Rotor structure capable of reducing maximum stress of silicon steel sheets of high-speed permanent magnet synchronous motor

Abstract

The invention discloses a rotor structure capable of reducing the maximum stress of a silicon steel sheet of a high-speed permanent magnet synchronous motor. The rotor structure comprises a hollow shaft, a silicon steel sheet iron core, a rounded-corner bread-shaped permanent magnet and a carbon fiber sheath. The permanent magnet rotor presents three pairs of magnetic poles to the stator, four permanent magnet slotted holes with the same shape and a rounded corner bread shape are formed in the circumferential direction of a silicon steel sheet iron core below each magnetic pole and used for embedding the permanent magnets with the rounded corner bread shape, and an isosceles trapezoid air magnetic isolation hole with a rounded corner is formed in the silicon steel sheet iron core between six adjacent magnetic poles. The silicon steel sheet iron core and the hollow shaft are in interference fit to transmit torque, and the carbon fiber sheath and the silicon steel sheet iron core are in interference fit to provide pre-pressure for the silicon steel sheet iron core. The maximum stress of the silicon steel sheet iron core is reduced by means of the design of the round-corner bread-shaped permanent magnet slotted holes, the round-corner isosceles trapezoid air magnetic isolation holes and the carbon fiber sheath, and the demagnetization resistance is improved by designing the radial thickness of the round-corner bread-shaped permanent magnets. And the harmonic content of a permanent magnet air-gap magnetic field is reduced by adjusting the tangential angle occupied by the slotted hole area of the rounded-corner bread-shaped permanent magnet.

Description

Technical Field

[0001] The invention belongs to the field of electrical engineering and relates to a rotor structure capable of reducing the maximum stress of silicon steel sheets of a high-speed permanent magnet synchronous motor. Background Art

[0002] Flywheel energy storage systems have the advantages of high power density, deep discharge depth, long service life and environmental friendliness. They are widely used in uninterruptible power supplies, grid frequency regulation, rail transit and high-power pulse power supplies. High-speed permanent magnet synchronous motors are often used in flywheel energy storage systems to realize the conversion between kinetic energy and electrical energy in flywheel energy storage systems.

[0003] In order to improve the energy storage density of the flywheel energy storage system, the maximum speed of the rotating shaft system of the flywheel energy storage system is designed to be higher and higher. In the built-in rotor of the high-speed permanent magnet synchronous motor, the silicon steel core on the outside of the rotor is subjected to a certain centrifugal force in addition to a large centrifugal force of the permanent magnet, which causes the magnetic bridge of the silicon steel core to be subjected to a large tensile stress, causing the maximum stress of the silicon steel core to appear near the magnetic bridge. If the maximum stress value exceeds the yield strength of the silicon steel material, the silicon steel sheet will undergo irreversible plastic deformation, endangering the safe operation of the rotating shaft system of the flywheel energy storage system. When designing the built-in rotor structure of the high-speed permanent magnet synchronous motor, the maximum stress of the silicon steel core should be limited, and sufficient stress safety margin should be reserved. When the flywheel energy storage system releases the kinetic energy stored in the flywheel, the speed of the rotating shaft system gradually decreases from the highest to the lowest. High-speed permanent magnet synchronous motors generate electrical energy at constant power within the range of maximum speed to minimum speed. At the lowest speed, the phase current amplitude of the stator winding is large, and the amplitude of the armature reaction magnetomotive force is large, causing the permanent magnet part near the cross axis of the permanent magnet rotor to be subjected to a large demagnetization magnetomotive force. If the amplitude of the demagnetization magnetomotive force exceeds the knee magnetic field strength on the demagnetization curve of the permanent magnet material at the operating temperature, the permanent magnet will suffer irreversible residual magnetism loss, causing the electromagnetic performance to continue to decline. When designing the built-in rotor structure of a high-speed permanent magnet synchronous motor, it is also necessary to resolve the contradiction between increasing the radial thickness of the permanent magnet as much as possible to improve the anti-demagnetization performance and minimizing the amount of permanent magnets to reduce the cost of the motor. Summary of the invention

[0004] In order to solve the above-mentioned technical problems existing in high-speed permanent magnet synchronous motors for megawatt-level high-power flywheel energy storage, the present invention proposes a rotor structure that can reduce the maximum stress of silicon steel sheets of high-speed permanent magnet synchronous motors, so as to ensure that the maximum stress value of the high-speed permanent magnet synchronous motor is small when running at high speed, and the permanent magnet has strong anti-demagnetization ability and low harmonic content of the permanent magnet air gap magnetic field.

[0005] The present invention provides a rotor structure capable of reducing the maximum stress of silicon steel sheets of a high-speed permanent magnet synchronous motor, comprising: a hollow shaft (1), a silicon steel sheet core (2), a bread-shaped permanent magnet with rounded corners (3) and a carbon fiber sheath (4); the structure is characterized in that: the permanent magnet rotor presents three pairs of magnetic poles to the stator, the six magnetic poles are evenly distributed at intervals of 60 degrees along the circumferential direction, the silicon steel sheet core (2) under each magnetic pole has four bread-shaped permanent magnet slots (2-1) with rounded corners in the circumferential direction for embedding the bread-shaped permanent magnet with rounded corners (3), and there is one isosceles trapezoidal air magnetic isolation hole (2-2) with rounded corners on the silicon steel sheet core (2) between the six adjacent magnetic poles.

[0006] The midpoint of the upper top arc of the rounded bread-shaped permanent magnet slot hole (2-1), the midpoint of the lower bottom line segment and the center of the inner circle of the silicon steel sheet iron core (2) are on a straight line, the rounded bread-shaped permanent magnet slot hole (2-1) is symmetrical about the line segment between the midpoint of the upper top arc and the midpoint of the lower bottom line segment, and the radius of the upper bottom arc of the rounded bread-shaped permanent magnet slot hole (2-1) is smaller than the line segment distance from the midpoint of the upper top arc to the center of the inner circle of the silicon steel sheet iron core (2); the silicon steel sheet iron core (2) between two adjacent rounded bread-shaped permanent magnet slot holes (2-1) The parallel ribs are parallel ribs. The larger the width of the parallel ribs, the smaller the maximum stress value of the silicon steel sheet core (2), but the larger the permanent magnet leakage coefficient of the rotor; the radius of the two upper fillets of the rounded bread-shaped permanent magnet slot (2-1) that are tangent to the upper top arc and the waist line segment are the same, and the radius of the two lower fillets that are tangent to the lower bottom line segment and the waist line segment are the same. The smaller the radii of the upper fillets and the lower fillets, the greater the maximum stress of the silicon steel sheet core (2), but the longer the waist line segment of the rounded bread-shaped permanent magnet (3), the larger the radial thickness, and the stronger the anti-demagnetization ability.

[0007] The midpoint of the upper top line segment, the midpoint of the lower bottom line segment and the center of the inner circle of the silicon steel sheet core (2) of the rounded isosceles trapezoidal air magnetic isolation hole (2-2) are on a straight line, the midpoint of the lower bottom line segment of the rounded isosceles trapezoidal air magnetic isolation hole (2-2) is symmetrical about the line segment between the midpoint of the upper top line segment and the midpoint of the lower bottom line segment, and the line segment distance from the midpoint of the lower bottom line segment of the rounded isosceles trapezoidal air magnetic isolation hole (2-2) to the center of the inner circle of the silicon steel sheet core (2) is equal to the line segment distance from the midpoint of the lower bottom line segment of the rounded bread-shaped permanent magnet slot hole (2-1) to the center of the inner circle of the silicon steel sheet core (2); the two upper circles of the rounded isosceles trapezoidal air magnetic isolation hole (2-2) are tangent to both the upper top line segment and the waist line segment. The corner radii are the same, and the radii of the two lower fillets that are tangent to the lower bottom line segment and the waist line segment are the same, and in order to reduce the maximum stress of the silicon steel sheet core (2), the radius of the upper fillet is greater than the radius of the lower fillet; the silicon steel sheet core (2) between the rounded isosceles trapezoidal air magnetic isolation hole (2-2) and the adjacent rounded bread-shaped permanent magnet slot hole (2-1) is a parallel rib, and the width of all parallel ribs of the silicon steel sheet core (2) is the same; adjusting the tangential angle occupied by the rounded bread-shaped permanent magnet slot hole (2-1) area and the rounded isosceles trapezoidal air magnetic isolation hole (2-2) area is equivalent to adjusting the pole arc coefficient of the rotor, which can reduce the harmonic content of the permanent magnet air gap magnetic density.

[0008] The rounded bread-shaped permanent magnet (3) is made of sintered NdFeB permanent magnet material and has the same shape as the rounded bread-shaped permanent magnet slot (2-1), and is divided into K sections along the axial direction, the sum of the axial lengths of the K sections of the rounded bread-shaped permanent magnet (3) is equal to the axial length of the rounded bread-shaped permanent magnet slot (2-1); the rounded bread-shaped permanent magnet (3) is magnetized in parallel with two polarities, including an N-polarity rounded bread-shaped permanent magnet (3-1) and an S-polarity rounded bread-shaped permanent magnet (3-2), and the N-polarity rounded bread-shaped permanent magnet (3-1) is magnetized in parallel with the S-polarity rounded bread-shaped permanent magnet (3-2). The parallel magnetization direction of the permanent magnet (3-1) is from the midpoint of the lower bottom line segment to the midpoint of the upper top circular arc, and the parallel magnetization direction of the S-polarity bread-shaped permanent magnet (3-2) is from the midpoint of the upper top circular arc to the midpoint of the lower bottom line segment; 12K pieces of N-polarity bread-shaped permanent magnets (3-1) are needed for the three N-polarity magnetic poles, and 12K pieces of S-polarity bread-shaped permanent magnets (3-2) are needed for the three S-polarity magnetic poles. All permanent magnets are magnetized before being installed in the bread-shaped permanent magnet slots (2-1) with rounded corners of the silicon steel sheet iron core (2).

[0009] A hollow shaft (1) is machined from a high-strength alloy material, and a plane is milled out of the outer cylindrical surface of the hollow shaft (1). The inner cylindrical surface of the silicon steel sheet core (2) protrudes a plane of the same size. The outer cylindrical surface of the hollow shaft (1) with a plane milled out is interference-fitted with the inner cylindrical surface of the silicon steel sheet core (2) with a plane of the same size protruding. In four rounded bread-shaped permanent magnet slots (2-1) radially facing the inner cylindrical plane of the silicon steel sheet core (2), K pieces of N-polarity rounded bread-shaped permanent magnets (3-1) are stacked axially in each of the rounded bread-shaped permanent magnet slots (2-1). The K pieces of N-polarity rounded bread-shaped permanent magnets (3-1) are tightly connected to the outer cylindrical surface of the silicon steel sheet core (2). The axial space of the rounded bread-shaped permanent magnet slot holes (2-1) is densely filled, and the 4K N-polarity rounded bread-shaped permanent magnets (3-1) in the four rounded bread-shaped permanent magnet slot holes (2-1) together form an N-polarity magnetic pole; starting from the N-polarity magnetic pole radially opposite to the inner circular plane of the silicon steel sheet core (2), the four rounded bread-shaped permanent magnet slot holes (2-1) and one rounded isosceles trapezoidal air magnetic isolation hole (2-2) in the adjacent magnetic pole area are skipped along the circumference in the counterclockwise direction, and in the four rounded bread-shaped permanent magnet slot holes (2-1) in the next magnetic pole area, each rounded bread-shaped permanent magnet slot hole (2-1) is tightly filled along the axial direction. K pieces of N-polarity bread-shaped permanent magnets (3-1) with rounded corners are closely stacked to form a second N-polarity magnetic pole; starting from the second N-polarity magnetic pole, four bread-shaped permanent magnet slots (2-1) with rounded corners and one rounded isosceles trapezoidal air magnetic isolation hole (2-2) are skipped in the counterclockwise direction along the circumference of the adjacent magnetic pole area; in the four bread-shaped permanent magnet slots (2-1) with rounded corners in the next magnetic pole area, K pieces of N-polarity bread-shaped permanent magnets (3-1) are closely stacked along the axial direction in each bread-shaped permanent magnet slot (2-1) with rounded corners to form a third N-polarity magnetic pole; three S-polarity magnetic poles are formed between the three N-polarity magnetic poles. In the four rounded bread-shaped permanent magnet slots (2-1) of each S-polarity magnetic pole region, each rounded bread-shaped permanent magnet slot (2-1) has K pieces of S-polarity rounded bread-shaped permanent magnets (3-2) tightly stacked along the axial direction to form three S-polarity magnetic poles respectively; thus, the 12K pieces of N-polarity rounded bread-shaped permanent magnets (3-1) and the 12K pieces of S-polarity rounded bread-shaped permanent magnets (3-2) loaded into the rounded bread-shaped permanent magnet slots (2-1) together form six permanent magnet magnetic poles with N polarity and S polarity alternating; and the outer cylindrical surface of the silicon steel sheet core (2) and the inner cylindrical surface of the carbon fiber sheath (4) are interference-fitted.

[0010] The present invention reduces the maximum stress of the silicon steel sheet core by optimizing the geometrical shapes of the bread-shaped permanent magnet slots with rounded corners and the isosceles trapezoidal air magnetic isolation holes with rounded corners, and the interference fit between the carbon fiber sheath and the outer circumference of the silicon steel sheet core; improves the anti-demagnetization capability by designing the radial thickness of the bread-shaped permanent magnets with rounded corners; and reduces the harmonic content of the permanent magnet air gap magnetic density by adjusting the tangential angles occupied by the bread-shaped permanent magnet slots with rounded corners and the isosceles trapezoidal air magnetic isolation holes with rounded corners. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The cross-sectional diagram of the rotor structure is a schematic diagram of a high-speed permanent magnet synchronous motor that can reduce the maximum stress of the silicon steel sheet. In the figure, 1 is a hollow shaft, 2 is a silicon steel sheet core, 3 is a bread-shaped permanent magnet with rounded corners, 3-1 is an N-polar bread-shaped permanent magnet with rounded corners, 3-2 is an S-polar bread-shaped permanent magnet with rounded corners, 4 is a carbon fiber sheath, and the "arrow" in the bread-shaped permanent magnet with rounded corners represents the direction of parallel magnetization of the permanent magnet.

[0012] Figure 2 The diagram is a schematic diagram of the distribution of the bread-shaped permanent magnet slots with rounded corners and the isosceles trapezoidal air magnetic isolation holes with rounded corners in the silicon steel core. In the figure, 2 is the silicon steel core, 2-1 is the bread-shaped permanent magnet slots with rounded corners, and 2-2 is the isosceles trapezoidal air magnetic isolation holes with rounded corners.

[0013] Figure 3 This is a dimension parameter diagram of the rounded bread-shaped permanent magnet slot and rounded isosceles trapezoidal air magnetic isolation hole in the silicon steel core. o is the radius of the outer circle of the silicon steel core; w is the width of all parallel ribs in the silicon steel core; α m R is the tangent angle between the center lines of the parallel ribs on both sides of the rounded bread-shaped permanent magnet slot; m is the radius of the top arc of the bread-shaped permanent magnet slot with rounded corners; b1 is the line segment distance from the center of the top arc of the bread-shaped permanent magnet slot with rounded corners to the center of the inner circle of the silicon steel sheet core; h m is the radial maximum thickness of the bread-shaped permanent magnet slot with rounded corners; α a h is the tangent angle between the center lines of the parallel ribs on both sides of the isosceles trapezoidal air magnetic isolation hole with rounded corners; a is the radial thickness of the isosceles trapezoidal air magnetic isolation hole with rounded corners; b2 is the line segment distance from the midpoint of the lower bottom line segment of the bread-shaped permanent magnet slot with rounded corners to the center of the inner circle of the silicon steel sheet core, and is also the line segment distance from the midpoint of the lower bottom line segment of the isosceles trapezoidal air magnetic isolation hole with rounded corners to the center of the inner circle of the silicon steel sheet core.

[0014] Figure 4 This is a line segment name labeling diagram of a rounded bread-shaped permanent magnet slot.

[0015] Figure 5This is a line segment name-labeled diagram of an isosceles trapezoidal air magnetic isolation hole with rounded corners.

[0016] Figure 6 This is a schematic diagram of the parallel magnetization direction of an N-polarity rounded bread-shaped permanent magnet. The "arrow" in the figure represents the parallel magnetization direction of the permanent magnet.

[0017] Figure 7 This is a schematic diagram of the parallel magnetization direction of an S-polarity rounded bread-shaped permanent magnet. The "arrow" in the figure represents the parallel magnetization direction of the permanent magnet. DETAILED DESCRIPTION

[0018] Combine the following Figures 1 to 7 The present invention provides a rotor structure capable of reducing the maximum stress of silicon steel sheets of a high-speed permanent magnet synchronous motor.

[0019] like Figure 1 As shown, the present invention proposes a rotor structure capable of reducing the maximum stress of silicon steel sheets of a high-speed permanent magnet synchronous motor, comprising a hollow shaft (1), a silicon steel sheet core (2), a rounded bread-shaped permanent magnet (3) and a carbon fiber sheath (4), and the permanent magnet rotor presents three pairs of magnetic poles to the stator, and the six magnetic poles are evenly distributed at 60° intervals along the circumferential direction.

[0020] like Figure 2 As shown, each magnetic pole lower silicon steel sheet core (2) has four identically shaped bread-shaped permanent magnet slots (2-1) with rounded corners in the circumferential direction for embedding bread-shaped permanent magnets (3) with rounded corners, and each of the six adjacent magnetic poles has one isosceles trapezoidal air magnetic isolation hole (2-2). All bread-shaped permanent magnet slots (2-1) with rounded corners have the same radius of two upper rounded corners tangent to the upper top arc and waist line segment, and the same radius of two lower rounded corners tangent to the lower bottom line segment and waist line segment; all isosceles trapezoidal air magnetic isolation holes (2-2) with rounded corners have the same radius of two upper rounded corners tangent to the upper top line segment and waist line segment, and the same radius of two lower rounded corners tangent to the lower bottom line segment and waist line segment.

[0021] Silicon steel core (2) is composed of many Figure 2 and Figure 3 The punched and sheared silicon steel sheet core punchings shown are stacked axially.

[0022] like Figure 3 , Figure 4 and Figure 5 As shown, the outer radius of the silicon steel core (2) is R o, there are parallel ribs between the rounded bread-shaped permanent magnet slots (2-1) on the silicon steel sheet core (2), and between the rounded bread-shaped permanent magnet slots (2-1) and the rounded isosceles trapezoidal air magnetic isolation holes (2-2), and the width of all parallel ribs is w; the center lines of all parallel ribs pass through the center of the inner circle of the silicon steel sheet core (2); the tangential angle between the center lines of the parallel ribs on both sides of the rounded bread-shaped permanent magnet slots (2-1) is α m The tangential angle between the center lines of the parallel ribs on both sides of the rounded isosceles trapezoidal air magnetic isolation hole (2-2) is α a The radial center line of each rounded isosceles trapezoidal air magnetic isolation hole (2-2) divides it into two parts, the left and right magnetic poles, and the angle occupied by each magnetic pole in the circumferential direction is α a / 2+α m +α m +α m +α m +α a / 2=4α m +α a =60°. The center of the top circular arc of the rounded bread-shaped permanent magnet slot hole (2-1), the midpoint of the top circular arc, the midpoint of the bottom line segment and the center of the inner circle of the silicon steel sheet iron core (2) are on a straight line, the line segment distance from the center of the top circular arc of the rounded bread-shaped permanent magnet slot hole (2-1) to the center of the inner circle of the silicon steel sheet iron core (2) is b1, and the radius of the top circular arc is R m The distance between the midpoint of the top arc and the outer circle of the silicon steel sheet core (2) along the symmetric center line of the rounded bread-shaped permanent magnet slot (2-1) is (R o -b1-R m ), the line segment distance between the midpoint of the lower bottom line segment of the rounded bread-shaped permanent magnet slot hole (2-1) and the midpoint of the upper top arc is h m ,h m The maximum radial thickness of the rounded bread-shaped permanent magnet slot (2-1) is the line distance b2 from the midpoint of the lower bottom line segment to the center of the inner circle of the silicon steel sheet core (2) is (b1+R m -h m ); When selecting the radius of the two upper fillets of the rounded bread-shaped permanent magnet slot hole (2-1) that are tangent to both the upper arc and the waist line segment, and the radius of the two lower fillets that are tangent to both the lower bottom line segment and the waist line segment, the maximum stress of the silicon steel sheet core (2) and the anti-demagnetization ability of the rounded bread-shaped permanent magnet (3) should be considered comprehensively. The line segment distance from the midpoint of the lower bottom line segment of the rounded isosceles trapezoidal air isolation hole (2-2) to the center of the inner circle of the silicon steel sheet core (2) is b2, and the line segment distance between the midpoint of the upper top line segment and the midpoint of the lower bottom line segment is h a The distance between the midpoint of the top line segment along the symmetric center line of the rounded isosceles trapezoidal air magnetic isolation hole (2-2) and the outer circle of the silicon steel sheet core (2) is (Ro -b2-h a ). The radius of the two upper fillets of the rounded isosceles trapezoidal air magnetic isolation hole (2-2) that are tangent to both the upper top line segment and the waist line segment is the same, and the radius of the two lower fillets that are tangent to both the lower bottom line segment and the waist line segment is the same, and in order to reduce the maximum stress of the silicon steel sheet core (2), the radius of the upper fillet is greater than the radius of the lower fillet. Adjusting the tangential angle occupied by the rounded bread-shaped permanent magnet slot hole (2-1) area and the rounded isosceles trapezoidal air magnetic isolation hole (2-2) area is equivalent to adjusting the rotor pole arc coefficient, which can reduce the harmonic content of the permanent magnet air gap magnetic flux density.

[0023] like Figure 1 As shown, the rounded bread-shaped permanent magnet (3) is made of sintered NdFeB permanent magnet material and has the same shape as the rounded bread-shaped permanent magnet slot (2-1) and is divided into K segments along the axial direction. The sum of the axial lengths of the K segments of the rounded bread-shaped permanent magnet (3) is equal to the axial length of the rounded bread-shaped permanent magnet slot (2-1). Figure 6 and Figure 7 As shown, the bread-shaped permanent magnet with rounded corners (3) adopts parallel magnetization of two polarities, including an N-polar bread-shaped permanent magnet with rounded corners (3-1) and an S-polar bread-shaped permanent magnet with rounded corners (3-2). The parallel magnetization direction of the N-polar bread-shaped permanent magnet with rounded corners (3-1) is from the midpoint of the lower bottom line segment to the midpoint of the upper top circular arc, and the parallel magnetization direction of the S-polar bread-shaped permanent magnet with rounded corners (3-2) is from the midpoint of the upper top circular arc to the midpoint of the lower bottom line segment; 3 N-polar magnetic poles require a total of 12K N-polar bread-shaped permanent magnets (3-1), and 3 S-polar magnetic poles require a total of 12K S-polar bread-shaped permanent magnets (3-2). All permanent magnets are magnetized before being installed in the bread-shaped permanent magnet slot hole (2-1) of the silicon steel sheet iron core (2).

[0024] A hollow shaft (1) is machined from a high-strength alloy material, and a plane is milled out of the outer cylindrical surface of the hollow shaft (1). The inner circle of a silicon steel sheet iron core (2) protrudes a plane of the same size. The outer cylindrical surface of the hollow shaft (1) with a plane milled out is interference-fitted with the inner cylindrical surface of the silicon steel sheet iron core (2) with a plane of the same size protruding. The plane of the outer cylindrical surface of the hollow shaft (1) and the interference fit play a role in transmitting torque.

[0025] In four rounded bread-shaped permanent magnet slots (2-1) radially facing the inner circular plane of the silicon steel sheet iron core (2), each rounded bread-shaped permanent magnet slot (2-1) is stacked with K N-polarity rounded bread-shaped permanent magnets (3-1) along the axial direction, and the K N-polarity rounded bread-shaped permanent magnets (3-1) tightly fill the axial space of the rounded bread-shaped permanent magnet slot (2-1). The 4K N-polarity rounded bread-shaped permanent magnets (3-1) in the four rounded bread-shaped permanent magnet slots (2-1) together form an N-polarity magnetic pole; starting from the N-polar magnetic pole radially opposite to the inner circular plane of the silicon steel sheet core (2), skipping the four rounded bread-shaped permanent magnet slots (2-1) and one rounded isosceles trapezoidal air magnetic isolation hole (2-2) in the adjacent magnetic pole area along the circumference counterclockwise, in the next four rounded bread-shaped permanent magnet slots (2-1) in the magnetic pole area, each rounded bread-shaped permanent magnet slot (2-1) is tightly stacked with K N-polar rounded bread-shaped permanent magnets (3-1) along the axial direction to form the second N-polar magnetic pole; continuing from the second Starting from an N-polarity magnetic pole, the 4 rounded bread-shaped permanent magnet slots (2-1) and 1 rounded isosceles trapezoidal air magnetic isolation hole (2-2) of the adjacent magnetic pole area are skipped along the circumference counterclockwise. In the 4 rounded bread-shaped permanent magnet slots (2-1) of the next magnetic pole area, each rounded bread-shaped permanent magnet slot (2-1) is tightly stacked with K N-polarity rounded bread-shaped permanent magnets (3-1) along the axial direction to form the third N-polarity magnetic pole; three S-polarity magnetic pole areas are formed between the three N-polarity magnetic poles. In the four bread-shaped permanent magnet slots (2-1) with rounded corners in each S-polarity magnetic pole region, each bread-shaped permanent magnet slot (2-1) has K pieces of S-polarity bread-shaped permanent magnets (3-2) tightly stacked along the axial direction, respectively forming three S-polarity magnetic poles; thus, the 12K pieces of N-polarity bread-shaped permanent magnets (3-1) and the 12K pieces of S-polarity bread-shaped permanent magnets (3-2) loaded into the bread-shaped permanent magnet slots (2-1) together form six permanent magnet poles with alternating N polarity and S polarity.

[0026] The outer cylindrical surface of the silicon steel core (2) and the inner cylindrical surface of the carbon fiber sheath (4) are interference-fitted. The permanent magnet rotor has the characteristics of small maximum stress value, strong anti-demagnetization ability, low harmonic content of permanent magnet air gap magnetic density, and relatively low various losses on the rotor, and is particularly suitable for high-speed permanent magnet synchronous motors.

[0027] Although the present invention has been described above in conjunction with the drawings, the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can make many modifications without departing from the purpose of the present invention, all of which are within the protection of the present invention.

Claims

1. A rotor structure capable of reducing the maximum stress of silicon steel sheets of a high-speed permanent magnet synchronous motor, comprising: A hollow shaft (1), a silicon steel sheet core (2), a bread-shaped permanent magnet with rounded corners (3) and a carbon fiber sheath (4); characterized in that the permanent magnet rotor presents three pairs of magnetic poles to the stator, and the six magnetic poles are evenly distributed at intervals of 60 degrees along the circumferential direction, and the silicon steel sheet core (2) under each magnetic pole has four bread-shaped permanent magnet slots (2-1) with rounded corners in the circumferential direction for embedding the bread-shaped permanent magnet with rounded corners (3), and there is an isosceles trapezoidal air magnetic isolation hole (2-2) with rounded corners on the silicon steel sheet core (2) between the six adjacent magnetic poles.

2. A rotor structure capable of reducing the maximum stress of silicon steel sheets of a high-speed permanent magnet synchronous motor according to claim 1, characterized in that: The midpoint of the upper top arc of the rounded bread-shaped permanent magnet slot hole (2-1), the midpoint of the lower bottom line segment and the center of the inner circle of the silicon steel sheet iron core (2) are on a straight line, the rounded bread-shaped permanent magnet slot hole (2-1) is symmetrical about the line segment between the midpoint of the upper top arc and the midpoint of the lower bottom line segment, and the radius of the upper bottom arc of the rounded bread-shaped permanent magnet slot hole (2-1) is smaller than the line segment distance from the midpoint of the upper top arc to the center of the inner circle of the silicon steel sheet iron core (2); the silicon steel sheet iron core (2) between two adjacent rounded bread-shaped permanent magnet slot holes (2-1) The parallel ribs are parallel ribs. The larger the width of the parallel ribs, the smaller the maximum stress value of the silicon steel sheet core (2), but the larger the permanent magnet leakage coefficient of the rotor; the radius of the two upper fillets of the rounded bread-shaped permanent magnet slot (2-1) that are tangent to the upper top arc and the waist line segment are the same, and the radius of the two lower fillets that are tangent to the lower bottom line segment and the waist line segment are the same. The smaller the radii of the upper fillets and the lower fillets, the greater the maximum stress of the silicon steel sheet core (2), but the longer the waist line segment of the rounded bread-shaped permanent magnet (3), the larger the radial thickness, and the stronger the anti-demagnetization ability.

3. The rotor structure capable of reducing the maximum stress of silicon steel sheets of a high-speed permanent magnet synchronous motor according to claim 1, characterized in that: The midpoint of the upper top line segment, the midpoint of the lower bottom line segment and the center of the inner circle of the silicon steel sheet core (2) of the rounded isosceles trapezoidal air magnetic isolation hole (2-2) are on a straight line, the midpoint of the lower bottom line segment and the center of the inner circle of the silicon steel sheet core (2) are symmetrical about the line segment between the midpoint of the upper top line segment and the midpoint of the lower bottom line segment, and the line segment distance from the midpoint of the lower bottom line segment of the rounded isosceles trapezoidal air magnetic isolation hole (2-2) to the center of the inner circle of the silicon steel sheet core (2) is equal to the line segment distance from the midpoint of the lower bottom line segment of the rounded bread-shaped permanent magnet slot hole (2-1) to the center of the inner circle of the silicon steel sheet core (2); the two upper rounded corners of the rounded isosceles trapezoidal air magnetic isolation hole (2-2) that are tangent to both the upper top line segment and the waist line segment The two lower fillets have the same radius, and the radius of the two lower fillets that are tangent to the lower bottom line segment and the waist line segment are the same. In order to reduce the maximum stress of the silicon steel sheet core (2), the radius of the upper fillet is greater than the radius of the lower fillet. The silicon steel sheet core (2) between the rounded isosceles trapezoidal air magnetic isolation hole (2-2) and the adjacent rounded bread-shaped permanent magnet slot hole (2-1) is a parallel rib, and the width of all parallel ribs of the silicon steel sheet core (2) is the same. Adjusting the tangential angle occupied by the rounded bread-shaped permanent magnet slot hole (2-1) area and the rounded isosceles trapezoidal air magnetic isolation hole (2-2) area is equivalent to adjusting the pole arc coefficient of the permanent magnet rotor, which can reduce the harmonic content of the permanent magnet air gap magnetic density.

4. A rotor structure capable of reducing the maximum stress of silicon steel sheets of a high-speed permanent magnet synchronous motor according to claim 1 and claim 2, characterized in that: The rounded bread-shaped permanent magnet (3) is made of sintered NdFeB permanent magnet material and has the same shape as the rounded bread-shaped permanent magnet slot (2-1), and is divided into K sections along the axial direction, the sum of the axial lengths of the K sections of the rounded bread-shaped permanent magnet (3) is equal to the axial length of the rounded bread-shaped permanent magnet slot (2-1); the rounded bread-shaped permanent magnet (3) is magnetized in parallel with two polarities, including an N-polarity rounded bread-shaped permanent magnet (3-1) and an S-polarity rounded bread-shaped permanent magnet (3-2), and the N-polarity rounded bread-shaped permanent magnet (3-1) is magnetized in parallel with the S-polarity rounded bread-shaped permanent magnet (3-2). The parallel magnetization direction of the permanent magnet (3-1) is from the midpoint of the lower bottom line segment to the midpoint of the upper top circular arc, and the parallel magnetization direction of the S-polarity bread-shaped permanent magnet (3-2) is from the midpoint of the upper top circular arc to the midpoint of the lower bottom line segment; 12K pieces of N-polarity bread-shaped permanent magnets (3-1) are needed for the three N-polarity magnetic poles, and 12K pieces of S-polarity bread-shaped permanent magnets (3-2) are needed for the three S-polarity magnetic poles. All permanent magnets are magnetized before being installed in the bread-shaped permanent magnet slots (2-1) with rounded corners of the silicon steel sheet iron core (2).

5. A rotor structure capable of reducing the maximum stress of silicon steel sheets of a high-speed permanent magnet synchronous motor according to claim 1 to claim 4, characterized in that: A hollow shaft (1) is machined from a high-strength alloy material, and a plane is milled out on the outer cylindrical surface of the hollow shaft (1), and a plane of the same size is protruded from the inner cylindrical surface of the silicon steel sheet core (2). The outer cylindrical surface of the hollow shaft (1) with a plane milled out is interference-fitted with the inner cylindrical surface of the silicon steel sheet core (2) with a plane of the same size protruding. In four rounded bread-shaped permanent magnet slots (2-1) radially facing the inner cylindrical plane of the silicon steel sheet core (2), K pieces of N-polarity rounded bread-shaped permanent magnets (3-1) are stacked axially in each of the rounded bread-shaped permanent magnet slots (2-1). The K pieces of N-polarity rounded bread-shaped permanent magnets (3-1) are The axial space of the rounded bread-shaped permanent magnet slots (2-1) is tightly filled, and the 4K N-polarity rounded bread-shaped permanent magnets (3-1) in the four rounded bread-shaped permanent magnet slots (2-1) together form an N-polarity magnetic pole; starting from the N-polarity magnetic pole radially opposite to the inner circular plane of the silicon steel sheet core (2), the four rounded bread-shaped permanent magnet slots (2-1) and one rounded isosceles trapezoidal air magnetic isolation hole (2-2) in the adjacent magnetic pole area are skipped along the circumference in the counterclockwise direction, and in the four rounded bread-shaped permanent magnet slots (2-1) in the next magnetic pole area, each rounded bread-shaped permanent magnet slot (2-1) is axially K pieces of N-polarity bread-shaped permanent magnets (3-1) with rounded corners are stacked tightly to form a second N-polarity magnetic pole; starting from the second N-polarity magnetic pole, four bread-shaped permanent magnet slots (2-1) with rounded corners and one rounded isosceles trapezoidal air magnetic isolation hole (2-2) are skipped in the counterclockwise direction of the circumference in the adjacent magnetic pole area; in the four bread-shaped permanent magnet slots (2-1) with rounded corners in the next magnetic pole area, K pieces of N-polarity bread-shaped permanent magnets (3-1) are stacked tightly along the axial direction in each bread-shaped permanent magnet slot (2-1) with rounded corners to form a third N-polarity magnetic pole; three S-polarity magnetic poles are formed between these three N-polarity magnetic poles. In the four rounded bread-shaped permanent magnet slots (2-1) of each S-polarity magnetic pole region, each rounded bread-shaped permanent magnet slot (2-1) has K pieces of S-polarity rounded bread-shaped permanent magnets (3-2) tightly stacked along the axial direction to form three S-polarity magnetic poles respectively; thus, the 12K pieces of N-polarity rounded bread-shaped permanent magnets (3-1) and the 12K pieces of S-polarity rounded bread-shaped permanent magnets (3-2) loaded into the rounded bread-shaped permanent magnet slots (2-1) together form six permanent magnet magnetic poles with N polarity and S polarity alternating; and the outer cylindrical surface of the silicon steel sheet core (2) and the inner cylindrical surface of the carbon fiber sheath (4) are interference-fitted.

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