Rotor for Asynchronous Starting Permanent Magnet Motor and Asynchronous Starting Permanent Magnet Motor

Abstract

The present invention relates to a rotor for an induction-start permanent magnet motor and an induction-start permanent magnet motor. The rotor includes: a rotating shaft, an iron core, and a squirrel cage. The rotating shaft passes through the center of the iron core, and the squirrel cage is disposed on the outer peripheral portion of the iron core. Among them, at least two-pole permanent magnets are embedded in the iron core, and each pole of permanent magnet has at least a double-layer arrangement in the radial direction, so as to at least include a first-layer permanent magnet and a second-layer permanent magnet. The second-layer permanent magnet is disposed on the outer side of the first-layer permanent magnet away from the center o of the rotating shaft. Among them, in the cross-section of the rotor, the total length L2 of the second-layer permanent magnet is within the range of 40% to 100% of the total length L1 of the first-layer permanent magnet. The waveform of the air-gap flux density of the induction-start permanent magnet motor including this rotor is closer to an ideal sine wave efficiency, and the efficiency and performance of the motor are both improved.

Description

Technical Field

[0001] The invention relates to the field of asynchronous starting permanent magnet motors, and more specifically to a rotor with double-layer permanent magnets of the asynchronous starting permanent magnet motor. Background Art

[0002] This section provides background information related to the present disclosure which does not necessarily constitute prior art.

[0003] The asynchronous start permanent magnet motor is a permanent magnet motor with self-starting capability, which has the characteristics of both induction motor and permanent magnet synchronous motor. The motor relies on the asynchronous torque generated by the interaction between the stator rotating magnetic field and the cage rotor to achieve starting. During steady-state operation, the rotor rotates at the synchronous speed, the cage rotor no longer works, and there is no rotor resistance loss. Compared with the speed-regulating permanent magnet motor, there are squirrel cage bars on its rotor, which can achieve self-starting at a certain voltage and frequency; compared with the electrically excited synchronous motor, it uses permanent magnets to replace the excitation winding, and eliminates the collector ring brushes, so the structure is simpler and the operation is more reliable. At present, the asynchronous start permanent magnet motor can be used as a compressor for air conditioners and refrigerators or as a motor to drive vehicles.

[0004] In the design of asynchronous start permanent magnet motors, the way permanent magnets are arranged in the rotor directly affects the air gap flux, leakage flux and performance of the motor. If the rotor structure of the asynchronous start permanent magnet motor is too complicated, it will increase the uncertainty of the motor design and the requirements for the production process. The current common rotor structure is a structure in which the permanent magnets of two adjacent poles are connected in parallel, in series or in a mixed design, and the permanent magnets of each pole are usually single-layer. However, the air gap flux density waveform and electromotive force waveform of the current asynchronous start permanent magnet synchronous motor contain more harmonic components, resulting in reduced motor efficiency.

[0005] Therefore, it is necessary to provide an improved asynchronous start permanent magnet motor that reduces the harmonics in the air gap flux waveform and the electromotive force waveform without excessively increasing the complexity of its rotor structure, thereby improving the motor efficiency. Summary of the invention

[0006] This section provides a general summary of the invention, and is not a comprehensive disclosure of its full scope or all of its features.

[0007] The object of the present invention is to provide a rotor for an asynchronous starting permanent magnet motor which is simple, reliable and highly efficient.

[0008] According to one aspect of the present invention, there is provided a rotor for an induction-start permanent magnet motor, the rotor comprising: a rotating shaft, an iron core, and a squirrel cage, the rotating shaft passing through the center of the iron core, and the squirrel cage being disposed on the outer peripheral portion of the iron core, wherein at least two-pole permanent magnets are embedded in the iron core, and each pole of permanent magnet has at least a double-layer arrangement in the radial direction, so as to at least include a first-layer permanent magnet and a second-layer permanent magnet, and the second-layer permanent magnet is disposed on the outer side away from the center o of the rotating shaft of the first-layer permanent magnet. Wherein, in the cross-section of the rotor, the total length L2 of the second-layer permanent magnet is in the range of 40% to 100% of the total length L1 of the first-layer permanent magnet.

[0009] Optionally, in the cross-section of the rotor, the total length L2 of the second-layer permanent magnet is in the range of 80% to 95% of the total length L1 of the first-layer permanent magnet.

[0010] Optionally, the rotor is a two-pole structure rotor. For each pole, when the rotation angle of the rotor is in the range of 0° to 20° and 160° to 180°, the air-gap flux density of the rotor is less than or equal to 20% of the peak value.

[0011] Optionally, the rotor is a two-pole structure rotor. For each pole, when the rotation angle of the rotor is in the range of 20° to 160°, the waveform of the air-gap flux density of the rotor is close to a sine waveform.

[0012] Optionally, the rotor is a two-pole structure rotor. For each pole, the waveform of the air-gap flux density of the rotor has at least two steps, and the highest step is a curve with a flat top.

[0013] Optionally, the first-layer permanent magnet is configured as a straight shape, a V shape, a U shape, or an arc shape, and the second-layer permanent magnet is configured as a straight shape, a V shape, a U shape, or an arc shape. Preferably, the first-layer permanent magnet is configured as a U-shaped permanent magnet group composed of three sections of permanent magnets, and the second-layer permanent magnet is also configured as a U-shaped permanent magnet group composed of three sections of permanent magnets.

[0014] Optionally, the rotor is a four-pole structure rotor or a multi-pole structure rotor with more than four poles.

[0015] Optionally, each pole of permanent magnet has a three-layer arrangement or a multi-layer arrangement with more than three layers in the radial direction.

[0016] According to another aspect of the present invention, there is further provided an induction-start permanent magnet motor, the induction-start permanent magnet motor comprising the rotor as described above.

[0017] In general, the asynchronous start permanent magnet synchronous motor according to the present invention arranges the permanent magnets in the rotor into two layers and makes the one layer of permanent magnets and the second layer of permanent magnets satisfy a certain size relationship, thereby reducing the harmonics contained in the air gap flux density waveform and the harmonics contained in the electromotive force waveform, making the waveform of the air gap flux density closer to the ideal sinusoidal waveform, thereby increasing the torque of the asynchronous start permanent magnet synchronous motor and improving the efficiency of the asynchronous start permanent magnet synchronous motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The foregoing and other features and characteristics of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings, which are provided as examples only and are not necessarily drawn to scale. In the accompanying drawings, the same reference numerals are used to indicate the same components, and in the drawings:

[0019] Figure 1 A cross-sectional view of a rotor of an asynchronous start permanent magnet synchronous motor of the related art is shown, wherein a double-layer permanent magnet is built into the rotor core;

[0020] Figure 2 Show Figure 1 The waveform diagram of the magnetomotive force of the rotor of the asynchronous starting permanent magnet synchronous motor;

[0021] Figure 3a and Figure 3b 1. cross-sectional views respectively showing a rotor and a rotor core of an asynchronous start permanent magnet synchronous motor according to a first embodiment of the present invention;

[0022] Figure 4 Show Figure 3a Waveform diagram of air gap flux density of the rotor of the asynchronous start permanent magnet synchronous motor;

[0023] Figure 5a and Figure 5b 1. cross-sectional views respectively showing a rotor and a rotor core of an asynchronous start permanent magnet synchronous motor according to a second embodiment of the present invention;

[0024] Figure 6a and Figure 6b 1. cross-sectional views respectively showing a rotor and a rotor core of an asynchronous start permanent magnet synchronous motor according to a third embodiment of the present invention;

[0025] Figure 7a and Figure 7b 1. cross-sectional views respectively showing a rotor and a rotor core of an asynchronous start permanent magnet synchronous motor according to a fourth embodiment of the present invention;

[0026] Figure 8 A cross-sectional view showing a rotor and a rotor core of an asynchronous start permanent magnet synchronous motor according to a fifth embodiment of the present invention, wherein a four-pole permanent magnet is built into the rotor core;

[0027] Figure 9 Show Figure 1 Waveform comparison diagram of the electromotive force of the rotor of the asynchronous starting permanent magnet synchronous motor in the related art and the rotor of the asynchronous starting permanent magnet synchronous motor in the first to fourth embodiments of the present invention;

[0028] Figure 10 Show Figure 1 Column comparison diagram of the electromotive force harmonics of the rotor of the asynchronous starting permanent magnet synchronous motor in the related art and the rotor of the asynchronous starting permanent magnet synchronous motor in the first to fourth embodiments of the present invention. Detailed Embodiments

[0029] Now, the preferred embodiments of the present invention will be described in detail with reference to the attached Figures 1 to 10 The following description is essentially exemplary and not intended to limit the present invention and its applications or uses. In the various views, corresponding components or parts are denoted by the same reference numerals.

[0030] Figure 1 Shows the rotor 10 of the asynchronous starting permanent magnet synchronous motor in the related art. As Figure 1 shown, the rotor 10 of the asynchronous starting permanent magnet synchronous motor mainly includes an iron core 50, a squirrel cage 30 provided on the outer periphery of the iron core 50, and end rings 20 mounted at both ends of the squirrel cage 30. The iron core 50 can be a laminated iron core, and a through hole 53 for installing a rotating shaft is provided at the center thereof, and a groove for installing aluminum bars of the squirrel cage 30 is provided on the outer periphery, and a notch for embedding a permanent magnet 60 is provided between the through hole 53 and the groove. The permanent magnet 60 is configured as a two-pole structure, including permanent magnets 601, 601' constituting the N pole and permanent magnets 602, 602' constituting the S pole. Each pole permanent magnet is arranged in a double layer in the radial direction and each permanent magnet 601, 601', 602, 602' is linear.

[0031] In the asynchronous starting permanent magnet synchronous motor, the electromagnetic torque is composed of a permanent magnet torque generated by the interaction of the permanent magnet magnetic field and the armature reaction magnetic field and a reluctance torque caused by the asymmetry of the d, q axis magnetic circuits of the asynchronous starting permanent magnet synchronous motor, where the d axis is defined as the connecting line from the center o of the rotating shaft to the center of each pole permanent magnet in the circumferential direction, and the q axis is defined as the connecting line from the center o of the rotating shaft to the center in the circumferential direction between the two pole permanent magnets. The permanent magnets 601, 601' and the permanent magnets 602, 602' are symmetrically arranged on both sides of the q axis with respect to the q axis in the iron core 50, and the second layer permanent magnet 601' is parallel to the first layer permanent magnet 601 at a certain interval, and the second layer permanent magnet 602' is parallel to the first layer permanent magnet 602 at a certain interval.

[0032] Figure 2 Shows in Figure 1The magnetomotive force waveform diagram detected at the specified position of the rotor 10 (the position marked 0°), where the vertical axis represents the magnetomotive force of the rotor 10 and the horizontal axis represents the rotation angle of the rotor. Assuming that the rotor 10 rotates in the clockwise direction, the permanent magnet 601 reaches Figure 1 The position shown was not detected before the magnetomotive force.

[0033] from Figure 2 It can be seen that when the rotor 10 just starts to rotate, that is, when the rotation angle of the rotor is near 0°, the detected magnetomotive force of the permanent magnet 601 is very small. As the rotor 10 rotates, the magnetomotive force formed by the permanent magnet 601 increases and reaches the first peak, and this state is maintained within a certain rotation angle, thereby forming the first step of the waveform. When the rotor 10 rotates further and the permanent magnet 601' reaches the position marked 0°, due to the superposition of the magnetomotive force generated by the permanent magnet 601', the detected magnetomotive force further increases and reaches the second peak, and this state is maintained within a certain rotation angle, thereby forming the second step (i.e., the highest step) of the waveform. Subsequently, the detected magnetomotive force decreases from the second peak to the first peak, and after being maintained within a certain rotation angle, it continues to decrease from the first peak. When the rotor rotates to near 180°, the detected magnetomotive force of the permanent magnet 601 is very small. In this process, the rotor 10 rotates 180°, that is, in the range of the rotor rotation angle of 0° to 180°, the magnetomotive force is positive, constituting a half cycle of the magnetomotive force change. Then the rotor 10 continues to rotate, and when the rotor rotation angle is in the range of 180° to 360°, the waveform of the magnetomotive force formed by the permanent magnets 602, 602' is the same as and opposite to the waveform of the magnetomotive force in the range of the rotation angle of 0° to 180°, forming another half cycle of the magnetomotive force change. The rotor 10 rotates continuously, that is, a continuous magnetomotive force waveform can be generated.

[0034] In practical applications, due to the presence of harmonics, the magnetomotive force waveform often presents a roughly rectangular or V-shaped shape. In addition, since the magnetomotive force generated by the adjacent permanent magnets of different poles has the opposite driving direction to the rotor, the electromagnetic torque of the rotor is reduced. Although the permanent magnet 60 is set as a double-layer structure, so that the roughly rectangular magnetomotive force waveform is improved to a waveform with two steps, it is obvious that the magnetomotive force waveform presents a relatively drastic change due to the presence of harmonics, especially the highest step is almost V-shaped, which is quite different from the ideal sinusoidal waveform. In this case, since the air gap magnetic flux density is proportional to the magnetomotive force and has the same phase, the waveform of the air gap magnetic flux density and even the waveform of the electromotive force will also contain more harmonics, resulting in a decrease in efficiency caused by harmonics and a reduction in rotor torque.

[0035] In view of the above technical problems, the present invention improves the rotor structure of the related-art asynchronous starting permanent magnet synchronous motor. Generally speaking, the present invention improves the arrangement of permanent magnets within a limited space, thereby improving the output characteristics of the motor. Specifically, the improved rotor structure of the asynchronous starting permanent magnet synchronous motor according to several preferred embodiments of the present invention will be described in detail below with reference to Figures 3a to 8 The main structures of the rotor, such as the squirrel cage 300, the end ring 200, and the iron core 500, are similar to those of the related-art rotor in each embodiment, and thus will not be described in detail one by one.

[0036] Figure 3a and Figure 3b FIGS. Figure 3b and Figure 4 respectively show cross-sectional views of the rotor 100 and the iron core 500 of the asynchronous starting permanent magnet synchronous motor according to the first embodiment of the present invention. Among them, permanent magnets 610 are embedded in the iron core 500. The permanent magnets 610 are of a two-pole structure, including permanent magnets 611, 611' constituting the N pole and permanent magnets 612, 612' constituting the S pole. Each pole of permanent magnets is arranged in a double layer in the radial direction. The permanent magnets 611, 611' and the permanent magnets 612, 612' are symmetrically arranged on both sides of the q-axis with respect to the q-axis in the iron core 500, and the permanent magnets 611, 611' and the permanent magnets 612, 612' are symmetric with respect to the d-axis themselves. Among them, the first-layer permanent magnets 611, 612 are respectively constructed as linear permanent magnets, while the second-layer permanent magnets 611', 612' are respectively constructed as permanent magnet groups composed of two segments of permanent magnets and arranged in a V shape. The second-layer permanent magnets 611', 612' are respectively disposed outside the first-layer permanent magnets 611, 612 away from the center of the rotating shaft. Now, taking the permanent magnets 612, 612' constituting the S pole as an example, in combination with Figure 4 The further structural arrangement of the permanent magnets and the air-gap flux density waveform generated by the permanent magnets 612, 612' constituting the S pole will be described.

[0037] In addition, in the cross-section of the rotor, the total length of the first-layer permanent magnet 612 is L1, and the total length of the two segments of the second-layer permanent magnet 612' is L2, where the length L2 is in the range of 40% to 100% of the length L1. Preferably, the length L2 is in the range of 60% to 100% of the length L1. More preferably, the length L2 is in the range of 80% to 95% of the length L1. It should be noted that the numerical ranges in the present invention include the endpoint values.

[0038] Assume that the rotor 100 rotates in the clockwise direction. When the rotor 100 rotates from 0° to approximately 20°, the first-layer permanent magnet 612 reaches the position marked 0°. Corresponding to Figure 4, when the rotation angle of the rotor 100 is in the range of 0° to 20°, the air-gap flux density of the rotor 100 is less than or equal to 20% of its peak value. As the rotor 100 rotates, the air-gap flux density increases and reaches the first peak, and this state is maintained within a certain rotation angle, thereby forming the first step of the waveform. When the rotor 100 rotates further and the second-layer permanent magnet 612' reaches the position marked 0°, due to the superposition of the magnetic field generated by the second-layer permanent magnet 612', the air-gap flux density of the rotor 100 further increases and reaches the second peak, and this state is maintained within a certain rotation angle, thereby forming the second step (i.e., the highest step) of the waveform. As the rotor 100 rotates further and the second-layer permanent magnet 612' leaves the position marked 0°, the air-gap flux density decreases from the second peak to the first peak, and after being maintained within a certain rotation angle, it continues to decrease from the first peak. When the rotor 100 rotates to approximately 160°, the first-layer permanent magnet 612 leaves the position marked 0°, and as shown in Figure 4 , when the rotation angle of the rotor 100 is in the range of 160° to 180°, the air-gap flux density of the rotor 100 is very small, less than or equal to 20% of its peak value.

[0039] In this process, the rotor 100 rotates 180°, that is, within the range of the rotation angle of the rotor 100 from 0° to 180°, the air-gap flux density is positive, constituting half a cycle of the air-gap flux density waveform. Subsequently, the rotor 100 continues to rotate. Within the range of the rotation angle of the rotor from 180° to 360°, the waveform of the air-gap flux density is opposite to the waveform of the air-gap flux density in the range of the rotation angle from 0° to 180°, constituting the waveform of the other half cycle. The rotor 100 rotates continuously, that is, a continuous air-gap flux density waveform can be generated.

[0040] As can be seen from Figure 4 , for the rotor according to the first embodiment of the present invention, the waveform of its air-gap flux density contains fewer harmonics. In particular, the highest step presents a curve with a relatively flat top rather than a V shape. Generally speaking, the waveform of the air-gap flux density is closer to the ideal sine waveform. Correspondingly, the electromotive force waveform of this rotor also contains fewer harmonics, reducing the motor current, thereby improving the motor efficiency and the torque performance of the motor.

[0041] Figure 5a and Figure 5bCross-sectional views of the rotor 100 and the iron core 500 of the asynchronous starting permanent magnet synchronous motor according to the second embodiment of the present invention are respectively shown. Among them, permanent magnets 620 are embedded in the iron core 500. The permanent magnets 620 are of a two-pole structure, including permanent magnets 621, 621' constituting the N pole and permanent magnets 622, 622' constituting the S pole. Each pole of permanent magnets is arranged in a double layer in the radial direction. The symmetrical design of the permanent magnets 621, 621' and the permanent magnets 622, 622' with respect to the q-axis and the d-axis is the same as that in the first embodiment of the present invention, and will not be elaborated here one by one. The difference is that the first-layer permanent magnets 621, 622 are respectively constructed as linear permanent magnets, while the second-layer permanent magnets 621', 622' are respectively constructed as permanent magnet groups composed of three segments of permanent magnets and arranged in a U shape. Among them, in the cross-section of the rotor, the total length L1 of the first-layer permanent magnet 621 or 622, and the total length of the three segments of the second-layer permanent magnet 621' or 622' is L2, where the length L2 is in the range of 40% to 100% of the length L1. Preferably, the length L2 is in the range of 60% to 100% of the length L1. More preferably, the length L2 is in the range of 80% to 95% of the length L1.

[0042] The air-gap flux density waveform diagram of the rotor in the second embodiment shows results similar to those of the rotor in the first embodiment. Taking half a cycle as an example, when the rotation angle of the rotor 100 is in the range of approximately 0° to 20° and 160° to 180°, the air-gap flux density of the rotor 100 is very small, less than or equal to 20% of its peak value. When the rotation angle of the rotor 100 is in the range of 20° to 160°, as the rotor 100 rotates, the air-gap flux density increases and reaches the first peak value, and this state is maintained within a certain rotation angle, thereby forming the first step of the waveform; subsequently, the air-gap flux density of the rotor 100 further increases and reaches the second peak value, and this state is maintained within a certain rotation angle, thereby forming the second step (i.e., the highest step) of the waveform; then the air-gap flux density decreases from the second peak value to the first peak value, continues to decrease from the first peak value after being maintained within a certain rotation angle.

[0043] For the rotor according to the second embodiment of the present invention, its air-gap flux density waveform contains fewer harmonics. In particular, the top of the highest step is relatively flat instead of V-shaped. Generally speaking, the waveform of the air-gap flux density is closer to the ideal sine waveform. Correspondingly, the electromotive force waveform of this rotor also contains fewer harmonics, reducing the motor current and thus improving the motor efficiency and the torque performance of the motor.

[0044] Figure 6a and Figure 6bCross-sectional views of the rotor 100 and the iron core 500 of an asynchronous starting permanent magnet synchronous motor according to the third embodiment of the present invention are respectively shown. Among them, permanent magnets 630 are embedded in the iron core 500. The permanent magnets 630 have a two-pole structure, including permanent magnets 631, 631' constituting the N pole and permanent magnets 632, 632' constituting the S pole. Each pole of permanent magnets is arranged in a double layer in the radial direction. The symmetrical design of the permanent magnets 631, 631' and the permanent magnets 632, 632' with respect to the q-axis and the d-axis is the same as that in the first embodiment of the present invention, and will not be elaborated here one by one. The difference is that the first-layer permanent magnets 631, 632 are respectively configured as permanent magnet groups composed of three sections of permanent magnets and arranged in a U shape, and the second-layer permanent magnets 631', 632' are also respectively configured as permanent magnet groups composed of three sections of permanent magnets and arranged in a U shape. The first-layer permanent magnet 631 is parallel to the second-layer permanent magnet 631', and the first-layer permanent magnet 632 is parallel to the second-layer permanent magnet 632'. Among them, in the cross-section of the rotor, the total length of the three sections of permanent magnets of the first-layer permanent magnet 631 or 632 is L1, and the total length of the three sections of permanent magnets of the second-layer permanent magnet 631' or 632' is L2, where the length L2 is in the range of 40% to 100% of the length L1. Preferably, the length L2 is in the range of 60% to 100% of the length L1. More preferably, the length L2 is in the range of 80% to 95% of the length L1.

[0045] The air-gap flux density waveform diagram of the rotor in the third embodiment shows results similar to those of the rotor in the first embodiment. Taking half a cycle as an example, when the rotation angle of the rotor 100 is in the range of approximately 0° to 20° and 160° to 180°, the air-gap flux density of the rotor 100 is very small, less than or equal to 20% of its peak value. When the rotation angle of the rotor 100 is in the range of 20° to 160°, as the rotor 100 rotates, the air-gap flux density increases and reaches the first peak value, and this state is maintained within a certain rotation angle, thus forming the first step of the waveform; subsequently, the air-gap flux density of the rotor 100 further increases and reaches the second peak value, and this state is maintained within a certain rotation angle, thus forming the second step (i.e., the highest step) of the waveform; then the air-gap flux density decreases from the second peak value to the first peak value, continues to decrease from the first peak value after being maintained within a certain rotation angle.

[0046] For the rotor according to the third embodiment of the present invention, its air-gap flux density waveform contains fewer harmonics. In particular, the top of the highest step is relatively flat instead of V-shaped. Generally speaking, the waveform of the air-gap flux density is closer to the ideal sine waveform. Correspondingly, the electromotive force waveform of this rotor also contains fewer harmonics, reducing the motor current and thus improving the motor efficiency and the torque performance of the motor.

[0047] Figure 7a andFigure 7b FIG. 1 shows a cross-sectional view of a rotor 100 and an iron core 500 of an induction-start permanent magnet synchronous motor according to a fourth embodiment of the present invention. Among them, a permanent magnet 640 is embedded in the iron core 500. The permanent magnet 640 has a two-pole structure, including permanent magnets 641, 641' constituting the N pole and permanent magnets 642, 642' constituting the S pole. Each pole of the permanent magnet is arranged in a double layer in the radial direction. The symmetric design of the permanent magnets 641, 641' and the permanent magnets 642, 642' with respect to the q-axis and the d-axis is the same as that in the first embodiment of the present invention, and will not be described in detail here. The difference is that one layer of the permanent magnets 641, 642 are respectively configured as arc-shaped permanent magnets, and the second layer of the permanent magnets 641', 642' are also respectively configured as arc-shaped permanent magnet groups. The first layer of the permanent magnet 641 is parallel to the second layer of the permanent magnet 641', and the first layer of the permanent magnet 642 is parallel to the second layer of the permanent magnet 642'. Among them, in the cross-section of the rotor, the total length of one layer of the permanent magnets 641 or 642 is L1 (at this time, it is the arc length), and the total length of the second layer of the permanent magnets 641' or 642' is L2 (at this time, it is the arc length), where the length L2 is in the range of 40% to 100% of the length L1. Preferably, the length L2 is in the range of 60% to 100% of the length L1. More preferably, the length L2 is in the range of 80% to 95% of the length L1.

[0048] The air-gap flux density waveform diagram of the rotor in the fourth embodiment shows similar results to the rotor in the first embodiment. Taking half a cycle as an example, when the rotation angle of the rotor 100 is in the range of approximately 0° to 20° and 160° to 180°, the air-gap flux density of the displayed rotor 100 is very small, less than or equal to 20% of its peak value. When the rotation angle of the rotor 100 is in the range of 20° to 160°, as the rotor 100 rotates, the air-gap flux density increases and reaches the first peak value, and this state is maintained within a certain rotation angle, thereby forming the first step of the waveform; subsequently, the air-gap flux density of the rotor 100 further increases and reaches the second peak value, and this state is maintained within a certain rotation angle, thereby forming the second step (i.e., the highest step) of the waveform; then the air-gap flux density decreases from the second peak value to the first peak value, and after being maintained within a certain rotation angle, it continues to decrease from the first peak value.

[0049] For the rotor according to the fourth embodiment of the present invention, the air-gap flux density waveform contains fewer harmonics. In particular, the top of the highest step is relatively flat instead of V-shaped. Generally speaking, the waveform of the air-gap flux density is closer to the ideal sine waveform. Correspondingly, the electromotive force waveform of this rotor also contains fewer harmonics, reducing the motor current and thus improving the motor efficiency and the torque performance of the motor.

[0050] Those of ordinary skill in the art should understand that the arrangement of the double-layer permanent magnets in the rotor structure of the asynchronous starting permanent magnet synchronous motor of the present invention can be applied not only to the rotors of two-pole structures, but also to multi-pole rotors such as four-pole, six-pole or eight-pole. The specific shapes of the first-layer permanent magnet and the second-layer permanent magnet in the permanent magnet can be selected according to needs. For example, they can be constructed as linear permanent magnets, a permanent magnet group composed of two segments of permanent magnets and arranged in a V shape, a permanent magnet group composed of three segments of permanent magnets and arranged in a U shape, or arc-shaped permanent magnets and other permanent magnets with suitable shapes, as long as the total length L2 of the second-layer permanent magnet is in the range of 40% to 100% of the total length L1 of the first-layer permanent magnet, preferably in the range of 60% to 100%, and more preferably in the range of 80% to 95%. Figure 8 Fig. shows a schematic diagram of a four-pole rotor and its iron core of an asynchronous starting permanent magnet synchronous motor according to the present invention, including linear, arc-shaped, V-shaped and U-shaped permanent magnet arrangements. Similar to the results shown for the two-pole rotor, the four-pole rotor with the above-mentioned permanent magnet arrangement also shows good effects such as a lower harmonic content in the air-gap flux density waveform and electromotive force waveform, a waveform of the air-gap flux density closer to an ideal sine wave, a reduced motor current, an improved motor torque performance, and an increased motor efficiency.

[0051] The following Table 1 shows the comparison results of the performance of an asynchronous starting permanent magnet synchronous motor of the related art with the rotor structure as shown in Figure 1 and Figure 2 and the performance of an asynchronous starting permanent magnet synchronous motor with the rotor structure according to the first to third embodiments of the present invention.

[0052] Table 1

[0053]

[0054] As can be seen from Table 1, the current of the asynchronous starting permanent magnet synchronous motor with the rotor structure in the first to third embodiments of the present invention is lower than that of the asynchronous starting permanent magnet synchronous motor of the related art, the efficiency is increased, and the maximum torque is increased. In particular, for the rotor in the third embodiment where both the first-layer permanent magnet and the second-layer permanent magnet are U-shaped, the working efficiency and the maximum torque are both significantly improved, and the working performance is significantly improved.

[0055] Figure 9 Fig. shows a waveform comparison diagram of the electromotive force of an asynchronous starting permanent magnet synchronous motor of the related art with the rotor structure as shown in Figure 1 and Figure 2 and the electromotive force of an asynchronous starting permanent magnet synchronous motor with the rotor structure according to the first to third embodiments of the present invention. Figure 10 Fig. then shows a comparison diagram of the harmonics contained in the waveform of the electromotive force in Figure 9 in the form of a bar chart. FromFigure 9 and Figure 10 It can be further seen from Figure 10 that the electromotive force waveform of the induction-start permanent magnet synchronous motor with the rotor structure in the first to third embodiments of the present invention contains fewer harmonics, resulting in less loss caused by harmonics and higher efficiency of the induction-start permanent magnet synchronous motor.

[0056] The working fluid circulation system according to the preferred embodiments of the present invention has been described above in conjunction with specific embodiments. It is understood that the above description is only exemplary and not restrictive. Without departing from the scope of the present invention, those skilled in the art can conceive of various variations and modifications based on the above description. These variations and modifications are also included in the protection scope of the present invention.

Claims

1. A rotor (100) for an induction-start permanent magnet motor, the rotor (100) comprising: A rotating shaft; A core (500) through which the rotating shaft passes through the center of the core (500); And A squirrel cage (300) disposed on the outer peripheral portion of the core (500), Wherein at least two-pole permanent magnets (610, 620, 630, 640) are embedded in the core (500), and each pole of permanent magnet (610, 620, 630, 640) has at least a double-layer arrangement in the radial direction so as to at least include a first-layer permanent magnet and a second-layer permanent magnet, and the second-layer permanent magnet is disposed outside the first-layer permanent magnet away from the center o of the rotating shaft, Characterized in that in the cross-section of the rotor (100), the total length L2 of the second-layer permanent magnet is in the range of 40% to 100% of the total length L1 of the first-layer permanent magnet.

2. The rotor (100) for an induction-start permanent magnet motor according to claim 1, in the cross-section of the rotor (100), the total length L2 of the second-layer permanent magnet is in the range of 80% to 95% of the total length L1 of the first-layer permanent magnet.

3. The rotor (100) for an induction-start permanent magnet motor according to claim 1 or 2, wherein, The rotor (100) is a two-pole structured rotor, and for each pole, when the rotation angle of the rotor (100) is in the range of 0° to 20° and 160° to 180°, the air-gap flux density of the rotor (100) is less than or equal to 20% of the peak value.

4. The rotor (100) for an induction-start permanent magnet motor according to claim 1 or 2, wherein, The rotor (100) is a two-pole structured rotor, and for each pole, when the rotation angle of the rotor (100) is in the range of 20° to 160°, the waveform of the air-gap flux density of the rotor (100) is close to a sine waveform.

5. The rotor (100) for an induction-start permanent magnet motor according to claim 1 or 2, wherein, The rotor (100) is a two-pole structured rotor, and for each pole, the waveform of the air-gap flux density of the rotor (100) has at least two steps, wherein the highest step is a curve with a flat top.

6. The rotor (100) for an induction-start permanent magnet motor according to claim 1 or 2, wherein, The first-layer permanent magnet is configured as a straight line, V-shaped, U-shaped or arc-shaped, and the second-layer permanent magnet is configured as a straight line, V-shaped, U-shaped or arc-shaped.

7. The rotor (100) for an induction-start permanent magnet motor according to claim 6, wherein, The first-layer permanent magnet is configured as a U-shaped permanent magnet group composed of three segments of permanent magnets, and the second-layer permanent magnet is also configured as a U-shaped permanent magnet group composed of three segments of permanent magnets.

8. The rotor (100) for an induction-start permanent magnet motor according to claim 1 or 2, the rotor is a four-pole structured rotor or a multi-pole structured rotor with more than four poles.

9. The rotor (100) for an induction-start permanent magnet motor according to claim 1 or 2, each pole of permanent magnet has a three-layer arrangement or a multi-layer arrangement with more than three layers in the radial direction.

10. An asynchronous starting permanent magnet motor, wherein, The induction-start permanent magnet motor includes the rotor (100) for an induction-start permanent magnet motor according to any one of claims 1 to 9.

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