JP6984426B2 - Electromagnetic field analyzer, electromagnetic field analysis method, and program - Google Patents

Description

The present invention relates to an electromagnetic field analyzer, an electromagnetic field analysis method, and a program, and is particularly suitable for use in analyzing magnetic characteristics including the magnetic flux density of an excited magnetic material.

Conventionally, numerical analysis of magnetic properties including the magnetic flux density of an excited magnetic material has been performed. At this time, if the basic equation (governing equation) is finely discretized and three-dimensional numerical analysis is performed, the magnetic characteristics can be analyzed accurately. However, such a method increases the calculation time. For example, when evaluating the performance of an electric device including a magnetic material such as a motor, it is necessary to numerically analyze the magnetic characteristics of the magnetic material excited according to the operating conditions of the electric device. In this case, it is necessary to obtain the magnetic characteristics for each of the various operating conditions. Therefore, the calculation time becomes very long.

Therefore, there is a technique described in Non-Patent Document 1 as a technique for numerically analyzing the magnetic properties of an excited magnetic material so that the calculation accuracy is not significantly reduced and the calculation time is not lengthened.
In Non-Patent Document 1, a three-dimensional non-stationary unsteady finite element method analysis in which the conductivity in the thickness direction of the electrical steel sheet is 0 (zero) using an element thicker than the electrical steel sheet is performed in the plane of the electrical steel sheet. By obtaining the magnetic flux density of the directional component (plate surface direction component) and performing a one-dimensional unsteady finite element method analysis in the thickness direction of the electrical steel sheet, assuming that the magnetic flux density of the in-plane component of the electrical steel sheet is known, the electrical steel sheet can be obtained. It is described that the distribution of the magnetic flux density of the in-plane component in the thickness direction of the electrical steel sheet is obtained.

Katsumi Yamazaki, Rin Satomi, "Characteristic analysis of induction motors by finite element method directly considering eddy current of electrical steel sheet", Institute of Electrical Engineers of Japan Magnetics Study Group materials, MAG-08-32, SA-08-20, RM- 08-20, p. 39-44, January 25, 2008 Takayoshi Nakata, Norio Takahashi, "Limited Element Method of Electrical Engineering", 2nd Edition, Morikita Publishing Co., Ltd., April 1986

However, in the technique described in Non-Patent Document 1, there is no reference to magnetic permeability (reciprocal of magnetic permeability), and the same thing is used in the three-dimensional nonlinear unsteady finite element method analysis and the one-dimensional unsteady finite element method analysis. Probably used. That is, in the technique described in Non-Patent Document 1, it is considered that the magnetic permeability in the element is the same. Therefore, in the one-dimensional unsteady finite element method analysis, the influence of the skin effect cannot be fully considered. Therefore, the accuracy of the magnetic characteristics including the magnetic flux density of the excited magnetic material may decrease.

The present invention has been made in view of the above problems, and when the magnetic characteristics including the magnetic flux density of the excited magnetic material are obtained by numerical analysis, the calculation load is reduced and the calculation accuracy is lowered. The purpose is to achieve both suppression and suppression.

The electromagnetic field analysis device of the present invention is an electromagnetic field analysis device that analyzes the magnetic properties of an excited magnetic material at each time step by numerical analysis based on the Maxwell equation, and is a value of an in-plane component of the magnetic flux density in the magnetic material. Is derived by numerical analysis for each of the first small regions of the three dimensions obtained by dividing the region of the magnetic material, with the first derivation means executed at each time step and the first derivation. For each of the three-dimensional second small regions obtained by dividing the first small region in the direction perpendicular to the in-plane direction based on the value of the in-plane component of the magnetic flux density derived by the means. In addition, the second derivation means for executing the derivation of the value of the in-plane component of the magnetic flux density in the magnetic material by numerical analysis at each time step and the second subregion by the second derivation means. Based on the value of the in-plane component of the magnetic flux density in the magnetic material derived from the above, the value of the in-plane component of the magnetic permeability of the magnetic material in the second small region can be derived. It has a third derivation means executed in a time step, and the magnetic permeability has a origin in a curve showing the relationship between the magnetic flux density and the magnetic field strength and a point on the curve determined according to the magnetic flux density. Represented by the slope of the connecting straight line, the second derivation means is used to derive the value of the in-plane component of the magnetic flux density in the magnetic material by numerical analysis for each of the second small regions at a certain time step. In addition, in the time step prior to the time step, the value of the in-plane component of the magnetic permeability of the magnetic material derived with respect to the second small region by the third derivation means is set to the second. It is characterized in that it is used as the value of the in-plane component of the magnetic permeability of the magnetic material in the small region of.

The electromagnetic field analysis method of the present invention is an electromagnetic field analysis method for analyzing the magnetic properties of an excited magnetic material at each time step by numerical analysis based on the Maxwell equation, and is a value of an in-plane component of the magnetic flux density in the magnetic material. Is derived by numerical analysis for each of the first small regions of the three dimensions obtained by dividing the region of the magnetic material, that is, the first derivation step executed at each time step and the first derivation. For each of the three-dimensional second small regions obtained by dividing the first small region in the direction perpendicular to the in-plane direction based on the value of the in-plane component of the magnetic flux density derived by the step. In addition, the second derivation step of performing numerical analysis to derive the value of the in-plane component of the magnetic flux density in the magnetic material at each time step and the second small region by the second derivation step. Based on the value of the in-plane component of the magnetic flux density in the magnetic material derived from the above, the value of the in-plane component of the magnetic permeability of the magnetic material in the second small region can be derived. It has a third derivation step performed in a time step, and the magnetic permeability has a origin in a curve showing the relationship between the magnetic flux density and the magnetic field strength and a point on the curve determined according to the magnetic flux density. Represented by the slope of the connecting straight line, the second derivation step is when the value of the in-plane component of the magnetic flux density in the magnetic material is derived by numerical analysis for each of the second small regions in a certain time step. In addition, in the time step prior to the time step, the value of the in-plane component of the magnetic permeability of the magnetic material derived for the second small region by the third derivation step is set to the second. It is characterized in that it is used as a value of an in-plane component of the magnetic permeability of the magnetic material in a small region of.

The program of the present invention causes a computer to function as each means of an electromagnetic field analyzer.

According to the present invention, when the magnetic characteristics including the magnetic flux density of the excited magnetic material are obtained by numerical analysis, it is possible to realize both the reduction of the calculation load and the suppression of the decrease in the calculation accuracy.

FIG. 1 is a diagram showing an example of a functional configuration of an electromagnetic field analyzer. FIG. 2 is a diagram conceptually showing an example of an element set on an electromagnetic steel sheet. FIG. 3 is a diagram conceptually showing an example of the magnetic flux in the first element and the magnetic flux in each of the second elements. FIG. 4 is a diagram conceptually showing an example of magnetic permeability. FIG. 5 is a flowchart illustrating an example of the electromagnetic field analysis method. FIG. 6 is a diagram showing an example of calculation results of hysteresis loss, eddy current loss, and iron loss.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiment, the case where the finite element method is used as the numerical analysis will be described as an example. Further, a case where the magnetic material to be the target of the numerical analysis is an electromagnetic steel sheet, which is a kind of soft magnetic material, will be described as an example. Further, a case where the magnetic characteristics of a veneer (one electromagnetic steel sheet) excited by a veneer magnetic property tester is obtained by a finite element method will be described as an example. However, the numerical analysis is not limited to the finite element method, and may be, for example, a finite difference method. Further, the magnetic material to be analyzed is not limited to the electromagnetic steel sheet, and may be, for example, permalloy. Further, the composition of the magnetic material to be analyzed is not limited to a single plate, and may be a plurality of sheets, and may be, for example, a stator core of a rotary electric machine (motor, generator). Further, in the present embodiment, the case where the in-plane direction component of the electromagnetic steel plate is represented by the x component and the y component in the x-yz orthogonal coordinate system and the thickness direction component is represented by the z-axis component is taken as an example. As described above, the in-plane component of the electromagnetic steel plate may be represented by circular coordinates (radial component and angular component).

<Structure of electromagnetic field analyzer 100>
FIG. 1 is a diagram showing an example of a functional configuration of the electromagnetic field analyzer 100. The electromagnetic field analysis device 100 is realized by using, for example, a CPU, a ROM, a RAM, an HDD, an information processing device having various interfaces, or dedicated hardware.

[Data storage unit 101]
The data storage unit 101 stores various known data used by the two-dimensional analysis unit 102 and the one-dimensional analysis unit 103. The data storage unit 101 stores, for example, excitation condition data, conductivity σ of an electromagnetic steel sheet, and magnetic characteristic data.
The excitation condition data is data that specifies the _{excitation current density J 0 at each time in one cycle.}
The electrical conductivity σ of the electrical steel sheet is a material property of the electrical steel sheet. The conductivity σ of the electromagnetic steel sheet is determined for each material (steel type) of the electromagnetic steel sheet.

Magnetic characteristic data, the magnetic flux density (the x and y components) B _x electromagnetic steel plates, and B _y, the permeability (of the x and y components) mu _x, the relationship between the mu _y each frequency, for each material It is the data to show. In the present embodiment, as data indicating a magnetic flux density of the electromagnetic steel sheet (the x and y components) B _x, and B _y, the magnetic field strength H (in x and y components) H _x, the relationship between the H _y, first The case of using the data of the magnetization characteristics will be described as an example. For such magnetic property data, for example, the initial magnetization characteristics (curve showing the initial magnetization characteristics) of the electrical steel sheet are individually created for each of the x component and the y component from the results of the (actual) magnetic property test on the electrical steel sheet. and, from the first magnetization characteristics, the magnetic flux density (the x and y components) B _x, (x and y components of) permeability at B _y mu _x, obtained by determining the mu _y. The magnetic permeability is a straight line connecting the origin of the curve showing the relationship between the magnetic flux density and the magnetic field strength (the curve showing the initial magnetization characteristics in this embodiment) and the point on the curve determined according to the magnetic flux density. It is expressed by the inclination.

In this embodiment, the magnetic characteristic data, the x component B _x of a magnetic flux density of the electromagnetic steel sheets, a table that associates and stores each other and x components mu _x permeability, y component B _y of the magnetic flux density of the electromagnetic steel plates And a table for storing the y component μ _y of the magnetic permeability in association with each other.
The values not stored in this table can be derived, for example, by interpolation processing or extrapolation processing using the values stored in this table. Further, the relational expression showing the above-mentioned relationship may be used as the magnetic characteristic data without using the table.
In addition, the data storage unit 101 stores various data used by the two-dimensional analysis unit 102 and the one-dimensional analysis unit 103.

[Two-dimensional analysis unit 102]
The two-dimensional analysis unit 102 performs electromagnetic field analysis using the non-stationary unsteady two-dimensional finite element method, so that each of the first elements has the magnetic flux density (x) of the electromagnetic steel plate when excited according to the excitation condition data. and y components) B _x, derives the B _y. FIG. 2 is a diagram conceptually showing an example of an element set on an electromagnetic steel sheet. In the present embodiment, as shown in FIG. 2A, the thickness direction of the electrical steel sheet is not divided, and each three-dimensional region in which the electrical steel sheet is divided in the in-plane direction (x-axis direction and y-axis direction) is divided. Let it be the first element.

Further, in the present embodiment, a case where the A−φ method is used as a method of electromagnetic field analysis using the finite element method will be described as an example. In this case, the basic equations for performing electromagnetic field analysis are given by the following equations (1) to (4) based on Maxwell's equations. In each equation, → indicates that it is a vector. Since the method for performing electromagnetic field analysis is a general method as described in Non-Patent Document 2 and the like, detailed description thereof will be omitted.

In equations (1) to (4), μ is the magnetic permeability, A is the vector potential, σ is the conductivity, J ₀ is the exciting current density, and Je is the eddy current. It is a density, and B is a magnetic flux density. In equations (1) to (4), the x component A _x and y component A _y of the vector potential and ∂ / ∂z are set to 0 (zero), respectively (A _x = A _y = 0, ∂ / ∂z =). 0), (1) and (2) are solved simultaneously to obtain the z component A _z of the vector potential and the scalar potential φ, and then the x component of the magnetic flux density is obtained from the equations (3) and (4). and B _x and y components B _y, obtaining a x component Je _x and y components Je _y eddy current density for each of the first element. In equation (1), in order to simplify the notation, the equation when the x component μ _x , y component μ _y , and z component μ _{z of} magnetic permeability are equal (when μ _x = μ _y = μ _z ) is used. show.

At this time, the two-dimensional analysis unit 102 reads out the _{magnetic permeability (x component and y component) μ x} and μ _y from the magnetic characteristic data corresponding to the excitation frequency specified by the excitation condition data and the material of the magnetic steel sheet. .. In the electromagnetic field analysis by the two-dimensional analysis unit 102, the magnetic permeability (x component and y component) μ _x and μ _y in one first element have the same value.

Two-dimensional analysis section 102, as described above, the magnetic flux density (the x and y components) B _x of the electromagnetic steel sheets in each of the first element, deriving a B _y, stored in the data storage unit 101 This is performed at each time step t in one cycle in the excitation condition data. In the present embodiment, the value of the time step t at the beginning of one cycle in the excitation condition data is 0 (zero), and the value of the time step t at the end is t _max . Further, let Δt be the interval between time steps t that are adjacent in time.

[One-dimensional analysis unit 103]
The one-dimensional analysis unit 103 performs electromagnetic field analysis using the non-stationary unsteady one-dimensional finite element method, so that each of the first elements has the magnetic flux density (x) of the electromagnetic steel plate when excited according to the excitation condition data. and y components) B _x, deriving a z of axial distribution of B _y. A specific example of the processing of the one-dimensional analysis unit 103 will be described below.

First, as shown in FIG. 2B, the one-dimensional analysis unit 103 divides each of the first elements shown in FIG. 2A into a plurality of parts in the z-axis direction to generate a plurality of second elements. .. In this way, a plurality of second elements are included in one first element. In FIG. 2B, a case where nine second elements are included in one first element is shown as an example. One-dimensional analysis unit 103, based on the following (5a) expression and (5b) wherein deriving the respective second element, the magnetic flux density of the electromagnetic steel sheet (the x and y components) B _x, the B _y By doing so, the distribution of the magnetic flux densities (x component and y component) B _x and By _{y in} the z-axis direction is derived.

In the equations (5a) and (5b), the magnetic permeability μ is expressed for each of the x component, the y component, and the z component in the equation (1), and then the z component A _z , ∂ / ∂x, and ∂ of the vector potential. It is obtained by setting / ∂y to 0 (zero) (A _z = 0, ∂ / ∂x = 0, ∂ / ∂y = 0).

(5a) expression and (5b) formula is diffusion equation of the magnetic flux density distribution in the in-plane direction of the magnetic flux density of the electromagnetic steel sheet (x and y components of the magnetic flux density) B _x, B _y) is, z-axis It is a diffusion equation expressing how it is distributed (diffused) in the direction (thickness direction) using the conductivity σ and the magnetic permeability (x component and y component) μ _x and μ _{y of the electromagnetic steel plate.}

When solving the equations (5a) and (5b), the total amount of magnetic flux at the boundary surface of the first element and the boundary surface whose normal direction faces the x-axis direction is relative to the first element. A boundary condition indicating that the magnetic flux represented by the product of _{the magnetic flux density (x component) B x} derived by the two-dimensional analysis unit 102 and the area of the boundary surface is equal is used. Further, the total amount of magnetic flux at the boundary surface of the first element and the boundary surface whose normal direction faces the y-axis direction is the magnetic flux density derived from the two-dimensional analysis unit 102 for the first element. and y component) B _y, the boundary condition indicating that equal the magnetic flux represented by the product of the area of the boundary surface is used. Specifically, in the present embodiment, the following equations (6a) to (6d) are used as the boundary conditions of the first element.

In the formulas (6a) to (6d), h is the plate thickness of the electrical steel sheet. Equations (6a) and (6c) are boundary conditions for the first element on the surface of the first element. Equations (6b) and (6d) are boundary conditions of the first element at the center of the electromagnetic steel sheet of the first element in the plate thickness direction (z-axis direction). _{B x (t), B y} (t) is, x component of the magnetic flux density of the first element that is derived by the two-dimensional analysis unit 102 at time step t, the y-component _{(B x (t), B} y (T) is a value for each time step t and for each first element).

Under the above boundary conditions, the one-dimensional analysis unit 103 solves the equations (5a) and (5b) by the nonlinear unsteady one-dimensional finite element method, so that the vector potential (x component of) is obtained in each of the second elements. , Y component) A _x , A _y are derived. Then, the one-dimensional analysis unit 103 sets the vector potentials (x component and y component) A _x and A _{y in the second element to A z} = 0, ∂ / ∂x = 0 and ∂ / in the equation (4). by providing the ∂y = 0 and the equations to derive the magnetic flux density (the x and y components) of the second element B _x, the B _y. One-dimensional analysis unit 103 performs such magnetic flux density (the x and y components) B _x, the derivation of B _y in each of the second element. Since the initial conditions and the boundary conditions of the electrical steel sheet can be appropriately set in the same manner as known techniques, detailed description thereof will be omitted here.

FIG. 3 is a diagram conceptually showing an example of the magnetic flux in the first element and the magnetic flux in each of the second elements.
The left figure of FIG. 3 conceptually represents the magnetic flux (x component and y component) in the first element. The two-dimensional analysis unit 102 derives the magnetic flux densities (x component and y component) B _x and By by one for each first _element. Therefore, in the example shown on the left side of FIG. 3, the total amount of the magnetic flux in the x-axis direction in the first element is the magnetic flux density (x component) B _x of the first element and the x of the first element. It is the value obtained by multiplying the area of the cross section perpendicular to the axis. Similarly, the total amount of y-axis direction of the magnetic flux in the first element, said the first element of the magnetic flux density (y components) B _y, multiplied by the area of the cross section perpendicular to the y axis of the first element Value. The arrow line in the left figure of FIG. 3 represents the total amount of magnetic flux in the x-axis direction and the y-axis direction in the first element.

The one-dimensional analysis unit 103 solves the equations (5a) and (5b) according to the boundary conditions of the equations (6a) to (6d), so that the magnetic flux density in each of the second elements included in the first element (the x and y components) B _x, derives the B _y. Then, the arrow lines (total amount of magnetic flux in the x-axis direction and the y-axis direction in the first element) shown in the left figure of FIG. 3 are distributed to each of the second elements included in the first element, and the figure is shown. It becomes like the arrow line shown in the right figure of No. 3 (the magnetic flux in the x-axis direction and the y-axis direction in each of the second elements included in the first element). By doing so, the electromagnetic field analysis considering the skin effect can be performed in a much shorter time than the case where the electromagnetic field analysis is performed by the nonlinear unsteady three-dimensional finite element method as a fine element without setting the limitation of the conductivity. be able to.

Returning to the explanation of FIG. 2, the one-dimensional analysis unit 103 has the vector potentials (x component and y component) A _x and A _y in the second element, and the conductivity of the electromagnetic steel plate stored in the data storage unit 101. and sigma, the x component, based on the representation for each y component (3) performing eddy current density (the x component, y component) Je _x, in each of the second element to derive Je _y .. The gradeφ of the equation (3) used at this time is 0 (zero).

Further, the one-dimensional analysis unit 103 determines the magnetic flux density in the second element from the magnetic characteristic data corresponding to the excitation frequency specified by the excitation condition data stored in the data storage unit 101 and the material of the magnetic steel sheet. x and y components) B _x, x and y components of the corresponding permeability (in B _y) mu _x, reads out the mu _y. As described above, when the desired data is not stored in the magnetic characteristic data, the one-dimensional analysis unit 103 can derive the data by performing interpolation processing or extrapolation processing.

One-dimensional analysis unit 103, for each of the first element as described above, in each of the second element, the magnetic flux density (the x and y components) of the electromagnetic steel sheets B _x, B _y, eddy currents density (in the x component, y component) Je _x, Je _y, and permeability (the x and y components) mu _x, deriving a mu _y, in the actuated condition data stored in the data storage unit 101 This is performed at each time step t (t = 0 to t _max ) in one cycle.

Thus, for each of the first element, the magnetic flux density (the x and y components) B _x electromagnetic steel plates, z-axis direction of the distribution of B _y, eddy current density (the x component, y component) Je _x, The distribution of Je _{y in} the z-axis direction and the distribution of magnetic permeability (x component and y component) μ _x and μ _{y in} the z-axis direction are derived.

Here, the one-dimensional analysis unit 103 at time step t, the second magnetic flux density of the electromagnetic steel plates in each element (x and y components of) B _x included in the first element, the B _y (5a ) And the magnetic permeability (x component and y component) derived for the first element in the time step t−Δt immediately before the time step t when deriving based on the equation (5b). The distribution of μ _x and μ _{y in} the z-axis direction is used. However, in the first time step t (= 0), the one-dimensional analysis unit 103 determines the magnetic flux density (x component and y component) B _{x of the magnetic steel sheet in each of the second elements included in the first element.} , in deriving based B _y in (5a) expression and (5b) wherein the magnetic flux density (the x and y components) of the first element that is derived by the two-dimensional analysis section 102 B _x, B _The magnetic permeability (x component and y component) μ _x and μ _{y corresponding} to y are the magnetic characteristics corresponding to the exciting frequency and the material of the electrical steel sheet specified by the exciting condition data stored in the data storage unit 101. Read from the data and use.

Thus, in the first time step t (= 0), the magnetic permeability μ given to the equations (5a) and (5b) (the magnetic permeability (x component and y component) μ _x , μ in the first element) _y ) has no distribution in the z-axis direction and has the same value within one first element. On the other hand, in the second and subsequent time steps t, the magnetic permeability μ given to the equations (5a) and (5b) (permeability (x component and y component) μ _x , μ _{y in the first element} ). Has a distribution in the z-axis direction.

FIG. 4 is a diagram conceptually showing an example of magnetic permeability. FIG. 4 shows the initial magnetization characteristics (initial magnetization curve) as the relationship between the magnetic flux density B and the magnetic field strength H of the electrical steel sheet. Permeability μ is defined by the slope of a straight line passing through the origin of the magnetization curve (initial magnetization curve in FIG. 4) and a point on the magnetization curve (μ is the value obtained by dividing B by H (B = μH). Relationship). Therefore, when the magnetic flux density B changes, the position on the magnetization curve moves, so that the magnetic permeability μ also changes.

Therefore, as in the present embodiment, the element (first element) is divided in the thickness direction (z-axis direction) of the electrical steel sheet, and the magnetic flux density in each of the divided elements (second element) is derived. When the distribution of the magnetic flux density in the thickness direction of the electrical steel sheet is derived, the magnetic permeability of the electrical steel sheet also has a distribution in the thickness direction.

When the magnetic flux density is low, the magnetic steel sheet is not magnetically saturated (because the slope of the magnetization curve is constant), so that the magnetic permeability does not change much even if the magnetic flux density is different. Further, when the excitation frequency is low, the attenuation of the magnetic flux density due to the skin effect is small in the magnetic steel sheet, so that the magnetic permeability distribution of the electrical steel sheet is close to uniform. In these cases, even if the distribution of the magnetic permeability of the electromagnetic steel plate in the thickness direction is ignored and the magnetic permeability is calculated as being constant in the thickness direction of the electromagnetic steel plate (for example, as shown in FIG. 4A). , Even if it is calculated using the magnetic permeability represented by the inclination of the straight line 403 passing through the origin of the initial magnetization curve 401 and a certain point 402 in the low magnetic flux density region on the initial magnetization curve 401), the calculation accuracy. Is not considered to decrease significantly.

However, under exciting conditions such as high frequency and high magnetic flux density, the degree of attenuation of the magnetic flux density in the electromagnetic steel plate becomes large due to the skin effect, and the magnetic flux density changes greatly between the plate surface and the inside. Further, when the magnetic steel sheet is in a state of magnetic saturation or a state close to magnetic saturation, the magnetic permeability changes abruptly with a slight change in the magnetic flux density B due to the non-linearity of the magnetic characteristics. Therefore, assuming that the magnetic permeability is constant in the thickness direction of the electrical steel sheet, the actual phenomenon cannot be accurately reproduced, and the calculation accuracy may decrease.

Therefore, in the present embodiment, the magnetic permeability μ (magnetic permeability (x component and y component) μ _x , μ _y in the first element) given to the equations (5a) and (5b) is distributed in the z-axis direction. By having it, as shown in FIG. 4 (b), it is possible to adopt the magnetic permeability corresponding to each magnetic flux density (each point 402, 404, 405, 406 of the initial magnetization curve 401), and it is high. Even under excitation conditions such as frequency and high magnetic flux density, it is possible to suppress a decrease in calculation accuracy.

[Loss Derivation Unit 104]
The loss derivation unit 104 is used in each of the second elements by the one-dimensional analysis unit 103 _{in each time step t (t = 0 to t max} ) of one cycle in the excitation condition data stored in the data storage unit 101. , the magnetic flux density (the x and y components) B _x electromagnetic steel plates, B _y and eddy current density (the x component, y component) Je _x, when Je _y is derived, in each of the second element, Derivation of hysteresis loss and eddy current loss.

For example, the loss deriving unit 104, the magnetic flux density (the x and y components) of the second element B _x, derives the flux density vector from B _y, deriving the magnitude of the magnetic flux density vector, excitation It is performed at each time step t (t = 0 to t _max ) of one cycle in the condition data. _{From the result, the loss derivation unit 104 derives the difference B m} between the maximum value and the minimum value of the waveform showing the relationship between the magnitude of the magnetic flux density vector and the time, and the second element is derived from the following equation (7). Hysteresis loss Wh is derived.

In equation (7), f is the excitation frequency, Kh is the hysteresis loss coefficient, and β is a constant (for example, 1.6 or 2). The hysteresis loss coefficient Kh is obtained in advance by, for example, the dual frequency method.
The loss derivation unit 104 derives the above-mentioned hysteresis loss Wh for all the second elements, and derives the sum of the hysteresis loss Wh in all the second elements as the hysteresis loss of the electrical steel sheet. Incidentally, hysteresis loss may be derived in a known manner, the second element of the magnetic flux density (the x and y components) B _x, as long as it is a method for deriving with B _y, any method It may be derived with.

Moreover, the loss deriving unit 104, the eddy current density (the x component, y component) of the second element Je _x, derives the eddy current density vector from Je _y, to derive the magnitude Je of the eddy current density vector This is done at each time step t (t = 0 to t _max ) of one cycle in the excitation condition data. Then, the loss derivation unit 104 derives the eddy current loss We (classical eddy current loss) in the second element by the following equation (8).

In the equation (8), v is the volume of the second element, and T is the time corresponding to one cycle in the excitation condition data.
The loss derivation unit 104 derives the above eddy current loss We for all the second elements, and derives the sum of the eddy current losses We in all the second elements as the eddy current loss of the magnetic steel sheet. Incidentally, the eddy current loss can be derived in a known manner, the eddy current density (the x and y components) Je _x of the second element, as long as the method of deriving with Je _y, how It may be derived by any method.
Then, the loss derivation unit 104 derives the sum of the hysteresis loss and the eddy current loss of the electrical steel sheet as the iron loss of the electrical steel sheet.

[Output unit 105]
The output unit 105 outputs information including the hysteresis loss, the eddy current loss, and the iron loss of the electrical steel sheet derived by the loss derivation unit 104. As the form of output, for example, at least one of display on a computer display, storage in an internal / / and external storage medium of the electromagnetic field analyzer 100, and transmission to an external device can be adopted.

<Electromagnetic field analysis method>
FIG. 5 is a flowchart illustrating an example of an electromagnetic field analysis method using the electromagnetic field analysis device 100 of the present embodiment.
In step S501, the two-dimensional analysis unit 102 solves the equations (1) to (4) by the unsteady two-dimensional finite element method, so that the magnetic flux density (x component and y component) in each of the first elements is B _x, to derive the B _y.
Next, in step S502, the one-dimensional analysis unit 103 selects one unselected first element among the first elements.

Next, in step S503, the one-dimensional analysis unit 103 divides the first element selected in step S502 into a plurality of parts in the z-axis direction, and generates a plurality of second elements.
Next, in step S504, the one-dimensional analysis unit 103 sets the time step t to 0 (zero), which is an initial value. The initial value (= 0) of the time step t is the timing of the start of one cycle in the excitation condition data.
Next, in step S505, the one-dimensional analysis unit 103 performs the equations (5a) and (5a) under the boundary conditions (see equations (6a) to (6d)) at the initial value (= 0) of the time step t. By solving the equation 5b) by the unsteady one-dimensional finite element method, the vector potentials (x component and y component) A _x and A _y in each of the second elements generated in step S503 are derived. In step S505, (6a) formula ~ (6d) formula _{B x (t), B y} (t) , the first element is derived in step S501 with respect to the B _x selected in step S502 ( 0), and B _y (0).

As a result, the distribution of the vector potentials (x component and y component) A _x and A _y in the first element selected in step S502 in the z-axis direction at the initial value of the time step t is derived. In this step S505, the equations (5a) and (5b) are solved using the common magnetic permeability (x component and y component) μ _x and μ _{y in the first element selected in step S502.}

Next, in step S506, the one-dimensional analysis unit 103 _{determines the distribution of the vector potentials (x component and y component) A x} and A _y in the first element derived in step S505 in the z-axis direction. the second magnetic flux density in each element (the x and y components) B _x, B _y and eddy current density (the x component, y component) generated in step S503 Je _x, deriving a Je _y. Thus, the first magnetic flux density in the element (the x and y components) B _x, the B _y, and the distribution of the z-axis direction in the initial value of the time step t, the eddy current density (the x component, y component ) Je _x, of Je _y, and distribution of the z-axis direction in the initial value of the time step t is derived.

Next, in step S507, the one-dimensional analysis unit 103 has a magnetic flux density (x component and y component) B in the second element derived in step S506 from the magnetic characteristic data stored in the data storage unit 101. _x, (x and y components of) the corresponding magnetic permeability in the respective B _y mu _x, reads out the mu _y. As a result, the distribution of the magnetic permeability (x component and y component) μ _x and μ _y in the first element in the z-axis direction at the initial value of the time step t can be obtained. Then, the one-dimensional analysis unit 103 stores the distributions of the magnetic permeability (x component and y component) μ _x and μ _y in the first element in the z-axis direction.

Next, in step S508, the one-dimensional analysis unit 103 updates the time step t by adding the time Δt to the time step t.
Next, in step S509, the one-dimensional analysis unit 103 _{determines the distribution (latest) of the magnetic permeability (x component and y component) μ x} and μ _y in the first element selected in step S502 in the z-axis direction. Value) is read.

Next, in step S510, the one-dimensional analysis unit 103 performs the equations (5a) and (5b) under the boundary conditions (see equations (6a) to (6d)) in the time step t updated in step S508. ) Is solved by the unsteady one-dimensional finite element method to derive the _{vector potentials (x component and y component) A x} and A _{y in each of the second elements generated in step S503.} In step S510, (6a) formula ~ (6d) formula _{B x (t), B y} (t) , the first element is derived in step S501 with respect to the B _x selected in step S502 ( t), becomes B _y (t) (t is the time step t that is updated in step S508).

As a result, the distribution of the vector potentials (x component and y component) A _x and A _y in the first element selected in step S502 in the z-axis direction at the time step t updated in step S508 is derived. In this step S510, the magnetic permeability (x component and y component) μ _x and μ _{y in} the z-axis direction (latest value) of the magnetic permeability in the first element read out in step S509 are used in the equation (5a) and Solve equation (5b).

Next, in step S511, the one-dimensional analysis unit 103 _{determines the distribution of the vector potentials (x component and y component) A x} and A _y in the first element derived in step S510 in the z-axis direction. the second magnetic flux density in each element (the x and y components) B _x, B _y and eddy current density (the x component, y component) generated in step S503 Je _x, deriving a Je _y. Thus, the magnetic flux density (the x and y components) of the first element B _x, the B _y, and the distribution in the z-axis direction at time step t updated in step S508, the eddy current density (x-component , y components) Je _x, of Je _y, and the distribution in the z-axis direction at time step t that is updated in step S508 is derived.

Next, in step S512, the one-dimensional analysis unit 103 has a magnetic flux density (x component and y component) B in the second element derived in step S511 from the magnetic characteristic data stored in the data storage unit 101. _x, (x and y components of) the corresponding magnetic permeability in the respective B _y mu _x, reads out the mu _y. As a result, the distribution of the magnetic permeability (x component and y component) μ _x , μ _y in the first element in the time step t updated in step S508 is obtained in the z-axis direction. Then, the one-dimensional analysis unit 103 reads out the distribution in the z-axis direction of the magnetic permeability (x component and y component) μ _x and μ _{y in the first element already stored in this step S512.} the first permeability at elements (the x and y components) mu _x, mu rewrites the z of the axial distribution of _y, the permeability (of the x and y components) of the first element mu _x, mu _{Update the distribution of y in} the z-axis direction.

Next, in step S513, the one-dimensional analysis unit 103 determines whether or not the value of the current time step is the final value (= t _max). The final value (= t _max ) of the time step t is the timing of the end of one cycle in the excitation condition data. As a result of this determination, if the value of the current time step is not the final value (= t _max ), the calculation for one cycle in the excitation condition data has not been completed, and the process returns to step S508. Then, the processes of steps S508 to S513 are repeatedly executed until the value of the current time step reaches the final value (= t _max).

Then, when the value of the current time step reaches the final value (= t _max ), the process proceeds to step S514. In step S514, the one-dimensional analysis unit 103 determines whether or not all the first elements have been selected in step S502. As a result of this determination, if all the first elements are not selected, the calculation for all the first elements has not been completed, and the process returns to step S502. Then, the processes of steps S502 to S514 are repeatedly executed until all the first elements are selected in step S502.

When all the first elements are selected in step S502, the process proceeds to step S515. In step S515, the loss deriving unit 104, in each of the second element included in each of the first element, the magnetic flux density (the x and y components) of the electromagnetic steel sheets B _x, B _y and eddy current density ( the x component, y component) Je _x, based on Je _y, hysteresis loss of the electromagnetic steel sheets, eddy current loss, and derives the iron loss.
Finally, in step S516, the output unit 105 outputs information including the hysteresis loss, the eddy current loss, and the iron loss of the electrical steel sheet.

<Calculation example>
Next, a calculation example of this embodiment will be described. In this calculation example, the hysteresis of the electromagnetic steel sheet when the electromagnetic steel sheet of 35A360 is excited by the single plate magnetic tester described in JIS C2556 (2015) “Method for measuring magnetic characteristics of electrical steel strip by single plate tester”. Loss, eddy current loss, and iron loss were calculated.
The method described in this embodiment (the method described in the flowchart of FIG. 5) is used as an example of the invention. Further, in the flowchart of FIG. 5, the processes of steps S507, S509, and S512 are not performed, and in step S510 as well as in step S505, the magnetic permeability (x component and y component) μ _{x common to the first element.} , Μ _y (the magnetic permeability (x component and y component) μ _x and μ _y are constant so as not to have a distribution in the z-axis direction) is used as a comparative example. Further, a method of performing electromagnetic field analysis using a nonlinear unsteady three-dimensional finite element method without limiting the conductivity and setting elements finer than the plate thickness of the magnetic steel sheet is used as a reference example. Compared with the invention example and the comparative example, the method of the reference example can perform the electromagnetic field analysis more accurately, but the calculation time is longer.

Comparison of the hysteresis loss, eddy current loss, and iron loss of the electrical steel sheet derived by the methods of the invention example and the comparative example with the hysteresis loss, eddy current loss, and iron loss of the electromagnetic steel sheet derived by the method of the reference example. did. Further, in this calculation example, the first exciting condition that the exciting current of a sine wave having an exciting frequency of 1 kHz is applied so that the maximum value of the magnetic flux density of the electromagnetic steel plate is 1.5T, and the magnetic flux density of the electromagnetic steel plate An exciting current generated by an inverter is applied with a modulation factor m of 0.5 using a modulated wave having a frequency of 1.5 kHz and a carrier (carrier wave) having a frequency of 5 kHz so that the maximum value becomes 1.5 T. The above-mentioned calculation was performed under each of the second excitation conditions. The results are shown in FIG.

In FIGS. 6 (a) and 6 (b), the difference is the value obtained by subtracting the value of the reference example from the values of Invention Example 1, Invention Example 2, Comparative Example 1, and Comparative Example 2, and Invention Example 1 and Invention Example. 2. The ratio of the value obtained by subtracting the value of the reference example from the values of Comparative Example 1 and Comparative Example 2 to the value of the reference example is shown as a percentage.
Since the first excitation condition and the second excitation condition are high magnetic flux density and high frequency conditions, the eddy current loss is larger than the hysteresis loss as shown in FIGS. 6 (a) and 6 (b). Become. Comparing FIGS. 6 (a) and 6 (b), under both the first excitation condition and the second excitation condition, Invention Examples 1 and 2 are reference examples as compared with Comparative Examples 1 and 2. It can be seen that the result can be approached. As described above, in the method of the present embodiment, it is possible to realize both the reduction of the calculation load and the suppression of the deterioration of the calculation accuracy even under the excitation conditions of high magnetic flux density and high frequency. This makes it possible to derive the loss in a short time and with high accuracy in a motor that rotates at high speed using an inverter or the like, such as an electric vehicle or a hybrid vehicle, among AC motors such as a permanent magnet synchronous motor and an induction motor. Become.

<Summary>
As described above, in the present embodiment, the electromagnetic field analyzer 100 solves the diffusion equation of the magnetic flux density expressed by using the magnetic permeability μ in each time step t, so that the magnetic flux density (x component and x component of the magnetic steel sheet) of the electromagnetic steel sheet is solved. y component) B _x, by using the determining the z of axial distribution of B _y, the magnetic flux density of the electromagnetic steel sheet (the x and y components) B _x, and z of the axial distribution of B _y, magnetic steel The magnetic flux density (x component and y component of) μ _x and μ _y are derived in the z-axis direction. _{At this time, the electromagnetic field analyzer 100 uses the distribution of the magnetic permeability (x component and y component) μ x} and μ _y of the magnetic steel sheet derived in the previous time step t in the z-axis direction at the current time. Solve the diffusion equation of the magnetic flux density in step t. Therefore, it is possible to consider the distribution of magnetic permeability (x component and y component) μ _x and μ _{y of the magnetic steel sheet in the z-axis direction.} Therefore, when obtaining the magnetic characteristics including the magnetic flux density of the excited magnetic material by numerical analysis, it is possible to realize both the reduction of the calculation load and the suppression of the deterioration of the calculation accuracy.

<Modification example>
In this embodiment, the case where the nonlinear unsteady two-dimensional finite element method is used in the two-dimensional analysis unit 102 has been described as an example. However, it is not always necessary to use the two-dimensional finite element method, and a nonlinear unsteady three-dimensional finite element method is used in which the conductivity in the z-axis direction is 0 (zero) and the first element is larger than the thickness of the electromagnetic steel plate. You may do so. Even in this case, the element used in the nonlinear unsteady three-dimensional finite element method becomes the first element.

Further, in the present embodiment, in the second and subsequent time step t, the second magnetic flux density of the electromagnetic steel plates in each element (the x and y components) B _x included in the first element, the B _y ( When deriving based on the equations 5a) and (5b), the magnetic permeability (x component and y component) derived with respect to the first element in the time step t−Δt immediately before the time step t. ) The _{case of using the distribution of μ x} and μ _{y in} the z-axis direction has been described as an example. _{However, the distribution of magnetic permeability (x component and y component) μ x} and μ _y derived for the first element in the time step t−Δt immediately before the time step t is not necessarily distributed in the z-axis direction. There is no need to use.

For example, between step S512 and step S513, a step of determining the convergence of the distributions of magnetic permeability (x component and y component) μ _x and μ _{y in the first element derived in step S512 in the z-axis direction is performed.} You may add it. In this case, in this convergence test, if the distributions of magnetic permeability (x component and y component) μ _x and μ _y in the first element derived in step S512 are not converged in the z-axis direction, the process is performed in step. Return to S510.

When the process returns to step S510, the one-dimensional analysis unit 103 outputs _{the latest values of the magnetic permeability (x component and y component) μ x} and μ _{y in} the z-axis direction in the first element obtained in step S512. Is used to re-derive the distribution of the vector potentials (x component, y component) A _x and A _{y in the first element in the z-axis direction.} Then, in step S511, one-dimensional analysis unit 103, the magnetic flux density in the first element (the x and y components) B _x, and z of the axial distribution of B _y, eddy current density in the first element ( the x component, y component) Je _x, again derives a z of axial distribution of Je _y.

The above convergence test and the processing of steps S510 to S512 are performed in the convergence test in the z-axis direction of the _{magnetic permeability (x component and y component) μ x} and μ _{y of the first element obtained in step S512.} Repeat until it is determined that the distribution converges. In the convergence test, for example, the value representing the difference between the previous value and the current value of the distribution of the magnetic permeability (x component and y component) μ _x and μ _{y in the first element derived in step S512 in the z-axis direction is used.} This can be done by determining whether or not the value is equal to or less than a predetermined value. At this time, for example, for each position in the z-axis direction and for each direction (x-axis direction and y-axis direction), the magnetic permeability (x component and y component) μ _x and μ _y of the first element is the previous value from the current value. The value obtained by subtracting the value is obtained, and the sum of the obtained values is the difference between the previous value and the current value of the distribution _{of the magnetic permeability (x component and y component) μ x} and μ _{y in the first element in the z-axis direction.} Can be adopted as a value representing.

Further, in the present embodiment, the value of the in-plane direction component of the magnetic flux density is the value of the plate surface direction component of the electromagnetic steel sheet, and the direction perpendicular to the in-plane direction is the plate thickness direction of the electromagnetic steel sheet as an example. I mentioned and explained. However, it is not always necessary to do this. The surface of the in-plane direction component may be any surface as long as it is a two-dimensional plane. For example, the value of the in-plane component of the magnetic flux density may be the value of the plate thickness direction component of the electrical steel sheet. For example, magnetic flux flows in the thickness direction of the electrical steel sheet near the outer peripheral end of the stator core of the rotary electric machine. In such a case, it is preferable that the value of the in-plane component of the magnetic flux density is the value of the plate thickness direction component of the magnetic steel sheet, and the direction perpendicular to the in-plane direction is the radial direction of the stator core.

Further, if the eddy current loss of the electrical steel sheet is derived as in the present embodiment, it is preferable because the detailed loss of the electrical steel sheet can be obtained. However, it is possible to derive only the hysteresis loss without deriving the eddy current loss of the electrical steel sheet. When doing so, it is not necessary to derive the eddy current density (the x component, y component) Je _x, the Je _y.

In addition, 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.

100: Electromagnetic field analysis device, 101: Data storage unit, 102: Two-dimensional analysis unit, 103: One-dimensional analysis unit, 104: Loss derivation unit, 105: Output unit

Claims (11)

An electromagnetic field analyzer that analyzes the magnetic properties of an excited magnetic material at each time step by numerical analysis based on Maxwell's equations.
At each time step, it is executed to derive the value of the in-plane component of the magnetic flux density in the magnetic material by numerical analysis for each of the first small regions in three dimensions obtained by dividing the region of the magnetic material. The first derivation means to be
A three-dimensional first obtained by dividing the first small region in a direction perpendicular to the in-plane direction based on the value of the in-plane component of the magnetic flux density derived by the first derivation means. A second derivation means for performing numerical analysis to derive the value of the in-plane component of the magnetic flux density in the magnetic material for each of the two small regions,
The magnetic permeability of the magnetic material in the second small region is based on the value of the in-plane component of the magnetic flux density in the magnetic material derived for the second small region by the second derivation means. It has a third derivation means, which performs derivation of the value of the in-plane direction component at each time step.
The magnetic permeability is represented by the slope of a straight line connecting the origin in the curve showing the relationship between the magnetic flux density and the magnetic field strength and the point determined according to the magnetic flux density on the curve.
The second derivation means is prior to the time step when the value of the in-plane component of the magnetic flux density in the magnetic material is derived by numerical analysis for each of the second small regions in a certain time step. In the time step of, the value of the in-plane component of the magnetic permeability of the magnetic material derived for the second small region by the third derivation means is set to the value of the magnetic material in the second small region. An electromagnetic field analyzer characterized by being used as a value of an in-plane component of magnetic permeability. The second derivation means is the first derivation when the value of the in-plane component of the magnetic flux density in the magnetic material is derived by numerical analysis for each of the second small regions in the first time step. The in-plane component of the magnetic permeability of the magnetic material corresponding to the value of the in-plane component of the magnetic flux density in the magnetic material derived for the first small region including the second small region by means. The electromagnetic field analyzer according to claim 1, wherein the value is used as a value of an in-plane component of the magnetic permeability of the magnetic material in the second small region. In the second derivation means, the magnetic flux based on the value of the in-plane component of the magnetic flux density derived in a certain time step with respect to the first small region by the first derivation means is the first. The value of the in-plane component of the magnetic flux density in the magnetic material is a numerical value for each of the second small regions so as to be equal to the total amount of the magnetic flux at the time step in the second small region obtained by dividing the small region of. The electromagnetic field analysis apparatus according to claim 1 or 2, wherein the derivation by analysis is performed at each time step. The second derivation means is a diffusion equation derived based on Maxwell's equations as the numerical analysis, in which the value of the in-plane component of the magnetic flux density of the magnetic material is perpendicular to the in-plane direction. 1. The electromagnetic field analyzer according to any one of the above items. The second derivation means is one more than the time step when deriving the value of the in-plane component of the magnetic flux density in the magnetic material by numerical analysis for each of the second small regions in a certain time step. In the previous time step, the value of the in-plane component of the magnetic permeability of the magnetic material derived for the second small region by the third derivation means is set to the value in the second small region. The electromagnetic field analyzer according to any one of claims 1 to 4, wherein the magnetic material is used as a value of an in-plane component of magnetic permeability. The electromagnetic field analysis apparatus according to any one of claims 1 to 5, wherein the magnetic material includes one or a plurality of electromagnetic steel sheets. Further, a fourth derivation means for deriving the loss of the magnetic material based on the value of the in-plane component of the magnetic flux density in the magnetic material derived by the second derivation means for each of the second small regions. The electromagnetic field analyzer according to any one of claims 1 to 6, wherein the electromagnetic field analyzer is characterized by having. The electromagnetic field analysis apparatus according to any one of claims 1 to 7, wherein the numerical analysis is a numerical analysis by a finite element method. The electromagnetic field analysis apparatus according to any one of claims 1 to 8, wherein the curve showing the relationship between the magnetic flux density and the magnetic field strength is a curve showing the initial magnetization characteristic. An electromagnetic field analysis method that analyzes the magnetic properties of an excited magnetic material at each time step by numerical analysis based on Maxwell's equations.
At each time step, it is executed to derive the value of the in-plane component of the magnetic flux density in the magnetic material by numerical analysis for each of the first small regions in three dimensions obtained by dividing the region of the magnetic material. The first derivation process to be performed and
A three-dimensional first obtained by dividing the first small region in a direction perpendicular to the in-plane direction based on the value of the in-plane component of the magnetic flux density derived by the first derivation step. A second derivation step of performing numerical analysis to derive the value of the in-plane component of the magnetic flux density in the magnetic material for each of the two small regions is performed in each time step.
The magnetic permeability of the magnetic material in the second small region is based on the value of the in-plane component of the magnetic flux density in the magnetic material derived for the second small region by the second derivation step. It has a third derivation step of deriving the value of the in-plane direction component at each time step.
The magnetic permeability is represented by the slope of a straight line connecting the origin in the curve showing the relationship between the magnetic flux density and the magnetic field strength and the point determined according to the magnetic flux density on the curve.
The second derivation step is prior to the time step when the value of the in-plane component of the magnetic flux density in the magnetic material is derived by numerical analysis for each of the second small regions in a certain time step. In the time step of, the value of the in-plane component of the magnetic permeability of the magnetic material derived for the second small region by the third derivation step is set to the value of the magnetic material in the second small region. An electromagnetic field analysis method characterized in that it is used as a value of an in-plane component of magnetic permeability. A program for operating a computer as each means of the electromagnetic field analyzer according to any one of claims 1 to 9.

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