CN115308493A - Electrical steel iron core loss test method - Google Patents
Electrical steel iron core loss test method Download PDFInfo
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- CN115308493A CN115308493A CN202210812538.7A CN202210812538A CN115308493A CN 115308493 A CN115308493 A CN 115308493A CN 202210812538 A CN202210812538 A CN 202210812538A CN 115308493 A CN115308493 A CN 115308493A
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Abstract
The invention discloses a method for testing the loss of an electrical steel core. An exciting coil and an induction coil are wound on two sides of a circular ring sample, traditional sinusoidal voltage excitation (under the condition that sinusoidal voltage is added on a primary side, when magnetic flux density is close to saturation, current can be distorted to cause non-sinusoidal current waveform) is changed into the method that periodic current excitation is added on the primary side to measure iron core loss, current output of sine and other different waveforms is achieved through current feedback and PWM modulation, a series of hysteresis loop curves under a certain frequency are obtained through experiments, and an iron core loss value is obtained through BH curve integral calculation. The method has the advantages that the iron core loss value can be measured under various current waveforms, the defects that the excitation current is nonsinusoidal and the waveform is single in the original method for measuring the iron core loss by the magnetic ring sample are improved, the iron core loss under different working conditions can be measured more accurately, and the method is suitable for analysis and calculation occasions of the iron core loss of the ferromagnetic material in the motor environment.
Description
Technical Field
The invention relates to the field of calculation of ferromagnetic material core loss, in particular to a method for testing the loss of an electrical steel core in a motor.
Background
The core loss of the ferromagnetic material refers to energy consumed by the ferromagnetic material under an alternating magnetic field, and the core loss is composed of hysteresis loss, eddy current loss and relaxation loss. For mastering loss characteristics, the conventional method adopts an engineering calculation formula proposed by Stanfors in 1984, the calculation method summarizes average loss in a period into a relation between frequency of an excitation power supply and magnetic induction intensity, under the application working condition of sinusoidal excitation, for example, the working environment in a motor can be used for calculating iron loss under a certain frequency range and magnetic field change, the important point in the research on iron core loss on the macroscopic view of a ferromagnetic material is the measurement of a B-H curve, namely a hysteresis curve of a material, the currently general method is to utilize an Epstein square ring, a sine induction voltage is added to a primary side, and the relation between the magnetic field intensity and the magnetic flux density is indirectly obtained through the measurement of the induction voltage and current, but the method has low precision, the problem that the sine voltage added to the primary side cannot ensure that the current of the primary side is a sine waveform, so that the method is applied to the iron core loss model of the material under the motor environment is not accurate, a circular ring sample is used for replacing the Epstein square ring, the problem that the uneven current loss exists in the Epstein square ring is effectively solved, the original problem that the sinusoidal current loss is improved on the basis of the circular ring sample, and the invention is more accurate, and the iron core loss can be predicted, and the period and the iron core loss of the motor can be more accurate.
Disclosure of Invention
The invention mainly solves the technical problem of a brand-new method for measuring the iron core loss, the needed excitation current waveform is obtained through an H bridge, current feedback and PWM (pulse-width modulation), and the iron core loss prediction of the method in a motor environment is more accurate than that of the traditional method.
In order to solve the technical problems, the invention adopts a technical scheme that:
the invention provides a device and a method for testing the loss of an electrical steel core, which comprises the following steps:
1) Obtaining the minimum annular iron core structure size for ensuring the uniformity of the magnetic flux inside the iron core structure by using a finite element analysis method, and processing the iron core structure on the basis;
2) Uniformly winding an excitation winding and an induction winding on a silicon steel lamination of the annular iron core structure; the primary side is excited by adopting periodic current; under the excitation of periodic current, measuring the B-H curve of the ferromagnetic material to be measured with B in a certain range under a certain frequency, wherein the magnetic field intensity H and the magnetic induction intensity B of the sample to be measured are respectively measured by excitation current i 1 And an induced voltage u 2 Obtaining;
2) Obtaining the iron loss value of the current frequency by utilizing the B-H curve under a certain frequency obtained in the step 1) through the integration of the B-H curve;
3) Calculating the iron core loss P at the current frequency according to the following formula;
wherein: v is the volume of the annular iron core structure:
t is the current period;
h is the magnetic field intensity under the current frequency;
and B is the magnetic induction intensity at the current frequency.
As the preferred scheme of the invention, the specific generating device of the periodic current adopts an H-bridge circuit to realize DC-AC conversion, and the device mainly comprises a direct current power supply, a driver and a controller; the on-off of an ideal switch in an H-bridge circuit in the driver is controlled by the main control chip, a pulse width modulation strategy is used for the H-bridge to generate a sine current waveform, the current waveform fed back by the current sensor is compared with the ideal sine waveform in a difference mode, the on-off of the ideal switch in the H-bridge is further controlled by the main control chip according to the obtained result, and the ideal current waveform is finally obtained.
Preferably, the H-bridge circuit employs wide bandgap devices to provide current harmonics with switching frequencies up to 100 kHz.
As a preferable aspect of the present invention, the periodic current is obtained by any one of the following methods:
carrying out Fourier decomposition on a periodic current waveform, adjusting the PWM duty ratio according to a Fourier decomposition result to enable an H bridge to generate PWM voltage representing fundamental wave voltage, and carrying out difference comparison on the obtained current waveform and the periodic current waveform of an actual working condition on the basis, wherein the current waveform is obtained by a current feedback link; and superposing the higher harmonic PWM voltage on the original basis according to the obtained result to obtain the current waveform which is finally close to the actual working condition.
The second method comprises the following steps: through current feedback, the difference is made between the current waveform obtained by feedback in the current loop according to the current sampling link and the periodic current waveform, and the result is sent to a PID controller to control the modulation of PWM waves, so that the required periodic current waveform is generated.
As a preferred aspect of the present invention, the periodic current excitation in step 1) includes, but is not limited to, sinusoidal current excitation, square wave current excitation, and triangular wave current excitation.
As a preferred embodiment of the present invention, the periodic current excitation in step 1) is preferably a sinusoidal current excitation with higher harmonic components.
As a preferred embodiment of the present invention, in step 1),
N 2 the number of turns of the winding representing the secondary side, S is the cross-sectional area of the magnetic ring, u 2 Is an induced voltage.
As a preferred embodiment of the present invention, in step 1),
N 1 representing the number of turns of the primary winding, l being the equivalent length of the magnetic circuit of the annular sample, i 1 Is an excitation current;
l inner and outer diameter data d of passing magnet 1 、d 2 The calculation expression is obtained as follows:
the beneficial effects of the invention are:
1. different measurement methods of the iron core loss can be obtained by changing the waveforms of different excitation currents. Besides sinusoidal current, different current waveforms such as square waves, triangular waves and the like can be generated, and the excitation of different current waveforms can simulate real values of iron loss under different application scenes; the sine current excitation containing higher harmonic wave components can be closer to the iron loss condition in the real motor environment.
2. Compared with the original model, the prediction model obtained by sinusoidal current excitation is closer to the working condition of the ferromagnetic material in the real motor environment, and the prediction result is more accurate.
Drawings
FIG. 1 is a schematic diagram of an experimental apparatus;
FIG. 2 is a schematic diagram of a first waveform generation;
fig. 3 is a schematic diagram of a second waveform generation mode.
Detailed Description
The invention obtains the needed excitation current waveform through the H-bridge, current feedback and PWM modulation, and the prediction of the iron core loss of the method in the motor environment is more accurate than that of the traditional method. As shown in fig. 1, the specific generating device of the periodic current in this embodiment may use an H-bridge circuit to implement DC-AC conversion, and control the on/off of an electronic device in the H-bridge through a main control chip, and may use a pulse width modulation strategy for the H-bridge to generate any current waveform, and compare the current waveform fed back by a current sensor with an ideal waveform by making a difference, and further control the on/off of a switching device in the H-bridge through the main control chip according to an obtained result, so as to finally obtain the ideal current waveform. The electronic device in the H bridge can be but is not limited to a silicon-based MOSFET, a silicon-based IGBT, a SiC device and a GaN device.
The periodic current excitation may be sinusoidal current excitation, square wave current excitation, triangular wave current excitation, and the like. Taking sinusoidal current as an example, fig. 2 illustrates a schematic diagram of a first waveform generation manner; and carrying out Fourier decomposition on the periodic current waveform, adjusting the PWM duty ratio according to the Fourier decomposition result to enable the H bridge to generate PWM voltage representing fundamental wave voltage, comparing the obtained current waveform with an ideal sinusoidal current waveform on the basis, and superposing higher harmonic PWM voltage on the original basis according to the obtained result to obtain the current waveform which is close to the actual working condition finally.
Taking sinusoidal current as an example, fig. 3 illustrates a schematic diagram of a second waveform generation manner; through current feedback, the difference is made between the current waveform obtained by feedback in the current loop according to the current sampling link and the ideal sinusoidal current, and the result is sent to a PID controller to control the modulation of PWM waves, so that the required current waveform is generated.
Examples of the invention
1) A rotor yoke annular sample iron core is processed by adopting a 10JNEX900BH lamination, and an excitation winding and an induction winding are uniformly wound on the iron core. And the excitation winding and the induction winding are uniformly wound on the silicon steel lamination of the annular iron core structure. The original sine voltage excitation of the primary side is changed into sine current excitation, and because the annular iron core structure is equivalent to a small transformer, the current obtained when sine voltage is added to the primary side is known not to be sine wave but to be spike wave according to the transformer characteristics, and the iron core loss under the sine current excitation is measured. The B-H curve of the ferromagnetic material to be measured, the magnetic field intensity H and the magnetic induction intensity B of the sample to be measured are respectively measured by the excitation current i 1 And an induced voltage u 2 Obtaining;
in the step 1), the step (A) is carried out,
N 2 the number of turns of the winding representing the secondary side, S is the cross-sectional area of the magnetic ring, u 2 Is an induced voltage.
Preferably, in step 1),
N 1 representing the primary sideL is the equivalent length of the magnetic circuit of the annular sample, i 1 Is an excitation current;
l inner and outer diameter data d of passing magnet 1 、d 2 The calculation expression is obtained as follows:
2) And (2) obtaining the iron loss value of the current frequency by integrating the B-H curve by using the iron core loss obtained in the step 1) and the B-H curve at a certain frequency.
3) Calculating the iron core loss P at the current frequency according to the following formula;
wherein: v is the volume of the ring magnet:
t is a current period;
h is the magnetic field intensity under the current frequency;
and B is the magnetic induction intensity at the current frequency.
The inference of the iron core loss P of the step 3) is as follows: first, the core loss value is calculated according to the following steps:
in the above formula N 1 ，N 2 The numbers of turns of the primary winding and the secondary winding are respectively represented, and the iron core loss expression shows that in actual loss measurement, average iron loss in a period can be obtained only by measuring the induction voltage of the primary winding and the secondary winding and the current of a coil, and meanwhile, hysteresis curves under various conditions need to be measured in an experiment, and the measurement principle of B and H parameters is as follows:
because the magnetic circuit is even and has no magnetic leakage influence in the ring sample, the magnetic flux change in the iron core can generate induced voltage on the side of the induction winding, and the electromagnetic induction law can be obtained:
wherein S is the cross-sectional area of the magnetic ring, and the measurement expression of the magnetic induction intensity B can be obtained by changing the above expression:
from the ampere-loop theorem and the full current law, one can derive:
∫ l Hdl＝∑i
the above formula can be transformed into:
Hl＝N1i1
the current i can be adjusted through an excitation source, l is the equivalent length of a magnetic circuit of the annular sample, and the equivalent length can be adjusted through the inner diameter data d and the outer diameter data d of the magnet 1 d 2 The calculation expression is obtained as follows:
meanwhile, in combination with B, the expression of the iron core loss with respect to the magnetic induction intensity and the magnetic field intensity can be obtained by substituting the formula H into the iron loss calculation formula as follows:
where V is the volume of the ring magnet.
Because the iron core loss is closely related to the waveform of the exciting current adopted by the primary side, the different exciting current waveforms under different working conditions can lead to different real iron core loss values, and the iron core loss value obtained by the excitation of the original single sinusoidal voltage waveform is not accurate, so that the predicted value obtained by the sine current excitation is more accurate and reliable than the predicted value obtained by the original voltage sinusoidal current non-sinusoidal condition.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (7)
1. The method for testing the loss of the electrical steel core is characterized by comprising the following steps:
1) Obtaining the minimum iron core structure size for ensuring the uniformity of magnetic flux in the iron core structure through finite element analysis, and processing the iron core structure on the basis;
2) Uniformly winding an excitation winding and an induction winding on a silicon steel lamination of the annular iron core structure; the primary side is excited by adopting periodic current; under the excitation of periodic current, measuring the B-H curve of the ferromagnetic material to be measured with B in a certain range under a certain frequency, wherein the magnetic field intensity H and the magnetic induction intensity B of the sample to be measured are respectively measured by excitation current i 1 And an induced voltage u 2 Obtaining;
2) Obtaining an iron loss value of the current frequency by integrating the B-H curve under a certain frequency obtained in the step 1);
3) Calculating the iron core loss P at the current frequency according to the following formula;
wherein: v is the structural volume of the annular iron core:
t is a current period;
h is the magnetic field intensity under the current frequency;
and B is the magnetic induction intensity at the current frequency.
2. The electrical steel core loss test method according to claim 1, wherein a specific generating device of periodic current adopts an H-bridge circuit to realize DC-AC conversion, and the device mainly comprises a direct current power supply, a driver and a controller; the on-off of an ideal switch in an H-bridge circuit in the driver is controlled through a main control chip, a pulse width modulation strategy is used for the H-bridge to generate a sine current waveform, the current waveform fed back through a current sensor is compared with the ideal sine waveform in a difference mode, the on-off of the ideal switch in the H-bridge is further controlled through the main control chip according to the obtained result, and the ideal current waveform is finally obtained.
3. The electrical steel core loss testing method of claim 2, wherein the H-bridge circuit uses wide bandgap devices to provide current harmonics with switching frequencies up to 100 kHz.
4. The electrical steel core loss test method according to claim 1, wherein the periodic current is obtained by: carrying out Fourier decomposition on the periodic current waveform, adjusting the PWM duty ratio according to the Fourier decomposition result to enable the H bridge to generate PWM voltage representing fundamental wave voltage, and comparing the difference between the obtained current waveform and the actual working condition periodic current waveform on the basis, wherein the current waveform is obtained by a current feedback link; and superposing the higher harmonic PWM voltage on the original basis according to the obtained result to obtain the current waveform which is finally close to the actual working condition.
5. The electrical steel core loss test method according to claim 1, wherein the periodic current is obtained by: through current feedback, the difference is made between the current waveform obtained by feedback in the current loop according to the current sampling link and the periodic current waveform, and the result is sent to a PID controller to control the modulation of PWM waves, so that the required periodic current waveform is generated.
6. The electrical steel core loss testing method of claim 1, wherein the periodic current excitation in step 1) includes but is not limited to sinusoidal current excitation, square wave current excitation, triangular wave current excitation, and trapezoidal wave current excitation.
7. The electrical steel core loss test method according to claim 1, wherein the periodic current excitation in the step 1) is preferably a sinusoidal current excitation containing higher harmonic components.
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Cited By (1)
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| CN116559543A (en) * | 2023-03-08 | 2023-08-08 | 山东大学 | High-frequency transformer loss decomposition method and device based on different excitation |
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| CN201876536U (en) * | 2010-11-22 | 2011-06-22 | 沈阳工业大学 | Adjustable-magnetic-circuit measurement device for two-dimensional magnetic property of electrical sheets |
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