CN117747262A - Transformer excitation surge current suppression method based on saturated amorphous alloy iron core - Google Patents
Transformer excitation surge current suppression method based on saturated amorphous alloy iron core Download PDFInfo
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- CN117747262A CN117747262A CN202311827787.4A CN202311827787A CN117747262A CN 117747262 A CN117747262 A CN 117747262A CN 202311827787 A CN202311827787 A CN 202311827787A CN 117747262 A CN117747262 A CN 117747262A
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- 229910000808 amorphous metal alloy Inorganic materials 0.000 title claims abstract description 38
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 title claims abstract description 20
- 229920006395 saturated elastomer Polymers 0.000 title claims abstract description 17
- 230000005284 excitation Effects 0.000 title claims abstract description 13
- 230000001629 suppression Effects 0.000 title claims abstract description 11
- 238000004804 winding Methods 0.000 claims description 24
- 239000011521 glass Substances 0.000 claims description 12
- 230000005415 magnetization Effects 0.000 claims description 9
- 238000004364 calculation method Methods 0.000 claims description 8
- 230000004907 flux Effects 0.000 claims description 6
- 230000035699 permeability Effects 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 4
- 239000000853 adhesive Substances 0.000 claims description 3
- 230000001070 adhesive effect Effects 0.000 claims description 3
- 239000011248 coating agent Substances 0.000 claims description 2
- 238000000576 coating method Methods 0.000 claims description 2
- 230000000694 effects Effects 0.000 description 3
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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Abstract
The invention relates to the technical field of transformer excitation surge suppression, in particular to a transformer excitation surge suppression method based on a saturated amorphous alloy iron core. The amorphous alloy iron core is used, so that the loss of the iron core can be greatly reduced, the amorphous alloy iron core has low impedance in normal operation, has high impedance under the inrush current, and effectively eliminates the inrush current.
Description
Technical Field
The invention relates to the technical field of transformer excitation surge suppression, in particular to a transformer excitation surge suppression method based on a saturated amorphous alloy iron core.
Background
During the energizing of the transformer, the current through the transformer may be very large, which is commonly referred to as magnetizing inrush current. Although the magnetizing inrush current corresponds to a current smaller than the fault current, the inrush current frequently occurs under normal use conditions and the duration can be as long as tens of seconds, so that the inside of the transformer is damaged by mechanical stress generated by the inrush current, and a short circuit fault occurs in the inside of the transformer. In addition, transformer protection may be erroneously activated by the inrush current and simultaneously break down the insulation of the windings and conductors, thereby causing damage to the transformer and increasing the cost of transformer replacement. Meanwhile, the inrush current not only causes physical damage or life loss to the transformer, but also contains high-intensity harmonic waves, which can cause power quality problems, so that the problem needs to be solved.
Disclosure of Invention
In order to avoid and overcome the technical problems in the prior art, the invention provides a transformer excitation surge current suppression method based on a saturated amorphous alloy iron core. The invention can effectively eliminate the inrush current and inhibit the harmonic wave in the power supply process of the transformer.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a transformer excitation surge current suppression method based on a saturated amorphous alloy iron core comprises the following steps:
s1, constructing a transformer with an iron core made of a metallized glass ribbon;
s2, acquiring real-time direct current in the running process of the transformer, and enabling the real-time direct current to be not smaller than a minimum direct current threshold value;
s3, acquiring real-time voltage drop on the transformer winding, and enabling the real-time voltage drop to be not larger than a voltage drop threshold value.
As still further aspects of the invention: the specific steps of step S1 are as follows:
s11, coating an adhesive on the surface of a metallized glass ribbon, and winding the metallized glass ribbon to form an E-shaped iron core;
s12, respectively winding three groups of primary coils and three corresponding groups of secondary coils on the E-shaped iron core to form a three-phase transformer; the three phases of the three-phase transformer are a first phase, a second phase and a third phase respectively;
the inductance on the first phase is R l The resistance corresponding to the core loss of the limb is R cl Magnetization inductance is L ml The leakage inductance is L l ；
The inductance on the second phase is R r The resistance corresponding to the core loss of the limb is R cr Magnetization inductance is L mr The leakage inductance is L r ；
The inductance on the third phase is R m The resistance corresponding to the core loss of the limb is R cm Magnetization inductance is L mm The method comprises the steps of carrying out a first treatment on the surface of the The leakage inductance is L m 。
As still further aspects of the invention: the specific steps of step S2 are as follows:
s21, measuring real-time direct current I in each group of line groups of the transformer through an ammeter t ；
S22, calculating a direct current minimum threshold value in a direct current coil in the transformer through a direct current minimum threshold value calculation formula, wherein the direct current minimum threshold value calculation formula is specifically as follows:
wherein H is sat Is the saturation magnetic field strength; i ac Is the current flowing in the alternating current coil; i dc Is the current flowing in the DC coil; n (N) dc Turns of the direct current coil; n (N) ac Turns of the alternating current coil; l (L) c An average magnetic circuit of the iron core;
s23, when the real-time direct current I is obtained t And a current I flowing through the DC coil dc Then, the real-time direct current I in each group of windings is caused t All are larger than or equal to the current I flowing in the direct current coil dc 。
As still further aspects of the invention: the specific steps of step S3 are as follows:
s31, measuring real-time voltage drop V in each group of line groups of the transformer through a voltmeter t ；
S32, calculating a voltage drop threshold value in an alternating current coil in the transformer through a voltage drop threshold value calculation formula, wherein the voltage drop threshold value calculation formula is specifically as follows:
wherein V is ICL A voltage drop threshold in an ac coil in the transformer;is the variation of flux linkage in the alternating current coil; l (L) ICL Is an alternating current coil inductance; n (N) ac Turns of the alternating current coil; />Is I ac Is a variable amount of (a); a is that c Is the cross-sectional area of the magnetic core; />Is the variation of permeability mu;
s33, when the real-time pressure drop V is obtained t And a voltage drop threshold V in the AC coil ICL After that, the real-time pressure drop V t Less than or equal to the voltage drop threshold V in the AC coil ICL 。
As still further aspects of the invention: the three-phase transformer comprises two groups of primary alternating current coils, two corresponding groups of secondary alternating current coils, a group of primary direct current coils and a corresponding group of secondary direct current coils.
As still further aspects of the invention: the primary direct current coils and the corresponding secondary direct current coils are positioned on the middle winding posts of the E-shaped iron core, and the two primary alternating current coils and the corresponding secondary alternating current coils are respectively positioned on the winding posts on two sides of the E-shaped iron core.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a novel compact lightweight saturated amorphous alloy iron core, which is made of a metallized glass amorphous ribbon. The amorphous alloy core may saturate at a lower exciting dc current than conventional cores, which helps reduce the size of the dc power supply of the amorphous alloy core. The amorphous alloy iron core is used, so that the loss of the iron core can be greatly reduced, the amorphous alloy iron core has low impedance in normal operation, has high impedance under the inrush current, and effectively eliminates the inrush current.
Drawings
Fig. 1 is a main flow chart of the present invention.
Fig. 2 is an equivalent circuit of the amorphous alloy core transformer of the present invention.
Fig. 3 is an equivalent circuit of a conventional power frequency transformer according to the present invention.
Fig. 4 is a waveform diagram of magnetizing inrush current of a saturated amorphous transformer under different direct currents in the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1 to 4, the present invention provides a method for suppressing a transformer magnetizing inrush current based on a saturated amorphous alloy core, wherein the amorphous alloy core is manufactured by using a metallized glass amorphous ribbon. Since the metallized glass ribbon is very thin, having a thickness of only 23 μm, extra care is required in constructing the amorphous alloy core. When the metallized glass ribbon is rolled into an amorphous alloy core, glue is applied as an adhesive to join adjacent layers together to increase the mechanical structural strength of the amorphous alloy core. In this structure of an amorphous alloy core composed of metallized glass ribbon, the annular core and intermediate branches between the air gaps are not considered.
Winding a metallized glass ribbon to form an E-shaped iron core, and respectively winding three groups of primary coils and three corresponding groups of secondary coils on the E-shaped iron core to form a three-phase transformer; the three phases of the three-phase transformer are a first phase, a second phase and a third phase respectively. The two ac windings of the outer limb, i.e. the ac line groups of the first and third phases, are connected in series, but the direction of current flow in the two windings is opposite. A portion in the middle of the second phase.
Under normal working conditions, the magnetic field intensity generated by direct current keeps the amorphous alloy iron core saturated, and the alternating current impedance is very low. During transformer energization, if the inrush current is high enough to desaturate the amorphous alloy core, the impedance of the ac winding will increase and limit the peak value of the inrush current.
For any particular application of the amorphous alloy core, the number of turns of the dc coil should be carefully selected during design so that the ac impedance is normally low and high at large inrush currents. To ensure that the amorphous alloy core is not saturated during the transformer conduction process, the minimum direct current required can be expressed as formula (1):
the average magnetic diameter of the DC electromagnetic field is 2 (l) 1 +l 2 )＝2(l 3 +l 3 ) While the alternating magnetic field is the left half, i.e. l of the first phase 1 +l 2 L of the right half 2 +l 3 。l 1 Is the average magnetic length of the left side of the middle wing, l 2 Is the average magnetic length of the middle wing, l 2 Is the average magnetic length of the right side of the middle wing, l c ＝l 1 +l 2 ＝l 2 +l 3 。
The voltage drop across the ac winding of the amorphous alloy core can be expressed as formula (2), where the parameters other than the permeability μ are constant. Thus, the inductance varies with μ. Since the B-H curve is nonlinear, μ varies with saturation and tends to be relatively constant at saturation, when the relative permeability is nearly uniform. Lambda is the flux linkage. At saturation dμ/dt≡0, therefore, under normal operating conditions the voltage drop across the two ac windings can be expressed as (3):
the amorphous alloy iron core is designed by adopting the ratio of the voltage drop of the amorphous alloy iron core to the peak amplitude of the power supply voltage. The best design consideration for amorphous alloy cores is to keep the voltage drop as low as possible under normal operating conditions while ensuring a sufficient reduction of the inrush current during transformer energization.
FIG. 2 shows an equivalent circuit of a transformer composed of amorphous alloy cores in combination, wherein R l 、R r 、R m And L l 、L r 、L m The resistances and the leakage inductances of windings on the three branches respectively. R is R cl 、R cm 、R cr Corresponding resistances are lost for the three limb cores. L (L) ml ,L mm And L mr Is a magnetizing inductance of three branches. These magnetizing inductances are inversely proportional to the magnetic resistances, which vary with the B-H curve. R is R cl 、R cm 、R cr The adjustment may be made in a hysteresis function.
The dot polarity of the dc and ac windings of the amorphous alloy core transformer is placed in the equivalent circuit of fig. 2, which helps describe whether the magnetic fluxes generated by the ac and dc currents are additive or subtractive. For example, for a positive half cycle of the ac line current, the resultant flux of the left limb of the amorphous alloy core transformer is subtracted: phi (phi) l -φ m The method comprises the steps of carrying out a first treatment on the surface of the While the resultant flux of the right limb is additive: phi (phi) r+ φ m 。
The intermediate branch is excited by a dc source and therefore ideally it should not cause any core loss due to the time-varying component. However, the left and right limbs of the amorphous alloy core transformer carry alternating current which will affect the magnetization of the whole core including the middle limb. Although the effect of the alternating current on the magnetization of the centering arm is negligible, this effect is present. Thus magnetizing shunt resistor R cl 、R cm And R is cr Will be connected to the branch of the magnetic circuit.
An equivalent circuit of a single-phase conventional power frequency transformer for simulation is shown in FIG. 3, wherein R is as follows lT 、R rT Is resistance, L lT 、L rT Is the leakage inductance of the primary winding and the secondary winding. R is R cT Representing the resistance of the simulated core loss. L (L) mT The saturable magnetization inductance of the iron core has nonlinear characteristics.
Through simulation, as shown in fig. 4, the obtained result shows that the effect of suppressing the excitation surge current is better.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (6)
1. The transformer excitation surge current suppression method based on the saturated amorphous alloy iron core is characterized by comprising the following steps of:
s1, constructing a transformer with an iron core made of a metallized glass ribbon;
s2, acquiring real-time direct current in the running process of the transformer, and enabling the real-time direct current to be not smaller than a minimum direct current threshold value;
s3, acquiring real-time voltage drop on the transformer winding, and enabling the real-time voltage drop to be not larger than a voltage drop threshold value.
2. The transformer excitation surge current suppression method based on the saturated amorphous alloy iron core as set forth in claim 1, wherein the specific steps of step S1 are as follows:
s11, coating an adhesive on the surface of a metallized glass ribbon, and winding the metallized glass ribbon to form an E-shaped iron core;
s12, respectively winding three groups of primary coils and three corresponding groups of secondary coils on the E-shaped iron core to form a three-phase transformer; the three phases of the three-phase transformer are a first phase, a second phase and a third phase respectively;
the inductance on the first phase is R l The resistance corresponding to the core loss of the limb is R cl Magnetization inductance is L ml The leakage inductance is L l ；
The inductance on the second phase is R r The resistance corresponding to the core loss of the limb is R cr Magnetization inductance is L mr The leakage inductance is L r ；
The inductance on the third phase is R m The resistance corresponding to the core loss of the limb is R cm Magnetization inductance is L mm The method comprises the steps of carrying out a first treatment on the surface of the The leakage inductance is L m 。
3. The transformer excitation surge current suppression method based on the saturated amorphous alloy iron core as set forth in claim 2, wherein the specific steps of step S2 are as follows:
s21, measuring real-time direct current I in each group of line groups of the transformer through an ammeter t ；
S22, calculating a direct current minimum threshold value in a direct current coil in the transformer through a direct current minimum threshold value calculation formula, wherein the direct current minimum threshold value calculation formula is specifically as follows:
wherein H is sat Is the saturation magnetic field strength; i ac Is the current flowing in the alternating current coil; i dc Is the current flowing in the DC coil; n (N) dc Turns of the direct current coil; n (N) ac Turns of the alternating current coil; l (L) c An average magnetic circuit of the iron core;
s23, when the real-time direct current I is obtained t And a current I flowing through the DC coil dc Then, the real-time direct current I in each group of windings is caused t All are larger than or equal to the current I flowing in the direct current coil dc 。
4. The method for suppressing excitation surge current of a transformer based on a saturated amorphous alloy core as claimed in claim 3, wherein the specific steps of step S3 are as follows:
s31, measuring real-time voltage drop V in each group of line groups of the transformer through a voltmeter t ；
S32, calculating a voltage drop threshold value in an alternating current coil in the transformer through a voltage drop threshold value calculation formula, wherein the voltage drop threshold value calculation formula is specifically as follows:
wherein V is ICL A voltage drop threshold in an ac coil in the transformer;is the variation of flux linkage in the alternating current coil; l (L) ICL Is an alternating current coil inductance; n (N) ac Turns of the alternating current coil; />Is I ac Is a variable amount of (a); a is that c Is the cross-sectional area of the magnetic core; />Is the variation of permeability mu;
s33, when the real-time pressure drop V is obtained t And a voltage drop threshold V in the AC coil ICL After that, the real-time pressure drop V t Less than or equal to the voltage drop threshold V in the AC coil ICL 。
5. The method for suppressing magnetizing inrush current of a transformer based on a saturated amorphous alloy core of claim 4, wherein the three-phase transformer comprises two sets of primary ac coils and two corresponding sets of secondary ac coils, and one set of primary dc coils and one corresponding set of secondary dc coils.
6. The method for suppressing magnetizing inrush current of transformer based on saturated amorphous alloy iron core of claim 5, characterized in that the set of primary dc coils and the corresponding set of secondary dc coils are located on the middle winding leg of the E-shaped iron core, and the two sets of primary ac coils and the corresponding two sets of secondary ac coils are located on the winding legs on both sides of the E-shaped iron core, respectively.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311827787.4A CN117747262A (en) | 2023-12-28 | 2023-12-28 | Transformer excitation surge current suppression method based on saturated amorphous alloy iron core |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311827787.4A CN117747262A (en) | 2023-12-28 | 2023-12-28 | Transformer excitation surge current suppression method based on saturated amorphous alloy iron core |
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| CN117747262A true CN117747262A (en) | 2024-03-22 |
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| CN202311827787.4A Pending CN117747262A (en) | 2023-12-28 | 2023-12-28 | Transformer excitation surge current suppression method based on saturated amorphous alloy iron core |
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