CN103854841A - Error compensation method for current transformer capable of being accompanied by direct current - Google Patents

Abstract

The invention discloses an error compensation method for a current transformer capable of being accompanied by direct current. Ratio errors during the operation of the current transformer which is prepared from a composite iron core and is accompanied by the direct current can be reduced. The composite iron core consists of an iron core made of a soft magnetic material which is low in saturation magnetic flux density and high in magnetic conductivity and an iron core made of a soft magnetic material which is high in saturation magnetic flux density and low in magnetic conductivity. According to the iron core which is high in magnetic conductivity, transformer errors are quite small under sine alternating current, and the iron core is saturated when the transformer is accompanied by the direct current. Although the iron core which is low in magnetic conductivity is not saturated when the transformer is accompanied by the direct current, the transformer errors are certainly quite large if error compensation measures are not taken. By the adoption of the error compensation method, the ratio errors of the transformer which is accompanied by the direct current can be greatly reduced, so that requirements on the magnetic performance of the iron cores can be reduced, waste products can be reduced, the size of the iron cores can be reduced, the cost can be reduced, and the adjustment time of a watt hour meter can be shortened.

Description

Can be with the current transformer error compensation method of direct current

Technical field

The present invention relates to a kind of can be with the current transformer of direct current (C.T) error compensating method, the ratio of C.T when it can reduce primary current greatly with direct current, the present invention is specially adapted to do in kilowatt-hour meter the manufacture of the current transformer of current sampling.

Background technology

The conventional current transformer of kilowatt-hour meter is made current sampling element, the GB of " 1 grade exchanges active watt-hour meter with 2 grades of state types "----GB/T 7215-1998 regulation, this type of kilowatt-hour meter will do even-order harmonic test, will pass into half-wave sinusoidal current, and contains DC component in half-wave sinusoidal current.

The function admirable of the current transformer of being made by high magnetic permeability iron core, ratio and angular difference are little, but do not allow to contain larger flip-flop in primary current, otherwise unshakable in one's determination saturated, it is very big that transformer error becomes.Although the current transformer that constant magnetoconductivity material is made allows tested electric current to have large flip-flop, but cause the error of instrument transformer large because magnetic permeability is low, although constant error can compensate in the time that kilowatt-hour meter is adjusted, adjust time-consuming, and selling at exorbitant prices unshakable in one's determination, need external import.

By high saturated magnetic induction B _s, low magnetic permeability μ the unshakable in one's determination and low B that makes of soft magnetic material _s, the iron core made of high μ soft magnetic material can form composite iron core, the C.T being made by composite iron core can meet kilowatt-hour meter requirement.In the time passing into pure interchange, the accuracy of C.T ensures by high μ is unshakable in one's determination, and in the time passing into half-wave sinusoidal current, the accuracy of C.T ensures by low μ is unshakable in one's determination, but in the time of large half-sinusoid electric current, the ratio of C.T is often excessive, and percent defective is higher.

" can with the current transformer error compensation method of direct current ", can compensate by high B _s, low μ the soft magnetic material ring-shaped core and the low B that make _s, the ring-shaped core composition made of high μ soft magnetic material the ratio of the C.T that makes of composite iron core in the time that half-sinusoid work, thereby reduction is to high B _smagnetic permeability requirement unshakable in one's determination, becomes easily the production of C.T, has reduced cost.Because the ratio of C.T when the work of pure interchange and half-sinusoid is little, thereby shorten the adjustment time of kilowatt-hour meter.

Summary of the invention

" can with the current transformer error compensation method of direct current " of the present invention be at low saturation induction density B _s, high magnetic permeability μ the ring-shaped core made of soft magnetic material on enamelled wire around upper compensation winding N ₃circle, as a part for instrument transformer secondary winding, this iron core is in the time having continuous current excitation, saturated rapidly, then overcoat (or folded on) undersaturated in the time of continuous current excitation, by high saturated magnetic induction B _s, low magnetic permeability μ the ring-shaped core made of soft magnetic material, on 2 iron cores with enamelled wire around on N ₂-N ₃circle, as another part of instrument transformer secondary winding, above 2 winding forwards series connection, forms the secondary winding of instrument transformer; Or by high saturated magnetic induction B _s, low magnetic permeability μ the ring-shaped core made of soft magnetic material on around N ₃circle, as a part for instrument transformer secondary winding, the then low saturation induction density B of inner sleeve (or on folded) _s, high magnetic permeability μ the ring-shaped core made of soft magnetic material, on 2 iron cores with enamelled wire around on N ₂circle, as another part of instrument transformer secondary winding, above 2 winding differential concatenations, forms the secondary winding of instrument transformer.

Low saturation induction density B _s, high magnetic permeability μ soft magnetic material be ultramicro-crystal alloy or claim nanometer crystal alloy (as 1k107) and permalloy (as 1J77A, 1J85,1J86 etc.); High saturated magnetic induction B _s, low magnetic permeability μ soft magnetic material be Fe-based amorphous alloy (as 1k101) and constant permeable alloy (as 1J34h).

The compensation rate of contrast differences is N ₃/ N ₂=-f _i0(1-4 f _i0), f in formula _i0(N when uncompensated ₃=0) the instrument transformer ratio in the time of the DC component current testing of regulation.

Brief description of the drawings

Fig. 1 is can be with the current transformer error compensation method schematic diagram of direct current.

Reference numeral explanation:

The low saturation induction density B of 1-unshakable in one's determination _s, high magnetic permeability μ the ring-shaped core made of soft magnetic material;

2-high saturated magnetic induction B unshakable in one's determination _s, low magnetic permeability μ the ring-shaped core made of soft magnetic material;

I ₁-primary current;

I ₂-secondary current;

N ₁-winding;

N _2-3-genus secondary winding part;

N ₂-genus secondary winding part;

N ₃-compensation winding, belongs to secondary winding part;

R _bthe load of-instrument transformer.

Embodiment

The kilowatt-hour meter Current Transformer of 1, one rated primary current 10A of embodiment, maximum current 160A, rated secondary current 4mA, load resistance 10 Ω, unshakable in one's determination 1 is low B _s, high μ ultramicro-crystal alloy 1k107 material, its internal diameter is that Φ 17, external diameter are 19.4, height is 10, unshakable in one's determination 2 is high B _s, low μ Fe-based amorphous alloy 1k101 material, its internal diameter is that Φ 19.9, external diameter are 24, height is 10; These 2 iron cores are nested together, and with Φ 0.19QA enamelled wire wire-wound 2500 circles, are 0.5I at an effective value _maxhalf-wave sinusoidal current under, the ratio of instrument transformer is-2.5%, test shows this batch of Magnetic Performance Core disposable better.

Carry out coiling with the present invention now: first on the high μ iron core 1 of 1k107, use the QA enamelled wire of Φ 0.1 around 69 circle (N ₃), then put the low μ iron core 2 of 1k101, with Φ 0.19QA enamelled wire on 2 iron cores around 2431 circle (N ₂-N ₃), 69 circles and 2431 circles are just in series.At this moment be, 0.5I at an effective value _maxhalf-wave sinusoidal current under, the ratio of instrument transformer-2.5% being reduced to when uncompensated+0.1%, visible, the performance of instrument transformer is greatly improved.

Below in conjunction with embodiment, the present invention is made to further labor:

Known by Fig. 1, the number of turn that series connection winding forms on unshakable in one's determination 1 is N ₂circle, its induction reactance is Z ₂, the number of turn forming on unshakable in one's determination 2 is N ₂-N ₃circle, its induction reactance is Z _2-3, omitting iron loss, C.T secondary circuit resistance is R ₂₂(winding resistance and load resistance R _bsum), establishing coupling coefficient between winding is 1, obtains C.T secondary current to be by principle of reciprocity:

$I_2=I_1\frac{Z_2\frac{N_1}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000817974900011.png"\; state="\{\{state\}\}">N</figure-callout>}}_2}+Z_{2-3}\frac{N_1}{N_2-N_3}}{{\mathrm{<figure-callout\; id="2"\; label="Z"\; filenames="HSA00000817974900011.png"\; state="\{\{state\}\}">Z</figure-callout>}}_2+Z_{2-3}+R_{22}}$

$=I_1\frac{Z_2\frac{N_1}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000817974900011.png"\; state="\{\{state\}\}">N</figure-callout>}}_2}+Z_{2-3}\frac{N_1}{N_2(1-N_3{N}_2^{-1})}}{{\mathrm{<figure-callout\; id="2"\; label="Z"\; filenames="HSA00000817974900011.png"\; state="\{\{state\}\}">Z</figure-callout>}}_2+Z_{2-3}+R_{22}}$

$\&ap;I_1\frac{N_1}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000817974900011.png"\; state="\{\{state\}\}">N</figure-callout>}}_2}\&times;\frac{{\mathrm{<figure-callout\; id="2"\; label="Z"\; filenames="HSA00000817974900011.png"\; state="\{\{state\}\}">Z</figure-callout>}}_2+Z_{2-3}(1+N_3{N}_2^{-1})}{{\mathrm{<figure-callout\; id="2"\; label="Z"\; filenames="HSA00000817974900011.png"\; state="\{\{state\}\}">Z</figure-callout>}}_2+Z_{2-3}+R_{22}}$

Work as I ₁in while having large DC component, unshakable in one's determination 1 saturated, so Z ₂much smaller than Z _2-3so above formula is reduced to

${\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000817974900011.png"\; state="\{\{state\}\}">I</figure-callout>}}_2=I_1\frac{N_1}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000817974900011.png"\; state="\{\{state\}\}">N</figure-callout>}}_2}\&times;\frac{Z_{2-3}(1+N_3{N}_2^{-1})}{Z_{2-3}+R_{22}}$

$=I_1\frac{N_1}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000817974900011.png"\; state="\{\{state\}\}">N</figure-callout>}}_2}\&times;\frac{1+N_3{N}_2^{-1}}{{1+R}_{22}{Z}_{2-3}^{-1}}$

$=I_1\frac{N_1}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000817974900011.png"\; state="\{\{state\}\}">N</figure-callout>}}_2}\&times;(1+N_3{N}_2^{-1}+R_{22}^2{Z}_{2-3}^{-2}-R_{22}{Z}_{2-3}^{-1})$

Obtain C.T ratio by above formula

$f_I=N_3{N}_2^{-1}+R_{22}^2{Z}_{2-3}^{-2}$

Equation the right Section 1 is compensation rate above, and Section 2 is negative value, C.T ratio f when uncompensated _i0n ⁴ ₂/ (N ₂-N ₃) ⁴doubly (≈ 1+4N ₃/ N ₂≈ 1-4f _i0doubly), regulate N ₃the number of turn, regulates compensation rate N ₃/ N ₂=-f _i0(1-4f _i0).Known f in embodiment _i0=-2.5%, so N ₃=f _i0(1-4f _i0) N ₂=0.025 × (1+4 × 0.025) × 2500=68.75 ≈ 69 circles.

Claims (4)

1. " can with the current transformer error compensation method of direct current " of the present invention, is characterized in that: at low saturation induction density B _s, high magnetic permeability μ the ring-shaped core made of soft magnetic material on enamelled wire around upper compensation winding N ₃circle, as a part for secondary winding, this iron core is in the time having continuous current excitation, saturated rapidly, then overcoat (or folded on) undersaturated in the time of continuous current excitation, by high saturated magnetic induction B _s, low magnetic permeability μ the ring-shaped core made of soft magnetic material, on 2 iron cores with enamelled wire around on N ₂-N ₃circle, as another part of secondary winding, above 2 winding forwards series connection, forms the secondary winding of instrument transformer; Or by high saturated magnetic induction B _s, low magnetic permeability μ the ring-shaped core made of soft magnetic material on around upper compensation winding N ₃circle, as a part for secondary winding, the then low saturation induction density B of inner sleeve (or on folded) _s, high magnetic permeability μ the ring-shaped core made of soft magnetic material, on 2 iron cores with enamelled wire around on N ₂circle, as another part of secondary winding, above 2 winding differential concatenations, forms the secondary winding of instrument transformer;

Low saturation induction density B _s, high magnetic permeability μ soft magnetic material be ultramicro-crystal alloy or claim nanometer crystal alloy (as 1k107) and permalloy (as 1J77A, 1J85,1J86 etc.); High saturated magnetic induction B _s, low magnetic permeability μ soft magnetic material be Fe-based amorphous alloy (as 1k101) and constant permeable alloy (as 1J34h);

The compensation rate of contrast differences is N ₃/ N ₂=-f _i0(1-4f _i0), f in formula _i0(N when uncompensated ₃=0) the instrument transformer ratio in the time of the DC component current testing of regulation.

2. " can with the current transformer error compensation method of direct current " according to claim 1, is characterized in that:

At low B _s, high μ iron core on enamelled wire around upper compensation winding N ₃circle, as a part for secondary winding, then overcoat (or on folded) is by high B _s, the iron core made of low μ material, on 2 iron cores with enamelled wire around on N ₂-N ₃circle, as another part of secondary winding, above 2 winding forwards series connection, forms the secondary winding of instrument transformer; Or by high B _s, on the iron core made of low μ material around upper compensation winding N ₃circle, as a part for secondary winding, the then low B of inner sleeve (or on folded) _s, high μ iron core, on 2 iron cores with enamelled wire around on N ₂circle, as another part of secondary winding, above 2 winding differential concatenations, forms the secondary winding of instrument transformer.

3. " can with the current transformer error compensation method of direct current " according to claim 1, is characterized in that:

Low saturation induction density B _s, high magnetic permeability μ soft magnetic material be ultramicro-crystal alloy or claim nanometer crystal alloy (as 1k107) and permalloy (as 1J77A, 1J85,1J86 etc.); High saturated magnetic induction B _s, low magnetic permeability μ soft magnetic material be Fe-based amorphous alloy (as 1k101) and constant permeable alloy (as 1J34h).

4. " can with the current transformer error compensation method of direct current " according to claim 1, is characterized in that:

The compensation rate of contrast differences is N ₃/ N ₂=f _i0(1+4f _i0), f in formula _i0(N when uncompensated ₃=0) the instrument transformer ratio in the time of the DC component current testing of regulation.

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