JP6834670B2 - Magnetic property measurement system and magnetic property measurement method - Google Patents

Description

The present invention relates to a magnetic property measuring system and a magnetic property measuring method, and is particularly suitable for use in measuring the magnetic property of a magnetic material.

It is possible to measure the magnetic properties (for example, magnetic flux density, magnetic field strength, and iron loss) of a magnetic material for the purpose of designing a magnetic material such as an electromagnetic steel plate used for the core of an electric device. It has been broken. Non-Patent Documents 1 and 2 describe that the magnetic characteristics of a test piece are measured under the condition that the waveform of the magnetic flux density generated in the test piece made of an electromagnetic steel plate is close to a sine wave.

However, the waveform of the magnetic flux density generated in the magnetic material of an actual electric device is a waveform including a harmonic component and does not become a sine wave. For example, in a motor driven by an inverter, the waveform of the magnetic flux density generated in the core due to the shape of the core (stator core and rotor core) used in the motor, the number of poles of the motor, the driving conditions of the inverter, etc. , It becomes a complicated waveform including harmonic components.

Therefore, there is a technique described in Patent Document 1 as a technique for exciting a magnetic material under conditions close to the target magnetic flux density even if the target magnetic flux density is other than a sine wave. In Patent Document 1, the magnetic flux density of the magnetic material is measured, and the magnetic field strength corresponding to the measured magnetic flux density of the magnetic material is derived. Then, the value obtained by multiplying the ratio of the error between the derived magnetic field strength and the target magnetic field strength by the target exciting voltage is used as the correction amount of the exciting voltage. Further, it is determined whether or not the magnetic flux density of the magnetic material has converged based on the result of comparing the magnetic flux density of the magnetic material with the target magnetic flux density. As a result of this determination, when the magnetic flux density of the magnetic material has not converged, the magnetic material is excited with the target exciting voltage updated using the correction amount. Such an operation is repeated until the magnetic flux density of the magnetic material converges.

Japanese Unexamined Patent Publication No. 2016-114387

JIS C 2550-1: 2011 "Method for measuring electrical steel strips Part 1 Method for measuring magnetic properties of electrical steel strips with an Epstein tester" JIS C 2556: 2015 "Measuring method of magnetic properties of electrical steel strips with a single plate tester" Takayoshi Nakata, Norio Takahashi, "Limited Element Method of Electrical Engineering, 2nd Edition", Morikita Publishing Co., Ltd., April 1986 JIS C 2552: 2014 "Directional electromagnetic steel strip"

However, in the technique described in Patent Document 1, the magnetic flux density of the magnetic material is compared with the target magnetic flux density to determine whether or not the magnetic flux density has converged. Therefore, there is a concern that the magnetic properties of the magnetic material cannot be accurately derived (details of this point will be described later with reference to FIGS. 1 to 3). Further, in the technique described in Patent Document 1, when the arithmetic mean value of the error rate using the absolute value of the difference between the magnetic flux density and the target magnetic flux density at all sampling timings over one cycle is equal to or less than the threshold value, the magnetism It is determined that the magnetic flux density of the material has converged. In this case, since the absolute value of the difference between the magnetic flux density and the target magnetic flux density is averaged, it is not easy to bring the magnetic flux density close to the target magnetic flux density with high accuracy depending on the shape of the waveform of the target magnetic flux density. Therefore, when the magnetic flux density generated in the magnetic material is not a sine wave, there is a concern that the iron loss of the magnetic material cannot be derived accurately.

The present invention has been made in view of the above problems, and makes it possible to accurately derive the iron loss of the magnetic material even when the magnetic flux density generated in the magnetic material is not a sine wave. With the goal.

In the magnetic property measurement system of the present invention, an application means for applying an exciting voltage to an exciting coil for exciting a measurement sample made of a magnetic material, and an induction induced in a first coil by exciting the measurement sample. A first detecting means for detecting a voltage, a second detecting means for detecting an exciting current flowing through the exciting coil when the exciting voltage is applied to the exciting coil by the applying means, and a target of the induced voltage. By the acquisition means for acquiring the waveform, the determination means for determining whether or not the measurement waveform of the induced voltage detected by the first detection means has converged to the target waveform of the induced voltage, and the determination means. When it is determined that the measured waveform of the induced voltage does not converge to the target waveform of the induced voltage, the measured waveform of the induced voltage detected by the first detecting means and the target waveform of the induced voltage When it is determined by the correction means for correcting the exciting voltage and the determination means that the measurement waveform of the induced voltage has converged to the target waveform of the induced voltage based on the difference, the first detection means detects it. It has an iron loss deriving means for deriving the iron loss of the measurement sample based on the induced voltage and the exciting current detected by the second detecting means, and the applying means is the modification. When the exciting voltage is corrected by the means, the corrected exciting voltage is applied to the exciting coil, and the measurement waveform of the induced voltage detected by the determining means by the first detecting means is the measurement waveform of the induced voltage. Until it is determined that the target waveform of the induced voltage has converged, the correction of the exciting voltage by the correcting means, the application of the exciting voltage by the applying means, and the detection of the induced voltage by the first detecting means. is repeatedly performed, the determination means, the induced voltage absolute value of one cycle portion of the integrated value of the difference between the value of the induced voltage in the mutually corresponding time measurement waveform and the target waveform of the induced voltage, or, Based on the difference in amplitude between the plurality of frequency components included in the measured waveform of the induced voltage and the plurality of frequency components included in the target waveform of the induced voltage in the same frequency component , the measured waveform of the induced voltage is the induced. It is characterized in that it is determined whether or not the voltage has converged to the target waveform.

The magnetic property measuring method of the present invention includes an application step of applying an exciting voltage to an exciting coil for exciting a measurement sample made of a magnetic material, and an induction induced in a first coil by exciting the measurement sample. A first detection step of detecting a voltage, a second detection step of detecting an exciting current flowing through the exciting coil when the exciting voltage is applied to the exciting coil by the application step, and a target of the induced voltage. By the acquisition step of acquiring the waveform, the determination step of determining whether or not the measurement waveform of the induced voltage detected by the first detection step has converged to the target waveform of the induced voltage, and the determination step. When it is determined that the measured waveform of the induced voltage does not converge to the target waveform of the induced voltage, the measured waveform of the induced voltage detected by the first detection step and the target waveform of the induced voltage are combined. When it is determined by the correction step of correcting the exciting voltage and the determination step based on the difference that the measurement waveform of the induced voltage has converged to the target waveform of the induced voltage, it is detected by the first detection step. It has an iron loss derivation step of deriving the iron loss of the measurement sample based on the induced voltage generated and the exciting current detected by the second detection step, and the application step is the modification. When the exciting voltage is corrected by the step, the corrected exciting voltage is applied to the exciting coil, and the measured waveform of the induced voltage detected by the first detection step by the determination step is the measurement waveform of the induced voltage. Until it is determined that the target waveform of the induced voltage has converged, the correction of the exciting voltage by the correction step, the application of the exciting voltage by the application step, and the detection of the induced voltage by the first detection step are performed. is repeatedly performed, the judgment process, the absolute value integration value of one period of the difference between the values of the induced voltage in the mutually corresponding time of target waveform of the measured waveform and the induced voltage of the induced voltage, or, Based on the difference in amplitude between the plurality of frequency components included in the measured waveform of the induced voltage and the plurality of frequency components included in the target waveform of the induced voltage in the same frequency component , the measured waveform of the induced voltage is the induced. It is characterized in that it is determined whether or not the voltage has converged to the target waveform.

According to the present invention, even when the magnetic flux density generated in the magnetic material is not a sine wave, the iron loss of the magnetic material can be derived with high accuracy.

It is a figure which shows an example of the waveform of the output voltage of a PWM inverter. It is a figure which shows an example of the waveform of the magnetic flux density. It is a figure which shows an example of the result of having compared the iron loss when the PWM inverter was operated with different modulation rates. It is a figure which shows an example of the structure of a magnetic characteristic measurement system. It is a flowchart explaining an example of the structure of the magnetic characteristic measurement method. It is a figure which shows an example of the structure of an IPM motor. It is a figure which shows an example of the measurement waveform and the target waveform of the induced voltage in each of an invention example and a comparative example.

Before explaining the embodiment of the present invention, the findings obtained by the present inventors will be described.
FIG. 1 is a diagram showing an example of a waveform (relationship between voltage and time) of an output voltage of a PWM (Pulse Width Modulation) inverter. In FIG. 1, the voltage 101 is the output voltage of the PWM inverter when the PWM inverter is driven at a modulation factor smaller than the voltage 102. The same motor was driven by such voltages 101 and 102, respectively. The effective values of the voltages 101 and 102 are the same, and the rotation speed and torque of the motor are also the same.

FIG. 2 is a diagram showing an example of the waveform of the magnetic flux density (relationship between the magnetic flux density and time) at the same location of the stator core when the motor is driven by the voltages 101 and 102. As shown in FIG. 2, the magnetic flux densities 201 and 202 of the stator core are substantially the same regardless of which voltages 101 and 102 are used to drive the motor. The motor iron loss at this time (total iron loss generated in the stator core and the rotor core) was obtained by subtracting the mechanical output and the copper loss from the electric power input to the motor.

FIG. 3 is a diagram showing the result. In FIG. 3, A indicates that the motor was driven by the voltage 101, and B indicates that the motor was driven by the voltage 102. Further, the iron loss ratio indicates a relative value of the iron loss when the iron loss of the stator core when the motor is driven by the voltage 101 is set to "1". As shown in FIG. 3, it can be seen that the iron loss is significantly reduced when the motor is driven by the voltage 102 (B) than when the motor is driven by the voltage 101 (A). It has been confirmed that B has a higher motor efficiency of about 5% and an inverter efficiency of about 7% than A.
As described above, the present inventors have found that even if the magnetic flux density generated in the magnetic material is the same, the iron loss of the magnetic material is different if the waveform of the exciting voltage (relationship between the exciting voltage and time) is different. Obtained. It is considered that this is because the difference in the harmonics contained in the exciting voltage is the difference in the eddy current caused by the magnetic material constituting the core, which is the difference in the iron loss. On the other hand, since the induced voltage induced by exciting the magnetic material is integrated to obtain the magnetic flux density generated in the magnetic material, the signal of the high frequency component included in the induced voltage is the magnetic flux density by this integration. Since it is not included in the waveform, it is considered that the magnetic flux density is the same. Therefore, the present inventors set the target waveform (target waveform) of the induced voltage induced by exciting the magnetic material and the measured waveform (measured waveform) of the induced voltage, instead of the magnetic flux density. I came up with the idea of comparing. The following embodiments of the present invention have been made based on the above findings and ideas.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 4 is a diagram showing an example of the configuration of the magnetic characteristic measurement system. FIG. 5 is a flowchart illustrating an example of a magnetic characteristic measurement method using a magnetic characteristic measurement system. In the magnetic characteristic measurement system of the present embodiment, when a predetermined exciting voltage is applied to an exciting winding that excites a core of an electric device, a magnetic flux density generated in a predetermined region (position) of the core is generated in the measurement sample S. The measurement sample S is excited so as to do so. The magnetic material used as the measurement sample S and the magnetic material used for the core of the electric device are the same type of magnetic material. That is, it is manufactured from raw materials of the same component through the same manufacturing process, except for the variation that inevitably occurs in the manufacturing process, and the difference between the two depends on whether it is molded into the core shape of the electrical equipment or the measurement system. Is it molded into a different shape? Therefore, both have the same magnetic properties. In particular, when the magnetic material used for the core of the electric device has a plate shape, the thickness of the magnetic material used as the measurement sample S and the thickness of the magnetic material used for the core of the electric device are made the same.

The electrical equipment may be, for example, a rotary electric machine represented by a motor, a transformer, a current transformer, a current transformer, a reactor, or any other electrical equipment whose core is excited during operation. It may be an electric device. Further, in the present embodiment, the case where the magnetic material is an electromagnetic steel plate will be described as an example. However, the magnetic material may be any magnetic material used as a core, such as a soft magnetic material typified by an electromagnetic steel plate.

As described above, in the present embodiment, the target waveform of the induced voltage and the measurement waveform are compared, and the measurement sample S is excited so that the measurement waveform matches the target waveform.
It is assumed that the shape of the measurement sample S is simpler than that of the magnetic material constituting the core of the electric device. For example, the test piece set in the Epstein tester described in Non-Patent Document 1, the test piece set in the single plate tester described in Non-Patent Document 2, or the ring-shaped sample is designated as the measurement sample S. Can be done.

(Configuration of magnetic characteristic measurement system)
In FIG. 4, the magnetic characteristic measurement system includes an exciting power supply 401, an exciting coil 402, an ammeter 403, a search coil 404, a voltmeter 405, and a computing device 410.
The exciting power supply 401 applies an exciting voltage to the exciting coil 402. The waveform of the exciting voltage is a waveform that periodically repeats the waveform for one cycle determined by the waveform correction unit 413 in the arithmetic unit 410 described later. An exciting current flows through the exciting coil 402 due to this exciting voltage. The exciting power supply 401 is configured by using, for example, an arbitrary waveform generator and a power amplifier.

The exciting coil 402 is a coil for exciting the measurement sample S, and the exciting coil 402 is wound so as to surround the measurement sample S. When the measurement sample S is a single plate, the excitation coil 402 may be wound around a yoke that is magnetically coupled to the measurement sample S.

The ammeter 403 measures the exciting current flowing through the exciting coil 402.
The search coil 404 is a so-called B coil, and is a coil for detecting the induced voltage induced by the excitation of the measurement sample S. The search coil 404 is wound so as to surround the measurement sample S. That is, the search coil 404 is wound so as to surround the magnetic flux generated by the excitation of the measurement sample S.

The voltmeter 405 measures the voltage (induced voltage) across the search coil 404.
The arithmetic unit 410 acquires the exciting current measured by the ammeter 403 and the induced voltage measured by the voltmeter 405 as time-series data based on a predetermined sampling period. Further, the arithmetic unit 110 generates a waveform of the exciting voltage and instructs the exciting power supply 401, and at the same time, derives the magnetic characteristics (iron loss) of the measurement sample S.

(Configuration of arithmetic unit 410 and method for measuring magnetic characteristics)
An example of the function of the arithmetic unit 410 will be described below. The hardware of the arithmetic unit 410 is realized by using, for example, an information processing device including a CPU, ROM, RAM, HDD, and various interfaces, or dedicated hardware.

<Target waveform acquisition unit 411, S501>
The target waveform acquisition unit 411 acquires the target waveform for one cycle as the target waveform of the induced voltage (target value of the induced voltage at each time). The following two methods will be described as an example of the method of acquiring the target waveform of the induced voltage.

First, the first method will be described.
The search coil is wound around a predetermined region (area where the magnetic characteristics are to be measured) of the core of the electric device whose magnetic characteristics are to be measured. Then, the induced voltage (voltage across the search coil) induced in the search coil is measured by applying a predetermined exciting voltage to the exciting winding that excites the core of the electric device. The region around which the search coil is wound does not have to be exactly the same as the region where the magnetic characteristics are to be measured. For example, due to the structure of an electric device, it may not be possible to wind the search coil in a region that exactly matches the region in which the magnetic characteristics are to be measured. In this case, the search coil is wound around a region as close as possible to the region where the magnetic characteristics are to be measured.

Here, the induced voltage is V (t) [V]. Let the number of turns of the search coil be N [times]. Let the magnetic flux be φ (t) [wb]. Let the magnetic flux density be B (t) [T]. ^{Let S [m 2} ] be the cross-sectional area of the electrical steel sheet in the search coil. Then, the following equations (1) and (2) are established.
V (t) = −N × dφ (t) / dt ・ ・ ・ (1)
φ (t) = B (t) × S ・ ・ ・ (2)

Here, the number of turns and the area of the search coil 404 for the measurement sample S and the search coil for the electric device are different (in many cases). Therefore, according to this difference, it is necessary to convert the value of the induced voltage induced in the search coil for the electric device at each time into the value of the induced voltage induced in the search coil 404 for the measurement sample S at each time. .. Specifically, the number of turns of the search coil 404 for sample S, respectively N _A the cross-sectional area of the magnetic steel in the search coil 404, and S _A. Number of turns of the search coil for electrical equipment, respectively N _M a cross-sectional area of the magnetic steel in the search coil, and S _M. The voltage induced in the search coil for electric appliance and V _M (t). Then, the target waveform _VA (t) of the induced voltage is calculated by the following equation (3).
_{V A (t) = {(} N A × S A) ÷ (N M × S M)} × V M (t) ··· (3)
The cross-sectional area of the electromagnetic steel plate is the cross-sectional area obtained by cutting the electromagnetic steel plate in a direction perpendicular to the direction of the axis of the search coil (the direction of the magnetic path due to the magnetic flux generated in the measurement sample S when the measurement sample S is excited). The area.

Here, in order to reduce noise during measurement, it is preferable to perform the calculation of Eq. (3) after removing high-order harmonic components included in the induced voltage induced in the search coil for the electric device. For example, a fast Fourier transform is performed on the waveform of the induced voltage induced in the search coil for an electric device, and for example, the inverse Fourier transform is performed after removing the spectrum of harmonic components of the 20th order or higher. .. As a result, it is possible to remove high-order harmonic components included in the induced voltage induced in the search coil for the electric device.

The target waveform acquisition unit 411 can acquire the target waveform of the induced voltage by receiving the target waveform of the induced voltage from, for example, an external arithmetic unit that calculates the target waveform of the induced voltage in this way. Further, the target waveform acquisition unit 411 can acquire the target waveform of the induced voltage by inputting the induced voltage induced in the search coil for the electric device and calculating the target waveform of the induced voltage. In addition, the target waveform acquisition unit 411 can also acquire the target waveform of the induced voltage by reading the data of the target waveform of the induced voltage from the storage medium that stores the data of the target waveform of the induced voltage.

Next, the second method will be described.
Two-dimensional numerical analysis based on Maxwell's equation is performed on the magnetic flux density vector generated in a predetermined region of the core by applying a predetermined exciting voltage to the exciting winding that excites the core of the electrical equipment whose magnetic characteristics are to be measured. It is obtained by performing a numerical analysis (that is, a numerical analysis in a two-dimensional space) on a surface in a direction parallel to the plate surface of the electromagnetic steel plate constituting the core. The magnetic flux density vector obtained in this way has a component in the plate surface direction of the electromagnetic steel sheet constituting the core, and does not have a component in the plate thickness direction. Numerical analysis is performed by a computer.

As the numerical analysis, for example, the finite element method can be used. For example, the shape of the electromagnetic steel plate, the size of a minute region (so-called mesh), the data of the BH curve (the curve representing the relationship between the magnetic flux density B and the magnetic field strength H), and the exciting conditions (for example, the exciting voltage at each time). Is adopted as a parameter of the physical quantity for finding the solution of the numerical analysis. That is, taking these parameters into consideration, a magnetic flux density vector can be obtained for each minute region as a numerical solution of Maxwell's equation.

The basic equations for calculating the magnetic flux density vector B and the eddy current vector J _e are generally given by the following equations (4) to (7).

In equations (4) to (7), μ is the magnetic permeability [H / m], A is the vector potential [Tm], and σ is the conductivity [S / m]. J ₀ is the exciting current density [A / m ² ], and φ is the scalar potential [V].
After solving equations (4) and (5) at the same time to obtain the vector potential A and the scalar potential φ, the magnetic flux density vector B and the eddy current vector J _e are obtained from the equations (6) and (7). It is calculated.
Since the method of obtaining the magnetic flux density vector and the eddy current vector in this way can be realized by a known technique as described in Non-Patent Document 3, detailed description thereof will be omitted here. ..
Then, from the magnetic flux density vector for one cycle in the predetermined region of the core of the electric device obtained as described above, the waveform for one cycle of the induced voltage is obtained based on the equations (1) and (2). The obtained waveform is used as the target waveform of the induced voltage.

Here, in order to reduce errors during numerical analysis such as rounding error, the (formal) induced voltage is obtained by removing the higher-order harmonic components included in the target waveform of the induced voltage calculated as described above. It is preferable to use a target waveform. For example, the fast Fourier transform is performed on the target waveform of the induced voltage calculated as described above, and the inverse Fourier transform is performed after removing the spectrum of the harmonic component of, for example, the 20th order or higher. By doing so, it is possible to remove the higher-order harmonic components included in the target waveform of the induced voltage calculated as described above.

The target waveform acquisition unit 411 can acquire the target waveform of the induced voltage by calculating the target waveform of the induced voltage as described above. In addition, the target waveform acquisition unit 411 receives the data of the target waveform of the induced voltage transmitted from the external computing device that calculates the target waveform of the induced voltage by the same method as the above-described method, thereby increasing the induced voltage. It is also possible to acquire the target waveform. Further, the target waveform acquisition unit 411 can also acquire the target waveform of the induced voltage by reading the data of the target waveform of the induced voltage from the storage medium that stores the data of the target waveform of the induced voltage.

<Target waveform storage unit 412, S502>
The target waveform storage unit 412 stores the target waveform of the induced voltage acquired by the target waveform acquisition unit 411.
<Waveform correction unit 413, S503>
The waveform correction unit 413 removes high-order harmonic components included in the measurement waveform of the induced voltage measured by the voltmeter 405. For example, a fast Fourier transform is performed on the measured waveform of the induced voltage, and for example, the spectrum of harmonic components of the 20th order or higher is removed, and then the inverse Fourier transform is performed. As a result, higher-order harmonic components included in the induced voltage induced in the search coil 404 with respect to the measurement sample S can be removed. Next, the waveform correction unit 413 sets the value of the induced voltage measurement waveform from which the harmonic component is removed at a certain time to the value of the time corresponding to the time of the target waveform of the induced voltage stored in the target waveform storage unit 412. The value subtracted from is obtained at each time in one cycle (hereinafter, the value obtained in this way is referred to as a difference). Then, the waveform correction unit 413 adds the value obtained by multiplying the difference obtained for a certain time by the relaxation coefficient to the value of the time corresponding to the time of the waveform of the current excitation voltage. The waveform correction unit 413 performs correction by such addition at each time in one cycle. The relaxation coefficient is for suppressing the hunting of the exciting voltage, and has a value of more than 0 (zero) and less than 1. For example, a value of 0.2 to 0.3 can be adopted as the relaxation coefficient. Further, the relaxation coefficient may be set to 1, and the difference may be added as it is to the waveform of the current exciting voltage. Here, by removing the harmonic component from the measured waveform of the induced voltage in advance, it is possible to suppress the hunting of the indicated waveform of the exciting voltage, which cannot be suppressed even by using the relaxation coefficient.

At the start of measurement, there is no measurement waveform of the induced voltage. Therefore, the waveform correction unit 413 adopts the target waveform of the induced voltage stored in the target waveform storage unit 412 as the initial value of the indicated waveform of the exciting voltage. In this way, from the beginning of the measurement, the exciting voltage having the same waveform as the target waveform is output from the exciting power supply 401, and the time until the induced voltage is determined to have converged by the convergence test unit 414 described later. Is preferable because it accelerates. However, the initial value of the indicated waveform of the exciting voltage is not limited to the target waveform of the induced voltage, and may be any waveform.

<Convergence determination unit 414, S503 to S504>
The convergence determination unit 414 determines whether or not the measurement waveform of the induced voltage measured by the voltmeter 405 has converged to the target waveform of the induced voltage stored in the target waveform storage unit 412. In the present embodiment, the convergence determination unit 414 targets the measured waveform of the induced voltage by using the integrated value for one cycle of the absolute value of the difference between the target waveform of the induced voltage and the measured waveform at the time corresponding to each other. Determine if it has converged to the waveform. Specifically, the target waveform of the induced voltage is V _A (t), the measured waveform of the induced voltage is V _P (t), one cycle initiation of, t _s end times, respectively, when t _e, convergence The determination unit 414 determines that the measured waveform of the induced voltage has converged to the target waveform when the following equation (8) is satisfied, and determines that the measured waveform of the induced voltage has not converged to the target waveform otherwise. To do. Further, the convergence test unit 414 may use the following equation (9) instead of the equation (8).

Equation (8) is an example in which the integrated value for one cycle of the absolute value of the difference between the target waveform of the induced voltage and the measured waveform at the time corresponding to each other is used as it is. In equation (9), the integrated value for one cycle of the absolute value of the difference between the target waveform of the induced voltage and the measured waveform at the time corresponding to each other is the integrated value for one cycle of the absolute value of the target waveform of the induced voltage. This is an example when expressed as a ratio to the integrated value.

In order to reduce noise during measurement, the convergence test unit 414 removes higher-order harmonic components contained in the induced voltage induced in the search coil 404 for the measurement sample S, and then uses Eq. (8) or (9). It is preferable to calculate the formula. For example, the convergence determination unit 414 performs a fast Fourier transform on the waveform of the induced voltage induced in the search coil 404 for the measurement sample S, for example, removes the spectrum of the harmonic component of the 20th order or higher, and then Fourier inverse. Perform the conversion. By doing so, it is possible to remove high-order harmonic components included in the induced voltage induced in the search coil 404 with respect to the measurement sample S.

When the convergence determination unit 414 determines that the measured waveform of the induced voltage has not converged to the target waveform, the waveform correction unit 413 corrects the above-mentioned excitation voltage indicated waveform. That is, the waveform correction unit 413 repeatedly corrects the above-mentioned excitation voltage instruction waveform until it is determined by the convergence test unit 414 that the measured waveform of the induced voltage has converged to the target waveform of the induced voltage.

<Magnetic flux density derivation unit 415, S505>
When the flux density deriving unit 415 determines that the induced voltage measurement waveform has converged to the target waveform by the convergence determination unit 414, and the convergence determination unit 414 determines that the induced voltage measurement waveform has converged to the target waveform. The measurement waveform of the induced voltage measured in 1 is V (t), the number of turns of the search coil 404 with respect to the measurement sample S is N, and the cross-sectional area of the electromagnetic steel plate in the search coil 404 with respect to the measurement sample S is S. ) And (2), the magnetic flux density B (t) in the measurement sample S is obtained for one cycle. In order to reduce noise during measurement, the magnetic flux density derivation unit 415 is the higher order included in the induced voltage induced in the search coil 404 for the measurement sample S, as described in the section of the convergence determination unit 414. It is preferable to perform the calculation based on the equations (1) and (2) after removing the harmonic component of.

<Magnetic field strength derivation unit 416, S506>
When the convergence determination unit 414 determines that the measured waveform of the induced voltage has converged to the target waveform, the magnetic field strength deriving unit 416 determines that the measured waveform of the induced voltage has converged to the target waveform by the convergence determination unit 414. The exciting current measured by the current meter 403 at the same timing as the measured waveform of the induced voltage measured at this time is I (t) [A], the number of turns of the exciting coil 402 is N _1, and the magnetic path of the measurement sample S. With the length as l [m], the magnetic field strength H (t) in the measurement sample S is obtained for one cycle by the following equation (10).
H (t) = N ₁ × I (t) ÷ l ・ ・ ・ (10)

In order to reduce noise during measurement, it is preferable that the magnetic field strength derivation unit 416 performs the calculation of Eq. (10) after removing the higher-order harmonic components contained in the exciting current. For example, the magnetic field strength derivation unit 416 performs a fast Fourier transform on the waveform of the exciting current, removes the spectrum of a harmonic component of, for example, the 20th order or higher, and then performs the inverse Fourier transform. By doing so, it is possible to remove high-order harmonic components contained in the exciting current.

<Iron loss derivation unit 417, S507>
The iron loss derivation unit 417 is a BH curve (hysteresis curve) from the magnetic flux density B (t) derived by the magnetic flux density derivation unit 415 and the magnetic field strength H (t) derived by the magnetic field strength derivation unit 416. To create. The BH curve (hysteresis curve) created in this way reflects not only the hysteresis loss but also the contribution due to the eddy current loss. Therefore, the iron loss deriving unit 417 derives the area of the BH curve as the iron loss of the measurement sample S. When creating the BH curve, the iron loss derivation unit 417 extracts a set of values at the same time t as a set of the magnetic flux density B (t) and the magnetic field strength H (t). In this case, the induced voltage measured by the voltmeter 405 and the value at the same time as the exciting current measured by the ammeter 403 are input to the magnetic flux density derivation unit 415 and the magnetic field strength derivation unit 416, respectively.

<Output unit 418, S508>
The output unit 418 outputs information on the iron loss of the measurement sample S derived by the iron loss derivation unit 417. As the output form, for example, at least one of display on a computer display, transmission to an external device, and storage in an external or internal storage medium of the arithmetic unit 410 can be adopted.

(Example)
Next, an embodiment will be described.
FIG. 6 is a diagram showing an example of the configuration of an IPM (Interior Permanent Magnet) motor 600, which is an electric device whose magnetic characteristics are to be measured. FIG. 6A shows a cross section of the IPM motor 600 cut along a direction perpendicular to its rotation axis, and FIG. 6B shows an enlarged view of the broken line region of FIG. 6A. Is. The specifications of the IPM motor 600 used in this embodiment are outlined below.
Number of phases: 3
Number of poles: 4
Outer diameter of stator: φ112 [mm]
Number of stator slots: 24
Rotor outer diameter: φ55 [mm]
Rotor stacking thickness: 60 [mm]
Material of stator core and rotor core: 35A300
Here, 35A300 is a non-oriented electrical steel sheet described in Non-Patent Document 4.

As shown in FIG. 6B, the magnetic characteristics (iron loss) in the region 601 at the tip of the teeth of the stator core of the IPM motor 600 were obtained by the method of the invention example and the method of the comparative example, respectively. The method of the invention example is the method described in this embodiment. In the method of the comparative example, in the arithmetic unit 410 described in the present embodiment, when the indicated waveform of the induced voltage is generated and the convergence is determined, the target waveform and the measurement of the magnetic flux density are replaced with the target waveform and the measured waveform of the induced voltage. This is a method that uses waveforms.

FIG. 7 is a diagram showing an example of the measured waveform of the induced voltage and the target waveform. FIG. 7A shows a comparative example, and FIG. 7B shows an invention example.
As shown in FIGS. 7 (a) and 7 (b), it can be seen that the measured waveform of the induced voltage in the invention example is closer to the target waveform than in the comparative example. The iron loss of the measurement sample S obtained in the comparative example was lower than the iron loss of the measurement sample S obtained in the invention example by about 2 [%]. This is because, in the comparative example, the deviation between the measured waveform of the induced voltage and the target waveform causes a deviation in the magnetic field strength because the exciting current corresponding to the target waveform of the induced voltage is not obtained. It is considered that this is because the harmonic component contained in the voltage is not included in the waveform of the magnetic field density.

(Summary)
As described above, in the present embodiment, the waveform of the induced voltage detected in the predetermined region of the core when the core of the electric device is excited under the predetermined excitation conditions is set as the target waveform of the induced voltage. The waveform correction unit 413 corrects the indicated waveform of the exciting voltage according to the difference between the measurement waveform of the induced voltage induced in the measurement sample S and the target waveform, and the convergence determination unit 414 targets the measurement waveform of the induced voltage. Repeat until it is determined that the waveform has converged. The convergence determination unit 414 measures the induced voltage when the value using the integrated value for one cycle of the absolute value of the difference between the measured waveform of the induced voltage and the target waveform at each time is equal to or less than the reference value. It is determined that the waveform has converged to the target waveform. Then, the iron loss derivation unit 417 determines the induced voltage measured by the voltmeter 405 and the ammeter 403, the magnetic flux density based on the exciting current, and the magnetic field strength when it is determined that the measured waveform of the induced voltage has converged to the target waveform. Based on this, the iron loss of the measurement sample S is derived. Therefore, even when the exciting voltage contains a harmonic component and the magnetic flux density in the measurement sample S contains a harmonic component, the harmonic component can be extracted. Moreover, since the averaged value is not used when determining whether or not the measured waveform of the induced voltage has converged to the target waveform, the induced voltage is measured even when the target waveform of the induced voltage contains a harmonic component. The waveform can be converged to the target waveform with high accuracy. Therefore, even if the magnetic flux density in the local region of the core of the electric device is not a sine wave, the iron loss in the region can be derived with high accuracy.

(Modification example)
In the present embodiment, the convergence determination unit 414 uses the integrated value of the absolute value of the difference between the target waveform of the induced voltage and the measured waveform at the time corresponding to each other for one cycle, and the measured waveform of the induced voltage is the target waveform. Judge whether or not it has converged to. However, it is not always necessary to do this. The convergence determination unit 414 induces the measurement waveform of the induced voltage by using the result of obtaining (absolute value) of the amplitude difference (absolute value) of the same frequency component of the target waveform of the induced voltage and the measured waveform for each of the plurality of frequency components. It may be determined whether or not the target waveform of the voltage has converged. For example, the convergence test unit 414 performs a fast Fourier transform on each of the target waveform and the measurement waveform of the induced voltage, and obtains spectra (amplitudes) for each of a plurality of frequency components. Then, the convergence test unit 414 obtains the absolute value of the difference between the spectra of the same frequency component for each of the plurality of frequency components. As the plurality of frequency components, a frequency component of the fundamental wave and a frequency component corresponding to the 2nd to nth harmonics (n is an integer of 3 or more) can be adopted. Then, the convergence test unit 414 determines whether or not the absolute value of the difference between the spectra of a certain frequency component is equal to or less than a reference value preset for the frequency component of the plurality of frequency components. Do for each. Then, the convergence determination unit 414 determines that the measured waveform of the induced voltage is the induced voltage when the absolute value of the difference in the spectrum is equal to or less than the reference value preset for the frequency component for all of the plurality of frequency components. It is determined that the waveform has converged to the target waveform of the induced voltage, and if not, it is determined that the measured waveform of the induced voltage has not converged to the target waveform of the induced voltage.
Further, each part of the arithmetic unit 410 may be composed of a plurality of devices.

The embodiment of the present invention described above can be realized by executing a program by a computer. Further, a computer-readable recording medium on which the program is recorded and a computer program product such as the program can also be applied as an embodiment of the present invention. As the recording medium, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a non-volatile memory card, a ROM, or the like can be used.
In addition, the embodiments of the present invention described above are merely examples of embodiment of the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. It is a thing. That is, the present invention can be implemented in various forms without departing from the technical idea or its main features.

(Relationship with claims)
An example of the correspondence between the claims and the embodiments will be described below. It should be noted that the description of the claims is not limited to the description of the embodiment, as described in the modified examples and the like.
<Claims 1 and 6>
The application means is realized by using, for example, an exciting power supply 401.
The first coil is realized, for example, by using the search coil 404.
The first detection means is realized by using, for example, a voltmeter 405.
The second detection means is realized, for example, by using an ammeter 403.
The acquisition means is realized, for example, by using the target waveform acquisition unit 411.
The determination means is realized, for example, by using the convergence test unit 414.
The correction means is realized, for example, by using the waveform correction unit 413.
The iron loss derivation means is realized by using, for example, a magnetic flux density derivation unit 415, a magnetic field strength derivation unit 416, and an iron loss derivation unit 417.
Integrated value of one period of the absolute value of the difference between the value of the induced voltage in the mutually corresponding time measurement waveform and the target waveform of the induced voltage of the induced voltage, for example, the target waveform of the induced voltage and the measured waveform The difference (absolute value) at the time corresponding to each other is used as it is, or the integrated value for one cycle of the absolute value of the difference between the target waveform of the induced voltage and the measurement waveform at the time corresponding to each other is used as the induced voltage. It is realized by taking the ratio of the value of the target waveform of to the integrated value for one cycle of the absolute value (see the left side of the equation (8) and the left side of the equation (9)).
The difference in amplitude between the plurality of frequency components included in the measured waveform of the induced voltage and the plurality of frequency components included in the target waveform of the induced voltage in the same frequency component is, for example, between the target waveform of the induced voltage and the measured waveform. It is realized by obtaining the spectra of multiple frequency components from each and taking (absolute value) the difference (absolute value) of the spectra of the same frequency component in the target waveform and the measured waveform of the induced voltage for each of the multiple frequency components ((deformation) Example)).
<Claim 2>
The waveform of the induced voltage induced in the second coil wound around the predetermined region of the core is, for example, a search coil wound around a predetermined region (region for measuring magnetic characteristics) of the core of an electric device. It is realized by using the waveform of the induced voltage induced in.
<Claims 3 and 5>
The numerical solution of the magnetic flux density vector in the two-dimensional space of the core is, for example, a magnetic flux density vector generated in a predetermined region of the core by applying a predetermined exciting voltage to the exciting winding that excites the core of the electric device. , Obtained by performing a two-dimensional numerical analysis based on Maxwell's equation.
The waveform of the induced voltage in the predetermined region of the core obtained based on the numerical solution of the magnetic flux density vector in the two-dimensional space of the core is, for example, the magnetic flux density for one cycle in the predetermined region of the core of the electric device. It is obtained by obtaining the waveform for one cycle of the induced voltage from the vector based on the equations (1) and (2).
<Claim 4>
The numerical solution of the magnetic flux density vector in the two-dimensional space of the core has a component in the plate surface direction of the magnetic material and does not have a component in the plate thickness direction of the magnetic material. The density vector corresponds to having a component in the plate surface direction of the electromagnetic steel plate constituting the core and not having a component in the plate thickness direction.

401: Exciting power supply, 402: Exciting coil, 403: Ammeter, 404: Search coil, 405: Voltmeter, 410: Computational device, 411: Target waveform acquisition unit, 412: Target waveform storage unit, 413: Waveform correction unit, 414: Convergence judgment unit, 415: Magnetic flux density derivation unit, 416: Magnetic field strength derivation unit, 417: Iron loss derivation unit, 418: Output unit, S: Measurement sample

Claims (7)

An application means for applying an exciting voltage to an exciting coil for exciting a measurement sample made of a magnetic material, and
A first detection means for detecting an induced voltage induced in the first coil by exciting the measurement sample, and
A second detecting means for detecting the exciting current flowing through the exciting coil when the exciting voltage is applied to the exciting coil by the applying means.
An acquisition means for acquiring the target waveform of the induced voltage, and
A determination means for determining whether or not the measurement waveform of the induced voltage detected by the first detecting means has converged to the target waveform of the induced voltage.
When the determination means determines that the measured waveform of the induced voltage does not converge to the target waveform of the induced voltage, the measured waveform of the induced voltage detected by the first detecting means and the induced voltage A correction means for correcting the excitation voltage based on the difference from the target waveform of
When it is determined by the determination means that the measurement waveform of the induced voltage has converged to the target waveform of the induced voltage, the induced voltage detected by the first detecting means and the second detecting means detect the induced voltage. It has an iron loss deriving means for deriving the iron loss of the measurement sample based on the excited current.
When the exciting voltage is corrected by the correcting means, the applying means applies the corrected exciting voltage to the exciting coil.
Until it is determined by the determination means that the measurement waveform of the induced voltage detected by the first detection means has converged to the target waveform of the induced voltage, the correction of the exciting voltage by the correction means and the correction of the excitation voltage. The application of the exciting voltage by the applying means and the detection of the induced voltage by the first detecting means are repeatedly performed.
Said determining means, measured waveform and the integrated value of one period of the absolute value of the difference between the value of the induced voltage in the mutually corresponding time of target waveform of the induced voltage of the induced voltage, or of the induced voltage Based on the difference in amplitude between the plurality of frequency components included in the measurement waveform and the plurality of frequency components included in the target waveform of the induced voltage in the same frequency component , the measured waveform of the induced voltage is the target waveform of the induced voltage. A magnetic characteristic measurement system characterized in determining whether or not convergence has occurred. The acquisition means is used in a predetermined region of the core when the core of an electric device having a core made of the same type of magnetic material as the magnetic material constituting the measurement sample is excited under predetermined excitation conditions. The waveform of the induced voltage is acquired as the target waveform of the induced voltage.
The waveform of the induced voltage in a predetermined region of the core is a measured waveform of the induced voltage for the electric device.
The magnetic characteristic according to claim 1, wherein the measured waveform of the induced voltage for the electric device is a waveform of the induced voltage induced in the second coil wound around the predetermined region of the core. Measurement system. The acquisition means is used in a predetermined region of the core when the core of an electric device having a core made of the same type of magnetic material as the magnetic material constituting the measurement sample is excited under predetermined excitation conditions. The waveform of the induced voltage is acquired as the target waveform of the induced voltage.
The waveform of the induced voltage in a predetermined region of the core is an analysis waveform of the induced voltage for the electric device.
The analysis waveform of the induced voltage for the electric device is a waveform of the induced voltage in the predetermined region of the core obtained based on a numerical solution of the magnetic flux density vector in the two-dimensional space of the core. Item 1. The magnetic characteristic measurement system according to Item 1. The core has a plurality of plate-shaped magnetic materials stacked on each other.
The shape of the magnetic material constituting the measurement sample is plate-like.
3. The numerical solution of the magnetic flux density vector in the two-dimensional space of the core is characterized in that it has a component in the plate surface direction of the magnetic material and does not have a component in the plate thickness direction of the magnetic material. The magnetic property measurement system described in. The acquisition means numerically analyzes the numerical solutions of the magnetic flux density vector and the eddy current vector generated in the two-dimensional space of the core when the core of the electric device is excited under a predetermined excitation condition, based on Maxwell's equation. 3 or 4 is characterized in that the waveform of the induced voltage obtained based on the numerical solution of the obtained magnetic flux density vector is obtained as the target waveform of the induced voltage in the measurement sample. The magnetic characteristic measurement system described in. The correction means removes higher-order harmonic components included in the measurement waveform of the induced voltage detected by the first detecting means, and then based on the difference between the induced voltage and the target waveform. The magnetic characteristic measuring system according to any one of claims 1 to 5, wherein the exciting voltage is corrected. An application process in which an exciting voltage is applied to an exciting coil for exciting a measurement sample made of a magnetic material, and
The first detection step of detecting the induced voltage induced in the first coil by exciting the measurement sample, and
A second detection step of detecting the exciting current flowing through the exciting coil by applying the exciting voltage to the exciting coil by the application step, and
The acquisition process for acquiring the target waveform of the induced voltage and
A determination step of determining whether or not the measurement waveform of the induced voltage detected by the first detection step has converged to the target waveform of the induced voltage.
When it is determined by the determination step that the measured waveform of the induced voltage does not converge to the target waveform of the induced voltage, the measured waveform of the induced voltage detected by the first detection step and the induced voltage The correction step of correcting the excitation voltage based on the difference from the target waveform of
When it is determined by the determination step that the measurement waveform of the induced voltage has converged to the target waveform of the induced voltage, the induced voltage detected by the first detection step and the detection by the second detection step are detected. It has an iron loss derivation step of deriving the iron loss of the measurement sample based on the excited current.
In the application step, when the exciting voltage is corrected by the correction step, the corrected exciting voltage is applied to the exciting coil.
The correction of the excitation voltage by the correction step and the correction of the excitation voltage by the correction step until it is determined by the determination step that the measurement waveform of the induced voltage detected by the first detection step has converged to the target waveform of the induced voltage. The application of the exciting voltage by the application step and the detection of the induced voltage by the first detection step are repeatedly performed.
The determining step, measured waveform and the integrated value of one period of the absolute value of the difference between the value of the induced voltage in the mutually corresponding time of target waveform of the induced voltage of the induced voltage, or of the induced voltage Based on the difference in amplitude between the plurality of frequency components included in the measurement waveform and the plurality of frequency components included in the target waveform of the induced voltage in the same frequency component , the measured waveform of the induced voltage is the target waveform of the induced voltage. A method for measuring magnetic characteristics, which comprises determining whether or not the voltage has converged to.

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