Additional air gap bearingless hybrid excitation doubly salient motor and suspension control method

Abstract

The embodiment of the invention discloses an additional air gap bearingless hybrid excitation doubly salient motor and a suspension control method, and relates to the technical field of bearingless motors. The permanent magnet excitation source and the electric excitation excitation source are adopted, and the phase flux linkage and the electromotive force can be flexibly adjusted by adjusting the direct-current excitation current. The additional air gap is additionally arranged right below the position, opposite to the position where the permanent magnet is embedded, in the stator iron core, a magnetic flux circulation path of an electric excitation part is optimized, a bias magnetic field which is the same as an original bias magnetic field is generated in the air gap between the stator and the rotor when smaller excitation current is introduced into an excitation winding, and the overall stator excitation efficiency is improved. And when faults such as electrical excitation loss occur, stable suspension of the motor rotor can be continuously realized by adjusting the current passing through the suspension winding, so that the reliability of the motor is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of bearingless double-salient-pole motors, and in particular to an additional air gap bearingless hybrid excitation double-salient-pole motor and a suspension control method. Background Art

[0002] A bearingless motor is a new type of motor that integrates magnetic bearing functions with drive or power generation functions. It features a compact structure and high space utilization. In a bearingless doubly salient motor, the excitation magnetic field generated by the excitation winding is superimposed on the suspension magnetic field generated by the suspension winding, resulting in different air gap magnetic flux densities on both sides of the stator, thereby achieving stable suspension of the rotor. Permanent magnet doubly salient motors have the advantages of high efficiency and high power density. However, the main air gap magnetic field of a permanent magnet doubly salient motor is provided by permanent magnets, making it difficult to adjust. Furthermore, it is difficult to demagnetize the motor in the event of a fault, resulting in low operational reliability. A hybrid excitation doubly salient motor, with the main air gap magnetic field jointly provided by permanent magnets and the excitation winding, combines the advantages of high efficiency and high power density of permanent magnet doubly salient motors with the convenient magnetic adjustment of electrically excited doubly salient motors.

[0003] However, current bearingless hybrid-excitation doubly salient motors also have some drawbacks. Because of the presence of permanent magnets, the magnetic flux generated in the excitation winding must pass through them. Permanent magnets have a magnetic permeability similar to that of air, and typically have a high reluctance. This reduces the effectiveness of the excitation winding in generating a magnetic field in the motor's main air gap, reducing the motor's overall excitation efficiency.

[0004] Therefore, how to optimize the traditional bearingless hybrid excitation double-pole motor and enhance the overall excitation efficiency of the motor has become an engineering and technical problem that needs to be solved urgently. Summary of the Invention

[0005] The embodiments of the present invention provide an additional air gap bearingless hybrid excitation double-salient pole motor and a suspension control method, which can optimize the traditional bearingless hybrid excitation double-salient pole motor and enhance the overall excitation efficiency and reliability of the motor.

[0006] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0007] In the first aspect, an embodiment of the present invention provides an additional air gap bearingless hybrid excitation double-salient pole motor, comprising: a stator core, a rotor core, a permanent magnet, an armature winding, an excitation winding, an X-axis suspension winding and a Y-axis suspension winding; the motor adopts a 12 / 8-pole double-salient pole structure; the rotor core is a salient pole structure, which is composed of slot-type core laminations and forms 8 rotor poles, and the rotor poles are neither composed of permanent magnets nor wound with coils, and the magnetic flux flows through the rotor core; the stator core is a salient pole structure, with a total of 12 stator poles, and the gaps between adjacent stator poles form stator slots; the number of permanent magnets in the motor is four, the size and shape of the permanent magnets are the same, and the four permanent magnets are embedded in the stator core yoke; the length of the permanent magnet along its magnetization direction is l PM , the height of the permanent magnet is h PM , the thickness of the permanent magnet along the motor axis is equal to the stator core length l Fe An additional air gap is added just below the position where the permanent magnets are embedded in the stator core.

[0008] In this embodiment, the permanent magnets embedded in the stator core yoke include: permanent magnet I, permanent magnet II, permanent magnet III and permanent magnet IV, wherein the tangentially magnetized permanent magnets are located in the stator core yoke, and the magnetization directions of the permanent magnets corresponding to adjacent stator poles are opposite; additional air gaps I to IV are respectively added directly below the positions where permanent magnets I to IV are embedded in the stator core; the thickness of each permanent magnet along the axial direction of the motor is equal to the length of the stator core, and the depth of each additional air gap along the axial direction of the motor is equal to the length of the stator core. Additional air gap I is added directly below the position where permanent magnet I is embedded in the stator core, additional air gap II is added directly below the position where permanent magnet II is embedded in the stator core, additional air gap III is added directly below the position where permanent magnet III is embedded in the stator core, and additional air gap IV is added directly below the position where permanent magnet IV is embedded in the stator core, and the length of the additional air gap along the direction of flow of the electromagnetic excitation flux is δ add , the additional air gap height is h add The depth of the additional air gap along the motor axis is equal to the stator core length l Fe ;

[0009] In this embodiment, one permanent magnet and a corresponding additional air gap are considered as a group, and the stator core between every two groups is considered as a part, thereby dividing the stator core into four parts; specifically, four permanent magnets and four additional air gaps divide the stator core into four parts, namely, stator core part I, stator core part II, stator core part III and stator core part IV. The main magnetic circuit generated by permanent magnet I is stator core part I—air gap—rotor core—air gap—stator core part IV—permanent magnet I—stator core part I; the main magnetic circuit generated by permanent magnet II is stator core part I—air gap—rotor core—air gap—stator core part II—permanent magnet II—stator core part I; the main magnetic circuit generated by permanent magnet III is stator core part III—air gap—rotor core—air gap—stator core part II—permanent magnet III—stator core part III; the main magnetic circuit generated by permanent magnet IV is stator core part III—air gap—rotor core—air gap—stator core part IV—permanent magnet IV—stator core part III.

[0010] Each part includes a stator pole consisting of three stator tooth poles, an excitation coil is embedded on each stator pole, and all the excitation coils are connected in series in sequence to form an excitation winding; wherein, each set of excitation coils is wound in the same way and each set of excitation coils has a first terminal and a second terminal, wherein, the second terminal of the first set of excitation coils is connected in series with the second terminal of the second set of excitation coils in the clockwise direction, the first terminal of the second set of excitation coils is connected in series with the second terminal of the third set of excitation coils in the clockwise direction, and the first terminal of the third set of excitation windings is connected in series with the second terminal of the fourth set of excitation coils in the clockwise direction. Specifically, the magnetic path of the magnetic flux part generated by the excitation winding and passing through the stator core part I and the stator core part II passes through the rotor core-air gap-stator core part II-additional air gap II-stator core part I-air gap-rotor core to form a closed loop; the magnetic path of the magnetic flux part generated by the excitation winding and passing through the stator core part II and the stator core part III passes through the rotor core-air gap-stator core part II-additional air gap III-stator core part III-air gap-rotor core to form a closed loop. Closed loop; the magnetic path of the magnetic flux portion generated by the excitation winding and passing through the stator core portion III and the stator core portion IV passes through the rotor core - air gap - stator core portion IV - additional air gap IV - stator core portion III - air gap - rotor core to form a closed loop; the magnetic path of the magnetic flux portion generated by the excitation winding and passing through the stator core portion IV and the stator core portion I passes through the rotor core - air gap - stator core portion IV - additional air gap I - stator core portion I - air gap - rotor core to form a closed loop;

[0011] Furthermore, an armature coil is wound around each stator tooth pole, and the same-phase armature coils are connected in series to form an armature winding; until the armature windings of phase A, phase B and phase C are formed. m And three adjacent stator poles are combined into one group, with a total of 4 groups of armature coils N m The first output terminal A+ of the A-phase armature winding and the second output terminal A- of the A-phase armature winding are connected to the external torque control circuit. The connection method of the B-phase armature winding and the C-phase armature winding is the same as that of the A-phase armature winding. Among them, the three armature coils in each group belong to the A-phase, B-phase and C-phase respectively. The armature coils N of the same phase in each group m The armature winding W that constitutes this phase m .

[0012] In this embodiment, a set of suspension coils is wound around each of the two symmetrical stator poles. Each set of suspension coils has two terminals. The two symmetrical sets of suspension coils are connected in series to form a suspension winding, which is divided into an X-axis suspension winding and a Y-axis suspension winding according to the direction of the coordinate axis. The X-axis suspension winding and the Y-axis suspension winding are each composed of two diametrically opposed sets of suspension coils connected in series, each set of suspension coils having two terminals. The first terminal of the first set of X-axis suspension coils serves as the first output terminal X+ of the X-axis suspension winding. The second terminal of the first set of X-axis suspension coils is connected to the first terminal of the second set of X-axis suspension coils. The second terminal of the second set of X-axis suspension coils serves as the second output terminal X- of the X-axis suspension winding. The Y-axis suspension winding is connected in the same manner as the X-axis suspension winding. The output terminals of the X-axis suspension winding are connected to an external X-axis suspension control circuit, and the output terminals of the Y-axis suspension winding are connected to an external Y-axis suspension control circuit. Taking the Y-axis suspension winding as an example, the main magnetic flux generated by the Y-axis suspension winding passes through stator core section IV—additional air gap I—stator core section I—additional air gap II—stator core section II—air gap—rotor core—air gap—stator core section IV, forming a closed loop. The other main magnetic flux passes through stator core section IV—additional air gap IV—stator core section III—additional air gap III—stator core section II—air gap—rotor core—air gap—stator core section IV, forming a closed loop.

[0013] Among them, the X-axis suspension winding W sxThe control circuit includes: a first MOS switch tube Q1 and a second MOS switch tube Q2 connected in series, and a third MOS switch tube Q3 and a fourth MOS switch tube Q4 connected in series; the drain of the first MOS switch tube Q1 and the drain of the third MOS switch tube Q3 are both connected to the positive electrode of the DC voltage source Us; the source of the second MOS switch tube Q2 and the source of the fourth MOS switch tube Q4 are both connected to the negative electrode of the DC voltage source Us; the two output terminals of the X-axis suspension winding are respectively connected to the source of the first MOS switch tube Q1 and the source of the third MOS switch tube Q3, and the capacitor C1 is connected in parallel to both ends of the voltage source Us; the Y-axis suspension winding W sy The control circuit includes: a fifth MOS switch transistor Q5 and a sixth MOS switch transistor Q6 connected in series, and a seventh MOS switch transistor Q7 and an eighth MOS switch transistor Q8 connected in series; the drain of the fifth MOS switch transistor Q5 and the drain of the seventh MOS switch transistor Q7 are both connected to the positive electrode of a DC voltage source Us; the source of the sixth MOS switch transistor Q6 and the source of the eighth MOS switch transistor Q8 are both connected to the negative electrode of the DC voltage source Us; two output terminals of a Y-axis suspension winding are connected to the source of the fifth MOS switch transistor Q5 and the source of the seventh MOS switch transistor Q7, respectively; and a capacitor C2 is connected in parallel to both ends of the voltage source Us.

[0014] In a second aspect, an embodiment of the present invention provides a method comprising:

[0015] S1. Collect the operating state parameters of the motor rotor through the radial displacement sensors in the X-axis and Y-axis directions installed on the motor end cover, and determine the given values ​​of the suspension force in the X-axis and Y-axis directions;

[0016] S2. According to the obtained suspension force given value, obtain the duty cycle signal of the suspension control circuit of the X-axis and Y-axis; set the suspension force given value F required in the X-axis direction x * And the required suspension force F in the Y-axis direction y * The rotor position angle, armature current and suspension current obtained by the same sampling are transformed into the suspension current given value i after coordinate transformation. sx * and i sy * . Set the X-axis suspension winding current to a given value i sx * and the X-axis suspension winding current feedback value i sx The difference between the two is passed through the PI control module to obtain the duty cycle signal of the X-axis suspension control circuit; the Y-axis suspension winding current is given by i sy * and the Y-axis suspension winding current feedback value i sy The difference is passed through the PI control module to obtain the duty cycle signal of the Y-axis suspension control circuit;

[0017] S3. The switching tubes are controlled on and off by adjusting the duty ratios of the switching tubes in the respective suspension control circuits of the X-axis and Y-axis, thereby tracking the X-axis suspension winding current and the Y-axis suspension winding current to a given value and ensuring that the resultant suspension force acting on the rotor conforms to a preset suspension force model.

[0018] In this embodiment, S1 includes: detecting the radial position of the motor rotor by an X-axis radial displacement sensor installed on the motor end cover, and obtaining the actual position x of the motor rotor in the X-axis direction, and then subtracting it from the rotor position set value x*; the obtained difference is input into the X-axis displacement PID control module, and the X-axis displacement PID control module outputs the required suspension force set value F in the X-axis direction. x * The radial position of the motor rotor is detected by a radial displacement sensor in the Y-axis direction installed on the motor end cover, and the actual position y of the motor rotor in the Y-axis direction is obtained, and then the difference is made with the rotor position given value y*; the obtained difference is input into the Y-direction displacement PID control module, and the Y-direction displacement PID control module outputs the required suspension force given value F in the Y-axis direction. y * .

[0019] The preset suspension force model includes:

[0020] Among them, F sy Indicates the resultant suspension force on the rotor, F u Indicates the force of attraction between single-phase stator and rotor teeth, F d Indicates the force of attraction between single-phase stator and rotor teeth, F y Represents the magnetic potential generated by the Y-axis suspension winding, R δ Indicates the air gap reluctance that the magnetic flux passes through from the stator to the rotor, R add is the reluctance of a single additional air gap, F PM is the magnetic potential generated by a single permanent magnet, R PM is the reluctance of a single permanent magnet, F Wf is the magnetic potential generated by the excitation winding, S is the force-bearing area, and μ0 is the vacuum permeability. The derivation process for the X-axis levitation force calculation model is similar, differing from the Y-axis levitation force calculation model in that the magnetic potential generated by the Y-axis levitation winding is replaced by the magnetic potential generated by the X-axis levitation winding.

[0021] l PM is the length of the permanent magnet along its magnetization direction, h PM is the height of the permanent magnet, l Fe is the stator core length, μ0 is the vacuum permeability, μ ris the relative magnetic permeability of the permanent magnet;

[0022] δ add h is the length of the additional air gap along the direction of the electromagnetic flux flow, add is the additional air gap height.

[0023] The additional air gap bearingless hybrid excitation double-pole motor and suspension control method provided in the embodiment of the present invention adopts two excitation sources, permanent magnet and electric excitation, and can flexibly adjust the phase flux linkage and electromotive force by adjusting the DC excitation current. An additional air gap is added directly below the position where the permanent magnet is embedded in the stator core, which optimizes the magnetic flux flow path of the electric excitation part, and realizes that a smaller excitation current is passed through the excitation winding to generate the same bias magnetic field as the original in the air gap between the stator and rotor, thereby improving the overall stator excitation efficiency. When a fault such as demagnetization of the electric excitation occurs, the stable suspension of the motor rotor can be continued by adjusting the current passing through the suspension winding, which greatly improves the reliability of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a structural diagram of a bearingless hybrid excitation doubly salient pole motor with an additional air gap according to an embodiment of the present invention;

[0026] Figure 2 A schematic diagram of the winding of a bearingless hybrid excitation doubly salient pole motor with an additional air gap according to an embodiment of the present invention;

[0027] Figure 3 Schematic diagram of the bias magnetic field circuit of the bearingless hybrid excitation doubly salient pole motor with an additional air gap according to an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the magnetic circuit of the levitation magnetic field generated by the Y-axis levitation winding of the bearingless hybrid excitation doubly salient motor with an additional air gap according to an embodiment of the present invention;

[0029] FIG5( a ) is an equivalent magnetic circuit diagram of the bias magnetic field of a bearingless hybrid excitation doubly salient pole motor with an additional air gap according to an embodiment of the present invention;

[0030] FIG5( b ) is an equivalent magnetic circuit diagram of the suspension magnetic field generated by the Y-axis suspension winding of the bearingless hybrid excitation doubly salient motor with an additional air gap according to an embodiment of the present invention;

[0031] FIG6( a ) and FIG6 ( b ) are schematic structural diagrams of permanent magnets and an additional air gap in a bearingless hybrid excitation doubly salient pole motor with an additional air gap according to an embodiment of the present invention;

[0032] FIG7( a ) and FIG7 ( b ) are schematic diagrams of the control circuits of the X-axis suspension winding and the Y-axis suspension winding of the bearingless hybrid excitation doubly salient pole motor with additional air gap according to an embodiment of the present invention;

[0033] Figure 8 This is a block diagram of the suspension control principle of an additional air-gap bearingless hybrid excitation doubly salient-pole motor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention will be described in detail below, with examples of the embodiments illustrated in the accompanying drawings. Throughout, identical or similar reference numerals represent identical or similar elements or elements having identical or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and intended only to explain the present invention and are not to be construed as limiting the present invention. Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a," "an," "said," and "the" used herein may also include the plural forms. It should be further understood that the term "comprising" as used in the description of the present invention refers to the presence of the stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or intervening elements may be present. Furthermore, "connected" or "coupled" as used herein may include wireless connections or couplings. The term "and / or" as used herein includes any and all combinations of one or more associated listed items. It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as such herein.

[0035] Figure 1This is a schematic diagram of the structure of a bearingless hybrid excitation double-salient-pole motor with an additional air gap according to an embodiment of the present invention. The motor adopts a 12 / 8-pole double-salient-pole structure. The rotor core is a salient-pole structure composed of slot-type core laminations, with a total of 8 rotor poles. The rotor poles are neither composed of permanent magnets nor wound with coils, and magnetic flux can flow through the rotor core. The stator core is a salient-pole structure with a total of 12 stator poles, and the gaps between adjacent stator poles form stator slots. The number of permanent magnets in the motor is four, and the permanent magnets are of the same size and shape. The length of the permanent magnet along its magnetization direction is l PM , the height of the permanent magnet is h PM , the thickness of the permanent magnet along the motor axis is equal to the stator core length l Fe The permanent magnets embedded in the stator core yoke include permanent magnet I, permanent magnet II, permanent magnet III, and permanent magnet IV. Tangentially magnetized permanent magnets are located in the stator core yoke, and the magnetization directions of the permanent magnets corresponding to adjacent stator poles are opposite. An additional air gap I is added directly below the position where permanent magnet I is embedded in the stator core. An additional air gap II is added directly below the position where permanent magnet II is embedded in the stator core. An additional air gap III is added directly below the position where permanent magnet III is embedded in the stator core. An additional air gap IV is added directly below the position where permanent magnet IV is embedded in the stator core. The four permanent magnets and four additional air gaps divide the stator core into four parts: stator core part I, stator core part II, stator core part III, and stator core part IV.

[0036] Figure 2This is a schematic diagram of the winding structure of the bearingless hybrid excitation double-salient pole motor with additional air gap according to an embodiment of the present invention. The excitation winding is embedded in the stator pole composed of three stator tooth poles. Each set of excitation coils is wound in the same manner and each set of excitation coils has a first terminal and a second terminal. The second terminal of the first set of excitation coils is connected in series with the second terminal of the second set of excitation coils in the clockwise direction, the first terminal of the second set of excitation coils is connected in series with the second terminal of the third set of excitation coils in the clockwise direction, and the first terminal of the third set of excitation windings is connected in series with the second terminal of the fourth set of excitation coils in the clockwise direction. All the excitation coils are connected in series in sequence to form the excitation winding. The X-axis suspension winding and the Y-axis suspension winding are both composed of two sets of suspension coils connected in series in radial direction. Each set of suspension coils has two terminals, namely the first terminal and the second terminal. The first terminal of the first set of X-axis suspension coils serves as the first output terminal X+ of the X-axis suspension winding, and the first set of X+ serves as the output terminal X+ of the X-axis suspension winding. The second terminal of the X-axis suspension coil is connected to the first terminal of the second set of X-axis suspension coils, and the second terminal of the second set of X-axis suspension coils serves as the second output terminal X- of the X-axis suspension winding; the connection method of the Y-axis suspension winding is the same as that of the X-axis suspension winding; the output terminal of the X-axis suspension winding is connected to the external X-axis suspension control circuit, and the output terminal of the Y-axis suspension winding is connected to the external Y-axis suspension control circuit; taking the magnetic flux part generated by the Y-axis suspension winding passing through the stator core part I, the stator core part II and the stator core part III as an example, the main magnetic flux of this part passes through the stator core part I—additional air gap I—stator core part II—additional air gap II—stator core part III—air gap—rotor core—air gap—stator core part I to form a closed loop; the armature coils of the same phase are connected in series in sequence to form an armature winding, and an armature coil N is wound on each stator pole. m And three adjacent stator poles are combined into one group, with a total of 4 groups of armature coils N m The first output terminal A+ of the A-phase armature winding and the second output terminal A- of the A-phase armature winding are connected to the external torque control circuit. The connection method of the B-phase armature winding and the C-phase armature winding is the same as that of the A-phase armature winding. Among them, the three armature coils in each group belong to the A-phase, B-phase and C-phase respectively. The armature coils N of the same phase in each group m The armature winding W that constitutes this phase m .

[0037] Figure 3This is a schematic diagram of the bias magnetic field circuit for a bearingless hybrid-excitation doubly salient motor with an additional air gap according to an embodiment of the present invention. The main magnetic circuit generated by permanent magnet I is stator core section I—air gap—rotor core—air gap—stator core section IV—permanent magnet I—stator core section I; the main magnetic circuit generated by permanent magnet II is stator core section I—air gap—rotor core—air gap—stator core section II—permanent magnet II—stator core section I; the main magnetic circuit generated by permanent magnet III is stator core section III—air gap—rotor core—air gap—stator core section II—permanent magnet III—stator core section III; and the main magnetic circuit generated by permanent magnet IV is stator core section III—air gap—rotor core—air gap—stator core section IV—permanent magnet IV—stator core section III. The magnetic path of the magnetic flux part generated by the excitation winding and passing through the stator core part I and the stator core part II passes through the rotor core - air gap - stator core part II - additional air gap II - stator core part I - air gap - rotor core to form a closed loop; the magnetic path of the magnetic flux part generated by the excitation winding and passing through the stator core part II and the stator core part III passes through the rotor core - air gap - stator core part II - additional air gap III - stator core part III - air gap - rotor core to form a closed loop ; The magnetic circuit of the magnetic flux part generated by the excitation winding and passing through the stator core part III and the stator core part IV passes through the rotor core-air gap-stator core part IV-additional air gap IV-stator core part III-air gap-rotor core to form a closed loop; the magnetic circuit of the magnetic flux part generated by the excitation winding and passing through the stator core part IV and the stator core part I passes through the rotor core-air gap-stator core part IV-additional air gap I-stator core part I-air gap-rotor core to form a closed loop.

[0038] Figure 4 This diagram shows the magnetic circuit diagram of the levitation magnetic field generated by the Y-axis levitation winding of a bearingless hybrid-excitation doubly salient motor with an additional air gap according to an embodiment of the present invention. The main magnetic flux generated by the Y-axis levitation winding forms a closed loop, passing through stator core section IV, additional air gap I, stator core section I, additional air gap II, stator core section II, air gap, rotor core, air gap, and stator core section IV. The other main magnetic flux path forms a closed loop, passing through stator core section IV, additional air gap IV, stator core section III, additional air gap III, stator core section II, air gap, rotor core, air gap, and stator core section IV.

[0039] Figure 5(a) shows the equivalent magnetic circuit diagram of the bias magnetic field of a bearingless hybrid excitation doubly salient motor with an additional air gap according to an embodiment of the present invention. The motor's bias magnetic field is generated by both permanent magnets and the field winding. Without considering the effects of nonlinear factors such as core magnetic saturation and magnetic leakage, the equivalent magnetic circuit equations can be written based on the equivalent magnetic circuit diagram, as shown in Equation (1):

[0040]

[0041] Among them, F PM is the magnetic potential generated by a single permanent magnet, F Wf is the magnetic potential generated by the excitation winding, R PM is the reluctance of a single permanent magnet, R add is the reluctance of a single additional air gap, is the magnetic flux flowing through the additional air gap branch, is the magnetic flux flowing through the permanent magnet branch, is the magnetic flux flowing through the air gap due to the bias magnetic field. PM It can be expressed as:

[0042]

[0043] Where, l PM is the length of the permanent magnet along its magnetization direction, h PM is the height of the permanent magnet, l Fe is the stator core length, μ0 is the vacuum permeability, μ r is the relative magnetic permeability of the permanent magnet. add It can be expressed as:

[0044]

[0045] Where, δ add h is the length of the additional air gap along the direction of the electromagnetic flux flow, add is the additional air gap height. From formula (1), we can get the magnetic flux of the bias magnetic field flowing through the air gap:

[0046]

[0047] The X-axis suspension winding and the Y-axis suspension winding are both composed of two sets of suspension coils connected in series in a radially opposite manner. Each set of suspension coils has two terminals, namely the first terminal and the second terminal. The first terminal of the first set of X-axis suspension coils serves as the first output terminal X+ of the X-axis suspension winding, and the second terminal of the first set of X-axis suspension coils is connected to the first terminal of the second set of X-axis suspension coils, and the second terminal of the second set of X-axis suspension coils serves as the second output terminal X- of the X-axis suspension winding. The connection method of the Y-axis suspension winding is the same as that of the X-axis suspension winding. The output terminal of the X-axis suspension winding is connected to the external X-axis. The Y-axis suspension winding is connected to the suspension control circuit, and the output end of the Y-axis suspension winding is connected to the external Y-axis suspension control circuit; one main magnetic flux generated by the Y-axis suspension winding passes through the stator core part IV—additional air gap I—stator core part I—additional air gap II—stator core part II—air gap—rotor core—air gap—stator core part IV to form a closed loop, and the other passes through the stator core part IV—additional air gap IV—stator core part III—additional air gap III—stator core part II—air gap—rotor core—air gap—stator core part IV to form a closed loop.

[0048] Figure 5(b) shows the equivalent magnetic circuit diagram of the bias magnetic field of the bearingless hybrid excitation doubly salient motor with an additional air gap according to an embodiment of the present invention. The Y-direction bias magnetic field of the motor is generated by the Y-axis suspension winding. Without considering the influence of nonlinear factors such as core magnetic saturation and magnetic leakage, the equivalent magnetic circuit equation can be written based on the equivalent magnetic circuit diagram, as shown in Equation (5):

[0049]

[0050] Among them, F y is the magnetic potential generated by the Y-axis suspension winding, It is the magnetic flux of the Y-axis suspension magnetic field flowing through the air gap.

[0051] From formula (5), the magnetic flux of the Y-axis suspension magnetic field flowing through the air gap can be obtained:

[0052]

[0053] According to Maxwell's stress tensor law, there is a formula for the force generated by the magnetic field on the surface of an object:

[0054]

[0055] In the formula is the magnetic flux, S is the force area, and μ0 is the vacuum permeability. Without considering the armature current, according to formula (7), it can be obtained that the magnitude of the force of attraction between the stator and rotor teeth of phase A is F u for:

[0056]

[0057] The force F of attraction between the stator and rotor teeth of phase A below d The size is:

[0058]

[0059] Since the directions of the forces at these two locations are opposite, the resultant radial force acting on the rotor at this time can be used to calculate the resultant suspension force acting on the rotor, as shown in formula (10):

[0060]

[0061] Figure 6 (a) and Figure 6 (b) are schematic diagrams of the structure of the permanent magnet and the additional air gap in the bearingless hybrid excitation double-salient pole motor with additional air gap according to an embodiment of the present invention. PM , the height of the permanent magnet is h PM , the thickness of the permanent magnet along the motor axis is equal to the stator core length l Fe The tangentially magnetized permanent magnets are located in the stator core yoke, and the magnetization directions of the permanent magnets corresponding to adjacent stator poles are opposite. The length of the additional air gap along the direction of the electromagnetic flux flow is δ add , the additional air gap height is h add The depth of the additional air gap along the motor axis is equal to the stator core length l Fe .

[0062] FIG7( a ) shows an X-axis suspension winding W of a bearingless hybrid excitation doubly salient motor with an additional air gap according to an embodiment of the present invention. sx Schematic diagram of the control circuit. The first MOS switch Q1 and the second MOS switch Q2 are connected in series, the third MOS switch Q3 and the fourth MOS switch Q4 are connected in series, the drain of the first MOS switch Q1 and the drain of the third MOS switch Q3 are connected to the positive electrode of the DC voltage source Us, the source of the second MOS switch Q2 and the source of the fourth MOS switch Q4 are connected to the negative electrode of the DC voltage source Us, and the X-axis suspension winding W sx The Lsx and the resistor R1 are equivalent, and the two output terminals thereof are respectively connected to the source of the first MOS switch tube Q1 and the source of the third MOS tube Q3, and the capacitor C1 is connected in parallel to the two ends of the voltage source Us.

[0063] FIG7( b ) shows the Y-axis suspension winding W of the bearingless hybrid excitation doubly salient motor with additional air gap according to an embodiment of the present invention. sy Schematic diagram of the control circuit. The fifth MOS switch Q5 and the sixth MOS switch Q6 are connected in series, the seventh MOS switch Q7 and the eighth MOS switch Q8 are connected in series, the drain of the fifth MOS switch Q5 and the drain of the seventh MOS switch Q7 are connected to the positive electrode of the DC voltage source Us, the source of the sixth MOS switch Q6 and the source of the eighth MOS switch Q8 are connected to the negative electrode of the DC voltage source Us, and the Y-axis suspension winding W is connected to the Y-axis suspension winding W. syThe Lsy and the resistor R2 are equivalent, and the two output terminals thereof are respectively connected to the source of the fifth MOS switch tube Q5 and the source of the seventh MOS tube Q7, and the capacitor C2 is connected in parallel to the two ends of the voltage source Us.

[0064] Figure 8 This is a block diagram of the suspension control principle of a bearingless hybrid-excitation doubly salient motor with an additional air gap according to an embodiment of the present invention. The radial position of the motor rotor is detected by an X-axis radial displacement sensor mounted on the motor end cap to obtain the actual X-axis position x of the motor rotor. This actual position x is then subtracted from the rotor position setpoint x*. The resulting difference is then input into the X-axis displacement PID control module, which then outputs the X-axis required suspension force setpoint F. x * The radial position of the motor rotor is detected by a radial displacement sensor in the Y-axis direction installed on the motor end cover to obtain the actual position y of the motor rotor in the Y-axis direction. The actual position y is then subtracted from the rotor position given value y*. The obtained difference is input into the Y-direction displacement PID control module, and the Y-direction displacement PID control module outputs the required suspension force given value F in the Y-axis direction. y * The required suspension force in the X-axis direction is given as F x * And the required suspension force F in the Y-axis direction y * The rotor position angle, armature current and suspension current obtained by the same sampling are transformed into the suspension current given value i after coordinate transformation. sx * and i sy * . Set the X-axis suspension winding current to a given value i sx * and the X-axis suspension winding current feedback value i sx The difference between the two is passed through the PI control module to obtain the duty cycle signal of the X-axis suspension control circuit; the Y-axis suspension winding current is given by i sy * and the Y-axis suspension winding current feedback value i sy The difference between the two values ​​is passed through a PI control module to obtain a duty cycle signal of the Y-axis suspension control circuit; and the switching tube duty cycles of the X-axis suspension control circuit and the Y-axis suspension control circuit are adjusted to control the on and off of the respective switching tubes to respectively achieve tracking of the X-axis suspension winding current and the Y-axis suspension winding current to a given value.

[0065] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited to this. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A bearingless hybrid excitation double-salient pole motor with additional air gap, characterized in that: include: Stator core, rotor core, permanent magnet, armature winding, excitation winding, X-axis suspension winding and Y-axis suspension winding; The motor adopts a 12 / 8 pole double salient pole structure; The rotor core is a salient pole structure, composed of slotted core laminations and forming eight rotor poles, through which magnetic flux flows; The stator core is a salient pole structure with a total of 12 stator poles, and the gaps between adjacent stator poles form stator slots; There are four permanent magnets in the motor, all of which are identical in size and shape, and are embedded in the stator core yoke. An additional air gap is added just below the position where the permanent magnets are embedded in the stator core.

2. The additional air gap bearingless hybrid excitation double-salient pole motor according to claim 1, characterized in that: The permanent magnets embedded in the stator core yoke include permanent magnet I, permanent magnet II, permanent magnet III and permanent magnet IV; Additional air gaps I to IV are respectively provided directly below the positions where permanent magnets I to IV are embedded in the stator core; The thickness of each permanent magnet along the axial direction of the motor is equal to the length of the stator core, and the depth of each additional air gap along the axial direction of the motor is equal to the length of the stator core.

3. The additional air gap bearingless hybrid excitation double-salient pole motor according to claim 1, characterized in that: A permanent magnet and a corresponding additional air gap are regarded as a group, and the stator core between every two groups is regarded as a part, thereby dividing the stator core into four parts; Each part includes a stator pole consisting of three stator tooth poles, each stator pole is embedded with an excitation coil, and all the excitation coils are connected in series in sequence to form an excitation winding; Each set of excitation coils is wound in the same manner and each set of excitation coils has a first terminal and a second terminal, wherein the second terminal of the first set of excitation coils is connected in series with the second terminal of the second set of excitation coils in the clockwise direction, the first terminal of the second set of excitation coils is connected in series with the second terminal of the third set of excitation coils in the clockwise direction, and the first terminal of the third set of excitation windings is connected in series with the second terminal of the fourth set of excitation coils in the clockwise direction.

4. The additional air gap bearingless hybrid excitation double-salient pole motor according to claim 1 or 3, characterized in that: An armature coil is wound on each stator tooth pole, and the armature coils of the same phase are connected in series to form the armature winding; This continues until the armature windings for phases A, B, and C are formed.

5. The additional air gap bearingless hybrid excitation doubly salient pole motor according to claim 1, characterized in that: A set of suspension coils is wound on each of the two symmetrical stator poles. Each set of suspension coils has two terminals. The two symmetrical suspension coils are connected in series to form a suspension winding. According to the direction of the coordinate axis, they are divided into X-axis suspension winding and Y-axis suspension winding. The outgoing wire end of the X-axis suspension winding is connected to the external X-axis suspension control circuit, and the outgoing wire end of the Y-axis suspension winding is connected to the external Y-axis suspension control circuit.

6. The additional air gap bearingless hybrid excitation doubly salient pole motor according to claim 1 or 5, characterized in that: The X-axis suspension winding W sx The control circuit includes: a first MOS switch transistor Q1 and a second MOS switch transistor Q2 connected in series, and a third MOS switch transistor Q3 and a fourth MOS switch transistor Q4 connected in series; the drain of the first MOS switch transistor Q1 and the drain of the third MOS switch transistor Q3 are both connected to the positive electrode of a DC voltage source Us; the source of the second MOS switch transistor Q2 and the source of the fourth MOS switch transistor Q4 are both connected to the negative electrode of the DC voltage source Us; two output terminals of an X-axis suspension winding are respectively connected to the source of the first MOS switch transistor Q1 and the source of the third MOS switch transistor Q3; and a capacitor C1 is connected in parallel to both ends of the voltage source Us. Suspended winding W on the Y axis sy The control circuit includes: a fifth MOS switch transistor Q5 and a sixth MOS switch transistor Q6 connected in series, and a seventh MOS switch transistor Q7 and an eighth MOS switch transistor Q8 connected in series; the drain of the fifth MOS switch transistor Q5 and the drain of the seventh MOS switch transistor Q7 are both connected to the positive electrode of a DC voltage source Us; the source of the sixth MOS switch transistor Q6 and the source of the eighth MOS switch transistor Q8 are both connected to the negative electrode of the DC voltage source Us; two output terminals of a Y-axis suspension winding are connected to the source of the fifth MOS switch transistor Q5 and the source of the seventh MOS switch transistor Q7, respectively; and a capacitor C2 is connected in parallel to both ends of the voltage source Us.

7. A suspension control method for a bearingless hybrid excitation doubly salient pole motor with additional air gap, characterized in that: include: S1. Collect the operating state parameters of the motor rotor through the radial displacement sensors in the X-axis and Y-axis directions installed on the motor end cover, and determine the given values ​​of the suspension force in the X-axis and Y-axis directions; S2. Obtain duty cycle signals of the respective suspension control circuits of the X-axis and Y-axis according to the obtained suspension force given value; S3. The switching tubes are controlled on and off by adjusting the duty ratios of the switching tubes in the respective suspension control circuits of the X-axis and Y-axis, thereby tracking the X-axis suspension winding current and the Y-axis suspension winding current to a given value and ensuring that the resultant suspension force acting on the rotor conforms to a preset suspension force model.

8. The additional air gap bearingless hybrid excitation doubly salient pole motor according to claim 7, characterized in that: S1 includes: The radial position of the motor rotor is detected by the X-axis radial displacement sensor installed on the motor end cover, and the actual position x of the motor rotor in the X-axis direction is obtained, and then the difference is made with the rotor position given value x*; the obtained difference is input into the X-direction displacement PID control module, and the X-direction displacement PID control module outputs the required suspension force given value F in the X-axis direction. x * ; The radial position of the motor rotor is detected by a radial displacement sensor in the Y-axis direction installed on the motor end cover, and the actual position y of the motor rotor in the Y-axis direction is obtained, and then the difference is made with the rotor position given value y*; the obtained difference is input into the Y-direction displacement PID control module, and the Y-direction displacement PID control module outputs the required suspension force given value F in the Y-axis direction. y * .

9. The additional air gap bearingless hybrid excitation doubly salient pole motor according to claim 7, characterized in that: The preset suspension force model includes: Among them, F sy Indicates the resultant suspension force on the rotor, F u Indicates the force of attraction between single-phase stator and rotor teeth, F d Indicates the force of attraction between single-phase stator and rotor teeth, F y Indicates the magnetic potential generated by the Y-axis suspension winding, F x Represents the magnetic potential generated by the X-axis suspension winding, R δ Indicates the air gap reluctance that the magnetic flux passes through from the stator to the rotor, R add is the reluctance of a single additional air gap, F PM is the magnetic potential generated by a single permanent magnet, R PM is the reluctance of a single permanent magnet, F Wf is the magnetic potential generated by the excitation winding, S is the force area, and μ0 is the vacuum permeability.

10. The additional air gap bearingless hybrid excitation doubly salient pole motor according to claim 9, characterized in that: l PM is the length of the permanent magnet along its magnetization direction, h PM is the height of the permanent magnet, l Fe is the stator core length, μ0 is the vacuum permeability, μ r is the relative magnetic permeability of the permanent magnet; δ add h is the length of the additional air gap along the direction of the electromagnetic flux flow, add is the additional air gap height.

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