CN102384715B - A kind of piezoelectric current sensor - Google Patents

Abstract

A kind of piezoelectric current sensor, it is characterized in that: current sensor is by electrical conductor (1), piezoelectric (2), electrode (3), insulation crust (4), web member (5), signal lead (6) and signal transacting and display system (7) composition, pressure electrical conductor (1) deformation produced by web member (5) is passed to piezoelectric (2) by insulation crust (4) and is formed precompression on piezoelectric (2), the voltage signal that piezoelectric produces is drawn by electrode (3) and signal lead (6) and is transferred to signal transacting and display system (7).Novel pressure electric-type current sensor can measure the pulse current of high frequency alternating current and transition in large dynamic range, have that structure is simple, volume is little, high insulation isolation, good temp characteristic little by electromagnetic interference (EMI) feature.

Description

A kind of piezoelectric current sensor

Technical field

The present invention relates to and a kind ofly adopt piezoelectric device to measure the current sensor of conductor deformation based on the deformation of electrical conductor pressurized; specific use is had in power supply and the current measurement of converting equipment and controlling party mask; also the current measurement of industrial products and equipment, control, calibration and overcurrent protection and monitoring be can be widely used in, the measurement of a railway car momentary current detection and the industry such as metal smelt and chemical industry big current, control and scheduling co-design comprised.

Background technology

Current sense and to measure be the research topic related generally in engineering and scientific research, as current measurement and the control of power supply and converting equipment, the current measurement of industrial products and equipment, control, calibration and overcurrent protection and monitoring.Current sensor traditional at present has ammeter, the current sensor based on Hall effect and the fibre optic current sensor based on Faraday effect.Tradition ammeter uses simple but needs to connect with electrical conductor to use, and it is little to measure electric current; Structure based on the current sensor of Hall effect is simple but temperature characterisitic is not good, and the impact by temperature drift is large, big current causes iron core magnetic saturated; Fibre optic current sensor based on Faraday effect is little by electromagnetic interference (EMI) but impact by temperature drift is large, and complex structure, and cost is higher, the fibre optic current sensor of existing market also rare maturation.Above-mentioned three kinds of current sensors are active sensor, need power supply during work.

The invention provides a kind of piezoelectric current sensor based on the deformation of electrical conductor pressurized, adopt piezoelectric device to measure conductor deformation and conductor current.The piezoelectric current sensor of electrical conductor distortion measurement is a kind of passive electrical flow sensor.Current sensor provided by the invention has the feature of simple, the high insulation isolation of structure, good temp characteristic little by electromagnetic interference (EMI).The measurement range of this New type of current sensor is wide, the response time is short, can detect the non-detectable big current value of conventional current sensors, powers and the current measurement of converting equipment and control provide a kind of robust techniques means for high power.

Summary of the invention

Principle of the present invention is as follows:

Principle of the present invention is based on the deformation of electrical conductor pressurized and adopts piezoelectric device to measure the current sensor of conductor deformation.If electric current I is the endless cylindrical conductor of a by radius.Current density, J in cylindricality wire is I/ (π a ²).The magnetic field H that electric current produces is parallel to cross section and perpendicular to the radial r of cylinder, as shown in Figure 1.According to Ampère circuital theorem, the magnetic field H that conduction current produces is:

$H=\frac{I}{2\mathrm{\πa}}(r=a),$

$H=\frac{\mathrm{rI}}{2\mathrm{\&pi;}{a}^2}(r<a).$

Get the sector crosssection that a little angle is δ θ, the Lorentz pressure F suffered by unit length sector crosssection is:

$F=\&Integral;j\&times;\mathrm{BdV}=\frac{{\mathrm{\&mu;}}_0{I}^2}{6{\mathrm{\&pi;}}^{2}a}\mathrm{\&delta;\&theta;},$

In formula, B is magnetic induction density (B=μ ₀h, μ ₀for permeability of vacuum).The direction of Lorentz force F is parallel to the radial direction of cylindricality wire and points to axle center.The pressure f of damaged surface is:

$f=\frac{{\mathrm{\&mu;}}_0{I}^2}{6{\left(\mathrm{\&pi;a}\right)}^2},$

The size of pressure is proportional to square I of electric current ², be inversely proportional to the sectional area π a of cylinder ².The Lorentz pressure P acting on unit length cartridge outer surface is:

$P=\frac{{\mathrm{\&mu;}}_0{I}^2}{3\mathrm{\&pi;a}}.$

If cylindrical conductor is ferromagnetic material (Fe, Co, Ni and alloy thereof), then magnetic permeability μ is μ=μ ₀μ _r, μ in formula _rfor relative permeability.The relative permeability of common metal conductor is μ _r≈ 1.Due to the relative permeability of ferromagnetic material very high (for pure iron, μ _r≈ 5000), therefore the deformation that caused by ferromagnetic material of electric current is very large.The Lorentz pressure that electric current is produced by unit length ferromagnetic material cartridge outer surface is:

$P=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_r{I}^2}{3\mathrm{\&pi;a}}.$

Under the function of current, the radial variations δ r that cylinder produces is:

$\mathrm{\&delta;r}=-\frac{\mathrm{\&beta;}{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_r{I}^2}{6\mathrm{\&pi;}},$

In formula, β is the compressibility coefficient of conductor.For pure iron, β=6.135 × 10 ^-12(m ²/ N).The numerical value of the radial variations estimated by above formula is: δ r=-2 × 10 ^-15i ²(m).If electrical current is 1000A, then radial variations value is 2nm.All very large pressure can be subject to by the conductor of big current.Lorentz force makes cylindricality wire produce deformation.The size of pressure and deformation is proportional to square I of electric current ².If the frequency of exchange current is f, then the frequency of wire deformation is 2f.The frequency of exchange current is generally 50Hz or 60Hz, and the frequency of therefore wire deformation is 100Hz or 120Hz, is in audio range.The electric current by cylindrical conductor can be measured by the pressure or deformation detecting damaged surface.The present invention adopts piezoelectric device to detect the deformation of damaged surface.The frequency produced by extracting piezoelectric device is the voltage signal of 2f and the detectable electric current by cylindrical conductor.Frequency due to exchange current is f, and therefore New type of current sensor is little by the electromagnetic interference (EMI) of conduction current.At 2f frequency place, the voltage signal magnitude V that piezoelectric device produces and the pass between exchange current and ringing pulse electric current I are:

I＝kV，

In formula, k is proportionality constant.When a known exchange current by the voltage signal measuring piezoelectric device during conductor and produce, determine that proportionality constant is k, and complete the demarcation to system.The response time of piezoelectric device is short, dynamic range wide, and therefore New type of current sensor can measure the pulse current of high frequency alternating current and transition in large dynamic range.

Accompanying drawing explanation

Below in conjunction with accompanying drawing, the present invention is described in further detail:

Fig. 1 is cylindrical electrical conductor force analysis schematic diagram;

Fig. 2 is the structural representation being connected to electrical conductor current sensor;

Fig. 3 is connected to the structural representation that electrical conductor is the current sensor of ferromagnetic material.

Specific embodiment

Embodiment 1: the current sensor of electrical conductor distortion measurement is made up of electrical conductor 1, piezoelectric 2, electrode 3, insulation crust 4, web member 5, signal lead 6 and signal transacting and display system 7, as shown in Figure 2.Pressure electrical conductor 1 deformation produced by web member 5 is passed to piezoelectric 2 by insulation crust 4 and forms precompression on piezoelectric 2, and the voltage signal that piezoelectric produces is drawn by electrode 3 and signal lead 6 and is transferred to signal transacting and display system 7.Piezoelectric can be crystalline material (α-SiO ₂, ZnO, LiNbO ₃, LiTaO ₃, AlPO ₄, BaTiO ₃deng), stupalith (BaTiO ₃-pottery, PZT etc.), high polymer piezoelectric material (PVDF etc.).The sandwich construction that the piezoelectric device be made up of piezoelectric 2 and electrode 3 can be single layer structure or is composed in series.The Al of insulation crust 4 optional select a good opportunity tool and good insulation preformance ₂o ₃the insulating material such as-pottery or phenolics.At 2f frequency place, the voltage signal magnitude V that piezoelectric device produces and frequency are the pass between the exchange current of f and ringing pulse electric current I is I=kV, and in formula, k is proportionality constant.When a known exchange current Ir is by conductor 1, if the measured value of the voltage signal of piezoelectric device generation is Vr, then proportionality constant is: k=Ir/Vr.After system calibrating, the pass between the voltage signal V that exchange current and ringing pulse electric current I and piezoelectric device produce is: I=IrV/Vr.

Embodiment 2: the current sensor of electrical conductor distortion measurement is made up of be energized ferroelectric conductor 1, piezoelectric 2, electrode 3, insulation crust 4, signal lead 5 and signal transacting and display system 6, as shown in Figure 3.The pressure that the ferroelectric conductor deformation that is energized produces is passed to piezoelectric 2 by insulation crust 4; The voltage signal that piezoelectric produces is drawn by electrode 3 and signal lead 5 and is transferred to signal transacting and display system 6.Piezoelectric can be crystalline material (α-SiO ₂, ZnO, LiNbO ₃, AlPO ₄, BaTiO ₃deng), stupalith (BaTiO ₃-pottery, PZT etc.), high polymer piezoelectric material (PVDF etc.).The sandwich construction that the annular piezoelectric device be made up of piezoelectric 2 and electrode 3 can be single layer structure or is composed in series.The Al of insulation crust 4 optional select a good opportunity tool and good insulation preformance ₂o ₃the insulating material such as-pottery or phenolics.The ferroelectric conductor 1 of column type and annular piezoelectric device are tight fit connection and form precompression on piezoelectric devices 2.Due to the relative permeability of ferromagnetic material very high (for pure iron, μ _r≈ 5000), therefore the deformation that caused by ferromagnetic material of electric current is very large.The Lorentz pressure that electric current is produced by unit length ferromagnetic material cartridge outer surface is:

$P=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_r{I}^2}{3\mathrm{\&pi;a}}.$

Under the function of current, the radial variations δ r that cylinder produces is:

$\mathrm{\&delta;r}=-\frac{\mathrm{\&beta;}{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_r{I}^2}{6\mathrm{\&pi;}},$

In formula, β is the compressibility coefficient of conductor.For pure iron, β=6.135 × 10 ^-12(m ²/ N).The numerical value of the radial variations estimated by above formula is: δ r=-2 × 10 ^-15i ²(m).If electrical current is 1000A, then radial variations value is 2nm.All very large pressure can be subject to by the conductor of big current.The voltage signal magnitude V that piezoelectric device produces and the pass between exchange current and ringing pulse electric current I are I=kV, in formula, k is proportionality constant, when a current known Ir by the measured value of the voltage signal of setting piezoelectric device to produce during conductor 1 as Vr, then proportionality constant is: k=Ir/Vr.After system calibrating, the pass between the voltage signal V that exchange current and ringing pulse electric current I and piezoelectric device produce is: I=IrV/Vr.

In the present invention because piezoelectric is highly-resistant material, the height that therefore can realize electrical conductor and current sensor insulate and isolates.If adopt quartz piezoelectric crystal AT section make piezoelectric device, then the temperature performance of piezoelectric device and current sensor stablize, little by the impact of temperature drift.New type of current sensor is the electric current that the voltage signal being 2f by the frequency of extraction piezoelectric device generation detects by wire.Frequency due to exchange current is f, and therefore New type of current sensor is little by the electromagnetic interference (EMI) of conduction current.The response time of piezoelectric device is short, dynamic range wide, and therefore New type of current sensor can measure the pulse current of high frequency alternating current and transition in large dynamic range.Current sensor provided by the invention has that structure is simple, volume is little, high insulation isolation, good temp characteristic little by electromagnetic interference (EMI) feature.

Claims (4)

1. a piezoelectric current sensor, it is characterized in that: current sensor is by electrical conductor (1), piezoelectric (2), electrode (3), insulation crust (4), web member (5), signal lead (6) and signal transacting and display system (7) composition, pressure electrical conductor (1) deformation produced by web member (5) is passed to piezoelectric (2) by insulation crust (4) and is formed precompression on piezoelectric (2), the voltage signal that piezoelectric produces is drawn by electrode (3) and signal lead (6) and is transferred to signal transacting and display system (7).

2. a kind of piezoelectric current sensor as claimed in claim 1, is characterized in that: electrical conductor (1) is made up of ferromagnetic conductor material.

3. a kind of piezoelectric current sensor as claimed in claim 1, is characterized in that: the sandwich construction that the piezoelectric device be made up of piezoelectric (2) and electrode (3) can be single layer structure or is composed in series.

4. a kind of piezoelectric current sensor as claimed in claim 1, it is characterized in that: the multilayer ring texture that the piezoelectric device be made up of piezoelectric (2) and electrode (3) can be individual layer ring texture or is composed in series, the pressure that column type electrical conductor (1) deformation produces is passed to single or multiple lift annular piezoelectric device by insulation crust (4).