AU2018417306B2

AU2018417306B2 - Axial phase-split permanent bearingless switched reluctance flywheel motor with sleeve pole shoe gear

Info

Publication number: AU2018417306B2
Application number: AU2018417306A
Authority: AU
Inventors: Linjing SHAO; Yukun Sun; Wei Zhang; Hailang ZHU; Jin Zhu; Zhiying Zhu
Original assignee: Nanjing Institute of Technology
Current assignee: Nanjing Institute of Technology
Priority date: 2018-04-03
Filing date: 2018-11-21
Publication date: 2021-08-12
Anticipated expiration: 2038-11-21
Also published as: WO2019192188A1; CN108448808A; CN108448808B; AU2018417306A1

Abstract

The present invention relates to an axial phase-split permanent bearingless switched reluctance flywheel motor with a sleeve pole shoe gear, comprising a rotor iron core, a rotor sleeve, a stator sleeve, a stator iron core, a permanent magnet, and a flywheel. The rotor iron core, the rotor sleeve, and the flywheel are concentrically embedded from inside to outside to form a whole. The stator iron core and the stator sleeve are concentrically embedded and mounted on a fixed shaft. The stator iron core and the rotor iron core are divided into m sections according to the number of phases along an axial direction. Twelve rotor poles are arranged at equal intervals at an inner side of each phase of rotor iron core. Each phase of stator iron core is provided with eight torque poles and four suspension poles. The torque poles and the suspension poles are selected from pole shoe gears. Control coils are wound on the torque poles and the suspension poles, separately. An axial magnetized permanent magnet is mounted between two phase stators. According to the present invention, the suspension poles and the torque poles are modified into pole shoe gears, which improves the space of a stator groove, effectively improves the density and suspension output of a motor torque, significantly improves the utilization rate of a permanent magnet, decreases the number of permanent magnets, and achieves the effects of saving costs and improving the output.

Description

AXIAL SPLIT-PHASE PERMANENT-MAGNET BEARINGLESS SWITCHED RELUCTANCE FLYWHEEL MOTOR WITH SLEEVES AND POLE SHOE TEETH

Technical Field

[0001] The present invention relates to the field of bearingless switched reluctance motors (BSRMs), and in particular, to an axial split-phase permanent-magnet bearingless switched reluctance flywheel motor with sleeves and pole shoe teeth.

Background

[0002] A flywheel energy storage (FES) system is a physical energy storage device which works by mechanical-electrical energy conversion, and has such advantages as high specific energy, high specific power, a small size, long service life, fast charging and discharging, and no pollution. Therefore, the system has broad application prospect in many fields such as aerospace (for satellite energy storage batteries, integrated power, and attitude control), military industry (for high-power electromagnetic cannons), electric power (for electric peak shaving), communications (for uninterruptible power supply), and automotive industry (for hybrid electric vehicles). Bearingless motors combine two functions: contactless suspension with magnetic bearings and motor rotation. The application of the bearingless motors in FES can simplify the system structure and enhance the critical speed of rotation, achieving unique advantages in the FES field. BSRMs, in addition to having all excellent characteristics of switched reluctance motors, are further improved in high-speed performance and operating efficiency of the system by means of active control on its own radial force. The application of the BSRMs in FES can significantly reduce system size and loss, improve the suspension property, and enhance the critical speed of rotation and power density. Therefore, the BSRM is one of ideal choices for implementing flywheel suspension support and energy conversion.

[0003] In 1990s, Japanese scholars, Chiba A and Takemoto M, first carried out the research into BSRMs, and proposed a typical 12/8 pole double winding structure. With a double winding structure, such a motor jointly uses a current-carrying primary winding and a current-carrying suspension winding to generate an air-gap field, which results in strong electromagnetic coupling between motor suspension and electromagnetic torque. Moreover, a dead zone exists in generation of a suspension force, increasing the difficulty in analysis and control, which immensely restricts the entry of the BSRMs into engineering applications. In recent years, some scholars try to weaken electromagnetic coupling from the perspective of the motor structure. They put forward various structures such as a dual-stator structure, hybrid-rotor structure, hybrid-stator structure, and permanent magnet biased structure. These new structures effectively alleviate the problem of electromagnetic coupling, but still have many shortcomings when applied in flywheel batteries. For example, the dual-stator structure increases the difficulty in integration of the motor and the flywheel, and its inner and outer stator windings easily rise in temperature but cannot dissipate heat effectively, reducing system efficiency under high-speed operation of the motor. In the hybrid-rotor structure, the motor still has a long axial length, limiting the critical speed of rotation of the flywheel. The hybrid-stator structure and the permanent magnet biased structure both use an outer stator, making it difficult to integrate the motor and the flywheel. In addition, a permanent magnet is provided at the side of the outer stator, resulting in large consumption of permanent magnet materials and making the structure less cost-effective.

[0004] To meet performance requirements of the flywheel battery for easy integration, low power consumption, and high rotation speed operation, the invention patent No. ZL201610864124.3 provides an axial split-phase bearingless switched reluctance flywheel motor with an inner-stator and permanent magnet biased structure. This motor uses an inner-stator structure to integrate a motor rotor and the flywheel, thus reducing the system size and enhancing the critical speed of rotation; resorts to an axial split-phase design to realize suspension support at four degrees of freedom, improving the suspension property of the system; and uses a permanent magnet to produce a biased magnetic flux, reducing the loss in suspension support and improving system efficiency and power density. However, suspension poles and torque poles of this motor are in the shape of rectangular teeth. Thus, the inner-stator structure has small slot space, and can only be fitted with a limited number of torque windings and suspension windings, so that the motor still has a low torque density and suspension force output. Moreover, in this invention, the permanent magnet-biased magnetic flux of the motor is required to pass through a stator core and a rotor core that are formed by axially laminating silicon steel sheets, and an axial magnetic circuit needs to frequently pass through an insulating layer between the silicon steel sheets, resulting in low magnetic conductivity. Therefore, it is needed to consume a large quantity of permanent magnet materials in order to produce a certain magnetic flux, causing low utilization of the permanent magnet and increasing the costs.

Summary of the Invention

[0005] In order to further improve the specific power and the suspension property of the flywheel battery, save the permanent magnetic materials, and reduce the costs, the present invention provides an axial split-phase permanent-magnet bearingless switched reluctance flywheel motor with sleeves and pole shoe teeth. In the present invention, suspension poles and torque poles are changed from the shape of rectangular teeth to the shape of pole shoe teeth, enlarging the space of a stator slot and effectively enhancing a torque density and a suspension force output of the motor. In addition, a magnetically conductive sleeve is additionally disposed on the inner side of a stator and the outer side of a rotor, improving the axial magnetic conductivity of a permanent magnet-biased magnetic circuit. Consequently, the utilization of a permanent magnet is greatly enhanced, and the usage of permanent magnet materials is reduced, thus saving the costs and improving the force output.

[0006] To achieve the foregoing objectives, the present invention is implemented through the following technical solutions: The present invention provides an axial split-phase permanent-magnet bearingless switched reluctance flywheel motor with sleeves and pole shoe teeth, which includes a rotor core, a rotor sleeve, a stator sleeve, a stator core, a permanent magnet, and a flywheel, where the rotor core, the rotor sleeve, and the flywheel are concentrically nested as a whole from inside to outside, and the stator core and the stator sleeve are concentrically nested on a stationary shaft; the stator core and the rotor core are axially divided into m sections according to the number of phases, twelve rotor poles are provided at equal intervals on the inner side of the rotor core in each phase, and eight torque poles and four suspension poles are provided on the stator core in each phase; the torque poles and the suspension poles are designed into the shape of pole shoe teeth, a pole shoe width of each suspension pole is equal to a rotor pole pitch, and a pole shoe width of each torque pole is equal to a rotor tooth width; a magnetic isolation component is provided between the torque poles and the suspension poles; a control coil is wound around each torque pole and each suspension pole, the control coils on the eight torque poles in each phase are connected in series to form a torque winding of each phase, and the control coils on two opposite suspension poles in each phase are connected in series to form two sets of suspension windings in orthogonal directions; and an axially magnetized permanent magnet is provided between stators in the two phases.

[0007] As a further improvement to the present invention, the rotor core and the stator core are separately formed by axially laminating silicon steel sheets, and the rotor sleeve and the stator sleeve are both made of a whole piece of steel.

[0008] The present invention achieves the following advantageous effects: (1) In the present invention, a magnetically conductive sleeve is additionally disposed on the inner side of the stator and the outer side of the rotor, such that a permanent magnet-biased magnetic flux of the motor does not need to pass through the permanent magnet and an insulating layer between the stator core and the rotor core, thus improving the magnetic conductivity. By use of the magnetically conductive sleeve, the consumption of permanent magnetic materials is reduced, and the utilization of the permanent magnet is enhanced, reducing the costs. (2) In the present invention, the suspension poles and torque poles are changed from the shape of rectangular teeth to the shape of pole shoe teeth. The design of the rectangular teeth makes for small slot space of an inner-stator structure. After replacing it with pole shoe teeth, the space of the stator slot is enlarged, and thus more torque windings and suspension windings can be fitted, enhancing a torque density and a suspension force output of the motor. (3) In the present invention, the rotor sleeve not only can improve the magnetic conductivity, but also can further enhance the structural strength of the magnetically suspended rotor at a high rotation speed. (4) The stator sleeve has varied outer diameters. The outer diameter of the part near the permanent magnet is greater than that of the part at the inner side of the stator core, thus increasing a contact area of the stator sleeve and the permanent magnet. Consequently, the axially magnetized area is effectively increased, and the permanent magnet-biased magnetic field is improved.

Brief description of the Drawings

[0009] FIG. 1 is a schematic axial sectional diagram of a motor structure in the present invention;

[0010] FIG. 2 is a schematic radial sectional diagram of the motor structure in a phase A in the present invention;

[0011] FIG. 3 is a schematic diagram showing connection of motor windings in the phase A in the present invention; and

[0012] FIG. 4 is a schematic diagram of a permanent magnetic circuit of the motor in the present invention.

Detailed Description

[0013] To further understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and a specific embodiments. The embodiments are merely used for explaining the present invention, and do not constitute improper limitations to the scope of protection of the present invention.

[0014] As shown in FIG. 1 to FIG. 4, the present invention provides an axial split-phase permanent-magnet bearingless switched reluctance flywheel motor with sleeves and pole shoe teeth, which includes a rotor core 1, a rotor sleeve 2, a stator sleeve 4, a stator core 6, a permanent magnet 3, and a flywheel 5. The rotor core 1, the rotor sleeve 2, and the flywheel 5 are concentrically nested as a whole from inside to outside, and the stator core 6 and the stator sleeve 4 are concentrically nested on a stationary shaft. The rotor core 1 and the stator core 6 are separately formed by axially laminating silicon steel sheets. The rotor sleeve 2 and the stator sleeve 4 are both made of a whole piece of steel. An inner stator core and a stator sleeve, and an outer rotor core and a rotor sleeve are axially divided into sections according to the number of phases. The stator core 6 and the rotor core 1 are axially divided into m sections according to the number of phases. That is to say, the inner stator core and the stator sleeve, and the outer rotor core and the rotor sleeve are axially divided into m sections according to the number of phases. FIG. 1 shows a case where m=2, which are a phase-A section and a phase-B section. A permanent magnet ring, which is axially magnetized, is provided between the inner stator cores in each section, to produce a biased magnetic flux for generation of a radial suspension force. In each phase, twelve rotor poles 102 are provided at equal intervals along the circumference of the inner side of the rotor core 1. As shown in FIG. 2, in the phase A, four suspension poles 601 are provided on the stator core 6; two torque poles 602 are provided between every two suspension poles 601 at equal intervals, and there are eight torque poles 602 in total. The torque poles 602 and the suspension poles 601 are designed into the shape of pole shoe teeth. A pole shoe width of each suspension pole 601 is equal to a rotor pole pitch. At any position of the rotor, the aligned areas of the suspension poles and the rotor poles are constant. A pole shoe width of each torque pole 602 is equal to a rotor tooth width. A magnetic isolation component 603 is provided between the torque poles 602 and the suspension poles 601. A control coil is wound around each torque pole 602 and each suspension pole 601. The control coils on the eight torque poles 602 in each phase are connected in series to form a torque winding of each phase. As shown in FIG. 3, the control coils on every two suspension poles as pole shoe teeth in each section are connected in series, to form two sets of suspension windings in orthogonal directions. The control coils on two opposite suspension poles 601 in each phase are connected in series, to form two sets of suspension windings in orthogonal directions. A torque control coil and a suspension control coil are wound around the torque pole 602 and the suspension pole 601 respectively in the phase A. The control coils on the eight torque poles 602 in the phase A are mutually connected in series to form phase main-pole windings 605. There are two sets of phase-A suspension windings 604 in orthogonal directions, and each set is formed by reversely connecting in series the control coils on two opposite suspension poles in the respective direction. As shown in FIG. 4, an axially magnetized permanent magnet 3 is provided between stators in the two phases. A permanent magnetic circuit 608 flows in a direction from the pole N of the permanent magnet, through the phase-A stator sleeve, the phase-A stator core, a phase-A air gap, the phase-A rotor core, the rotor sleeve, the phase-B rotor core, a phase-B air gap, the phase-B stator core, and the phase-B stator sleeve, to the pole S of the permanent magnet.

[0015] In the present invention, suspension poles and torque poles are designed into the shape of pole shoe teeth, enlarging the space of a stator slot and effectively enhancing a torque density and a suspension force output of the motor. In addition, a magnetically conductive sleeve is additionally disposed on the inner side of the stator and the outer side of the rotor, improving the axial magnetic conductivity of a permanent magnet-biased magnetic circuit. Consequently, the utilization of a permanent magnet is greatly enhanced, and the usage of permanent magnet materials is reduced, thus saving the costs and improving the force output.

Claims

%_11lVL3

1. An axial split-phase permanent-magnet bearingless switched reluctance flywheel motor with sleeves and pole shoe teeth, comprising: a rotor core (1), a rotor sleeve (2), a stator sleeve (4), a stator core (6), a permanent magnet (3), and a flywheel (5), wherein the rotor core (1), the rotor sleeve (2), and the flywheel (5) are concentrically nested as a whole from inside to outside, and the stator core (6) and the stator sleeve (4) are concentrically nested on a stationary shaft; the stator core (6) and the rotor core (1) are axially divided into m sections according to the number of phases, twelve rotor poles (102) are provided at equal intervals on the inner side of the rotor core (1) in each phase, and eight torque poles (602) and four suspension poles (601) are provided on the stator core (6) in each phase; the torque poles (602) and the suspension poles (601) are designed into the shape of pole shoe teeth, a pole shoe width of each suspension pole (601) is equal to a rotor pole pitch, and a pole shoe width of each torque pole (602) is equal to a rotor tooth width; a magnetic isolation component (603) is provided between the torque poles (602) and the suspension poles (601); a control coil is wound around each torque pole (602) and each suspension pole (601), the control coils on the eight torque poles (602) in each phase are connected in series to form a torque winding of each phase, and the control coils on two opposite suspension poles (601) in each phase are connected in series to form two sets of suspension windings in orthogonal directions; and an axially magnetized permanent magnet (3) is provided between stators in the two phases.

2. The axial split-phase permanent-magnet bearingless switched reluctance flywheel motor with sleeves and pole shoe teeth according to claim 1, wherein the rotor core (1) and the stator core (6) are separately formed by axially laminating silicon steel sheets, and the rotor sleeve (2) and the stator sleeve (4) are both made of a whole piece of steel.