Semi-analytical calculation method for eddy current loss of permanent magnet of axial permanent magnet motor

Abstract

The invention discloses an axial permanent magnet motor permanent magnet eddy current loss semi-analytical calculation method, and relates to the technical field of motor design, and the method comprises the steps: S1, building a semi-analytical model according to the size and structure of a permanent magnet; s2, performing block sampling on the permanent magnet in the quasi-three-dimensional finite element model to obtain a time-varying relationship of the flux density of the permanent magnet in each region; s3, acquiring an eddy current resistance expression in the permanent magnet under a rectangular coordinate system; s4, considering the influence of the skin effect, and calculating the eddy current induced electromotive force of each harmonic wave; s5, respectively calculating eddy-current loss generated by each harmonic, and finally calculating the sum of the eddy-current loss of each harmonic; the eddy-current loss semi-analytical calculation method provided by the invention has good universality, only needs very short calculation time under the condition of ensuring high accuracy, and provides a good basis for subsequent design and optimization of the motor.

Description

Technical Field

[0001] The invention relates to the technical field of motor design, and in particular to a semi-analytical calculation method for permanent magnet eddy current loss of an axial permanent magnet motor. Background Art

[0002] Axial permanent magnet motors, also known as disc motors, have received extensive attention and applications in the fields of electric vehicles, wind power generation, aerospace, etc. in recent years. Compared with traditional radial flux motors, axial flux motors have higher power density, more compact structure and higher efficiency; these characteristics make axial flux motors have significant advantages in applications where space and weight are strictly restricted.

[0003] However, when a permanent magnet motor is running at high speed, eddy currents will be generated inside its permanent magnets; these eddy currents will not only cause unnecessary energy loss, but may also cause the motor temperature to rise, reducing the motor's operating efficiency and reliability. For axial flux motors, this eddy current loss problem becomes particularly prominent due to their three-dimensional flux distribution and structural characteristics. Therefore, how to quickly and accurately calculate the eddy current loss of axial permanent magnet motors is of great significance for subsequent motor design optimization, loss suppression, etc.

[0004] At present, the calculation methods for eddy current loss of axial flux motors mainly include full analytical method and finite element simulation method. The full analytical method directly calculates eddy current loss by establishing a mathematical model of the motor using analytical methods, which has the advantages of fast calculation speed and clear results. However, due to the complex structure of the axial flux motor, the full analytical method has certain limitations when dealing with complex geometric shapes and multi-physical field coupling problems. The finite element simulation method uses finite element analysis and other means to numerically solve the electromagnetic field of the motor, which can accurately simulate the actual situation, but the calculation time is long, the resource consumption is large, and the results depend on the partial accuracy of the simulation model and the setting of boundary conditions. Therefore, there is an urgent need for a method to quickly calculate the eddy current loss of the axial permanent magnet motor with high accuracy. Summary of the invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of the present invention is to provide a semi-analytical calculation method for the eddy current loss of the permanent magnet of an axial permanent magnet motor, taking into account the eddy current skin effect, ensuring the rapid calculation of the eddy current loss of the axial permanent magnet motor with high accuracy, reducing the time and complexity of calculating the eddy current loss, thereby facilitating the subsequent design optimization and efficiency improvement of the motor.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A semi-analytical calculation method for eddy current loss of permanent magnets of an axial permanent magnet motor comprises the following steps:

[0008] Step S1, establishing a semi-analytical model of eddy current loss according to the size and structure of the permanent magnet;

[0009] Step S2, in a quasi-three-dimensional finite element model, the permanent magnets are sampled in blocks, and a curve of the change of the magnetic density of the permanent magnets in each region over time is obtained by simulation, and the curve of the change of the magnetic density of the permanent magnets in each region over time obtained by the above simulation is harmonically decomposed to obtain a curve of the change of each harmonic of the magnetic density in each region over time;

[0010] Step S3, obtaining an expression of eddy current resistance in the permanent magnet in the rectangular coordinate system established in step S1;

[0011] Step S4, taking into account the influence of the skin effect, calculating the penetration depth of each harmonic eddy current, and further calculating the induced electromotive force generated by each harmonic eddy current;

[0012] Step S5, calculating the eddy current loss of each harmonic permanent magnet, and finally obtaining the total eddy current loss of the permanent magnet.

[0013] As a further solution of the present invention: the specific method of establishing the eddy current loss semi-analytical model in step S1 is:

[0014] By transforming the sector-shaped permanent magnet into a rectangular permanent magnet and taking the center point of the transformed rectangular permanent magnet as the origin of coordinates, a rectangular coordinate system is established to obtain a semi-analytical model of eddy current loss.

[0015] The conversion principle of the sector-shaped permanent magnet into the rectangular permanent magnet is to keep the flow area S of the eddy current path C unchanged.

[0016] As a further solution of the present invention: the sector-shaped permanent magnet is converted into a rectangular permanent magnet in the following specific manner:

[0017] The outer diameter R of the sector permanent magnet o With inner diameter R i The difference is converted into the width of the rectangular permanent magnet, and the arc length R at the average radius of the sector permanent magnet is converted into ave =(R i +R o ) / 2 is converted to the length of the rectangular permanent magnet.

[0018] As a further solution of the present invention: the eddy current loss semi-analytical model in step S1 has the following constraints:

[0019] 1) Permanent magnet conductivity δ and relative magnetic permeability μ r remain unchanged;

[0020] 2) Ignore the winding end effect and leakage flux;

[0021] 3) The magnetic flux passes vertically through the permanent magnet;

[0022] 4) The eddy current circulates in a rectangular form, and the ratio of the width y to the length x is a, and the aspect ratio of the rectangular eddy current is the same as the aspect ratio of the converted rectangular permanent magnet. The ratio a is expressed as follows:

[0023]

[0024] Where x is a variable, and its range is (0, R ave / 2), R o is the outer diameter of the sector permanent magnet, R i is the inner diameter of the sector permanent magnet, R ave is the arc length at the average radius of the sector-shaped permanent magnet.

[0025] As a further solution of the present invention: in step S2, the permanent magnet is divided into k and m rectangular regions horizontally and vertically, and the center point of each region is taken as the magnetic density sampling point. The magnetic density change curve B of each region over time is obtained by simulation in the quasi-three-dimensional finite element model. bc (t), where b and c indicate that the region is the bth region in the transverse segmentation and the cth region in the longitudinal segmentation of the permanent magnet; on this basis, the magnetic flux density waveform B of each region is calculated. bc (t) Perform harmonic decomposition to obtain the curve B of each harmonic of magnetic density in each area changing with time n-bc (t), where n is the harmonic order.

[0026] As a further solution of the present invention: in step S2, the requirements for the number of transverse and longitudinal segments k and m of the permanent magnet are: k≥3, m≥2, and k and m are positive integers.

[0027] As a further solution of the present invention: the square of the time derivative of the nth harmonic magnetic flux density of the permanent magnet can be expressed as follows:

[0028]

[0029] Where dB n-bc (t) / dt is the time derivative of the nth harmonic magnetic flux density in the cth region of the bth longitudinal segment of the permanent magnet transverse segment.

[0030] As a further solution of the present invention: the expression of the eddy current resistance in the permanent magnet in step S3 is as follows:

[0031]

[0032] Where δ is the conductivity of the permanent magnet, h pm is the thickness of the permanent magnet.

[0033] As a further solution of the present invention: in step S4, the induced electromotive force E generated by each harmonic eddy current under the condition of skin effect is considered n The expression is as follows:

[0034]

[0035] Among them B n (t) is the relationship between the nth harmonic magnetic flux density and time, d n is the penetration depth of the harmonics, expressed as follows:

[0036]

[0037] Among them, ω n is the nth harmonic angular velocity of the magnetic field, μ0 is the vacuum permeability, μ r Relative magnetic permeability of permanent magnets respectively.

[0038] ω n =2πn r n;

[0039] Among them, n r is the motor speed, and n is the harmonic order.

[0040] As a further solution of the present invention: the eddy current loss of the nth harmonic permanent magnet in step S5 can be expressed as follows:

[0041]

[0042] The total eddy current loss of permanent magnet can be expressed as follows:

[0043]

[0044] Beneficial effects of the present invention:

[0045] The semi-analytical axial permanent magnet motor permanent magnet eddy current loss calculation method provided by the present invention takes into account the skin effect of eddy current. Under the condition of ensuring high calculation accuracy, by adopting a method combining analytical calculation and quasi-three-dimensional finite element model, the calculation time is greatly saved, and a method for quickly calculating the eddy current loss of permanent magnets with high accuracy is provided. At the same time, the calculation method of the invention is only related to the size structure of the permanent magnet, has universality, can effectively reduce the calculation time and complexity of eddy current loss, and provides a good foundation for subsequent motor design optimization and efficiency improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be further described below in conjunction with the accompanying drawings.

[0047] Figure 1 It is a schematic diagram of the flow chart of the calculation method of the present invention;

[0048] Figure 2 It is a schematic diagram of the conversion of the sector-shaped permanent magnet into a rectangular permanent magnet according to the present invention;

[0049] Figure 3It is a schematic diagram of the magnetic density sampling of permanent magnet blocks in the quasi-three-dimensional finite element model of the present invention;

[0050] Figure 4 The curve B of the change of magnetic density over time in the second horizontal segment and the first vertical segment when k=3 and m=2 in the present invention is 21 (t) Schematic diagram;

[0051] Figure 5 It is a schematic diagram of the topological structure of the axial permanent magnet motor of the present invention;

[0052] Figure 6 It is a schematic diagram of the permanent magnet in the axial permanent magnet motor of the present invention;

[0053] Figure 7 The present invention is a curve diagram of the change of permanent magnet eddy current loss with current density at a fixed speed obtained by three-dimensional finite element and semi-analytical methods respectively;

[0054] Figure 8 The present invention obtains a curve diagram showing the change of eddy current loss of a permanent magnet with rotation speed under a fixed current density by using three-dimensional finite element and semi-analytical methods respectively.

[0055] In the figure: 1. stator core; 2. winding coil; 3. permanent magnet; 4. rotor core. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] The present invention provides a semi-analytical calculation method for eddy current loss of permanent magnets of an axial permanent magnet motor, comprising the following steps:

[0058] Step S1, establishing a semi-analytical model of eddy current loss according to the size and structure of the permanent magnet;

[0059] Specifically, Figure 2 As shown, by converting the sector-shaped permanent magnet into a rectangular permanent magnet, a rectangular coordinate system is established with the center point of the converted rectangular permanent magnet as the origin of the coordinate, and a semi-analytical model of eddy current loss is obtained;

[0060] The conversion principle of the sector-shaped permanent magnet to the rectangular permanent magnet is to keep the flow area S of the eddy current path C unchanged;

[0061] The specific conversion method is to convert the outer diameter R of the sector permanent magnet o With inner diameter R iThe difference is converted into the width of the rectangular permanent magnet, and the arc length R at the average radius of the sector permanent magnet is converted into ave =(R i +R o ) / 2 is converted to the length of the rectangular permanent magnet.

[0062] And the above eddy current loss semi-analytical model has the following constraints:

[0063] 1) Permanent magnet conductivity δ and relative magnetic permeability μ r remain unchanged;

[0064] 2) Ignore the winding end effect and leakage flux;

[0065] 3) The magnetic flux passes vertically through the permanent magnet;

[0066] 4) The eddy current circulates in a rectangular form, and the ratio of the eddy current width y to the eddy current length x is a, and the aspect ratio of all rectangular eddy currents is the same as the aspect ratio of the converted rectangular permanent magnet. The ratio a can be expressed as follows:

[0067]

[0068] Where x is a variable, and its range is (0, R ave / 2),R o is the outer diameter of the sector permanent magnet, R i is the inner diameter of the sector permanent magnet, R ave is the arc length at the average radius of the sector-shaped permanent magnet.

[0069] Step S2, in a quasi-three-dimensional finite element model, the permanent magnet is sampled in blocks, and a curve of the permanent magnet magnetic density of each region varying with time is obtained by Ansys Maxwell simulation; the curve of the permanent magnet magnetic density varying with time of each region obtained by the above simulation is harmonically decomposed to obtain a curve of the magnetic density harmonic of each region varying with time;

[0070] Among them, Figure 3 As shown in the figure, in the quasi-three-dimensional finite element model (the axial permanent magnet motor is expanded into a linear motor along the radial direction, and the corresponding two-dimensional finite element model is established), the permanent magnet is divided into k and m rectangular regions in the horizontal and vertical directions, where k and m are positive integers. The center point of each region is taken as the magnetic density sampling point, and the magnetic density change curves of each region over time are obtained by simulation in the quasi-three-dimensional finite element model. bc (t), where b and c indicate that the region is the bth region in the transverse segment and the cth region in the longitudinal segment of the permanent magnet;

[0071] Further, Figure 4 The curve B shows the change of magnetic flux density over time in the second transverse segment and the first longitudinal segment of the permanent magnet when k=3 and m=2. 21(t).

[0072] On this basis, the magnetic density waveform B of each region is bc (t) Perform harmonic decomposition to obtain the curve B of each harmonic of magnetic density in each area changing with time n-bc (t), where n is the harmonic order.

[0073] Furthermore, the square of the time derivative of the nth harmonic magnetic flux density of the permanent magnet can be expressed as follows:

[0074]

[0075] dB n-bc (t) / dt is the time derivative of the nth harmonic magnetic flux density in the cth region of the bth longitudinal segment of the permanent magnet transverse segment.

[0076] Step S3, obtaining the expression of eddy current resistance in the permanent magnet in the rectangular coordinate system established in step S1, the expression is as follows:

[0077]

[0078] Where δ is the electrical conductivity of the permanent magnet (determined by the specific permanent magnet model, such as the permanent magnet model N38SH, whose permanent magnet conductivity is 34500s / m), h pm is the thickness of the permanent magnet.

[0079] Step S4, taking into account the influence of the skin effect, calculating the penetration depth of each harmonic eddy current, and further calculating the induced electromotive force generated by each harmonic eddy current.

[0080] The skin effect refers to the fact that when there is alternating current or an alternating electromagnetic field in a conductor, the current is unevenly distributed inside the conductor. The current is mainly concentrated in the "skin" part of the conductor, that is, the thin layer on the surface of the conductor. The closer to the surface of the conductor, the greater the current density, while the actual current inside the conductor is smaller.

[0081] The induced electromotive force E generated by each harmonic eddy current considering the skin effect n The expression is as follows:

[0082]

[0083] Among them B n (t) is the relationship between the nth harmonic magnetic flux density and time, d n is the penetration depth of the harmonics, which can be expressed as follows:

[0084]

[0085] Among them, ω nis the nth harmonic angular velocity of the magnetic field, which can be expressed by equation (6), μ0 is the vacuum permeability (usually 4π×10 -7 H / m)、μ r The relative magnetic permeability of the permanent magnet is determined by the specific permanent magnet model. For example, the relative magnetic permeability of the permanent magnet model N35SH is 1.072.

[0086] ω n =2πn r n (6);

[0087] Among them, n r is the motor speed, and n is the harmonic order.

[0088] Step S5, calculating the eddy current loss of each harmonic permanent magnet, and finally obtaining the total eddy current loss of the permanent magnet.

[0089] The nth harmonic permanent magnet eddy current loss can be expressed as follows:

[0090]

[0091] Substituting equation (8) into equation (7), the final expression of the eddy current loss of the nth harmonic permanent magnet is:

[0092]

[0093] The total eddy current loss of permanent magnet can be expressed as follows:

[0094]

[0095] Furthermore, in step S2 of the present method, the requirements for the number of transverse and longitudinal segments k and m of the permanent magnet are: k≥3, m≥2, and k and m are positive integers; when the loss calculation accuracy is required to be high, the values ​​of k and m can be appropriately increased.

[0096] Furthermore, in the method, the axial permanent magnet motor structure topology can be any one of single stator and single rotor, single stator and dual rotor, dual stator and single rotor, and dual stator and dual rotor.

[0097] Furthermore, a three-phase yokeless stator modular axial permanent magnet motor is taken as an example to specifically illustrate the technical effect of the calculation method of the present invention. The topology of the permanent magnet motor is as follows: Figure 5 As shown, it includes a stator core 1, a winding coil 2, a permanent magnet 3 and a rotor core 4. The permanent magnet 3 is shown in FIG. Figure 6 As shown, the permanent magnet rotor disks are placed on the surface of the rotor core 4 and are placed on both sides of the stator core 1. The rated speed of the motor is 2000r / min, and the slot current density is 3A / mm 2 .

[0098] First, a semi-analytical model of eddy current loss is established based on the size and structure of the permanent magnet. Figure 2 As shown, the difference between the inner and outer diameters of the sector-shaped permanent magnets (R o -R i ) is converted to the width of a rectangular permanent magnet and the arc length R at the average radius of a sector permanent magnet ave Convert to the length of a rectangular permanent magnet.

[0099] Then, the magnetic flux density of the permanent magnet is sampled in blocks in the quasi-three-dimensional finite element model. The quasi-three-dimensional finite element model is a linear motor model obtained by unfolding the axial permanent magnet motor; the thickness of the linear motor model is (R mo -R mi ), the length is the circumference of the motor at the average radius π(R mo +R mi ), where R mo is the outer diameter of the motor, R mi is the inner diameter of the motor. Figure 3 As shown, in this embodiment, the number of transverse segments of the permanent magnet is k=3, and the number of longitudinal segments is m=2. The extracted magnetic flux harmonics of each region are decomposed and inserted into formula (2), and the eddy current loss of the permanent magnet is finally calculated by formula (9) and formula (10) to be 53.57W; the eddy current loss of the permanent magnet calculated by three-dimensional finite element simulation is 57.6W, and the error between the two is 7.0%.

[0100] Table 1 below shows the model error and calculation schedule for different values ​​of k and m;

[0101]

[0102]

[0103] It can be seen from Table 1 that the calculation method of the present invention has good accuracy, and the error with the three-dimensional finite element simulation result is within 7%. In addition, the calculation time of the semi-analytical calculation method of the present invention is much lower than the calculation time of the three-dimensional finite element simulation, which can effectively reduce the calculation time and complexity of eddy current loss, and provide a good foundation for subsequent motor design optimization and efficiency improvement.

[0104] Further, Figure 7 The curves of the eddy current loss of permanent magnets at a fixed speed (2000r / min) obtained by semi-analytical calculation and three-dimensional finite element simulation are as follows: Figure 8 The semi-analytical method and three-dimensional finite element simulation are used to calculate the fixed current density (3A / mm 2 ) Curve of permanent magnet eddy current loss as a function of rotation speed.

[0105] Depend on Figure 7 and Figure 8It can be seen that the calculation method of the present invention has good accuracy at different motor speeds and slot current densities, and the error with the three-dimensional finite element simulation results is within 7%. At the same time, from the above examples, it can be seen that the calculation time of the method of the present invention is about 10 minutes, while the three-dimensional finite element calculation time is about 2 hours. It can be seen that the calculation method provided by the present invention takes into account both accuracy and calculation time, and can provide a good foundation for subsequent motor loss analysis and design optimization.

[0106] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A semi-analytical calculation method for eddy current loss of permanent magnets in axial permanent magnet motors, characterized in that: The steps include: Step S1, establishing a semi-analytical model of eddy current loss according to the size and structure of the permanent magnet; Step S2, in a quasi-three-dimensional finite element model, the permanent magnets are sampled in blocks, and a curve of the change of the magnetic density of the permanent magnets in each region over time is obtained by simulation, and the curve of the change of the magnetic density of the permanent magnets in each region over time obtained by the above simulation is harmonically decomposed to obtain a curve of the change of each harmonic of the magnetic density in each region over time; Step S3, obtaining an expression of eddy current resistance in the permanent magnet in the rectangular coordinate system established in step S1; Step S4, considering the influence of skin effect, calculating the penetration depth of each harmonic eddy current, and further calculating the induced electromotive force generated by each harmonic eddy current; Step S5, calculating the eddy current loss of each harmonic permanent magnet, and finally obtaining the total eddy current loss of the permanent magnet.

2. A semi-analytical calculation method for eddy current loss of permanent magnets of axial permanent magnet motor according to claim 1, characterized in that: The specific method for establishing the eddy current loss semi-analytical model in step S1 is: By transforming the sector-shaped permanent magnet into a rectangular permanent magnet and taking the center point of the transformed rectangular permanent magnet as the origin of coordinates, a rectangular coordinate system is established to obtain a semi-analytical model of eddy current loss. The conversion principle of the sector-shaped permanent magnet into the rectangular permanent magnet is to keep the flow area S of the eddy current path C unchanged.

3. A semi-analytical calculation method for eddy current loss of permanent magnets of axial permanent magnet motor according to claim 2, characterized in that: The specific method of converting a sector-shaped permanent magnet into a rectangular permanent magnet is: The outer diameter R of the sector permanent magnet o With inner diameter R i The difference is converted into the width of the rectangular permanent magnet, and the arc length R at the average radius of the sector permanent magnet is converted into ave =(R i +R o ) / 2 is converted to the length of the rectangular permanent magnet.

4. A semi-analytical calculation method for eddy current loss of permanent magnets of axial permanent magnet motor according to claim 3, characterized in that: The semi-analytical model of eddy current loss in step S1 has the following constraints: 1) Permanent magnet conductivity δ and relative magnetic permeability μ r remain unchanged; 2) Ignore the winding end effect and leakage flux; 3) The magnetic flux passes vertically through the permanent magnet; 4) The eddy current circulates in a rectangular form, and the ratio of the width y to the length x is a, and the aspect ratio of the rectangular eddy current is the same as the aspect ratio of the converted rectangular permanent magnet. The ratio a is expressed as follows: Where x is a variable, and its range is (0, R ave / 2), R o is the outer diameter of the sector permanent magnet, R i is the inner diameter of the sector permanent magnet, R ave is the arc length at the average radius of the sector-shaped permanent magnet.

5. A semi-analytical calculation method for eddy current loss of permanent magnets of axial permanent magnet motor according to claim 1, characterized in that: In step S2, the permanent magnet is divided into k and m rectangular regions horizontally and vertically, and the center point of each region is taken as the magnetic density sampling point. The magnetic density change curves of each region over time are obtained by simulation in the quasi-three-dimensional finite element model. bc (t), where b and c indicate that the region is the bth region in the transverse segmentation and the cth region in the longitudinal segmentation of the permanent magnet; on this basis, the magnetic flux density waveform B of each region is calculated. bc (t) Perform harmonic decomposition to obtain the curve B of each harmonic of magnetic density in each area changing with time n-bc (t), where n is the harmonic order.

6. A semi-analytical calculation method for eddy current loss of permanent magnets of axial permanent magnet motor according to claim 5, characterized in that: In step S2, the requirements for the number k and m of transverse and longitudinal segments of the permanent magnet are: k≥3, m≥2, and k and m are positive integers.

7. A semi-analytical calculation method for eddy current loss of permanent magnets of axial permanent magnet motor according to claim 5, characterized in that: The square of the time derivative of the nth harmonic magnetic flux density of a permanent magnet can be expressed as follows: Where dB n-bc (t) / dt is the time derivative of the nth harmonic magnetic flux density in the cth region of the bth longitudinal segment of the permanent magnet transverse segment.

8. A semi-analytical calculation method for eddy current loss of permanent magnets of axial permanent magnet motor according to claim 1, characterized in that: The expression of eddy current resistance in the permanent magnet in step S3 is as follows: Where δ is the conductivity of the permanent magnet, h pm is the thickness of the permanent magnet.

9. A semi-analytical calculation method for eddy current loss of permanent magnets of axial permanent magnet motor according to claim 1, characterized in that: In step S4, the induced electromotive force E generated by each harmonic eddy current when the skin effect is considered n The expression is as follows: Among them B n (t) is the relationship between the nth harmonic magnetic flux density and time, d n is the penetration depth of the harmonics, expressed as follows: Among them, ω n is the nth harmonic angular velocity of the magnetic field, μ0 is the vacuum permeability, μ r Relative magnetic permeability of permanent magnets respectively. oh n =2πb r ·n; Among them, n r is the motor speed, and n is the harmonic order.

10. A semi-analytical calculation method for eddy current loss of permanent magnets of axial permanent magnet motor according to claim 1, characterized in that: The eddy current loss of the nth harmonic permanent magnet in step S5 can be expressed as follows: The total eddy current loss of permanent magnet can be expressed as follows:

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