Self-starting squirrel cage rotor structure and permanent magnet synchronous motor

Abstract

The invention discloses a self-starting squirrel cage rotor structure and a permanent magnet synchronous motor, and belongs to the technical field of permanent magnet synchronous motors. The self-starting squirrel cage rotor structure comprises a rotating shaft, a rotor core, a squirrel cage unit and a plurality of magnetic pole units, the rotor iron core sleeves the rotating shaft; each mouse cage unit comprises a plurality of spaced outer cage bars and a plurality of spaced inner cage bars; the plurality of magnetic pole units are uniformly arranged along the circumferential direction of the rotating shaft and are located at the inner sides of the plurality of outer cage bars, each magnetic pole unit comprises two circumferential magnetic steels and two radial magnetic steels, and the two circumferential magnetic steels and the two radial magnetic steels are respectively inserted into magnetic steel grooves of the rotor iron core and are arranged in a U shape; and the plurality of inner cage bars of each inner cage bar group are positioned in the openings of the corresponding magnetic pole units. The self-starting squirrel cage rotor structure provided by the embodiment of the invention not only improves the rated efficiency of the motor, but also realizes synchronous lifting of the starting torque and the pull-in torque in combination with the double-cage design, reduces the starting current, and improves the starting performance.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet synchronous motor technology, specifically relating to a self-starting squirrel-cage rotor structure and a permanent magnet synchronous motor. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) utilize permanent magnets in their rotors instead of electromagnets that generate magnetic fields through electromagnetic induction, resulting in lower electromagnetic losses and higher efficiency. Consequently, they are finding increasingly widespread application in electric drive systems. The rotor structure is a crucial component of PMSMs, and the self-starting squirrel-cage rotor structure, with its dual advantages of asynchronous starting capability and synchronous operating efficiency (where the magnets provide the necessary excitation and the squirrel cage initiates motor startup), is gaining increasing penetration in industrial drives year by year.

[0003] However, in existing self-starting squirrel-cage rotor structures, the magnets and squirrel cage are usually set in separate areas, resulting in low integration and low magnetic flux density, which reduces rated efficiency. In addition, during the startup phase, the equivalent resistance and reactance are mismatched, and the startup current is generally as high as 7-10 times the rated current, causing grid voltage fluctuations. At the same time, the startup torque is insufficient, making it difficult to meet the synergistic optimization of startup torque and pull-in torque. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a self-starting squirrel-cage rotor structure and a permanent magnet synchronous motor. Its purpose is to not only effectively improve the magnetic flux density through the U-shaped magnetic cohesion structure and the integrated design of the magnets and inner and outer cage bars, thereby improving the rated efficiency of the motor, but also to achieve synchronous improvement of starting torque and pull-in torque by combining a double cage design, thereby reducing the starting current and improving starting performance.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a self-starting squirrel-cage rotor structure, the self-starting squirrel-cage rotor structure comprising a rotating shaft, a rotor core, a squirrel-cage unit, and multiple magnetic pole units; The rotor core is sleeved outside the rotating shaft; The rat cage unit includes multiple spaced outer cage bars and multiple spaced inner cage bars. The multiple outer cage bars are evenly inserted into the outer cage slots of the rotor core along the circumference of the rotor core and are located at the outer edge of the rotor core. The multiple inner cage bars are inserted into the inner cage slots of the rotor core along the circumference of the rotor core, and the multiple inner cage bars form multiple spaced inner cage bar groups. Each inner cage slot is connected to the corresponding outer cage slot. The two ends of the multiple outer cage bars and the two ends of the multiple inner cage bars are connected by end rings. Multiple magnetic pole units are evenly arranged circumferentially along the rotation axis and located inside the multiple outer cage bars. Each magnetic pole unit includes two circumferential magnets and two radial magnets. The two circumferential magnets are located between the two radial magnets. The two circumferential magnets and the two radial magnets are respectively inserted into the magnetic slots of the rotor core and arranged in a U-shape. Each circumferential magnet is arranged tangentially along the rotation axis, and each radial magnet is arranged radially along the rotation axis. Multiple inner cage bars of each inner cage bar group are located in the opening of the corresponding magnetic pole unit.

[0006] Optionally, the end of each radial magnet facing away from the rotating shaft is opposite to the corresponding outer cage bar.

[0007] Optionally, a plurality of spaced magnetic bridges are inserted into the rotor core, each magnetic bridge being located between the end of each radial magnet facing away from the rotating shaft and the corresponding outer cage bar.

[0008] Optionally, the thickness of each magnetic bridge in the radial direction of the rotating shaft is 0.8-1.5 mm.

[0009] Optionally, the outer cage bars and the inner cage bars satisfy the following formula:

[0010] Where M is the number of outer cage bars, N is the number of inner cage bars, p is the number of magnetic pole units, k is 0, 1, 2, 3, ..., n, and n is a positive integer.

[0011] Optionally, the outer cage trough and the inner cage trough are circular troughs, pear-shaped troughs, or convex troughs.

[0012] Optionally, both the circumferential magnet and the radial magnet are rectangular structures with the same dimensions.

[0013] Optionally, both the circumferential magnet and the radial magnet are made of neodymium iron boron.

[0014] Optionally, both the outer cage bars and the inner cage bars are made using a process of casting aluminum, stringing aluminum bars, or stringing copper bars.

[0015] In a second aspect, the present invention provides a permanent magnet synchronous motor, the permanent magnet synchronous motor comprising a self-starting squirrel cage rotor structure as described in the first aspect.

[0016] The aforementioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0017] In summary, the beneficial effects of the above-described technical solutions conceived by this invention compared with the prior art include: Regarding the self-starting squirrel-cage rotor structure provided in this embodiment of the invention, on one hand, multiple outer cage bars are uniformly inserted into the outer cage slots of the rotor core along the circumference of the rotor core and located at the outer edge of the rotor core. Multiple inner cage bars are inserted into the inner cage slots of the rotor core along the circumference of the rotor core, forming multiple spaced inner cage bar groups. Each inner cage slot is connected to the corresponding outer cage slot, thus forming a double-cage structure with inner and outer arrangements on the outer edge of the rotor core. For the double-cage structure, in the initial startup phase, the high resistance of the outer cage corresponding to the outer cage bars dominates, increasing the starting torque to 2.0-2.2 times the rated torque, thereby improving the starting torque. Furthermore, the starting current is controlled within 5 times the rated current, thus reducing the starting current. In the later startup phase, the low resistance of the inner cage corresponding to the inner cage bars intervenes, increasing the pull-in torque and ensuring smooth synchronization (starting time shortened to within 1.0s), ultimately achieving synchronous increase in starting torque and pull-in torque, while reducing the starting current.

[0018] On the other hand, for multiple magnetic pole units, two circumferential magnets and two radial magnets are respectively inserted into the magnet slots of the rotor core in a U-shaped arrangement. Each circumferential magnet is arranged tangentially along the shaft, thus ensuring that the distance between each circumferential magnet and the outer stator remains consistent. Each radial magnet is arranged radially along the shaft, and multiple inner cage bars of each inner cage bar group are located within the opening of the corresponding magnetic pole unit. This not only greatly improves the magnetic flux density through the U-shaped magnetic aggregation structure, but also divides the rotor core outside the shaft into multiple sector-shaped regions. In each sector-shaped region, the magnets, inner cage bars, and outer cage bars are fully integrated, and the magnet arrangement area is large, thereby further improving the magnetic flux density and thus increasing the rated efficiency of the motor.

[0019] In other words, the self-starting squirrel-cage rotor structure provided in this embodiment of the invention can not only effectively improve the magnetic flux density through the U-shaped magnetic cohesion structure and the integrated design of the magnets and inner and outer cage bars, thereby improving the rated efficiency of the motor, but also achieve synchronous improvement of starting torque and pull-in torque by combining the double cage design, reducing the starting current and improving starting performance. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a self-starting squirrel cage rotor structure provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a permanent magnet synchronous motor provided in an embodiment of the present invention.

[0021] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1. Shaft; 2. Rotor core; 3. Squirrel cage unit; 31. Outer cage bar; 32. Inner cage bar; 4. Magnetic pole unit; 41. Circumferential magnet; 42. Radial magnet; 5. Magnetic bridge; 6. Stator; 61. Stator slot. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0025] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0026] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0027] Example: Figure 1 This is a schematic diagram of a self-starting squirrel cage rotor structure provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the self-starting squirrel cage rotor structure includes a rotating shaft 1, a rotor core 2, a squirrel cage unit 3, and multiple magnetic pole units 4.

[0028] The rotor core 2 is mounted outside the rotating shaft 1.

[0029] The squirrel cage unit 3 includes multiple spaced outer cage bars 31 and multiple spaced inner cage bars 32 (wherein, the outer cage bars 31 and inner cage bars 32 extend along the axial direction of the rotating shaft 1). The multiple outer cage bars 31 are evenly inserted into the outer cage slots of the rotor core 2 along the circumference of the rotor core 2 and are located at the outer edge of the rotor core 2. The multiple inner cage bars 32 are inserted into the inner cage slots of the rotor core 2 along the circumference of the rotor core 2, and the multiple inner cage bars 32 form multiple spaced inner cage bar groups. Each inner cage slot is connected to the corresponding outer cage slot. The two ends of the multiple outer cage bars 31 and the two ends of the multiple inner cage bars 32 are connected by end rings.

[0030] Multiple magnetic pole units 4 are evenly arranged around the circumference of the rotating shaft 1 and located inside multiple outer cage bars 31. Each magnetic pole unit 4 includes two circumferential magnets 41 and two radial magnets 42. The two circumferential magnets 41 are located between the two radial magnets 42. The two circumferential magnets 41 and the two radial magnets 42 are respectively inserted into the magnetic slots of the rotor core 2 and arranged in a U-shape. Each circumferential magnet 41 is arranged tangentially along the rotating shaft 1, and each radial magnet 42 is arranged radially along the rotating shaft 1. Multiple inner cage bars 32 of each inner cage bar group are located in the opening of the corresponding magnetic pole unit 4 (the opening of the magnetic pole unit 4 faces the outer edge of the rotor core 2).

[0031] In the self-starting squirrel-cage rotor structure provided in this embodiment of the invention, on the one hand, multiple outer cage bars 31 are uniformly inserted into the outer cage slots of the rotor core 2 along the circumference of the rotor core 2 and located at the outer edge of the rotor core 2, and multiple inner cage bars 32 are inserted into the inner cage slots of the rotor core 2 along the circumference of the rotor core 2, and the multiple inner cage bars 32 form multiple spaced inner cage bar groups, each inner cage slot communicating with the corresponding outer cage slot, thereby forming a double-cage structure with inner and outer arrangements on the outer edge of the rotor core 2. For the double-cage structure, in the initial stage of startup, the high resistance of the outer cage corresponding to the outer cage bar 31 dominates, increasing the starting torque to 2.0-2.2 times the rated torque, thereby improving the starting torque, and controlling the starting current within 5 times the rated current, thereby reducing the starting current. In the later stages of startup, the low resistance of the inner cage corresponding to the inner cage bar 32 is introduced, which increases the pull-in torque and ensures smooth synchronization (the startup time is shortened to less than 1.0s). This ultimately achieves the synchronous increase of the starting torque and the pull-in torque (that is, the synergistic optimization between the starting torque and the pull-in torque is realized), and reduces the starting current.

[0032] On the other hand, for multiple magnetic pole units 4, two circumferential magnets 41 and two radial magnets 42 are respectively inserted into the magnet slots of the rotor core 2 and arranged in a U-shape. Each circumferential magnet 41 is arranged tangentially along the shaft 1, so that the distance between each circumferential magnet 41 and the outer stator is consistent. Each radial magnet 42 is arranged radially along the shaft 1, and multiple inner cage bars 32 of each inner cage bar group are located in the opening of the corresponding magnetic pole unit 4. This not only greatly improves the magnetic density through the U-shaped magnetic aggregation structure, but also divides the rotor core 2 outside the shaft 1 into multiple sector regions. In each sector region, the magnets, inner cage bars 32 and outer cage bars 31 are fully integrated, and the magnet arrangement area is large, thereby further improving the magnetic density and thus improving the rated efficiency of the motor.

[0033] In other words, the self-starting squirrel-cage rotor structure provided in this embodiment of the invention can not only effectively improve the magnetic flux density through the U-shaped magnetic cohesion structure and the integrated design of the magnets and inner and outer cage bars, thereby improving the rated efficiency of the motor, but also achieve synchronous improvement of starting torque and pull-in torque by combining the double cage design, reducing the starting current and improving starting performance.

[0034] Furthermore, the U-shaped magnetic cohesion structure formed by the four magnets ensures that the demagnetizing magnetomotive force is evenly distributed among the magnets. Combined with the magnetic circuit adjustment effect of the magnetic guide pads, the maximum demagnetization rate of the permanent magnets during the startup phase is reduced to below 8%, thus solving the problem of localized demagnetization. In addition, the self-starting squirrel-cage rotor structure has the advantage of lower demagnetization compared to traditional structures.

[0035] Furthermore, the U-shaped magnetic field structure increases the sinusoidal magnetic flux density of the air gap by 45%, and combined with the low-loss characteristics of the double cage, the average efficiency of the motor under rated operating conditions can reach 94%-98%; the four small rectangular magnets improve the material utilization rate by 20% compared with the integral U-shaped magnets, and reduce the amount of permanent magnets used by 15% under the same power, meeting the needs of heavy-duty start-up and efficient continuous operation in industry.

[0036] For example, both the circumferential magnet 41 and the radial magnet 42 are rectangular structures with the same dimensions, which facilitates processing. Preferably, there can be four magnetic pole units 4. In other embodiments of the present invention, there can also be six or eight magnetic pole units 4, which is not limited by the present invention.

[0037] In one implementation of the present invention, the end of each radial magnet 42 facing away from the rotating shaft 1 is directly opposite to the corresponding outer cage bar 31.

[0038] It is easy to understand that having one end of the radial magnet 42 aligned with the corresponding outer cage bar 31 not only ensures the uniform distribution of the radial magnet 42, but also prevents the magnet from being located between two outer cage bars 31, thereby further improving the magnetic density.

[0039] Furthermore, multiple spaced magnetic bridges 5 are inserted into the rotor core 2, with each magnetic bridge 5 located between the end of each radial magnet 42 facing away from the rotating shaft 1 and the corresponding outer cage bar 31. The magnetic bridges 5 can isolate the outer cage bar 31 and the radial magnet 42, reducing the excessive leakage flux coefficient of the magnets.

[0040] Preferably, the thickness of each magnetic bridge 5 in the radial direction of the rotating shaft 1 is 0.8-1.5 mm, and more preferably, the thickness of each magnetic bridge 5 in the radial direction of the rotating shaft 1 is 1.0 mm.

[0041] It should be noted that magnetic bridges are also provided between radial magnet 42 and circumferential magnet 41, or between circumferential magnet 41 and circumferential magnet 41.

[0042] In this embodiment, the outer cage bar 31 and the inner cage bar 32 satisfy the following formula:

[0043] Where M is the number of outer cage bars 31, N is the number of inner cage bars 32, p is the number of magnetic pole units 4, and k is 0, 1, 2, 3, ..., n, where n is a positive integer.

[0044] For example, when the number of outer cage bars 31 and the number of inner cage bars 32 are twice the number of magnetic pole units 4, it can be ensured that each of the two adjacent radial magnets 42 of the two magnetic pole units 4 is directly opposite an outer cage bar 31, and there are no other outer cage bars 31 between the two radial magnets 42. The distance between the two magnetic pole units 4 is small and the magnetic flux density is large.

[0045] In this embodiment, the outer cage trough and the inner cage trough can be circular troughs, pear-shaped troughs, or convex troughs.

[0046] It should be noted that in other embodiments of the present invention, the outer cage trough and the inner cage trough may also have other shapes, and the present invention does not limit them.

[0047] For example, both the circumferential magnet 41 and the radial magnet 42 are made of neodymium iron boron, which has excellent magnetic properties.

[0048] In addition, both the outer cage bars 31 and the inner cage bars 32 are made using cast aluminum, strung aluminum bars, or strung copper bars processes.

[0049] Figure 2 This is a schematic diagram of the structure of a permanent magnet synchronous motor provided in an embodiment of the present invention, as shown below. Figure 2 As shown, the permanent magnet synchronous motor includes a self-starting squirrel cage rotor structure as described above.

[0050] The stator 6 is located outside the rotor core 2, and the stator 6 has multiple stator slots 61 arranged at intervals in the circumferential direction.

[0051] The structure of the present invention will be described below with reference to specific structures: A self-starting squirrel-cage permanent magnet synchronous motor with a rated power of 5.5kW, a rated speed of 1500r / min, and 4 magnetic pole units (4). The stator has 36 slots (61 slots). The outer cage has 44 slots, which are circular with a radius of 3mm. The inner cage has 36 slots (44-8=36), which are also circular with a radius of 3.5mm. The rotor core (2) has an outer diameter of 154mm, an inner diameter of 48mm, and a stack thickness of 140mm. Each magnetic pole unit (4) corresponds to a magnetic slot with dimensions of 25mm×140mm×2.5mm, using rectangular neodymium iron boron magnets. In addition to circular slots, other slot shapes, such as pear-shaped or convex slots, can be used for the outer and inner cage slots, depending on the application.

[0052] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-starting squirrel cage rotor structure, characterized by, The self-starting squirrel cage rotor structure comprises a rotating shaft, a rotor core, a squirrel cage unit and a plurality of magnetic pole units; The rotor core is sleeved on the rotating shaft; The squirrel cage unit comprises a plurality of spaced outer bars and a plurality of spaced inner bars, the plurality of outer bars are evenly inserted into outer bar slots of the rotor core along a circumferential direction of the rotor core and located at outer edges of the rotor core, the plurality of inner bars are inserted into inner bar slots of the rotor core along the circumferential direction of the rotor core, and the plurality of inner bars form a plurality of spaced inner bar groups, each inner bar slot is communicated with a corresponding outer bar slot, and both ends of the plurality of outer bars and both ends of the plurality of inner bars are connected by end rings; The plurality of magnetic pole units are evenly arranged along a circumferential direction of the rotating shaft and located at inner sides of the plurality of outer bars, each magnetic pole unit comprises two circumferential magnetic steels and two radial magnetic steels, the two circumferential magnetic steels are located between the two radial magnetic steels, the two circumferential magnetic steels and the two radial magnetic steels are respectively inserted into magnetic steel slots of the rotor core and arranged in a U shape, each circumferential magnetic steel is tangentially arranged along the rotating shaft, each radial magnetic steel is radially arranged along the rotating shaft, and the plurality of inner bars of each inner bar group are located in openings of the corresponding magnetic pole unit.

2. A self-starting squirrel cage rotor structure according to claim 1, wherein One end of each radial magnetic steel away from the rotating shaft faces the corresponding outer bar.

3. A self-starting squirrel cage rotor structure according to claim 2, wherein A plurality of magnetic bridges are inserted into the rotor core and arranged at intervals, each magnetic bridge is located between one end of each radial magnetic steel away from the rotating shaft and the corresponding outer bar.

4. A self-starting squirrel cage rotor structure according to claim 3, wherein The thickness of each magnetic bridge in the radial direction of the rotating shaft is 0.8-1.5 mm.

5. A self-starting squirrel cage rotor structure as claimed in claim 2, wherein, The outer bar and the inner bar satisfy the following formula: wherein M is the number of the outer bars, N is the number of the inner bars, p is the number of the magnetic pole units, k is 0, 1, 2, 3,..., n, and n is a positive integer.

6. A self-starting squirrel cage rotor structure as claimed in claim 1, wherein, The outer bar slot and the inner bar slot are circular slots, pear-shaped slots or convex slots.

7. A self-starting squirrel cage rotor structure as claimed in claim 1, wherein, The circumferential magnetic steel and the radial magnetic steel are both rectangular structures and have the same size.

8. A self-starting squirrel cage rotor structure according to any one of claims 1-7, characterized in that, The circumferential magnetic steel and the radial magnetic steel are both made of neodymium iron boron material.

9. A self-starting squirrel cage rotor structure according to any one of claims 1-7, characterized in that, The outer bar and the inner bar are both made by casting aluminum, stringing aluminum bars or stringing copper bars.

10. A permanent magnet synchronous motor characterized by The permanent magnet synchronous motor comprises the self-starting squirrel cage rotor structure according to any one of claims 1-9.

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