and any bonding method may be used.

The piezoelectric element 1 of this embodiment uses ferroelectric ceramics as a material, is shaped into a cylindrical shape having an inner diameter of 7 mm, an outer diameter of 11 mm, and a length of 7 mm, and deposits metal on the inner and outer surfaces of the cylinder, respectively. (Not shown in the figure). la and lb are lead wires connected to both electrodes.

The magnetostrictive material 2 was formed into a cylindrical shape having an inner diameter of 11.5 mm, an outer diameter of 18 mm, and a length of 7 mm using a super magnetostrictive material “N2M-800” manufactured by Moritex Corporation.

[0019] FIG. 15 shows a characteristic graph of permeability and stress of the giant magnetostrictive material (N2M-800 manufactured by Moritex Co., Ltd.) used in this example.

As can be seen from this characteristic graph, when stress is generated in this material, the magnetic permeability decreases in inverse proportion to the stress. In particular, it has a characteristic that it rapidly decreases up to a predetermined stress and the decrease rate decreases beyond that.

In the present invention, when the operating range of the stress applied to the magnetostrictive material 2 is set in a region where the change in magnetic permeability is steep, the magnetic flux is amplitude-modulated by the distortion of the piezoelectric element 1. In addition, when this operating range is expanded to a region where the attenuation factor is sufficiently low, the magnetic flux becomes like being jobbed. The current sensor of the present invention operates in any state, but the drive circuit is appropriately determined according to the setting of the operating range. This characteristic graph shows permeability-stress characteristics, but stress and strain are correlated and can be replaced.

In the above embodiment, a magnetic material having particularly remarkable magnetostriction is used, but it is known that most of the magnetic materials have magnetostriction. In general, magnetic materials used for cores such as transformers generate so-called “sagging” due to magnetostriction, which causes noise pollution in large transformers such as substations. No magnetostriction Magnetic steel sheets with reduced magnetostriction, which are preferred by the company, have also been developed.

In the embodiment shown in FIGS. 5 and 6, when an AC voltage is applied to the piezoelectric element 1 through its lead wires la and lb !, the piezoelectric element 1 expands or contracts in the diameter direction. Since the magnetostrictive material 2 is mechanically coupled to the piezoelectric element 1, an example of this distortion is shown in FIG.

[0021] When an AC voltage is applied to a piezoelectric element to vibrate, the piezoelectric element is sometimes called a piezoelectric vibrator. In this case, the strain mode is sometimes called a vibration mode. There are many vibration modes in this vibration mode, with modes called radial vibration, long-side extension vibration, longitudinal vibration, thickness longitudinal vibration, and thickness shear vibration as representative vibration modes. In the present invention, an appropriate vibration mode can be selected from various vibration modes according to the embodiment. Therefore, the vibration mode that can be used in the embodiment is also the radial vibration illustrated in FIG. It is not limited.

In this embodiment, the current to be measured 4 passes through the inside of the cylindrical magnetostrictive material 2 and the piezoelectric element 1. Fig. 5 and Fig. 6 indicate the current that is measured by the reference numeral 4. Specifically, in addition to the current flowing through the conductor, the flow of ions in a gas or liquid, the flow of electrons in a vacuum, the flow of plasma Any flow may be used as long as it has a charge. The measured current 4 is a force that generates a magnetic field around it. This magnetic field generates a magnetic flux that circulates in the magnetostrictive material 2. The strength of the magnetic flux is proportional to the magnetic permeability of the magnetostrictive material 2 and the strength of the magnetic field. Here, if the measured current 4 is a constant DC current, the magnetomotive force is constant, and the magnetic flux is proportional to the magnetic permeability.

On the other hand, the magnetic permeability of the magnetostrictive material 2 can be changed by mechanical strain. Therefore, the magnetic permeability of the magnetostrictive material 2 can be varied by distorting the magnetostrictive material 2 with the piezoelectric element 1 mechanically coupled to the magnetostrictive material 2. As a result, the magnetic flux inside the magnetostrictive material 2 also changes. By distorting the piezoelectric element 1 by applying an AC voltage, the magnetic permeability of the magnetostrictive material 2 pulsates, and the strength of the magnetic flux also pulsates. Therefore, an electromotive force is generated in the coil 3 wound around the magnetostrictive material 2 in proportion to the pulsation amount of the magnetic flux. The amount of pulsation of this magnetic flux is proportional to the strength of the measured current 4 if the amplitude of the strain is constant. That is, the electromotive force generated in the coil 3 is proportional to the measured current 4.

[0024] Since the electromotive force generated in the coil 3 is alternating current synchronized with the drive voltage of the piezoelectric element 1, The measured current 4 can be measured by rectifying or detecting.

In particular, when detecting, the direction of the current to be measured 4 can be measured by performing synchronous detection based on the drive voltage of the piezoelectric element 1.

[0025] FIG. 10, FIG. 11, and FIG. 12 show block diagrams of electronic circuits for driving the current sensor MSM-cs of the present invention.

Fig. 10 shows the case where the electromotive force of the coil is output as it is. Fig. 11 shows the detection of the electromotive force of the coil.

V, when rectified and output, FIG. 12 shows a case where the electromotive force of the coil is amplified and synchronous detection is performed based on the drive voltage of the piezoelectric element 1.

In any of the circuits shown in FIGS. 10, 11, and 12, the piezoelectric element 1 is driven by the oscillation circuit 5. Further, the oscillation circuit 5, the detection rectification circuit 6, the amplification circuit 7, and the synchronous detection circuit 8 shown here may be any circuit means as long as they achieve the above object.

The embodiment of FIG. 6 is a case where the magnetostrictive material 2 and the piezoelectric element 1 are arranged opposite to the embodiment of FIG. 5, and the operation principle is the same as that of the embodiment of FIG. is there.

In the embodiment of FIG. 6, the piezoelectric element 1 is shaped into a cylindrical shape having an inner diameter of 8 mm, an outer diameter of 12 mm, and a length of 7 mm, and a metal is vapor-deposited on each of the inner surface and the outer surface of the cylindrical body to form an electrode. Wires la and lb were connected.

In addition, the magnetostrictive material 2 was shaped into a cylindrical shape having an inner diameter of 4 mm, an outer diameter of 7.5 mm, and a length of 7 mm, and inserted into the piezoelectric element 1 to couple both 1 and 2 together.

In the embodiment of FIG. 6, both the piezoelectric element 1 and the magnetostrictive material 2 are made of the same material as in the embodiment of FIG. 5 and only the dimensions are changed.

FIG. 8 shows that the piezoelectric element 1 is formed in an annular circle shape, and a magnetostrictive material 2 shaped in the same shape as that of the piezoelectric element 1 is bonded to the upper surface of the piezoelectric element 1 by bonding or the like. This is another example of the present invention current sensor in which No. 3 is wound. Accordingly, the same reference numerals as those in FIGS. 5 and 6 denote the same members, and the materials used are the same as in the previous example.

FIG. 9 shows a magnetostrictive material 2 formed in a cross-sectional (or front) substantially square shape, in which a piezoelectric element 1 is coupled to one outer peripheral side, and a coil 3 is wound around the magnetostrictive material 2. It is another example of this invention current sensor of form. Each component in the embodiment of FIG. 9 is also made of the same material as the previous embodiment. It is made of material. Therefore, the same reference numerals as in the previous example indicate the same members.

[0029] Since the current sensor MSM-cs of the present invention described above can be used as a power sensor for measuring power, this point will be described below. This power sensor can measure both AC and DC, but is particularly useful as a power sensor that can easily measure DC power.

[0030] The power can be obtained by multiplying the load current value and the load voltage value, and is divided into reactive power and active power. In the prior art, a method of measuring a load current value and a load voltage value by separate sensors and calculating the measured values by an electronic circuit or the like is common. When measuring AC power using this method, CT (Current Transformer) is often used as the current sensor and PT (Potential Transformer) is often used as the voltage sensor, but neither CT nor PT functions with DC.

[0031] On the other hand, a patent document also discloses a power sensor that can measure direct current, detects a load current value and a load voltage value with the same sensor, and performs physical multiplication by the sensor itself. Typical examples are as follows: 1) By measuring the current value according to the operating principle of the Hall element type current sensor and supplying a current proportional to the voltage to the current supply terminal of this Hall element, the current is proportional to the current and voltage. “Power meter” that outputs a signal as a power value (see Japanese Patent Laid-Open No. 11 108 971), 2) Intensity of light irradiated to a Faraday effect element by measuring the current value based on the operating principle of a Faraday effect type current sensor There is a “power sensor” (see Japanese Patent Laid-Open No. 1-162165) that outputs a signal proportional to the current and voltage as a power value by making the voltage proportional to the voltage. However, the power sensors disclosed in these patent documents directly incorporate the drawbacks of current sensors, which are the basis of their operating principles, and therefore have a narrow operating temperature range and a complicated structure. However, it has the disadvantages of being solid, difficult to miniaturize, and low accuracy.

In addition, as described above, conventional power sensors cannot meet the needs of the contents, including the small size, robustness, simplicity, high accuracy, and large current measurement that are required recently.

[0032] However, the power sensor using the above-described current sensor MSM-cs of the present invention has features of small size, robustness, simplicity, high accuracy, and large current measurement compared to the above-described conventional technology. A power sensor that can also measure DC power can be provided.

In other words, the power sensor using the current sensor MSM-cs of the present invention has a piezoelectric element 1 provided with electrodes so as to exhibit a piezoelectric effect, and a magnetostrictive material 2 mechanically coupled to the piezoelectric element 1 (having magnetostrictive characteristics). Magnetic material) and a coil 3 wound around the magnetostrictive material 2 so that the magnetic flux of the measured current 4 crosses the coil 3 through the magnetostrictive material 2 and is proportional to the measured voltage at the piezoelectric element 1. And a configuration in which the changed voltage is applied.

In other words, in the power sensor using the current sensor MSM-cs of the present invention, the magnetic flux of the current to be measured 4 is guided to the magnetostrictive material 2, and the fluctuation is proportional to the voltage to be measured in the piezoelectric element 1. Is applied to the piezoelectric element 1 to cause a strain that varies in proportion to the voltage to be measured, and the strain that the piezoelectric element 1 varies causes a strain that varies to the magnetostrictive material 2 to vary. By changing the magnetic permeability of the magnetostrictive material 2 due to strain, and by generating a magnetomotive force in the coil 3 that intersects with the magnetic flux by the changing magnetic flux generated by the changing magnetic permeability, this electromotive force is detected. A value proportional to both the measured current and the measured voltage, that is, the power value can be measured.

[0034] Since the power sensor using the current sensor MSM-cs of the present invention operates according to the above operating principle, even when the measured power is direct current and the magnetic flux does not vary, the magnetic flux intersecting with the coil varies. Therefore, DC power can be measured.

In addition, since this power sensor measures the instantaneous value of power, it is possible to measure active power and apparent power in AC power measurement. As a result, it is possible to obtain reactive power and power factor.

FIG. 13 is a block diagram of an example of the power sensor drive circuit, and FIG. 14 is a connection example of the power sensor using the current sensor of the present invention. This power sensor operates on the basis of the current detection principle of the magnetostrictive modulation type current sensor, and will be described below.

13 and 14, the same reference numerals are used for the same members and the same configurations.

In FIG. 13, in the modulation circuit 9, the alternating voltage obtained by the oscillation circuit 5 is modulated by a voltage 10 proportional to the load voltage applied to an arbitrary power load and applied to the piezoelectric element 1. The load current flowing through the load is passed through in a non-contact manner as the current to be measured 4, and the electromotive force generated in the coil 3 is amplified by the amplifier circuit 7 and output through the synchronous detection circuit 8. A value proportional to the power (power value) was obtained.

In FIG. 14, a load 12 is connected to a power source 11 by a conducting wire, and a measured current 4 flows. Therefore, a sensor in which an annular piezoelectric element 1 formed of the same material as the current sensor illustrated in FIG. 8 and having the same dimensions and a magnetostrictive material 2 are joined and integrated by bonding or the like, and a coil 3 is wound around them. The load current is passed through the MSM-cs as the measured current 4 in a non-contact manner to generate an electromotive force in the coil 3, while the output of the oscillation circuit 5 is supplied to the modulation circuit 9 at a voltage 10 proportional to the load voltage. Then, the signal is modulated and applied to the piezoelectric element 1.

At this time, the electromotive force generated in the coil 3 is amplified by the amplifier circuit 7, and this amplified output is output through the synchronous detection circuit 8 synchronized with the output of the oscillation circuit 5, thereby allowing the power value proportional to the power consumption of the load 12 to be obtained. Can be obtained.

Industrial applicability

[0038] The present invention is as described above, and the current sensor according to the present invention is composed of a core (magnetostrictive material), a coil, and a ceramic (piezoelectric element), so that the structure is very simple and force is sufficient. These members can also be formed of a material having sufficient heat resistance, and therefore a current sensor that can withstand a wide range of temperatures can be provided. The same reasoning power is also strong against radiation.

[0039] Further, in the current sensor of the present invention, since both the core and the coil have a single shear force and the shape of each member is simple, it is easy to be robust and downsized. In addition, since the structure is simple and the operating principle is directly linked to the physical laws, there are few error factors, so it is possible to easily improve the accuracy. Also, when measuring a large current, it is suitable for measuring a large current because it is not necessary to increase the drive power, as long as the core does not cause magnetic saturation.

That is, according to the present invention, a magnetostrictive current sensor capable of measuring a direct current having the features of small size, “robust”, “simple”, high accuracy and large current measurement, and is used in the field of electric vehicles in recent years. Can meet the demands of recent new technology fields such as applications in the fuel cell field, and can provide innovative current sensors that are completely comparable to those of conventional technologies. It can also be expected to make a significant contribution to the general public.

Brief Description of Drawings FIG. 1 is a perspective view schematically showing an example of a magnetostrictive magnetic field sensor for explaining the operating principle of the current sensor of the present invention.

FIG. 2 is a perspective view schematically showing another example of a magnetostrictive magnetic field sensor for explaining the operating principle of the current sensor of the present invention.

FIG. 3 is a schematic front view for explaining the distortion of the magnetic field sensor of FIG.

FIG. 4 is a schematic front view for explaining the distortion of the magnetic field sensor of FIG.

FIG. 5 is a perspective view schematically showing a first example of the current sensor of the present invention.

FIG. 6 is a perspective view schematically showing a second example of the current sensor of the present invention.

7 is a plan view for explaining the direction of distortion of the current sensor of the present invention shown in FIGS. 5 and 6. FIG.

FIG. 8 is a perspective view schematically showing a third example of the current sensor of the present invention.

FIG. 9 is a perspective view schematically showing a fourth example of the current sensor of the present invention.

FIG. 10 is a block diagram of a first example of a drive circuit of the current sensor (or magnetic field sensor) of the present invention.

FIG. 11 is a block diagram of a second example of the drive circuit of the current sensor (or magnetic field sensor) of the present invention.

FIG. 12 is a block diagram of a third example of the drive circuit of the current sensor (or magnetic field sensor) of the present invention.

FIG. 13 is a block diagram of an example of a drive circuit when the current sensor of the present invention functions as a power sensor.

FIG. 14 is a block diagram showing a connection example of the power sensor of FIG.

FIG. 15 is a graph showing the characteristics of magnetic permeability and stress of the magnetostrictive material used in the example of the current sensor of the present invention.

Explanation of symbols

[0042] MSM-cs current sensor of the present invention

1 Piezoelectric element

2 Magnetostrictive material

3 coils

4 Detected current

Claims

The scope of the claims

[1] A piezoelectric element provided with electrodes so as to exhibit a piezoelectric effect, a magnetostrictive material mechanically coupled to the piezoelectric element, and a coil wound with the magnetostrictive material, and the magnetic flux of the current to be measured is A magnetostrictive modulation type current sensor characterized in that it passes through the magnetostrictive material and intersects with the coil.

[2] A piezoelectric element provided with an electrode so as to exhibit a piezoelectric effect, a magnetostrictive material mechanically coupled to the piezoelectric element, and a coil wound with the magnetostrictive material, and the magnetic flux of the current to be measured is It passes through the magnetostrictive material and crosses with the coil, guides the magnetic flux of the current to be measured to the magnetostrictive material, and further varies the piezoelectric element by applying a varying voltage to the piezoelectric element. A strain is generated, a strain that fluctuates in the magnetostrictive material is generated due to a fluctuating strain of the piezoelectric element, a magnetic permeability of the magnetostrictive material is fluctuated by the fluctuating strain, and a fluctuating magnetic flux generated by the fluctuating magnetic permeability An electric current is measured by causing an electromotive force to be generated in the coil crossed with the magnetic flux and detecting the electromotive force.