Solid rotor structure of high-speed induction motor and motor

Abstract

The invention provides a high-speed induction motor solid rotor structure and a motor, the rotor structure comprises an integrated conductive and magnetic conductive rotor and a rotating shaft, the surface of the rotor is provided with two groups of grooves, any groove in any group and all grooves in the other group are arranged in a staggered manner along the circumferential direction of the rotor, and the two groups of grooves are arranged at intervals along the axial direction of the rotor. Distances are reserved between the far ends of the two groups of grooves and the close end faces of the rotor. The motor comprises the solid rotor structure. The two sections of non-penetrating rectangular straight grooves are axially formed in the surface of the rotor, so that the equivalent impedance of the rotor part is increased, the penetration depth of an air-gap magnetic field in the rotor is increased, the torque output capacity of the motor is improved, and meanwhile, the eddy current strength of the surface of the rotor is weakened.

Description

Technical Field

[0001] The present invention belongs to the technical field of motors, and particularly relates to a solid rotor structure of a high-speed induction motor and a motor. Background Art

[0002] Solid rotor induction motors are widely used in high-end industrial fields such as high-speed compressors, flywheel energy storage, machine tool spindles, and aerospace due to their advantages of low cost, strong robustness, and large starting torque. The rotor material and structure of solid rotor induction motors are special and are made of a whole piece of alloy steel. Its rotor magnetic circuit and electric circuit are mixed, that is, the solid rotor is both conductive and magnetic. The above characteristics make the motor have relatively large rotor eddy current losses and low power factor; by improving the rotor structure, the rotor impedance of the solid rotor induction motor can be reduced, the rotor eddy current can be suppressed, the rotor losses can be reduced, and the electromagnetic performance of the motor can be improved.

[0003] Solid rotor structures are generally divided into smooth solid rotors, coated solid rotors, cage solid rotors, and slotted solid rotors: The smooth solid rotor has a simple structure, is convenient to process, and has high mechanical strength, especially suitable for high-speed working conditions. However, air-gap harmonics will generate strong eddy currents on the rotor surface of the smooth solid rotor, resulting in a significant increase in the rotor losses of the motor. Moreover, since the rotor material of the smooth solid rotor is alloy steel that is both conductive and magnetic, the penetration depth of the air-gap magnetic field in the smooth solid rotor is small, and it is difficult to generate a large torque; The coated solid rotor can provide a main closed loop for the induced current on the rotor side of the motor, reducing the rotor eddy current losses. However, the presence of the coating increases the equivalent air gap of the motor, reduces the power factor of the motor, and the process implementation is complex; The electromagnetic torque of the cage solid rotor induction motor is mainly generated by the cage rotor bars, and the cage solid rotor is equipped with end rings. Therefore, compared with other types of solid rotor structure topologies, the cage solid rotor induction motor has a smaller slip ratio, higher efficiency, and power factor under rated conditions. However, compared with other types of topologies, the cage solid rotor topology has a greater manufacturing difficulty and is not suitable for ultra-high-speed operating conditions; Axially slitting the surface of the solid rotor can affect the distribution of the rotor surface eddy current, reduce the rotor impedance, thereby increasing the motor output torque and improving the electromagnetic performance of the motor. However, it still has the disadvantage of relatively large rotor surface harmonic eddy current losses.

[0004] In view of the problem of improving the electromagnetic performance of a general slotted solid rotor for a high-speed induction motor, it is necessary to explore a solid rotor structure of a high-speed induction motor with better electromagnetic performance. Summary of the Invention

[0005] The performance of a slotted solid rotor induction motor also depends on the selection of the rotor slot depth, slot width, and number of slots. The slot depth and width of a slotted solid rotor have a relatively significant impact on the generated torque, but the impact on the mechanical strength of the rotor needs to be considered. An appropriate number of rotor slots should be selected for the slotted solid rotor to have a proper match with the number of stator slots. If the match is improper, it will deteriorate the motor performance. For example, it may lead to additional losses and additional torques, reducing the motor efficiency and worsening the starting performance.

[0006] To solve the above technical problems, this application proposes a solid rotor structure and a motor for a high-speed induction motor. The specific technical solutions are as follows:

[0007] On the one hand, this application provides a solid rotor structure for a high-speed induction motor, including an integrally conductive and magnetically conductive rotor and a rotating shaft. The surface of the rotor has two groups of slots. Any slot in any one group is circumferentially misaligned with all the slots in the other group. The two groups of slots are axially spaced along the rotor, and there is a distance between the distal ends of the two groups of slots and the adjacent rotor end faces.

[0008] As a preferred solution, the length direction of the slot extends along the axial direction of the rotor, and the depth direction extends along the radial direction of the rotor.

[0009] As a preferred solution, the number of slots and the slot type dimensions of the two groups of slots are the same; each group of slots is evenly distributed circumferentially along the rotor.

[0010] As a preferred solution, the total number of slots on the rotor is Q, and the misalignment angle between the two groups of slots is 360° / Q.

[0011] As a preferred solution, the total number of slots on the rotor is twice the total number of slots on the external stator.

[0012] As a preferred solution, the axial length of the rotor is L1, the length direction dimension of the slot is L2, and the value of L2 / L1 is 0.4 - 0.48.

[0013] As a preferred solution, the depth direction dimension of the slot is H, the diameter of the rotor is D1, and the value of H / D1 is 0.2 - 0.25.

[0014] As a preferred solution, the total number of slots on the rotor is Q, the width of the slot is W, and the tooth pitch b of the rotor dr = 2πD1 / Q, and the value of W / b dr is 0.1 - 0.3.

[0015] As a preferred solution, the diameter of the rotor is D1, the diameter of the rotating shaft is D2, and the value of D2 / D1 is 0.2 - 0.4.

[0016] On the other hand, the present application provides a motor, which includes the solid rotor structure of the high-speed induction motor described in any one of the above.

[0017] The beneficial effects of the present invention are as follows:

[0018] (1) The present invention provides a solid rotor structure for a high-speed induction motor. This structure is an integrated rotor shaft, which is made of a single piece of alloy steel that is both conductive and magnetic. The entire rotor serves as the path for the rotor induced current, that is, the entire rotor can output torque. Axially, two non-through rectangular straight grooves are opened on the rotor surface. The presence of the rectangular grooves increases the equivalent impedance of the rotor part, and at the same time can increase the penetration depth of the air-gap magnetic field in the rotor, improving the torque output ability of the motor. The two ends of the rotor and the middle part between the two grooves are not milled through. The rotor end can provide a main closed loop for the rotor induced current, weakening the eddy current intensity on the rotor surface, while the connecting ribs can enhance the mechanical strength of the rotor.

[0019] (2) The present invention provides a solid rotor structure for a high-speed induction motor. The total number of grooves on the rotor of this structure is Q, and the number of stator slots is q. The two satisfy: Q = 2q, and the number of grooves in the two rectangular grooves on the rotor is equal, both Q / 2. When the rotor is grooved in the above manner, the stator first-order tooth harmonic magnetic field induces equal and in-phase induced electromotive forces on two adjacent rotor teeth on the same side. Therefore, no induced current will be generated between the two adjacent rotor teeth connected through the end part and the non-milled-through rotor area in the middle, significantly reducing the induced eddy current on the rotor surface, thereby reducing the additional loss induced by the harmonic magnetic field in the rotor.

[0020] (3) The present invention provides a solid rotor structure for a high-speed induction motor. The number of grooves in the two rectangular straight grooves opened on the rotor of this structure is both Q / 2. The groove shape dimensions of the two grooves are the same, and the positions of the two rectangular straight grooves are staggered by 360° / Q mechanical angle. Since the stator first-order tooth harmonic magnetic field will not induce current on the rotor teeth, the rotor tooth harmonic magnetic field induced by the stator harmonic magnetic field on the rotor teeth is eliminated, thereby suppressing the generation of asynchronous additional torque and improving the output smoothness of the torque. At the same time, since two rectangular grooves with the number of grooves both Q / 2 are axially opened on the rotor, a synchronous additional torque will be generated between the stator harmonic magnetic field and the rotor harmonic magnetic field induced by the stator harmonic magnetic field on the rotor, affecting the starting performance of the motor. In severe cases, the motor cannot start. However, the positions of the two rectangular grooves are staggered by 360° / Q mechanical angle, which can offset the torque depression caused by the synchronous additional torque, significantly improving the starting performance of the motor. Description of the Drawings

[0021] Figure 1 Shows a three-dimensional structural schematic diagram of the motor rotor assembly;

[0022] Figure 2 Shows the front view of the motor rotor assembly;

[0023] Figure 3 Shown is a side view of the motor rotor assembly;

[0024] Figure 4 Shown is a projected state diagram of the slots on the rotor end face;

[0025] Figure 5 Shown is a waveform comparison diagram of the finite element simulation torque varying with the rotational speed of the motor of the present application, a motor with ordinary slots, and a smooth solid rotor motor;

[0026] Figure 6 Shown is a waveform comparison diagram of the finite element simulation efficiency varying with the rotational speed of the motor of the present application, a motor with ordinary slots, and a smooth solid rotor motor;

[0027] Figure 7 Shown is a torque waveform diagram of the high-speed induction motor of the motor within the range of 0 - 90° rotor mechanical angle. Detailed implementation manners

[0028] In the following description, certain specific details are set forth in order to provide a thorough understanding of the various embodiments. However, those skilled in the art should understand that the present invention may be practiced without these details. In other instances, well-known structures have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments. Unless the context otherwise requires, throughout the specification and the appended claims, the word "comprising" shall be interpreted in an open, inclusive sense, i.e., as "including, but not limited to".

[0029] Figure 1 Shown is a structural schematic diagram of the motor rotor assembly in the present application. The motor rotor assembly includes a rotor 10 and a rotating shaft 20. The rotor 10 and the rotating shaft 20 are of an integral structure, and the rotor 10 and the rotating shaft 20 are coaxial. The above-mentioned motor rotor assembly in the present application is applied to a high-speed induction motor. The stator of the motor provides a rotating magnetic field environment during operation, enabling the motor rotor assembly to obtain a driving torque and rotate.

[0030] As the motor rotor assembly of the integral structure in the present application, it is made by processing a whole piece of alloy steel that is both conductive and magnetic. Generally speaking, the alloy steel used is carbon structural steel SAE1045.

[0031] In an embodiment, a plurality of slots 11 are provided on the surface of the rotor 10. These slots 11 are divided into two groups. All the slots 11 have two extending directions, that is, the length direction X extends along the axial direction of the rotor 10, and the depth direction Y extends along the radial direction of the rotor 10. In addition, these two groups of slots 11 are non-penetrating slot bodies, that is, when the slots 11 extend along the length direction X, they do not reach the ends of the rotor 10, and the two groups of slots 11 are also spaced apart in the axial direction of the rotor 10, so that both ends of each slot 11 are in a closed state in the length direction X. The end closed structure of the rotor 10 in the slots 11 provides a main closed loop for the rotor induced current.

[0032] In the present application, one of the purposes of arranging the two groups of slots 11 spaced apart in the axial direction of the rotor 10 is that the connecting ribs 12 formed by the spaced arrangement between the two groups of slots 11 are used to enhance the mechanical strength of the motor rotor assembly; another purpose is that the two groups of slots 11 can form a misalignment angle on the circumference of the rotor 10, thereby overcoming the problem that the motor cannot start due to a large synchronous additional torque of the motor.

[0033] In specific implementation, in addition to having a misalignment angle on the circumference of the rotor 10, the number of the two groups of slots 11 is the same, the slot shapes and sizes are the same, and each group of slots 11 is equally spaced on the circumference of the rotor 10.

[0034] In an embodiment, as Figure 2 shown, the axial length of the rotor 10 is L1, and the length of the slot 11 in the length direction X is L2. Then the value of L2 / L1 should be 40%-48%. In order to increase the motor output torque and reduce the rotor additional loss, when actually selecting L2, it should be noted that the value of L2 / L1 should not be too large or too small: if L2 / L1 is too small, that is, the lengths of the two end parts and the connecting ribs are longer, it will cause the rotor equivalent impedance to decrease and the motor output torque to decrease; if L2 / L1 is too large, that is, the lengths of the end parts and the connecting ribs are shorter, it will increase the influence of the rotor eddy current, resulting in an increase in the rotor additional loss, and at the same time will reduce the rotor mechanical strength.

[0035] In an embodiment, as Figure 3 shown, the diameter of the rotor 10 is D1, and the diameter of the rotating shaft 20 is D2. Then the value of D2 / D1 should be 20%-40%. In order to ensure the mechanical strength of the rotor while reducing the rotor air friction loss, an appropriate D2 needs to be selected: if the value of D2 / D1 is taken too large, it will cause an increase in the rotor air friction loss and reduce the motor efficiency; if the value of D2 / D1 is taken too small, it will cause a decrease in the critical speed of the motor and cannot ensure the rotor mechanical strength.

[0036] In an embodiment, if the depth of the slot 11 in the depth direction Y is H, then the value of H / D1 should be 20% - 25%. To increase the output torque of the motor, an appropriate slot depth H needs to be selected: a larger slot depth H can greatly enhance the torque output ability of the motor, but at the same time will significantly reduce the mechanical strength of the rotor; a smaller slot depth H will result in a poor torque output ability of the motor. The value of H / D1 and the value of L2 / L1 substantially jointly affect the torque output ability of the motor.

[0037] In an embodiment, the total number of slots on the rotor 10 is Q, the width of the slot 11 is W, and the rotor tooth pitch b dr = πD1 / (Q / 2) = 2πD1 / Q, and the ratio of the slot width to the slot depth W / b dr , and the value range of the ratio of the slot width to the rotor tooth pitch is 10% - 30%. To increase the output torque of the motor, an appropriate slot width needs to be selected: a larger slot width can enhance the torque output ability of the motor, but at the same time will reduce the mechanical strength of the rotor; a smaller slot width will result in a poor torque output ability of the motor.

[0038] In an embodiment, when the total number of slots on the rotor 10 is Q, and the number of slots on the corresponding stator (not shown in the figure) is q, then Q = 2q should be satisfied. This slotting method can reduce the additional losses induced by the air-gap harmonic magnetic field in the solid rotor. It should be noted that the structural improvement of the motor stator is not involved in this application.

[0039] According to the foregoing records, two sets of slots 11 need to form a misalignment angle on the circumference of the rotor 10. As Figure 4 shown, the solid lines in the figure represent the projection of one set of slots 11 on the end face of the rotor 10, and the dashed lines represent the projection of the other set of slots 11 on the end face of the rotor 10. It can be seen that there is a minimum angle α between any two adjacent slots 11 represented by solid lines and slots 11 represented by dashed lines, and the value of this angle α is 360° / Q.

[0040] Example 1

[0041] In this example, a motor rotor assembly and a supporting motor are provided. The main parameters of the motor are shown in Table 1.

[0042]

[0043] Table 1: Main parameters of the motor

[0044] For the motor described above, the value of L2 / L1 is 46.25%; the value of D2 / D1 is 36.52%; the value of H / D1 is 20.87%; and the value of W / b dr is 20.717%.

[0045] Figure 5Shown is a waveform comparison diagram of the finite element simulation torque varying with the rotational speed of this motor, a motor with ordinary slots, and a smooth solid rotor motor.

[0046] Regarding the motor with ordinary slots, it refers to an induction motor with a certain number of straight slots axially opened on the rotor shaft. And significantly different from this application, the straight slots on its rotor penetrate both ends of the rotor axially, becoming through-type straight slots. Referring to the parameters of the motor in Table 1, the motor with ordinary slots has the same parameter settings for the rotor slot depth and rotor slot width. The difference is that the total number of rotor slots is 22.

[0047] Regarding the smooth solid rotor motor, it is a structural design that further cancels the slots on the basis of the motor with ordinary slots.

[0048] Among them, for the high-speed induction motor with a solid rotor structure proposed in the present invention, when the rotational speed is 11496 rpm, the maximum torque is 66.7903 Nm, and when the rotational speed is 11880 rpm, the minimum torque is 35.5078 Nm; for the high-speed induction motor with an ordinary slotted solid rotor structure, when the rotational speed is 11496 rpm, the maximum torque is 63.8608 Nm, and when the rotational speed is 11880 rpm, the minimum torque is 33.7446 Nm; for the high-speed induction motor with an ordinary smooth solid rotor structure, when the rotational speed is 11496 rpm, the maximum torque is 37.4954 Nm, and when the rotational speed is 11880 rpm, the minimum torque is 17.8755 Nm; compared with the high-speed induction motor with an ordinary slotted solid rotor of the same parameters, the torque of the high-speed induction motor with a solid rotor structure proposed in the present invention is increased by 4.39% at a rotational speed of 11496 rpm; compared with the high-speed induction motor with an ordinary smooth solid rotor of the same parameters, the torque of the high-speed induction motor with a solid rotor structure proposed in the present invention is increased by 43.86% at a rotational speed of 11496 rpm.

[0049] Figure 6 Shown is a waveform comparison diagram of the finite element simulation efficiency varying with the rotational speed of this motor, a motor with ordinary slots, and a smooth solid rotor motor. Among them, for the high-speed induction motor with a solid rotor structure proposed in the present invention, when the rotational speed is 11592 rpm, the maximum efficiency is 98.3004%, and when the rotational speed is 11880 rpm, the minimum efficiency is 97.8211%; for the high-speed induction motor with an ordinary slotted solid rotor structure, when the rotational speed is 11592 rpm, the maximum efficiency is 98.2036%, and when the rotational speed is 11880 rpm, the minimum torque is 97.7773%; for the high-speed induction motor with an ordinary smooth solid rotor structure, when the rotational speed is 11712 rpm, the maximum efficiency is 97.4885%, and when the rotational speed is 11496 rpm, the minimum efficiency is 96.5823%; compared with the high-speed induction motors with an ordinary slotted solid rotor structure and an ordinary smooth solid rotor structure of the same parameters, the efficiency of the high-speed induction motor with a solid rotor structure proposed in the present invention has been improved.

[0050] Figure 7 Shown is the torque waveform diagram of the high-speed induction motor of this motor within the range of 0 - 90° rotor mechanical angle. Within the range of 0 - 90° rotor mechanical angle, the torque is all positive, where the maximum torque is 61.2975 Nm, the minimum torque is 49.0352 Nm, the torque ripple is 12.2624 Nm, and the average torque is 52.7625 Nm; it can be seen that the solid rotor structure proposed by the present invention effectively overcomes the problem that the motor cannot start due to the synchronous additional torque. And within the range of 0 - 90° rotor mechanical angle, the average torque of the high-speed induction motor with a common smooth solid rotor structure is 17.8118 Nm. Compared with the common smooth solid rotor, the average torque of the high-speed induction motor with the solid rotor structure proposed by the present invention is increased by nearly 3 times; the average torque of the high-speed induction motor with a common slotted solid rotor structure within the range of 0 - 90° rotor mechanical angle is 49.1225 Nm. Compared with the common slotted solid rotor, the average torque of the high-speed induction motor with the solid rotor structure proposed by the present invention is increased by 7.42%.

[0051] Example 2

[0052] Referring to the motor parameter settings in Table 1 of Example 1, change the value of L2 / L1 to 30%, 40%, 48%, and 49% respectively, and compare the torque variation with speed, the efficiency variation with speed, the average torque and torque ripple within the range of 0 - 90° rotor mechanical angle through finite element simulation respectively. The results are shown in Table 2.

[0053]

[0054] Table 2

[0055] It can be found through comparison that when the value of L2 / L1 is 30%, the high-speed torque and efficiency are both inferior to those of the common slotted motor. When the value of L2 / L1 is 40% and 48%, the high-speed torque is superior to that of the common slotted motor, and the high-speed efficiency is basically the same as that of the common slotted motor. When the value of L2 / L1 is 49%, although the high-speed torque is superior to that of the common slotted motor, compared with 48%, the high-speed torque has an obvious downward trend, the high-speed efficiency and average torque also decrease, and the torque ripple increases. More importantly, the additional loss also increases significantly, indicating that when the value of L2 / L1 exceeds 48%, the rotational performance of the motor begins to decline, and the optimal value range is 40 - 48%.

[0056] Example 3

[0057] Referring to the motor parameter settings in Table 1 of Embodiment 1, change the value of H / D1 to 15%, 20%, 25%, 30% and 35% respectively, and compare the torque variation with speed, efficiency variation with speed, average torque and torque ripple within the range of 0 - 90° rotor mechanical angle through finite element simulation respectively. The results are shown in Table 3.

[0058]

[0059] Table 3

[0060] Through comparison, it can be found that when the value of H / D1 is 15%, the high-speed torque and efficiency are both inferior to those of the ordinary slotted motor. When the value of H / D1 is 20% and 25%, the high-speed torque is better than that of the ordinary slotted motor, and the high-speed efficiency is also higher than that of the ordinary slotted motor. When the value of H / D1 is 30%, although the high-speed torque is better than that of the ordinary slotted motor, compared with 25%, the high-speed efficiency and average torque show a downward trend, and the torque ripple increases, indicating that when the value of H / D1 exceeds 25%, the rotational performance of the motor begins to decline, and the optimal value range is 20 - 25%.

[0061] Embodiment 4

[0062] Referring to the motor parameter settings in Table 1 of Embodiment 1, change the value of W / bdr to 5%, 10%, 30%, 35% and 40% respectively, and compare the torque variation with speed, efficiency variation with speed, average torque and torque ripple within the range of 0 - 90° rotor mechanical angle through finite element simulation respectively. The results are shown in Table 4.

[0063]

[0064]

[0065] Table 4

[0066] Through comparison, it can be found that when the value of W / b dr is 5%, although the high-speed torque is slightly higher than that of the ordinary slotted motor, the high-speed efficiency is inferior to that of the ordinary slotted motor, and the average torque is the lowest. When the value of W / b dr is 10% and 30%, the high-speed torque is better than that of the ordinary slotted motor, and the high-speed efficiency is also at a comparable level to that of the ordinary slotted motor. When the value of W / b dr is 35%, although the high-speed torque is better than that of the ordinary slotted motor, compared with 30%, the high-speed efficiency shows a downward trend, and the torque ripple increases, indicating that when the value of W / b dr exceeds 30%, the rotational performance of the motor begins to decline, and the optimal value range is 10 - 30%.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it.

Claims

1. High-speed induction motor solid rotor structure, characterized in that: It comprises an integrated conductive and magnetic rotor and a rotating shaft, wherein the surface of the rotor has two groups of grooves, any groove in any group is staggered with all the grooves in the other group along the circumferential direction of the rotor, the two groups of grooves are spaced apart along the axial direction of the rotor, and a distance is left between the far ends of the two groups of grooves and the adjacent rotor end faces.

2. The high-speed induction motor solid rotor structure according to claim 1, characterized in that: The length direction of the slot extends along the axial direction of the rotor, and the depth direction extends along the radial direction of the rotor.

3. The high-speed induction motor solid rotor structure according to claim 1, characterized in that: The two groups of slots have the same number of slots and slot-shaped dimensions; each group of slots is evenly spaced along the circumference of the rotor.

4. The high-speed induction motor solid rotor structure according to claim 3, characterized in that: The total number of slots on the rotor is Q, and the offset angle of the two groups of slots is 360° / Q.

5. The high-speed induction motor solid rotor structure according to claim 3, characterized in that: The total number of slots on the rotor is twice the total number of slots on the outer stator.

6. The high-speed induction motor solid rotor structure according to claim 3, characterized in that: The axial length of the rotor is L1, the length dimension of the slot is L2, and the value of L2 / L1 is 0.4-0.

48.

7. The high-speed induction motor solid rotor structure according to claim 3, characterized in that: The depth dimension of the groove is H, the diameter of the rotor is D1, and the value of H / D1 is 0.2 to 0.

25.

8. The high-speed induction motor solid rotor structure according to claim 1, characterized in that: The total number of slots on the rotor is Q, the width of the slot is W, and the tooth pitch of the rotor is b. dr =2πD1 / Q, W / b dr The value is 0.1~0.

3.

9. The high-speed induction motor solid rotor structure according to claim 1, characterized in that: The diameter of the rotor is D1, the diameter of the rotating shaft is D2, and the value of D2 / D1 is 0.2-0.

4.

10. A motor, characterized in that: It comprises the high-speed induction motor solid rotor structure as described in any one of claims 1 to 9.

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