CN101813723A - Non-contact type direct current measuring method - Google Patents

Abstract

The invention relates to a non-contact type direct current measuring method, which adopts an exciting current circuit and a phase displacement measuring circuit for forming a direct current measuring circuit. The method comprises the following steps: a. winding a winding W on a high-magnetoconductivity annular iron core A, wherein the winding W is connected in parallel with a voltage detection circuit; b. passing a conducting wire of a detected direct loop through the annular iron core A; c. introducing alternative symmetrical triangular wave magnetizing current i into the winding W so that a magnetic core is saturated, and measuring the phase displacement time t<+> and t<-> through detecting a voltage circuit; and d. and measuring the value of the measured direct current according to the phase displacement time t<+> and t<-> because the value of the direct current I is in linear relationship with (t<+>- t<->)/(t<+> + t<->). The invention has the advantages of simple structure, isolated measurement, temperature drift inhabitation, high precision, low cost and the like.

Description

A kind of method of non-contact type direct current measuring

Technical field

The present invention relates to the measuring method of DC current, especially relate to the method for non-contact type direct current measuring.

Background technology

In photovoltaic generating system, many component string loop all needs to measure the size of DC current, and the routine measurement method of DC current is the series circuit measurement, promptly disconnect after the DC circuit direct current table sealed in and measure, but under many circumstances, this method does not allow to use, and therefore adopting non-contact measurement is a kind of method that addresses this problem.At present, the non-cpntact measurement of DC current has two kinds of methods, and the one, adopt Hall element, but the Hall element cost is higher, is not suitable for extensive use.Another kind method is that the phase difference type magnetic modulation principle detects.

In invention disclosed patented claim 200610017348 on July 12 in 2006, disclosed a kind of like this measuring method, its concrete steps are: a, on the annular core of high magnetic permeability, twine 3 windings, b, the lead of detected DC loop is passed described annular core, c, feed alternation symmetrical triangular ripple exciting curent i to field winding W1 and make core sataration, detect the phase shift time Δ t that measures winding W2 by described testing circuit, d, by Δ t for just or be the negative direction of measured current I and the intensity roughly promptly known, feed the feedback current I0 opposite for then feedback winding W4 and be used for slackening the direct current biasing magnetic field that electric current I to be measured produces with the measured current I direction, when adjusting I0 to Δ t=0, the numerical value of I0 multiply by the size that the number of turn of feeding back winding W4 promptly gets measured current I with this moment.This method has realized high precision, the non-cpntact measurement of DC current on a large scale, but because required winding is more and need devices such as a plurality of power supplys, reometer, so complex structure, cost is very high, and measuring process is loaded down with trivial details.

Summary of the invention

The object of the invention is to provide a kind of simple in structure, contactless dc current measurement method that cost is low, easy and simple to handle.

For achieving the above object, the present invention can take following method to realize:

Contactless dc current measurement method of the present invention comprises following step:

A, twine a winding W on a high permeability annular core A, winding W is in parallel with a voltage detecting circuit;

B, the lead of detected DC loop is passed described annular core A;

C, feed alternation symmetric triangular ripple exciting curent i to winding W and make magnetic core saturated, record phase shift of time t by voltage detecting circuit ₊And t _-Described phase shift of time is meant: the D.C. magnetic field that the lead of detected DC loop produces can destroy the symmetry of the alternating flux in the iron core, measure winding both end voltage signal and will reflect the ruined degree of symmetry this moment, i.e. the phase shift of positive and negative half-wave, the shared time t of positive and negative half-wave this moment ₊And t _-Be above-mentioned phase shift of time t ₊And t _-

D, by recording time t+ and t-, can determine the size of measured DC.Computing formula is as follows:

$I=k_1\&times;\frac{t_{+}-t_{-}}{t_{+}+t_{-}}+k_2$

k ₁, k ₂Be constant, can record according to experiment.

According to the associated magnetic modulation theory, as can be known in above circuit:

t ₊+t _-＝T；

$t_{+}-t_{-}=4\mathrm{\&delta;}=\frac{H_0}{H_m}\&times;T=\frac{W_{1}I}{{\mathrm{WI}}_m}\&times;T$

Wherein:

T+: shared time of positive half-wave

T-: negative shared time of half-wave

T: the cycle of exciting current

H ₀: the magnetic field intensity during DC current I=0

H _m: the magnetic field intensity of DC current I＞0 o'clock

δ: be measured DC I＞0 o'clock, the phase shift of the positive and negative half-wave of core interior magnetization waveform

W: exciting circuit umber of turn

W ₁: tested DC circuit umber of turn

I: measured DC

I _m: exciting current

So

$\frac{t_{+}-t_{-}}{t_{+}+t_{-}}=\frac{W_{1}I}{{\mathrm{WI}}_m}$

Irrelevant with T, will get after the fortran:

$\frac{t_{+}-t_{-}}{t_{+}+t_{-}}\&times;\frac{{\mathrm{<figure-callout\; id="1"\; label="WI\; m\; W"\; filenames="HSA00000075239600012.png"\; state="\{\{state\}\}">WI</figure-callout>}}_m}{W_{}}=I$

As annular core, winding W, exciting current I _mAfter determining, and tested DC circuit winding W ₁Be 1 when circle then

$\frac{{\mathrm{WI}}_{\mathrm{<figure-callout\; id="1"\; label="m\; W"\; filenames="HSA00000075239600012.png"\; state="\{\{state\}\}">m</figure-callout>}}}{W_{}}$

Be constant, set it and be k ₁, systematic survey drift correction value is made as k ₂, promptly get formula:

$I=k_1\&times;\frac{t_{+}-t_{-}}{t_{+}+t_{-}}+k_2$

k ₁, k ₂Be constant, can record according to experiment.

Only the invention has the advantages that and on the annular core A of high permeability, to twine a field winding W, record t+ and t-,, can obtain the electric current of tested DC circuit the above-mentioned formula of its substitution by the voltage check device in parallel with winding W.Compared to existing technology, circuit of the present invention is simple, and the cost of realization significantly reduces, and is simultaneously simple and efficient to handle.

Description of drawings

Fig. 1 is that high permeability annular core A of the present invention goes up the structural representation that twines a winding W.

Fig. 2 is the data fitting curve among the embodiment.

A is the current waveform figure of alternation exciting curent i of the present invention among Fig. 3.

The magnetization oscillogram of annular core A when b is measured DC I=0 of the present invention among Fig. 3.

Voltage detecting circuit output voltage waveform when c is measured DC I=0 of the present invention among Fig. 3.

D is the magnetization oscillogram of measured DC I of the present invention ≠ 0 o'clock annular core A among Fig. 3.

E is measured DC I of the present invention ≠ 0 an o'clock voltage detecting circuit output voltage waveform among Fig. 3.

Embodiment

Below in conjunction with accompanying drawing technical scheme of the present invention is elaborated:

As shown in Figure 3, t ₊And t _-Be phase shift of time, non-contact measuring system for direct current of the present invention, it comprises following step:

A, twine a winding W on a high permeability annular core A, winding W is in parallel with a voltage detecting circuit;

B, the lead of detected DC loop is passed described annular core A;

C, feed alternation symmetric triangular ripple exciting curent i to winding W and make magnetic core saturated, record phase shift of time t by voltage detecting circuit ₊And t _-As shown in Figure 3, described phase shift of time is meant: the D.C. magnetic field that the lead of detected DC loop produces can destroy the symmetry of the alternating flux in the iron core, measure winding both end voltage signal and will reflect the ruined degree of symmetry this moment, be the phase shift of positive and negative half-wave, the shared time of positive and negative half-wave is respectively t ₊And t _-

D, by recording time t ₊And t _-, can determine the size of measured DC.Computing formula is as follows:

$I=k_1\&times;\frac{t_{+}-t_{-}}{t_{+}+t_{-}}+k_2$

k ₁, k ₂Be constant, can record according to experiment.

For example: winding W is 1000 circles, and it is the single-chip microcomputer of AT89C51 that metering circuit is selected chip for use, uses the method for external interrupt and counting to measure t+ and t-, according to connecting circuit shown in the accompanying drawing 1.

At first adjust measured current I, and record corresponding t by metering circuit by D.C. regulated power supply ₊And t _-, get 10 groups of data (i.e. 10 groups of corresponding I values and t arbitrarily ₊, t _-), data are done linearity curve and match, the data fitting curve is seen accompanying drawing 2, promptly tries to achieve the k of this system ₁, k ₂, be respectively k ₁=-6.6652, k ₂=4.6339, with the k that tries to achieve ₁, k ₂Be worth the substitution formula, then can get the computing formula of this measuring system $I=-6.6652\&times;\frac{t_{+}-t_{-}}{t_{+}+t_{-}}+4.6339$

Adjust measured DC I arbitrarily, measure corresponding t ₊And t _-, the computing formula of this measuring system of substitution then, I value that obtains and normalized current output valve are all coincide.

Claims (1)

1. the method for a non-contact type direct current measuring, it is characterized in that: it comprises following steps:

A, twine a winding W on a high permeability annular core A, winding W is in parallel with a voltage detecting circuit;

B, the lead of detected DC loop is passed described annular core A;

C, feed alternation symmetric triangular ripple exciting curent i to winding W and make magnetic core saturated, record the shared time t of positive and negative half-wave by described detection potential circuit ₊And t _-

D, time t by recording ₊And t _-, determine the size of measured DC, computing formula is as follows:

$I=k_1\&times;\frac{t_{+}-t_{-}}{t_{+}+t_{-}}+k_2$

k ₁, k ₂Be constant, record according to experiment.

Images