CN-122026648-A - Method for inhibiting eddy current loss by using open-loop grooves on surface of solid rotor of axial flux motor

Abstract

The invention discloses a method for inhibiting eddy current loss by an open-loop groove on the surface of a solid rotor of an axial flux motor, which relates to the technical field of axial flux motors and comprises the following steps of S1, obtaining a rotor magnetic flux density cloud chart of the axial flux motor and a B-H curve of a rotor material, calculating rotor magnetic permeability, S2, calculating harmonic angular velocity of each submagnetic field of the rotor, and calculating penetration depth of eddy current generated by each subharmonic according to the harmonic angular velocity of each submagnetic field of the rotor and the rotor magnetic permeability, S3, opening the annular groove on the outer surface of the rotor, S4, simulating the grooved axial flux motor, and adjusting the grooving number and/or grooving depth according to the simulation result of the eddy current loss and combining actual requirements, and by carrying out annular grooving on the rotor, part of eddy current paths can be effectively blocked, the effective circulation paths of eddy current are forced to be narrowed and lengthened, the resistance of the eddy current is greatly increased, and the eddy current loss is effectively inhibited under the condition that the high mechanical strength of the solid metal rotor is maintained.

Inventors

• SHAO LINGYUN
• LIU TAO

Assignees

• 南京航空航天大学

Dates

Publication Date

20260512

Application Date

20260123

Claims (10)

1. 1. The method for inhibiting eddy current loss by using the open-loop grooves on the surface of the solid rotor of the axial flux motor is characterized by comprising the following steps of: s1, acquiring a rotor flux density cloud chart and a B-H curve of a rotor material of an axial flux motor, and calculating the magnetic conductivity of the rotor; s2, calculating harmonic angular velocity of each submagnetic field of the rotor, and calculating penetration depth of eddy current generated by each subharmonic according to the harmonic angular velocity of each submagnetic field of the rotor and the rotor permeability obtained in the step S1; S3, opening an annular groove on the outer surface of the rotor, wherein the groove depth of the annular groove is equal to the penetration depth of the vortex generated by the fundamental wave in the step S2; and S4, simulating the axial flux motor with the grooved rotor, and adjusting the grooved quantity and/or grooved depth of the annular groove according to the eddy current loss simulation result and the actual requirement.
2. 2. The method for suppressing eddy current loss in an open-loop slot on the surface of a solid rotor of an axial flux motor according to claim 1, wherein calculating the rotor permeability in step S1 comprises taking the maximum magnetic density point on the obtained rotor magnetic density cloud chart, and calculating the permeability corresponding to the maximum magnetic density point, wherein the rotor permeability μ has the calculation formula: Wherein B i+1 and H i+1 are respectively the magnetic induction intensity and the magnetic field intensity of the first experimental test point at the right side of the B-H curve of the rotor material, and B i-1 and H i-1 are respectively the magnetic induction intensity and the magnetic field intensity of the first experimental test point at the left side of the B-H curve of the rotor material.
3. 3. The method for suppressing eddy current loss in an open-loop slot on a solid rotor surface of an axial-flux motor according to claim 2, wherein the calculation formula of the harmonic angular velocity ω k of each sub-magnetic field of the rotor in step S2 is: Wherein N is the rotation speed of the axial flux motor, N s is the number of stator slots of the axial flux motor, k is the harmonic frequency, and k is a positive integer.
4. 4. A method for suppressing eddy current loss in an open-loop groove in a solid rotor surface of an axial flux machine according to claim 3, wherein the eddy current skin depth δ r generated by each subharmonic in step S2 is calculated as: where σ is the conductivity of the rotor material.
5. 5. A method of suppressing eddy current losses in an open-loop groove in a solid rotor surface of an axial flux machine according to claim 1, wherein said annular groove is concentric with said rotor, and wherein the groove width of said annular groove is uniform in the depth direction.
6. 6. The method for suppressing eddy current loss in an open loop slot in a solid rotor surface of an axial flux machine of claim 5, wherein said annular slot is formed in a surface of said rotor adjacent to a permanent magnet.
7. 7. The method for suppressing eddy current loss in an open loop slot in a solid rotor surface of an axial flux machine of claim 5, wherein the annular slot is formed in a surface of the rotor on a side closer to the permanent magnets and a surface of the rotor on a side farther from the permanent magnets.
8. 8. A method of suppressing eddy current losses in an open loop slot in a solid rotor surface of an axial flux machine as claimed in claim 5, wherein the annular slot is open to a surface of the rotor on a side closer to the permanent magnets, a surface of the rotor on a side farther from the permanent magnets, and inner and/or outer axial surfaces of the rotor.
9. 9. The method for suppressing eddy current loss in an open-loop groove on a solid rotor surface of an axial flux machine according to claim 1, wherein adjusting the number of grooves and/or the groove depth of the annular groove comprises adjusting the number of grooves and the groove depth simultaneously when the number of grooves or the groove depth cannot be adjusted singly.
10. 10. The method for suppressing eddy current loss in an open-loop groove on a solid rotor surface of an axial flux machine according to claim 1, wherein adjusting the number of grooves and/or the groove depth of the annular groove comprises adjusting only the groove depth when the actual requirement can be met by adjusting the groove depth.

Description

Method for inhibiting eddy current loss by using open-loop grooves on surface of solid rotor of axial flux motor Technical Field The invention relates to the technical field of axial flux motors, in particular to a method for inhibiting eddy current loss by an open-loop groove on the surface of a solid rotor of an axial flux motor. Background The stator and the rotor of the axial flux motor are axially distributed, the axial dimension is smaller, and the radial dimension can be relatively larger, so that sufficient area is provided for energy conversion, the magnetic flux direction is parallel to the rotating shaft, the magnetic field path is shorter, and the magnetic resistance is lower. Therefore, the motor has the advantages of compact structure, light weight, high torque density, high efficiency and the like, and is widely applied to the fields of space and weight limitation, such as electric automobiles, aerospace and ship propulsion. At present, a rotor of an axial flux motor is often made of silicon steel sheets in a winding mode, but the thin disc-shaped and large-radius structural characteristics enable the rotor to bear huge centrifugal force when the rotor rotates at a high speed, the overall strength and tensile property of the silicon steel sheet winding structure are far lower than those of solid metal materials, the rotor is easy to deform and even fly, the rotor is often matched with a high-strength sheath for use, meanwhile, the rotor disc is required to bear axial magnetic pulling force, the rigidity and fixation of the winding structure in the axial direction are complex, the stability is poor, in addition, the process for winding the silicon steel sheets is complex, the cost is high, the interlayer thermal resistance is large, and a heat dissipation path is not smooth. In ultra-high speed applications, where the silicon steel sheet strength is insufficient, a solid metal rotor is used, and although the eddy current loss is large, the mechanical strength is a hard requirement, and only a part of efficiency can be sacrificed. The efficiency of the solid metal rotor is reduced slightly and the mass production cost is far lower than that of the coiled silicon steel sheet. The solid metal rotor such as 2Cr13 (Marshall stainless steel) adopts an integrated structure, thoroughly eliminates the hidden trouble of loosening between winding layers, has higher structural strength, can reliably bear huge centrifugal force and axial magnetic pulling force at high speed, and meanwhile, the structure can be molded by conventional forging and processing, has simple process and low cost, and has obvious advantages in application requiring high structural reliability. However, due to its high conductivity, strong eddy currents are induced on the rotor, resulting in reduced efficiency, increased temperature, and the risk of demagnetizing the heated permanent magnets, and therefore its application is limited. Disclosure of Invention The invention aims to provide a method for inhibiting eddy current loss by using open-loop grooves on the surface of a solid rotor of an axial flux motor, which solves the technical problems of reduced efficiency and increased temperature caused by high conductivity of a solid metal rotor and limited application caused by strong eddy current induced on the rotor and heating of a permanent magnet to cause demagnetization risk. The aim of the invention can be achieved by the following technical scheme: a method for inhibiting eddy current loss by using open-loop grooves on the surface of a solid rotor of an axial flux motor comprises the following steps: s1, acquiring a rotor flux density cloud chart and a B-H curve of a rotor material of an axial flux motor, and calculating the magnetic conductivity of the rotor; s2, calculating harmonic angular velocity of each submagnetic field of the rotor, and calculating penetration depth of eddy current generated by each subharmonic according to the harmonic angular velocity of each submagnetic field of the rotor and the rotor permeability obtained in the step S1; S3, opening an annular groove on the outer surface of the rotor, wherein the groove depth of the annular groove is equal to the penetration depth of the vortex generated by the fundamental wave in the step S2; and S4, simulating the axial flux motor with the grooved rotor, and adjusting the grooved quantity and/or grooved depth of the annular groove according to the eddy current loss simulation result and the actual requirement. Compared with the prior art, the method for inhibiting eddy current loss by using the open-loop grooves on the solid rotor surface of the axial flux motor has the following beneficial effects: The invention can effectively block part of eddy current paths by carrying out annular slotting on the rotor, forces the effective circulation path of eddy current to be narrowed and lengthened, greatly increases the resistance of eddy current, effectively inhibits ed