CN114400853A

CN114400853A - Bearingless switched reluctance motor

Info

Publication number: CN114400853A
Application number: CN202210157573.XA
Authority: CN
Inventors: 王泽林; 曹鑫; 邓智泉
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2022-02-21
Filing date: 2022-02-21
Publication date: 2022-04-26
Anticipated expiration: 2042-02-21
Also published as: CN114400853B

Abstract

The invention provides a bearingless switched reluctance motor, comprising: the stator comprises a first stator and a second stator, wherein 6 stator poles extending inwards in the radial direction are formed on the inner walls of the first stator and the second stator, the stator poles on the first stator are aligned with the stator poles on the second stator one by one, and an independently controlled excitation winding is wound on each stator pole; the rotor is positioned on the inner side of the stator, an air gap is reserved between the rotor and the stator, 3 rotor poles are distributed at the front end and the rear end of the rotor along the radial direction, and the rotor poles at the front end and the rotor poles at the rear end are staggered by a certain mechanical angle; the permanent magnet ring is of an axial magnetic ring structure and is connected with the first stator and the second stator. The annular permanent magnet ring is arranged between the double stators, so that axial magnetic flux can be effectively constructed, the output torque and the power density of the motor are improved, and five-degree-of-freedom suspension is ensured.

Description

Bearingless switched reluctance motor

Technical Field

The invention relates to the technical field of bearingless switched reluctance motors, in particular to an axial permanent magnet biased bearingless switched reluctance motor.

Background

The switched reluctance motor has the advantages of simple structure, strong fault-tolerant performance, good high-speed adaptability and the like, and has better application prospect in the fields of aerospace, turbomachinery and the like. Traditional switched reluctance motor adopts mechanical bearing to support the rotor, and the high speed or the hypervelocity of rotor can make mechanical bearing's frictional resistance increase, and wearing and tearing aggravation to lead to the motor scheduling problem that generates heat, not only reduced the work efficiency of motor, shortened motor and mechanical bearing's life-span, also increased the maintenance burden of motor and bearing. Therefore, the magnetic suspension bearing technology is applied to the switched reluctance motor, the traditional support mode can be fundamentally changed, and the characteristics of no contact, no abrasion, high speed, high precision and long service life are realized, so that the bearingless switched reluctance motor can be widely applied to the driving occasions with high speed, ultrahigh speed, large environmental temperature change or difficult maintenance.

However, the existing bearingless switched reluctance motor generally has the problems of low torque and low power density, and in order to solve the problem of low power, the traditional bearingless switched reluctance motor adopts a form of increasing the number of windings, which often leads to the volume of a motor system becoming huge. Therefore, it is a difficult point of current research to realize a bearingless switched reluctance motor with higher power density.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a bearingless switched reluctance motor capable of improving axial bearing capacity and system power density.

In order to achieve the above objects and other objects, the present invention includes the following technical solutions: the invention provides a bearingless switched reluctance motor, which is characterized by comprising the following components: the stator comprises a first stator and a second stator, wherein 6 stator poles extending inwards in the radial direction are formed on the inner walls of the first stator and the second stator, the stator poles on the first stator are aligned with the stator poles on the second stator one by one, and an independently controlled excitation winding is wound on each stator pole; the rotor is positioned on the inner side of the stator, an air gap is reserved between the rotor and the stator, 3 rotor poles are distributed at the front end and the rear end of the rotor along the radial direction, and the rotor poles at the front end and the rotor poles at the rear end are staggered by a certain mechanical angle; the permanent magnet ring is of an axial magnetic ring structure and is connected with the first stator and the second stator.

In one embodiment, the permanent magnet ring includes a first pole and a second pole, the first pole and the second pole have opposite polarities, one end of the first pole is connected to the first stator, the other end of the first pole is connected to one end of the second pole, and the other end of the second pole is connected to the second stator.

In one embodiment, the outer diameter Dp of the permanent magnet ring is equal to the outer diameter Ds of the stator, the inner diameter Dp of the permanent magnet ring is greater than the inner diameter Ds of the stator, and the width hp of the permanent magnet ring is equal to the distance Lr between the rotor poles at the front end and the rotor poles at the rear end of the rotor.

In one embodiment, the mechanical angle is 15 ° to 45 °.

In one embodiment, the mechanical angle is 30 °.

In one embodiment, the first stator and the second stator have the same structure, and the front end structure and the rear end structure of the rotor are the same.

In one embodiment, the pole arc width thetas of the stator pole is 6/25-2/7 of the pole arc width thetar of the rotor pole.

In one embodiment, the axial length hs of the first or second stator is equal to the axial length hr of the rotor pole.

In one embodiment, a total length Hs of the first stator, the second stator and the permanent magnet ring is equal to a total length Hr of the rotor.

In one embodiment, the air gap is 0.05-4 mm.

The invention adopts the structural design of the 6/3-pole bearingless switched reluctance motor, so that the number of excitation windings and the number of corresponding power devices can be reduced; by adopting the structural design of double stators, the four-degree-of-freedom radial suspension force can be provided; the output performance of the torque can be improved by adopting the structural design that the front end rotor pole and the rear end rotor pole of the rotor are staggered by a certain mechanical angle; by adopting the design of the permanent magnet ring, axial magnetic flux is constructed in the axial direction of the bearingless switched reluctance motor, the output torque of the motor is improved, the power density of the system is improved, the axial suspension of the motor can be realized by the axial force generated by the axial magnetic flux, and the axial force and the four-degree-of-freedom radial suspension provided by the double stators form a five-degree-of-freedom suspension system together. The torque control and the suspension force control are naturally decoupled, and the output torque and the power density of the motor can be improved under the condition of not additionally increasing the system volume of the control motor.

Drawings

Fig. 1 is a schematic structural diagram of an 6/3 pole bearingless switched reluctance motor according to the present invention.

Fig. 2 shows an isometric view of a stator and permanent magnets in the present invention and a front view of the stator.

Figure 3 shows an isometric view and a front view of a rotor according to the invention.

Fig. 4 shows an isometric view of a permanent magnet in the present invention.

Fig. 5A shows a radial flux distribution diagram of the present invention.

Fig. 5B shows a schematic view of the axial flux distribution of the present invention.

Fig. 6A shows a magnetic flux distribution diagram in embodiment 1 given a 3A excitation current.

Fig. 6B shows a magnetic flux distribution diagram in comparative example 1 given the 3A excitation current. .

Fig. 7 shows a graph comparing output torque during motoring for example 1 and comparative example 1 given a 3A field current.

Detailed Description

Please refer to fig. 1 to 7. The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification to understand and read by those skilled in the art, and are not used to limit the practical limit conditions of the present invention, so they have no technical significance, and any structural modification, ratio relationship change or size adjustment should still fall within the scope of the present invention without affecting the function and the achievable purpose of the present invention. Meanwhile, the terms such as "front", "rear" and "a" used in the present specification are for clarity of description only, and are not intended to limit the scope of the present invention, and changes or modifications of the relative relationship thereof may be regarded as the scope of the present invention without substantial changes in the technical content.

As shown in fig. 1, the present invention provides a bearingless switched reluctance motor including a stator 1, a rotor 2, a permanent magnet ring 3, and a winding 4. The stator 1 comprises a first stator 11 and a second stator 12, the first stator 11 and the second stator 12 have the same structure, and 6 stator poles 13 extending inwards in the radial direction are formed on the inner walls of the first stator 11 and the second stator 12, the stator poles 13 on the first stator 11 are aligned with the stator poles 13 on the second stator 12 one by one, and each stator pole 13 is wound with an independently controlled excitation winding 4. The first stator 11 and the second stator 12 are connected by the permanent magnet ring 3, the permanent magnet ring 3 is an axial magnetic ring structure and includes a first pole 31 and a second pole 32, the polarities of the first pole 31 and the second pole 32 are opposite, that is, the first pole 31 is an S pole, the second pole 32 is an N pole, or the first pole 31 is an N pole, and the second pole 32 is an S pole. One end of the first pole 31 is connected to the first stator 11, the other end of the first pole 31 is connected to one end of the second pole 32, and the other end of the second pole 32 is connected to the second stator 12. The rotor 2 is located on the inner side of the stator 1, and an air gap is reserved between the rotor 2 and the stator 1, and the air gap is 0.05-4 mm, such as 0.05 mm. The rotor 2 is an integrally formed structure, 3 rotor poles 21 are respectively distributed at the front end and the rear end of the rotor 2 along the radial direction, and the rotor pole 21 at the front end and the rotor pole 21 at the rear end are staggered by a certain mechanical angle to realize continuous torque output.

Because a single stator can provide two-degree-of-freedom radial suspension force, the structural design of the double stators can provide four-degree-of-freedom radial suspension force. In addition, the permanent magnet ring 3 is designed to form axial magnetic flux in the axial direction of the motor, so that the output torque of the motor is improved, the system power density is improved, the axial suspension of the motor can be realized through the axial force generated by the axial magnetic flux, and a five-degree-of-freedom suspension system is formed together with four-degree-of-freedom radial suspension provided by the double stators.

Referring to fig. 1 and fig. 2, the first stator 11 and the second stator 12 have the same structure, the axial length of the first stator 11 or the second stator 12 is hs, the outer diameter of the stator is Ds, the inner diameter of the stator is Ds, and the width of the pole arc of the stator pole 13 is θ s. The total length of the first stator 11, the second stator 12 and the permanent magnet ring 3 is Hs.

As shown in fig. 3, the total length of the rotor 2 is Hr, the rotor poles 21 at the front end and the rear end of the rotor 2 have the same structure, the distance between the rotor poles 21 at the front end and the rotor poles 21 at the rear end of the rotor 2 is Lr, the axial length of each rotor pole 21 is Hr, the rotor outer diameter is Dr, the rotor inner diameter is Dr, and the pole arc width of each rotor pole is θ r. The rotor pole 21 at the front end of the rotor 2 and the rotor pole 21 at the rear end of the rotor 2 are staggered by a certain mechanical angle r, the mechanical angle r is 15-45 degrees, and further the mechanical angle r is 30 degrees.

Referring to fig. 1 and 4, the S pole 31 and the N pole 32 have the same structure, the width of the permanent magnet ring 3 is hp, the outer diameter of the permanent magnet ring is Dp, and the inner diameter of the permanent magnet ring is Dp. Referring to FIG. 2, Dp is equal to Ds, and Dp is greater than Ds.

Please refer to fig. 2 to fig. 4, the hp is equal to the Lr. Hs is equal to Hr, and Hs is equal to Hr. Further, to naturally decouple torque control from levitation control, the pole arc width θ s of the stator poles is 6/25-2/7, e.g., 2/7, of the pole arc width θ r of the rotor poles.

The torque control and the suspension force control of the 6/3 pole bearingless switched reluctance motor are naturally decoupled. The specific working principle is as follows: the 12 sets of the excitation windings 4 are respectively and independently controlled, the current of each set of the excitation winding 4 is conducted in a single direction, when the excitation winding 4 is electrified, the current in the excitation winding 4 is equal in magnitude, the radial magnetic flux distribution of the motor is shown in fig. 5A, and the axial magnetic flux distribution of the motor is shown in fig. 5B.

Torque generation principle: when the rotor pole 21 and the stator pole 13 start to overlap, the excitation winding 4 on the stator pole 13 conducts current with the same magnitude, and the motor generates tangential magnetic pull force so as to drive the rotor 2 to rotate;

the principle of radial suspension force generation: when the rotor pole 21 and the stator pole 13 are completely overlapped, the excitation windings a1 and a2 on the adjacent stator poles 13 conduct asymmetric currents, so that the radial magnetic flux density of each air gap is different, and further, a radial levitation force is generated;

the principle of axial suspension force generation: when the rotor pole 21 and the stator pole 13 are completely overlapped, the excitation winding a1 on the stator pole 13 of the first stator 11 and the excitation winding B1 on the stator pole 13 of the second stator 12 conduct asymmetric currents, so that the axial magnetic flux densities of the air gap at the front end and the rear end are different, and axial levitation force is generated.

< model >

The models used for the validation were example 1 and comparative example 1. Fig. 1 shows an embodiment 1, a permanent magnet ring 3 in the embodiment 1 is changed into a common iron core material to obtain a comparative example 1, and specific structural parameters of the embodiment 1 and the comparative example 1 are shown in table 1.

Table 1 structural parameters of example 1 and comparative example 1

< evaluation >

The present invention establishes a finite element model based on the structural parameters in table 1, and performs the analysis and evaluation of the magnetic flux distribution and the output torque for example 1 and comparative example 1, and the evaluation results are shown in fig. 6 and 7.

As shown in fig. 6, the magnetic flux distribution in example 1 is shown in fig. 6A, fig. 6A (a) shows a perspective view of the magnetic flux distribution in example 1, fig. 6A (b) shows an axial magnetic flux distribution pattern in example 1, and fig. 6A (c) shows a radial magnetic flux distribution pattern in example 1, given an excitation current of 3A; the magnetic flux distribution in comparative example 1 is shown in fig. 6B, fig. 6B (a) shows a perspective view of the magnetic flux distribution in comparative example 1, fig. 6B (B) shows an axial magnetic flux distribution pattern in comparative example 1, and fig. 6B (c) shows a radial magnetic flux distribution pattern in comparative example 1. As can be seen from two topological magnetic flux distributions, the use of the permanent magnet 3 increases the axial magnetic flux, and can effectively improve the power density of the motor.

Fig. 7 shows a graph of output torque during motoring operation for example 1 and comparative example 1 given a 3A field current. The average torque of example 1 (i.e., curve-with permanent magnets) was 0.21N · m, the average torque of comparative example 1 (i.e., curve-without permanent magnets) was 0.082N · m, and the torque performance of example 1 was improved by a factor of 2.56. Therefore, the scheme of adopting the permanent magnet improves the output torque of the motor.

In conclusion, the structural design of the invention can solve the problems of low torque and low power density of the existing bearingless switched reluctance motor under the condition of not additionally increasing the system volume of the control motor. The annular permanent magnet ring is arranged between the double stators, so that axial magnetic flux can be effectively constructed, and the output torque and the power density of the motor are improved.

Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value. The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A bearingless switched reluctance machine comprising:

the stator comprises a first stator and a second stator, wherein 6 stator poles extending inwards in the radial direction are formed on the inner walls of the first stator and the second stator, the stator poles on the first stator are aligned with the stator poles on the second stator one by one, and an independently controlled excitation winding is wound on each stator pole;

the rotor is positioned on the inner side of the stator, an air gap is reserved between the rotor and the stator, 3 rotor poles are distributed at the front end and the rear end of the rotor along the radial direction, and the rotor poles at the front end and the rotor poles at the rear end are staggered by a certain mechanical angle;

the permanent magnet ring is of an axial magnetic ring structure and is connected with the first stator and the second stator.

2. The bearingless switched reluctance motor of claim 1, wherein the permanent magnet ring includes a first pole and a second pole, the first pole and the second pole having opposite polarities, one end of the first pole being connected to the first stator, the other end of the first pole being connected to one end of the second pole, the other end of the second pole being connected to the second stator.

3. The bearingless switched reluctance motor of claim 1, wherein the permanent magnet ring outer diameter Dp is equal to the stator outer diameter Ds, the permanent magnet ring inner diameter Dp is greater than the stator inner diameter Ds, and the width hp of the permanent magnet ring is equal to the distance Lr between the rotor poles at the front end and the rotor poles at the rear end of the rotor.

4. The bearingless switched reluctance machine of claim 1, wherein the mechanical angle is 15 ° to 45 °.

5. The bearingless switched reluctance machine of claim 4, wherein the mechanical angle is 30 °.

6. The bearingless switched reluctance machine of claim 1, wherein the first stator and the second stator have identical structures, and the front end structure and the rear end structure of the rotor are identical.

7. The bearingless switched reluctance machine of claim 6, wherein a pole arc width θ s of the stator pole is 6/25-2/7 of a pole arc width θ r of the rotor pole.

8. The bearingless switched reluctance machine of claim 6, wherein an axial length hs of the first stator or the second stator is equal to an axial length hr of the rotor pole.

9. The bearingless switched reluctance motor of claim 8, wherein a total length Hs of the first stator, the second stator and the permanent magnet ring is equal to a total length Hr of the rotor.

10. The bearingless switched reluctance motor according to claim 1, wherein the air gap is 0.05 to 4 mm.