An external rotor switched reluctance motor

Abstract

The application relates to the motor technical field, in particular to an outer rotor switched reluctance motor, which comprises a rotor, a stator, a three-phase winding and a permanent magnet, the rotor is coaxially nested on the outside of the stator, the rotor is a salient pole structure comprising rotor poles and a magnetic isolation sleeve, the magnetic isolation sleeve is enclosed into a cylindrical shape by a plurality of modules, a plurality of rotor poles are evenly connected to the inner surface of the magnetic isolation sleeve in the circumferential direction of the cylindrical shape, the stator is a salient pole structure comprising stator poles and a stator yoke, a plurality of stator poles are evenly arranged on the outside of the stator yoke, a winding slot is formed between two adjacent stator poles, the three-phase winding is embedded in the winding slot, and the permanent magnet is arranged at the slot opening of the winding slot and located on the outside of the three-phase winding. The application adopts the block outer rotor, trapezoidal air gap and full-pitch winding structure, and installs the permanent magnet at the winding slot opening for auxiliary excitation, so that the output torque density and efficiency of the switched reluctance motor are greatly improved, and the problems of low output torque density and efficiency of the traditional switched reluctance motor are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and in particular to an external rotor switched reluctance motor. Background Technology

[0002] Switched reluctance motors typically employ a doubly salient pole structure, where the windings are only mounted on the stator, and the rotor has neither windings nor permanent magnets. These structural features give them advantages such as simple structure, low cost, high reliability, strong fault tolerance, and a wide speed range. Based on these advantages, switched reluctance motors have broad application prospects in high-end equipment fields such as electric vehicles and aerospace. However, the torque density and efficiency of traditional switched reluctance motors are slightly lower than other types of motors, which limits their further application in high-end equipment.

[0003] To improve the output torque density and efficiency of switched reluctance motors (SRMs), scholars both domestically and internationally have conducted extensive research on the SRM itself. Some researchers have optimized the dimensions of traditional SRM structures, while others have proposed novel SRM structures, including segmented stator, segmented rotor, and axial flux designs. While these solutions can improve the performance of SRMs, their performance advantages compared to other types of motors are not yet significant. Furthermore, existing SRM structures mostly employ internal rotor structures and only utilize a single air gap structure or a single excitation method, making further performance improvements difficult. Summary of the Invention

[0004] The purpose of this invention is to provide an external rotor switched reluctance motor. By adopting a segmented external rotor, trapezoidal air gap, and full-pitch winding structure, and by installing permanent magnets at the winding slots for auxiliary excitation, the output torque density and efficiency of the switched reluctance motor are greatly improved, effectively solving the problem of low output torque density and efficiency of traditional switched reluctance motors.

[0005] To achieve the above objectives, the present invention provides an external rotor switched reluctance motor, which is a three-phase motor, including a rotor, a stator, three-phase windings, and a permanent magnet. The rotor is coaxially nested on the outside of the stator. The rotor has a salient pole structure, including rotor poles and a magnetic isolation sleeve. The magnetic isolation sleeve is formed into a cylindrical shape by several modules. Several rotor poles are uniformly connected to the inner surface of the magnetic isolation sleeve along the circumference of the cylindrical shape. The stator has a salient pole structure, including stator poles and a stator yoke. Several stator poles are uniformly arranged on the outside of the stator yoke. A winding slot is formed between two adjacent stator poles. The three-phase windings are embedded in the winding slots. The permanent magnet is located at the slot opening and outside the three-phase windings.

[0006] Preferably, the stator pole number of the three-phase motor is 6m and the rotor pole number is 4m, where m is an integer greater than or equal to 1.

[0007] Preferably, the module has an arc-shaped structure, with an arc-shaped protrusion on one side and an arc-shaped groove on the other side, and the arc-shaped protrusions and arc-shaped grooves of two adjacent modules are connected by insertion.

[0008] Preferably, the inner surface of the magnetic shielding sleeve is provided with a mounting groove, and the rotor pole is provided with a mounting protrusion, which is inserted into the mounting groove.

[0009] Preferably, the inner surface of the rotor pole and the outer surface of the stator pole are provided with trapezoidal concave-convex structures, and the concave-convex structures of the rotor pole and the stator pole are fitted together to form a trapezoidal air gap.

[0010] Preferably, the three-phase windings are powered by pulses, and the three-phase windings are full-pitch windings, with each phase winding consisting of m winding coils.

[0011] Preferably, when m equals 1, each phase winding consists of 1 winding coil; when m is greater than or equal to 2, the connection method of the m winding coils of each phase winding must be exactly the same.

[0012] Preferably, each winding coil has three stator poles inserted in it, and the coil sides on both sides of the winding coil are embedded in the winding slots, with the current flowing in opposite directions in the coil sides of two adjacent winding slots.

[0013] Preferably, the two ends of the permanent magnet abut against the stator poles, and the axial length of the permanent magnet is the same as the stack length of the stator.

[0014] Preferably, the permanent magnet is tangentially magnetized, and the direction of the magnetic field generated by the permanent magnet in the stator is opposite to the direction of the magnetic field generated by the coil side in the same slot in the stator.

[0015] The beneficial effects of this invention are:

[0016] (1) The present invention adopts an external rotor switched reluctance motor with the above structure. By adopting a segmented rotor structure, the magnetic flux generated by the winding coil can only form a closed magnetic circuit through two adjacent stator poles and rotor blocks, which greatly shortens the magnetic circuit length, not only increases the magnetic flux utilization rate, but also reduces the iron core loss, thereby improving the output torque and efficiency of the motor.

[0017] (2) The present invention adopts an external rotor switched reluctance motor with the above structure. By placing permanent magnets in the stator slots for auxiliary excitation, the air gap magnetic flux density of the motor under load is greatly increased, thereby improving the output torque and overload capacity of the motor.

[0018] (3) The present invention adopts an external rotor switched reluctance motor with the above structure. By adopting a trapezoidal air gap, the alignment area of ​​the stator and rotor poles at the alignment position is increased, the air gap reluctance is reduced, the air gap flux density and flux utilization are increased, and thus the output torque of the motor is increased.

[0019] (4) The present invention adopts an external rotor switched reluctance motor with the above structure. By adopting an external rotor structure, the stator is placed on the inner side, the outer diameter of the rotor is increased, and the end length of the full pitch winding is reduced. This not only improves the output torque density, but also reduces the amount of copper used in the motor and the winding resistance, thereby reducing the copper loss of the motor and improving the operating efficiency of the motor.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of an external rotor switched reluctance motor according to Embodiment 1 of the present invention;

[0022] Figure 2 This is a cross-sectional schematic diagram of an external rotor switched reluctance motor according to Embodiment 1 of the present invention;

[0023] Figure 3 This is a schematic diagram of the rotor structure of an external rotor switched reluctance motor according to Embodiment 1 of the present invention;

[0024] Figure 4 This is a schematic diagram of the stator structure of an external rotor switched reluctance motor according to Embodiment 1 of the present invention;

[0025] Figure 5 This is a schematic diagram of the stator structure of an external rotor switched reluctance motor according to Embodiment 1 of the present invention, without showing the permanent magnet;

[0026] Figure 6 This is a schematic diagram of the winding coil of an external rotor switched reluctance motor according to Embodiment 1 of the present invention;

[0027] Figure 7 This is a schematic diagram of the air gap structure of an external rotor switched reluctance motor according to Embodiment 1 of the present invention;

[0028] Figure 8 This is a schematic diagram of the winding and permanent magnet polarity distribution of an external rotor switched reluctance motor according to Embodiment 1 of the present invention;

[0029] Figure 9 This is a schematic diagram of the no-load magnetic flux path of an external rotor switched reluctance motor according to Embodiment 1 of the present invention;

[0030] Figure 10 This is a schematic diagram of the load flux path of an external rotor switched reluctance motor according to Embodiment 1 of the present invention (phase A is conducting);

[0031] Figure 11 This is a schematic diagram of the overall structure of an external rotor switched reluctance motor according to Embodiment 2 of the present invention;

[0032] Figure 12This is a schematic diagram of the winding and permanent magnet polarity distribution of an external rotor switched reluctance motor according to Embodiment 2 of the present invention;

[0033] Figure 13 This is a schematic diagram of the no-load magnetic flux path of an external rotor switched reluctance motor according to Embodiment 2 of the present invention;

[0034] Figure 14 This is a schematic diagram of the load flux path of an external rotor switched reluctance motor according to Embodiment 2 of the present invention.

[0035] Figure label:

[0036] 1. Rotor; 11. Rotor pole; 12. Magnetic shielding sleeve; 121. Module; 122. Arc-shaped protrusion; 123. Arc-shaped groove; 13. Mounting slot; 14. Mounting protrusion; 2. Stator; 21. Stator pole; 22. Stator yoke; 3. Winding coil; 31. Coil edge; 4. Permanent magnet; 5. Concave-convex structure; 6. Trapezoidal air gap. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0038] The present invention provides an external rotor switched reluctance motor, which is a three-phase motor. The number of stator poles (21) and rotor poles (11) are matched according to a 6m / 4m relationship, where the number of stator poles (21) is 6m and the number of rotor poles (11) is 4m, and m is an integer greater than or equal to 1. When m = 1, the number of stator poles (21) is 6 and the number of rotor poles (11) is 4; when m = 2, the number of stator poles (21) is 12 and the number of rotor poles (11) is 8, and so on.

[0039] Example 1

[0040] The value of m is equal to 1, so the number of stator poles 21 is 6, the number of rotor poles 11 is 4, and the number of permanent magnets 4 is 6.

[0041] Figure 1 This is a schematic diagram of the overall structure of an external rotor switched reluctance motor according to Embodiment 1 of the present invention, as shown below. Figure 1As shown, this invention provides an external rotor switched reluctance motor, which is a three-phase motor including a rotor 1, a stator 2, three-phase windings, and a permanent magnet 4. The rotor 1 is coaxially nested on the outside of the stator 2. This structure can increase the outer diameter of the rotor 1, enabling the motor to output greater torque within the same volume, thereby improving the output torque density of the motor and meeting more high-load demand scenarios. Furthermore, the rotor 1 can be directly connected to the driven component to achieve direct drive, reducing intermediate transmission components, minimizing useless space between the motor and the equipment, and avoiding energy loss caused by friction and vibration of transmission components in indirect drive, thus improving the drive efficiency of the entire motor system.

[0042] Figure 2 This is a cross-sectional schematic diagram of an external rotor switched reluctance motor according to Embodiment 1 of the present invention. Figure 3 This is a schematic diagram of the rotor structure of an external rotor switched reluctance motor according to Embodiment 1 of the present invention, as shown below. Figure 2 and Figure 3 As shown, the rotor 1 has a salient pole structure, including rotor poles 11 and a magnetic shielding sleeve 12. The magnetic shielding sleeve 12 is formed into a cylindrical shape by several modules 121. The modules 121 have an arc-shaped structure, with an arc-shaped protrusion 122 on one side and an arc-shaped groove 123 on the other side. The arc-shaped protrusions 122 and arc-shaped grooves 123 of two adjacent modules 121 are inserted and connected. By modularizing the magnetic shielding sleeve 12, the problem that the introduction of the trapezoidal air gap 6 prevents the stator 2 and rotor 1 from being assembled in the traditional way is solved. Four rotor poles 11 of the same size and shape are evenly connected to the inner surface of the magnetic shielding sleeve 12 along the circumference of the cylinder. The inner surface of the magnetic shielding sleeve 12 is provided with a mounting groove 13, and the rotor poles 11 are provided with mounting protrusions 14. The mounting protrusions 14 are inserted and connected to the mounting grooves 13, which improves the accuracy of the installation position of the rotor poles 11 and facilitates the installation and disassembly of the rotor poles 11, bringing great convenience to the production and maintenance of the motor.

[0043] Figure 4 This is a schematic diagram of the stator structure of an external rotor switched reluctance motor according to Embodiment 1 of the present invention. Figure 7 This is a schematic diagram of the air gap structure of an external rotor switched reluctance motor according to Embodiment 1 of the present invention, as shown below. Figure 4 , Figure 7As shown, the stator 2 has a salient pole structure, including stator poles 21 and a stator yoke 22. Six stator poles 21 of the same size and shape are evenly arranged on the outer side of the stator yoke 22. The inner surface of the rotor pole 11 and the outer surface of the stator pole 21 are both provided with trapezoidal concave-convex structures 5. The concave-convex structures 5 can be obtained by machining methods such as laser cutting or wire cutting. The concave-convex structures 5 of the rotor pole 11 and the concave-convex structures 5 of the stator pole 21 are fitted together to form a trapezoidal air gap 6. The motor adopts a trapezoidal air gap 6, which increases the overlap area of ​​the stator pole 21 and the rotor pole 11 in the aligned position. Without changing the outer diameter, stack length, and air gap length of the motor, the magnetic reluctance of the air gap can be reduced, and the magnetic flux density and magnetic flux utilization of the air gap can be increased, thereby effectively improving the output torque density and efficiency of the motor.

[0044] Figure 5 This is a schematic diagram of the stator structure of an external rotor switched reluctance motor according to Embodiment 1 of the present invention, excluding the permanent magnet. Figure 6 This is a schematic diagram of the winding coil of an external rotor switched reluctance motor according to Embodiment 1 of the present invention. Figure 8 This is a schematic diagram of the winding and permanent magnet polarity distribution of an external rotor switched reluctance motor according to Embodiment 1 of the present invention, as shown below. Figure 1 , Figure 5 , Figure 6 and Figure 8 As shown, a winding slot is formed between two adjacent stator poles 21, and the three-phase windings are embedded in the winding slots. The three-phase windings are powered by pulses, and each phase winding consists of a winding coil 3. The coil edges 31 on both sides of the winding coil 3 are embedded in the winding slot, and the current flows in opposite directions in the coil edges 31 of two adjacent winding slots. The three-phase windings are full-pitch windings, with a pitch of three for each phase winding, meaning that three stator poles 21 are inserted in each winding coil 3. For example, one coil edge 31 of the winding coil 3 is in the S1 winding slot, and the other coil edge 31 is in the S4 winding slot. This combination of winding coils 3 maximizes the number of turns per phase winding, thereby ensuring that the motor has a large induced electromotive force and output power. At the same time, it can optimize the magnetic circuit of the motor in conjunction with the motor structure, reduce magnetic reluctance and energy loss, and improve the efficiency of the motor.

[0045] like Figure 4 As shown, six permanent magnets 4 of the same size and shape are respectively arranged at the slot openings of the winding slots and located outside the three-phase windings. The two ends of the permanent magnets 4 abut against the stator poles 21, and the axial length of the permanent magnets 4 is the same as the stack length of the stator 2. The permanent magnets 4 are tangentially magnetized, and the direction of the magnetic field generated by the permanent magnets 4 in the stator 2 is opposite to the direction of the magnetic field generated by the coil side 31 arranged in the same slot in the stator 2.

[0046] Figure 9This is a schematic diagram of the no-load magnetic flux path of an external rotor switched reluctance motor according to Embodiment 1 of the present invention. As shown in the figure, when no current flows through the winding coil 3, only the magnetic flux generated by the permanent magnet 4 exists in the motor. The magnetic flux generated by the permanent magnet 4 starts from the N pole, first flows into the stator yoke 22 through the stator pole 21 in contact with it, and then returns to the S pole through the other stator pole 21 in contact with it, forming a closed magnetic circuit. No matter how the position of the rotor 1 changes, the magnetic flux generated by the permanent magnet 4 hardly passes through the air gap. Therefore, the cogging torque of the motor when it is no-load is close to zero.

[0047] Figure 10 This is a schematic diagram of the load flux path of an external rotor switched reluctance motor according to Embodiment 1 of the present invention (phase A is conducting). As shown in the figure, when current is applied to phase A, the motor simultaneously contains flux generated by the permanent magnet 4 and flux generated by the phase A winding coil 3. Since the direction of the flux generated by the phase A winding coil 3 is completely opposite to the direction of the flux generated by the permanent magnet 4 in the same slot in the stator pole 21 and stator yoke 22, they cancel each other out. Therefore, the flux generated by the permanent magnet 4 in the same slot as the phase A winding coil 3 can only start from the N pole, pass through the stator pole 21 in contact with it, enter the trapezoidal air gap 6, pass through the rotor pole 11, and then return to the S pole from the trapezoidal air gap 6 and the other stator pole 21 in contact with it, forming a closed loop. In addition, since the direction of the flux generated by the phase A winding coil 3 is completely opposite to the direction of the flux generated by the permanent magnet 4 in the adjacent slot in the stator pole 21, the flux generated by the permanent magnet 4 in the slot adjacent to the phase A winding coil 3 also forms a closed loop through the trapezoidal air gap 6 and the rotor pole 11. At this time, the magnetic flux generated by the permanent magnet 4 and the magnetic flux generated by the A-phase winding coil 3 are superimposed at the air gap, which increases the air gap magnetic flux density, greatly increases the output torque of the motor, and thus improves the overload capacity and operating efficiency of the motor.

[0048] Example 2

[0049] Figure 11 This is a schematic diagram of the overall structure of an external rotor switched reluctance motor according to Embodiment 2 of the present invention. As shown in the figure, the difference between this embodiment and Embodiment 1 is that the value of m is equal to 2, the number of stator poles 21 of the motor is 12, the number of rotor poles 11 is 8, and the number of permanent magnets 4 is 12.

[0050] Figure 12 This is a schematic diagram of the winding and permanent magnet polarity distribution of an external rotor switched reluctance motor according to Embodiment 2 of the present invention. As shown in the figure, each phase winding consists of two winding coils 3, and the connection method (series or parallel) of the two winding coils 3 constituting each phase winding is exactly the same to ensure the symmetry of the three-phase circuit and magnetic circuit of the motor.

[0051] Figure 13 This is a schematic diagram of the no-load magnetic flux path of an external rotor switched reluctance motor according to Embodiment 2 of the present invention; Figure 14This is a schematic diagram of the load magnetic flux path of an external rotor switched reluctance motor according to Embodiment 2 of the present invention. As shown in the figure, since the number of stator poles 21 is doubled, the number of paths forming closed magnetic circuits around each stator pole 21 is also doubled accordingly.

[0052] Therefore, the external rotor switched reluctance motor of the present invention, which adopts the above structure, can significantly improve the output torque density and efficiency of the switched reluctance motor, and solves the problem of low output torque density and efficiency of traditional switched reluctance motors.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An external rotor switched reluctance motor, wherein the motor is a three-phase motor, characterized in that: It includes a rotor, a stator, three-phase windings, and a permanent magnet. The rotor is coaxially nested on the outside of the stator. The rotor has a salient pole structure, including rotor poles and a magnetic shielding sleeve. The magnetic shielding sleeve is formed by several modules forming a cylindrical shape. Several rotor poles are uniformly connected to the inner surface of the magnetic shielding sleeve along the circumference of the cylindrical shape. The stator has a salient pole structure, including stator poles and a stator yoke. Several stator poles are uniformly arranged on the outside of the stator yoke. A winding slot is formed between two adjacent stator poles. The three-phase windings are embedded in the winding slots. The permanent magnet is located at the slot opening and on the outside of the three-phase windings. The module has an arc-shaped structure, with an arc-shaped protrusion on one side and an arc-shaped groove on the other side. The arc-shaped protrusions and arc-shaped grooves of two adjacent modules are connected by insertion. Both the inner surface of the rotor pole and the outer surface of the stator pole are provided with trapezoidal concave and convex structures, and the concave and convex structures of the rotor pole and the stator pole are fitted together to form a trapezoidal air gap. The three-phase winding is powered by pulse. The three-phase winding is a full-pitch winding. Each phase winding consists of m winding coils. The connection method of the m winding coils of each phase winding is exactly the same. Three stator poles are inserted in each winding coil. The coil sides on both sides of the winding coil are embedded in the winding slot. The current flows in opposite directions in the coil sides of two adjacent winding slots. The permanent magnet is tangentially magnetized, and the direction of the magnetic field generated by the permanent magnet in the stator is opposite to the direction of the magnetic field generated by the coil side in the same slot in the stator.

2. The external rotor switched reluctance motor according to claim 1, characterized in that: The stator pole number of a three-phase motor is 6m, and the rotor pole number is 4m, where m is an integer greater than or equal to 1.

3. The external rotor switched reluctance motor according to claim 1, characterized in that: The inner surface of the magnetic shielding sleeve is provided with a mounting groove, and the rotor pole is provided with a mounting protrusion, which is inserted into the mounting groove.

4. The external rotor switched reluctance motor according to claim 1, characterized in that: The two ends of the permanent magnet abut against the stator poles respectively, and the axial length of the permanent magnet is the same as the stack length of the stator.

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