U-shaped composite permanent magnet motor

Abstract

A U-shaped composite permanent magnet motor relates to the technical field of motors, and solves the technical problem of improving the weak magnetic field speed expansion capability. The motor comprises a stator and a rotor, and the rotor is provided with a plurality of permanent magnet units symmetrically arranged around the rotor axis, and the permanent magnet units include a central permanent magnet slot and two side permanent magnet slots; a composite magnet is embedded in the central permanent magnet slot, and the composite magnet is formed by stacking a first permanent magnet and a second permanent magnet, and the first permanent magnet is located on the outside of the second permanent magnet, and the coercive force of the first permanent magnet is greater than the coercive force of the second permanent magnet; a third permanent magnet is embedded in each side permanent magnet slot, and the coercive force of the third permanent magnet is the same as the coercive force of the first permanent magnet, and the layout shape of the two third permanent magnets is an eight-shaped shape with a narrow mouth facing inward, and the composite magnet is arranged in the narrow mouth of the eight-shaped shape. The motor provided by the present invention can meet the driving requirements of electric vehicles and hybrid electric vehicles.

Description

Technical Field

[0001] The invention relates to motor technology, in particular to a U-shaped composite permanent magnet motor technology. Background Art

[0002] Electric vehicle drive systems all use internal permanent magnet synchronous motors (IPMSM) as power sources. Internal permanent magnet synchronous motors use permanent magnet excitation, and their magnetic field is constant and cannot be adjusted, so there is a defect that weak magnetic field speed expansion is difficult. When the motor parameters and size are constant, 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 at constant power due to the limitation of the power supply voltage (the motor for electric vehicles is powered by batteries); in addition, on the direct axis (d axis) of the motor, the magnetic permeability of the permanent magnet is close to that of air, and the direct axis inductance Ld is small, which increases the difficulty of weak magnetic field speed increase.

[0003] The existing built-in permanent magnet synchronous motor must obtain magnetic resistance torque by adjusting the stator current (i.e. increasing the stator direct axis demagnetization current component -Id) through magnetic weakening. The weakening of the motor air gap magnetic field is equivalent to directly weakening the excitation magnetic field to achieve magnetic weakening. The magnetic weakening speed range is narrow, the stator loss is large, and the system (motor and controller) efficiency is low. At the same time, increasing the direct axis armature current -Id will lead to the risk of irreversible demagnetization of the magnetic steel, and thickening the magnetic steel will increase the centrifugal force and cost of the rotor. Therefore, the existing built-in permanent magnet synchronous motor has the defects of low power and torque density, narrow high-speed constant power range, large torque fluctuation, low overload capacity and system efficiency, high risk of magnetic steel demagnetization and poor reliability. These defects restrict the research and development of drive motors and their industrialization progress. Summary of the invention

[0004] In view of the defects existing in the above-mentioned prior art, the technical problem to be solved by the present invention is to provide a U-shaped composite permanent magnet motor with good weak magnetic field speed expansion capability.

[0005] In order to solve the above technical problems, the present invention provides a U-shaped composite permanent magnet motor, comprising a stator and a rotor, wherein a plurality of permanent magnet units are arranged on the rotor, and each permanent magnet unit is symmetrically spaced around the axis of the rotor, and is characterized in that:

[0006] The permanent magnet unit comprises three straight permanent magnet slots, one of which is a middle permanent magnet slot, and the other two permanent magnet slots are side permanent magnet slots;

[0007] A composite magnet is embedded in the middle permanent magnet slot, 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, the rotor direct axis divides the composite magnet into two symmetrical halves, and the coercive force of the first permanent magnet is greater than the coercive force of the second permanent magnet;

[0008] A third permanent magnet is embedded in each side permanent magnet slot, and the coercive force of the third permanent magnet is the same as that of the first permanent magnet. The two third permanent magnets are arranged in an eight-shaped shape with a narrow opening facing inward, and the composite magnet is arranged in the narrow opening of the eight-shaped shape.

[0009] Furthermore, the length of the first permanent magnet is the same as the length of the second permanent magnet.

[0010] Furthermore, the thickness of the first permanent magnet is smaller than the thickness of the second permanent magnet.

[0011] Furthermore, the length of the third permanent magnet is greater than the length of the first permanent magnet.

[0012] Furthermore, the thickness of the third permanent magnet is the same as the thickness of the first permanent magnet.

[0013] Furthermore, a first magnetic isolation groove is formed at each of the two ends of the composite magnet, and the first magnetic isolation grooves at the two ends of the composite magnet are isolated from each permanent magnet groove.

[0014] Furthermore, a second magnetic isolation groove is formed at the outer end of each third permanent magnet, and the second magnetic isolation groove at the outer end of each third permanent magnet is integrally connected with the side permanent magnet groove where the third permanent magnet is located.

[0015] Furthermore, the thickness of the second permanent magnet is 1.8 to 2.2 times the thickness of the first permanent magnet.

[0016] The U-shaped composite permanent magnet motor provided by the present invention utilizes the difference in coercive force characteristics between NdFeB and AlNiCo permanent magnet materials to form a composite magnet permanent magnet rotor connected in series on a magnetic circuit, which can not only obtain a higher air gap flux and improve efficiency, power and torque density, but also regulate the demagnetization and magnetization degree of AlNiCo with low coercive force in 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, so that a part of the main magnetic flux is locally bypassed by AlNiCo and becomes leakage magnetic flux, thereby achieving weak magnetic speed expansion, low-speed constant torque operation, high-speed constant power operation, and obtaining a wider constant power speed range than the existing permanent magnet synchronous motor, thereby greatly improving the comprehensive 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a partial radial cross-sectional schematic diagram of a U-shaped composite permanent magnet motor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following is a further detailed description of an embodiment of the present invention in conjunction with the accompanying drawings, but this embodiment is not intended to limit the present invention. All similar structures and similar variations of the present invention should be included in the protection scope of the present invention. The commas in the present invention represent the relationship of and, and the English letters in the present invention are case-sensitive.

[0019] like Figure 1 As shown, a U-shaped composite permanent magnet motor provided by an embodiment of the present invention comprises a stator (not shown) and a rotor 1, wherein a plurality of permanent magnet units are arranged on the rotor, and each permanent magnet unit is symmetrically spaced around the axis of the rotor, and is characterized in that:

[0020] The permanent magnet unit comprises three straight permanent magnet slots, one of which is a middle permanent magnet slot, and the other two permanent magnet slots are side permanent magnet slots;

[0021] A composite magnet is embedded in the middle permanent magnet slot, and the composite magnet is formed by stacking a first permanent magnet 21 and a second permanent magnet 22, and the first permanent magnet 21 is located on the outside of the second permanent magnet 22 (the side facing the outer circle of the rotor is the outside), and the rotor direct axis (magnetic pole center line, d axis) divides the composite magnet into two symmetrical halves, and the coercive force of the first permanent magnet 21 is greater than the coercive force of the second permanent magnet 22;

[0022] A third permanent magnet 23 is embedded in each side permanent magnet slot, and the coercive force of the third permanent magnet 23 is the same as the coercive force of the first permanent magnet 21. The two third permanent magnets 23 are arranged in an eight-shaped shape with a narrow opening facing inward, and the composite magnet is arranged in the narrow opening of the eight-shaped shape.

[0023] In the radial cross section of the rotor, the length of the first permanent magnet 21 is the same as the length of the second permanent magnet 22, the thickness h1 of the first permanent magnet 21 is less than the thickness h2 of the second permanent magnet 22 (assuming that the thickness of the composite magnet is h0, then h0=h1+h2), the length of the third permanent magnet 23 is greater than the length of the first permanent magnet 21, and the thickness h3 of the third permanent magnet 23 is the same as the thickness h1 of the first permanent magnet 21;

[0024] A first magnetic isolation groove 31 is formed at each end of the composite magnet, and the first magnetic isolation grooves 31 at both ends of the composite magnet are isolated from each permanent magnet groove. A second magnetic isolation groove 32 is formed at the outer end of each third permanent magnet 23, and the second magnetic isolation groove 32 at the outer end of each third permanent magnet is integrated with the side permanent magnet groove where the third permanent magnet is located.

[0025] In the embodiment of the present invention, a circular auxiliary slot 4 is provided in the middle of the permanent magnet unit. The auxiliary slot 4 can reduce core loss, improve the air gap magnetic field waveform, reduce torque fluctuation, and suppress static and dynamic armature reaction demagnetization, thereby achieving smooth operation with high efficiency, high power density, low speed constant torque and high speed constant power expansion.

[0026] In the composite magnet of the embodiment of the present invention, a preferred solution for the thickness ratio of the first permanent magnet 21 to the second permanent magnet 22 is: the thickness of the second permanent magnet is 1.8 to 2.2 times the thickness of the first permanent magnet.

[0027] In the embodiment of the present invention, the first magnetic isolation groove 31 and the second magnetic isolation groove 32 play a role in reducing magnetic leakage, the two third permanent magnets 23 and the composite magnet form a magnet array similar to a U-shaped structure, the magnet array and the pole shoe (rotor core) form a magnetic pole, the first permanent magnet and the third permanent magnet are neodymium iron boron magnets, the second permanent magnet is an aluminum nickel cobalt magnet, the first permanent magnet and the second permanent magnet are connected in series on the magnetic circuit, the remanence of the neodymium iron boron magnet and the aluminum nickel cobalt magnet are close, but the coercive force is very different, the neodymium iron boron magnet is difficult to demagnetize and magnetize, and the aluminum nickel cobalt magnet is easy to demagnetize and magnetize; optimizing the thickness ratio of the first permanent magnet and the second permanent magnet can not only obtain a higher air gap flux, improve efficiency and power, torque density, but also can generate a direct-axis armature reaction magnetic field through the direct-axis current vector id pulse of the rotor The kinetic potential is used to regulate the magnetization and demagnetization degree of the second permanent magnet with low coercive force in the composite magnet in the permanent magnet slot, thereby regulating the main magnetic flux of the air gap (enhancement or weakening); when the second permanent magnet is demagnetized, a part of the main magnetic flux is bypassed (short-circuited) through the second permanent magnet locally and becomes leakage magnetic flux, and the main magnetic flux of the air gap is weakened, achieving weak magnetic speed expansion, low-speed constant torque operation, high-speed constant power operation, and obtaining a wider constant power speed range than the existing permanent magnet synchronous motor; the strip-shaped rectangular composite magnets connected in series on the magnetic circuit to form an integral whole are embedded in the permanent magnet slot after magnetization, with a compact structure, resistant to high-speed centrifugal force, and 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 starting and smooth operation, meeting the driving requirements of electric vehicles and hybrid vehicles.

Claims

1. A U-shaped composite permanent magnet motor, comprising a stator and a rotor, wherein the rotor is provided with a plurality of permanent magnet units, each of which is symmetrically spaced around the axis of the rotor, characterized in that: The permanent magnet unit comprises three straight permanent magnet slots, one of which is a middle permanent magnet slot, and the other two permanent magnet slots are side permanent magnet slots; A composite magnet is embedded in the middle permanent magnet slot, a first magnetic isolation slot is formed at each end of the composite magnet, and the first magnetic isolation slots at both ends of the composite magnet are isolated from each 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 outside the second permanent magnet, and the rotor direct axis divides the composite magnet into two symmetrical halves, and the coercive force of the first permanent magnet is greater than the coercive force of the second permanent magnet; The length of the first permanent magnet is the same as the length of the second permanent magnet, and the thickness of the first permanent magnet is less than the thickness of the second permanent magnet; A third permanent magnet is embedded in each side permanent magnet slot, and the coercive force of the third permanent magnet is the same as the coercive force of the first permanent magnet. The two third permanent magnets are arranged in an eight-shaped shape with a narrow opening facing inward, and the composite magnet is arranged in the narrow opening of the eight-shaped shape. The length of the third permanent magnet is greater than that of the first permanent magnet, the thickness of the third permanent magnet is the same as that of the first permanent magnet, a second magnetic isolation groove is formed at the outer end of each third permanent magnet, and the second magnetic isolation groove at the outer end of each third permanent magnet is integrated with the side permanent magnet groove where the third permanent magnet is located.

2. The U-shaped composite permanent magnet motor according to claim 1, characterized in that: The thickness of the second permanent magnet is 1.8 to 2.2 times the thickness of the first permanent magnet.

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