WO2021007874A1

WO2021007874A1 - Composite permanent magnet motor

Info

Publication number: WO2021007874A1
Application number: PCT/CN2019/096926
Authority: WO
Inventors: 林德芳
Original assignee: 上海特波电机有限公司
Priority date: 2019-07-12
Filing date: 2019-07-19
Publication date: 2021-01-21
Also published as: CN110350689A

Abstract

Provided is a composite permanent magnet motor, which relates to the technical field of electric motors. The technical problem to be solved is to improve flux-weakening speed expansion capability. The motor comprises a stator and a rotor, wherein the rotor is provided with a plurality of permanent magnet units that are symmetrically arranged around an axis of the rotor at intervals, and each permanent magnet unit is divided into two symmetrical halves by a straight axis of the rotor; and the permanent magnet unit comprises a permanent magnet groove and a composite magnet embedded in the permanent magnet groove, the composite magnet is formed by stacking a first permanent magnet and a second permanent magnet, the first permanent magnet is located outside the second permanent magnet, and the first permanent magnet has a greater coercive force than the second permanent magnet. The motor provided by the present invention can meet the driving requirements of electric vehicles and hybrid vehicles.

Description

Compound permanent magnet motor

Technical field

The present invention relates to motor technology, in particular to a composite permanent magnet motor technology.

Background technique

Electric vehicle drive systems all use built-in permanent magnet synchronous motors (IPMSM) as the power source. The built-in permanent magnet synchronous motors use permanent magnet excitation, which has a constant magnetic field and cannot be adjusted. Therefore, it has the defect of difficulty in field weakening and speed expansion. When the motor parameters and size are fixed, the speed increases with the increase of voltage. In the constant power operation area above the base speed, as the speed increases, it is difficult to increase the speed with constant power due to the limitation of the supply voltage (electric vehicle motor is powered by the battery); In addition, on the direct shaft (d-axis) of the motor, the permeability of the permanent magnet is close to that of air, and the direct-axis inductance Ld is small, which increases the difficulty of magnetic field weakening and speed-up.

Existing built-in permanent magnet synchronous motors must be field weakened, and the reluctance torque must be obtained by adjusting the stator current (that is, increasing the stator direct shaft demagnetization current component -Id). The weakening of the motor air gap magnetic field is equivalent to direct Weakening the excitation magnetic field to achieve magnetic field weakening, narrow field weakening expansion range, large stator loss, low system (motor and controller) efficiency, while increasing the direct-axis armature current-Id will lead to the risk of irreversible demagnetization of the magnet, thickening the magnet It will increase the centrifugal force and cost of the rotor. Therefore, the existing built-in permanent magnet synchronous motors have defects such as low power and torque density, narrow high-speed constant power range, large torque fluctuations, low overload capacity and system efficiency, high risk of magnetic steel demagnetization, and poor reliability. These defects restrict Drive the research and development of the drive motor and its industrialization progress.

Summary of the invention

In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a composite permanent magnet motor with good field weakening and speed expansion capability.

In order to solve the above technical problems, the present invention provides a composite permanent magnet motor, which includes a stator and a rotor. The rotor is provided with a plurality of permanent magnet units, and each permanent magnet unit is arranged at symmetrical intervals around the axis of the rotor, and Each permanent magnet unit is divided into two symmetrical halves by the direct axis of the rotor; its characteristics are:

The permanent magnet unit includes a permanent magnet slot, and a composite magnet embedded in the permanent magnet slot. The composite magnet is formed by stacking a first permanent magnet and a second permanent magnet, and the first permanent magnet is located at the second permanent magnet. The coercive force of the first permanent magnet is greater than the coercive force of the second permanent magnet.

Further, the length of the first permanent magnet is the same as the length of the second permanent magnet.

Further, the thickness of the first permanent magnet is smaller than the thickness of the second permanent magnet.

Further, the permanent magnet groove and the composite magnet embedded in the permanent magnet groove are both in-line, and the thickness of the second permanent magnet is 1.8 to 2.2 times the thickness of the first permanent magnet.

Further, the permanent magnet groove is V-shaped, and two composite magnets are embedded in the V-shaped permanent magnet groove, and the two composite magnets in the permanent magnet groove are arranged in a V shape, and the second permanent magnet The thickness of the magnet is 1.6 to 2.0 times the thickness of the first permanent magnet.

Further, the permanent magnet unit has two in-line permanent magnet slots, and the two permanent magnet slots are arranged in order from the inside to the outside along the radial direction of the rotor, and the composite magnet is embedded in the inner permanent magnet slot, and the outside A third permanent magnet is embedded in the permanent magnet groove, and the coercive force of the third permanent magnet is the same as that of the first permanent magnet.

Further, the thickness of the third permanent magnet is the same as the thickness of the first permanent magnet.

Further, the length of the third permanent magnet is smaller than the length of the first permanent magnet.

Further, both ends of the composite magnet are each formed with an inner magnetic isolation groove, and the inner magnetic isolation grooves at both ends of the composite magnet are separated from the inner permanent magnetic groove.

Further, an outer magnetic isolation groove is formed at both ends of the third permanent magnet, and the outer magnetic isolation grooves at both ends of the third permanent magnet are separated from the outer permanent magnetic groove.

Further, the thickness of the second permanent magnet is 1.6 to 2.2 times the thickness of the first permanent magnet.

Further, the permanent magnet slot is V-shaped, and two composite magnets are embedded in the V-shaped permanent magnet slot, and the two composite magnets in the permanent magnet slot are arranged in a V shape;

The rotor is also provided with multiple magnetic barrier units, each magnetic barrier unit is arranged symmetrically spaced around the axis of the rotor, and each magnetic barrier unit is divided into two symmetrical halves by the rotor's quadrature axis, and each magnetic barrier unit includes two In the inner magnetic barrier groove, the two inner magnetic barrier grooves are arc-shaped grooves with the arc top facing inward and different radii, and the two inner magnetic barrier grooves are arranged concentrically from the inside to the outside along the radial direction of the rotor.

Further, each magnetic barrier unit further includes a surface magnetic barrier groove, and the surface magnetic barrier groove is an inwardly recessed groove opened on the circumferential surface of the rotor.

The composite permanent magnet motor provided by the present invention utilizes the difference in coercivity characteristics of neodymium iron boron and alnico permanent magnet materials to form a composite magnet permanent magnet rotor connected in series on the magnetic circuit, which can obtain higher air gap magnetic flux, Improve efficiency, power and torque density, and control the demagnetization and demagnetization of the low coercive force of the composite magnet in the permanent magnet slot through the direct axis armature reaction magnetomotive force generated by the stator direct axis current vector pulse. The degree of magnetization causes a part of the main magnetic flux to pass through the partial bypass of Al-Ni-Co and become a leakage flux, which can achieve weak magnetic field expansion, low-speed constant torque operation, high-speed constant power operation, and obtain a wider range than existing permanent magnet synchronous motors The range of constant power and speed greatly improves the overall quality of the motor, achieving high power density, wide speed regulation, fast response, frequent starting and smooth operation, and meeting the driving requirements of electric vehicles and hybrid vehicles.

Description of the drawings

Fig. 1 is a schematic diagram of a radial cross-section of a composite permanent magnet motor according to a first embodiment of the present invention;

2 is a schematic diagram of a radial cross-section of a composite permanent magnet motor according to a second embodiment of the present invention;

3 is a schematic partial radial cross-sectional view of a composite permanent magnet motor according to a third embodiment of the present invention;

4 is a schematic partial radial cross-sectional view of a composite permanent magnet motor according to a fourth embodiment of the present invention.

Detailed ways

The following describes the embodiments of the present invention in further detail with reference to the accompanying drawings, but this embodiment is not used to limit the present invention. Any similar structure and similar changes of the present invention should be included in the protection scope of the present invention. The comma in the middle all indicate the relationship of and, and the English letters in the present invention are case-sensitive.

As shown in Figure 1, a composite permanent magnet motor provided by the first embodiment of the present invention includes a stator 11 and a rotor 12. The rotor 12 is provided with a plurality of permanent magnet units, and each permanent magnet unit surrounds the rotor. The axis is symmetrically spaced, and each permanent magnet unit is divided into two symmetrical halves by the direct axis of the rotor (magnetic pole centerline, d-axis); its characteristics are:

The permanent magnet unit includes an in-line permanent magnet slot and an in-line composite magnet embedded in the permanent magnet slot. The composite magnet is formed by stacking a first permanent magnet 131 and a second permanent magnet 132, and The first permanent magnet 131 is located outside the second permanent magnet 132 (the side facing the outer circumference of the rotor is the outside), and the coercive force of the first permanent magnet 131 is greater than the coercive force of the second permanent magnet 132, and is in the diameter of the rotor. In the cross section, the length of the first permanent magnet 131 is the same as the length of the second permanent magnet 132, and the thickness h11 of the first permanent magnet 131 is smaller than the thickness h12 of the second permanent magnet 132 (assuming the thickness of the composite magnet is h10, then h10= h11+h12), and a magnetic isolation groove 14 is formed at both ends of the composite magnet, and the magnetic isolation grooves 14 at both ends of the composite magnet are integrated with the permanent magnet groove.

In the first embodiment of the present invention, the preferred solution of the thickness ratio of the first permanent magnet 131 to the second permanent magnet 132 is that the thickness h12 of the second permanent magnet is 1.8 to 2.2 times the thickness h11 of the first permanent magnet.

In the first embodiment of the present invention, the two magnetic isolation slots at both ends of the composite magnet play a role in reducing magnetic flux leakage. The inline composite magnet and the pole piece (rotor core) constitute magnetic poles, and the first permanent magnet is a neodymium iron boron magnet , The second permanent magnet is an AlNiCo magnet. The first permanent magnet and the second permanent magnet are connected in series in the magnetic circuit. The remanence of the NdFeB magnet and AlNiCo magnet is close, but the coercivity is very different. NdFeB magnets are difficult to demagnetize and magnetize, and AlNiCo magnets are easy to demagnetize and magnetize; optimizing the thickness ratio of the first permanent magnet to the second permanent magnet can not only obtain higher air gap magnetic flux, improve efficiency and power, The torque density can also control the magnetization and demagnetization degree of the second permanent magnet with low coercivity in the composite magnet in the permanent magnet slot through the direct-axis armature reaction magnetomotive force generated by the direct-axis current vector id pulse of the rotor , Thereby regulating the main magnetic flux of the air gap (increase or weaken); when the second permanent magnet is demagnetized, a part of the main magnetic flux is partially bypassed (short-circuited) by the second permanent magnet, and becomes the leakage flux, and the main magnetic flux of the air gap Attenuate, reach the weakening speed, low-speed constant torque operation, high-speed constant power operation, and obtain a wider range of constant power speed than the existing permanent magnet synchronous motor; the magnetic circuit is connected in series to form an integral strip rectangular composite magnet. The magnetic rear is embedded in the permanent magnet slot, compact structure, resistant to high-speed centrifugal force, can effectively reduce motor noise and torque fluctuations, significantly improve the overall quality of the motor, and achieve high power density, wide speed regulation, fast response, frequent start and stable Operation to meet the driving requirements of electric vehicles and hybrid vehicles.

As shown in FIG. 2, the difference between the second embodiment of the present invention and the first embodiment is that: in the second embodiment, the permanent magnet groove on the rotor 22 is in a V-shape, and the V-shaped permanent magnet groove is embedded There are two in-line composite magnets, and the two composite magnets in the permanent magnet slots are arranged in a V shape, and magnetic isolation slots 24 are formed at both ends of each composite magnet, and the magnetic isolation slots at both ends of the composite magnet 24 is connected with the permanent magnet groove as a whole.

In the composite magnet of the second embodiment of the present invention, the thickness ratio of the first permanent magnet 231 to the second permanent magnet 232 is preferably: the thickness of the second permanent magnet is 1.6 to 2.0 times the thickness of the first permanent magnet.

The working principle of the second embodiment of the present invention is similar to that of the first embodiment, and can also significantly improve the overall quality of the motor, realize high power density, wide speed regulation, fast response, frequent start and smooth operation, and meet the requirements of electric vehicles and hybrid vehicles Drive requirements; a wider range of constant power speed can be obtained than the existing V-shaped permanent magnet structure built-in permanent magnet synchronous motor;

For example: a motor with a rated power of 50KW, a rated speed of 3000 (r/min), a rated torque/maximum torque of 159/350 (Nm), the second embodiment of the present invention is compared with the existing V-shaped permanent magnet structure built-in permanent The efficiency of the magnetic synchronous motor is increased from 94.2% to 96.78%, the current under the rated torque (159Nm) is reduced from 158A to 150A, and the speed expansion range is increased from 0-7000r/min to 0-9500r/min. The structure of the second embodiment can increase the speed expansion capability of the motor by 1.35 times.

As shown in Figure 3, the difference between the third embodiment of the present invention and the first embodiment is that the permanent magnet unit in the third embodiment has two in-line permanent magnet slots, and the two permanent magnet slots are along the rotor. The composite magnet is embedded in the inner permanent magnet slot. The structure of the composite magnet is the same as that of the first embodiment. The outer permanent magnet slot is embedded with a third permanent magnet 333, and the third permanent magnet The coercive force of the magnet 333 is the same as that of the first permanent magnet 331, and in the radial section of the rotor 32, the thickness of the third permanent magnet 333 is the same as the thickness of the first permanent magnet 331, and the third permanent magnet 333 The length of is smaller than the length of the first permanent magnet 331.

In the third embodiment of the present invention, an inner magnetic isolation groove 341 is formed at each end of the composite magnet, and the inner magnetic isolation grooves 341 and the inner permanent magnetic groove at both ends of the composite magnet are separated from each other; the two third permanent magnets 333 An outer magnetic isolation groove 342 is formed at each end, and the outer magnetic isolation grooves 342 at both ends of the third permanent magnet are separated from the outer permanent magnetic grooves.

In the third embodiment of the present invention, the preferred solution for the thickness ratio of the first permanent magnet 331 to the second permanent magnet 332 is that the thickness of the second permanent magnet is 1.6 to 2.2 times the thickness of the first permanent magnet.

The working principle of the third embodiment of the present invention is similar to that of the first embodiment, and can also significantly improve the overall quality of the motor, realize high power density, wide speed regulation, fast response, frequent starting and smooth operation, and meet the requirements of electric vehicles and hybrid vehicles Drive requirements.

As shown in FIG. 4, the difference between the fourth embodiment of the present invention and the second embodiment is that the rotor 42 in the fourth embodiment is further provided with a plurality of magnetic barrier units, and each magnetic barrier unit is symmetrically spaced around the axis of the rotor. Each magnetic barrier unit is divided into two symmetrical halves by the quadrature axis of the rotor (center line between poles, q-axis). Each magnetic barrier unit includes two

inner barrier grooves

451, 452, and a surface magnetic Barrier groove 453, the two inner

magnetic barrier grooves

451, 452 are arc-shaped grooves with arc tops facing inward and different radii, and the two inner

magnetic barrier grooves

451, 452 are concentric from inside to outside along the radial direction of the rotor The surface magnetic barrier groove 453 is an inwardly recessed groove opened on the circumferential surface of the rotor.

Compared with the second embodiment, the fourth embodiment of the present invention adds a magnetic barrier unit. In addition to the characteristics of the second embodiment, the magnetic barrier unit also forms a direct-axis inductance greater than a quadrature-axis inductance, thereby obtaining magnetic Resistance torque, forming a double field weakening speed expansion structure, can further reduce loss compared with the second embodiment, improve system efficiency, power density and torque density, improve field weakening speed expansion capability, and expand constant power range operation.

Claims

A composite permanent magnet motor includes a stator and a rotor. The rotor is provided with a plurality of permanent magnet units. The permanent magnet units are arranged at symmetrical intervals around the axis of the rotor, and each permanent magnet unit is controlled by the direct axis of the rotor. Divided into two symmetrical halves; characterized by:

The permanent magnet unit includes a permanent magnet slot, and a composite magnet embedded in the permanent magnet slot. The composite magnet is formed by stacking a first permanent magnet and a second permanent magnet, and the first permanent magnet is located at the second permanent magnet. The coercive force of the first permanent magnet is greater than the coercive force of the second permanent magnet.
The composite permanent magnet motor according to claim 1, wherein the length of the first permanent magnet is the same as the length of the second permanent magnet.
The composite permanent magnet motor according to claim 1, wherein the thickness of the first permanent magnet is smaller than the thickness of the second permanent magnet.
The composite permanent magnet motor according to claim 3, wherein the permanent magnet slot and the composite magnet embedded in the permanent magnet slot are both in-line, and the thickness of the second permanent magnet is that of the first permanent magnet 1.8 to 2.2 times the thickness.
The composite permanent magnet motor according to claim 3, characterized in that: the permanent magnet groove is V-shaped, and two composite magnets are embedded in the V-shaped permanent magnet groove, and the permanent magnet groove The two composite magnets are arranged in a V shape, and the thickness of the second permanent magnet is 1.6 to 2.0 times the thickness of the first permanent magnet.
The composite permanent magnet motor according to claim 3, wherein the permanent magnet unit has two in-line permanent magnet slots, and the two permanent magnet slots are arranged from inside to outside along the radial direction of the rotor. The composite magnet is embedded in the inner permanent magnet groove, and the third permanent magnet is embedded in the outer permanent magnet groove, and the coercive force of the third permanent magnet is the same as that of the first permanent magnet.
The composite permanent magnet motor according to claim 6, wherein the thickness of the third permanent magnet is the same as the thickness of the first permanent magnet.
The composite permanent magnet motor according to claim 6, wherein the length of the third permanent magnet is smaller than the length of the first permanent magnet.
The composite permanent magnet motor according to claim 6, wherein an inner magnetic isolation groove is formed at both ends of the composite magnet, and the inner magnetic isolation grooves at both ends of the composite magnet are separated from the inner permanent magnetic groove.
The composite permanent magnet motor according to claim 6, wherein an outer magnetic isolation groove is formed at both ends of the third permanent magnet, and the outer magnetic isolation grooves at both ends of the third permanent magnet and the outer permanent magnet The slots are separated from each other.
The composite permanent magnet motor according to claim 6, wherein the thickness of the second permanent magnet is 1.6 to 2.2 times the thickness of the first permanent magnet.
The composite permanent magnet motor according to claim 3, characterized in that: the permanent magnet groove is V-shaped, and two composite magnets are embedded in the V-shaped permanent magnet groove, and the permanent magnet groove Two composite magnets are arranged in a V shape;

The rotor is also provided with multiple magnetic barrier units, each magnetic barrier unit is arranged symmetrically spaced around the axis of the rotor, and each magnetic barrier unit is divided into two symmetrical halves by the rotor's quadrature axis, and each magnetic barrier unit includes two In the inner magnetic barrier groove, the two inner magnetic barrier grooves are arc-shaped grooves with the arc top facing inward and different radii, and the two inner magnetic barrier grooves are arranged concentrically from the inside to the outside along the radial direction of the rotor.
The composite permanent magnet motor according to claim 12, wherein each magnetic barrier unit further comprises a surface magnetic barrier groove, and the surface magnetic barrier groove is an inwardly recessed groove opened on the circumferential surface of the rotor.