CN111884476B

CN111884476B - Linear homopolar motor and control method

Info

Publication number: CN111884476B
Application number: CN202010696677.9A
Authority: CN
Inventors: 徐伟; 罗德力; 唐一融; 刘毅
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2020-07-17
Filing date: 2020-07-17
Publication date: 2021-08-10
Anticipated expiration: 2040-07-17
Also published as: CN111884476A

Abstract

The invention discloses a linear homopolar motor and a control method, belonging to the field of motors, wherein the motor comprises: the magnetic field generator comprises a primary iron core, a secondary iron core, an armature winding, an excitation coil and a guide coil; the primary iron core is formed by sequentially connecting k E-shaped iron cores, wherein k is larger than or equal to 2, the k E-shaped iron cores are aligned along the connecting direction, the distances between the adjacent E-shaped iron cores are equal, a groove is formed between middle iron core arms of the adjacent E-shaped iron cores, and the tail ends of the iron core arms at two sides in the E-shaped iron cores are bent towards the inner side; the secondary iron core is composed of a plurality of segmented iron cores, the distance between two adjacent segmented iron cores is equal, and a section of air gap with equal length is formed between the secondary iron core and the primary iron core; armature windings are arranged in (k-1) slots in the primary core; the excitation coil is wound on the primary iron core; the guide coils are wound on the iron core arms on the two sides of the primary iron core. The invention enables the motor to integrate the functions of propelling, suspending and guiding, and reduces the cost of the motor.

Description

Linear homopolar motor and control method

Technical Field

The invention belongs to the field of motors, and particularly relates to a linear homopolar motor and a control method.

Background

In recent years, magnetic levitation trains have attracted much attention due to the advantages of high efficiency, low noise, high speed, and the like. The magnetic suspension train usually uses a linear synchronous motor or a linear induction motor as a driving motor. The linear induction motor has simple structure and low cost, but has lower power factor, and needs to be matched with a large-scale vehicle-mounted frequency converter, so that the weight of the train is increased; and when the speed increases, the thrust attenuation of the linear induction motor is serious, and the linear induction motor is only suitable for the occasions with medium and low speeds. The linear synchronous motor has high control precision and unobvious thrust attenuation, and is suitable for high-speed occasions; however, the track needs to be laid with a large number of windings or permanent magnets, which is costly. In addition, the existing magnetic suspension train mostly adopts an additional suspension and guide device to realize the stable and controllable suspension and guide functions, and the cost is higher.

Disclosure of Invention

Aiming at the defects and the improvement requirements of the prior art, the invention provides a linear homopolar motor and a control method thereof, and aims to reduce the cost on the basis that the motor has the functions of propulsion, suspension and guidance.

To achieve the above object, according to one aspect of the present invention, there is provided a linear homopolar motor including a primary core, a secondary core, an armature winding, an exciting coil, and a guide coil; the primary iron core is formed by sequentially connecting k E-shaped iron cores, k is an integer not less than 2, the k E-shaped iron cores are aligned along the connecting direction, the distances between adjacent E-shaped iron cores are equal, a groove is formed between middle iron core arms of the adjacent E-shaped iron cores, and the tail ends of the two iron core arms in the E-shaped iron cores are bent towards the inner side; the secondary iron core is composed of a plurality of segmented iron cores, the distance between two adjacent segmented iron cores is equal, and a section of air gap with equal length is formed between the secondary iron core and the primary iron core; the armature windings are disposed in (k-1) slots in the primary core; the excitation coil is wound on the primary iron core; the guide coils are wound on iron core arms on two sides of the primary iron core.

Furthermore, each groove is divided into three layers, the armature winding is a three-phase winding, each phase winding occupies one layer of the grooves, and two phases of the three-phase windings are placed in each groove.

Further, the sectional core of the secondary core has a trapezoidal cross section.

Furthermore, the outer edges of the tail ends of the two side iron core arms in the E-shaped iron core are provided with unfilled corner structures.

Further, the exciting coil is wound around the intermediate core arm of the primary core; the guide coil comprises two coils which are respectively wound on the iron core arms on the two sides of the primary iron core.

Further, the primary core is formed by transversely laminating multiple layers of silicon steel sheets.

Further, the secondary core is formed by iron casting.

According to another aspect of the present invention, there is provided a method of controlling a linear homopolar motor as described above, the method comprising: and D, introducing direct current into the excitation coil, and introducing three-phase sinusoidal alternating current into the armature winding to form an homopolar pulse vibration magnetic field and a traveling wave magnetic field which interact with each other in an air gap between the primary iron core and the secondary iron core so as to generate thrust.

Still further, when the primary core is offset from the center of the secondary core, the method further includes: and respectively introducing currents with corresponding difference values into the two coils of the guide coil according to the deviation between the primary iron core and the secondary iron core so as to generate a guide force for pushing the primary iron core to move towards the direction close to the center of the secondary iron core.

Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:

(1) the excitation coil is arranged on the primary iron core, and the secondary part is only composed of segmented iron cores, so that the cost is greatly reduced;

(2) the tail ends of the iron core arms at two sides of the primary iron core are arranged into structures bent towards the inner side, and the iron core arms at two sides of the primary iron core are wound with the guide coils, so that the motor integrates the functions of propulsion, suspension and guidance at the same time, and the complexity of a magnetic suspension system is reduced;

(3) the grooves in the primary iron core are divided into three layers, wherein two layers are used for placing armature windings, and the other layer is used for ventilation, so that the cooling effect of the motor is enhanced, overheating is avoided, and the safety and reliability of the motor are improved;

(4) the outer edges of the tail ends of the iron core arms at two sides of the primary iron core are arranged into unfilled corner structures, and the magnetic flux flowing through the unfilled corner parts is extremely little, so that the cost is reduced on the basis of not influencing the performance of the motor;

(5) the secondary iron core adopts a trapezoidal section, so that the cost is reduced.

Drawings

Fig. 1 is a schematic cross-sectional structure diagram of a linear homopolar motor and coil winding arrangement thereof according to the present invention;

fig. 2 is a schematic layout diagram of an armature winding in a linear homopolar motor according to the present invention;

fig. 3 is a schematic bottom view of a secondary core in a linear homopolar motor according to the present invention.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:

1 is primary iron core, 2 is secondary iron core, 3 is armature winding, 4 is excitation coil, 5 is guide coil, 6 is the recess, 11 is middle iron core arm, 12 is both sides iron core arm.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

Fig. 1 is a schematic cross-sectional structure diagram of a linear homopolar motor and coil winding arrangement thereof according to the present invention. Referring to fig. 1, a linear homopolar motor according to the present embodiment will be described in detail with reference to fig. 2 to 3.

The linear homopolar motor comprises a primary iron core 1, a secondary iron core 2, an armature winding 3, an excitation coil 4 and a guide coil 5.

The primary iron core 1 is formed by sequentially connecting k E-shaped iron cores, wherein k is an integer not less than 2. Referring to fig. 1, each of the "E" -shaped iron cores in the primary iron core 1 is composed of a middle iron core arm 11 located in the middle, two side iron core arms 12 located at both sides, and a yoke iron core connecting the middle iron core arm 11 and the side iron core arms 12. k E-shaped iron cores are aligned in sequence along a direction perpendicular to the E-shaped section and then connected to form a primary iron core 1. The distances between two adjacent E-shaped iron cores are equal, and the middle iron core arms 11 of the E-shaped iron cores are connected with each other from the bottom, so that grooves 6 are formed between the middle iron core arms 11 of the adjacent E-shaped iron cores, and the number of the grooves 6 is (k-1). The primary iron core 1 is formed by transversely laminating multiple layers of silicon steel sheets. Specifically, a plurality of silicon steel sheets are laminated layer by layer along a direction perpendicular to the section of the E-shaped iron core, thereby forming a primary iron core 1 having k E-shaped iron core segments.

The tail ends of the two side iron core arms 12 in the E-shaped iron core are bent towards the inner side direction, and the middle iron core arm 11 is not bent. Taking the "E" shaped iron core with the upward opening shown in fig. 1 as an example, the middle iron core arm 11 of the "E" shaped iron core is vertically arranged, and the ends of the left and right iron core arms are bent inward.

In the embodiment of the invention, the outer edges of the tail ends of the iron core arms 12 at two sides in the E-shaped iron core are in unfilled corner structures. Still take "E" style of calligraphy iron core that the opening is up shown in fig. 1 as an example, "E" style of calligraphy iron core left side iron core arm terminal upper left corner is lacked, right side iron core arm terminal upper right corner is lacked for the outside of both sides iron core arm 12 end forms the unfilled corner structure, on the basis that does not influence motor performance, the cost is reduced.

The secondary iron core 2 is a sectional iron core and is composed of a plurality of sectional iron cores, the distance between two adjacent sectional iron cores is equal, and an air gap with one end equal in length is formed between the secondary iron core 2 and the primary iron core 1. In the present embodiment, the number and length of the segment cores in the secondary core 2 may be set according to a desired stroke of the motor. Still taking the primary core 1 shown in fig. 1 with the opening facing upward as an example, the plurality of segment cores are located above the middle core arm 11 of the primary core 1.

In the embodiment of the invention, the cross section of each segmented iron core in the secondary iron core 2 is trapezoidal. Preferably, the cross section of each segmented core is an inverted trapezoid, and the bottom view of the inverted trapezoid segmented core is shown in fig. 3. The secondary core 2 is formed by iron casting.

The armature windings 3 are arranged in (k-1) slots 6 in the primary core 1. In the embodiment of the invention, the armature winding is a three-phase winding comprising A, B, C three phases, and each phase of winding comprises (k-1)/3 coils; dividing each groove 6 into three layers, for example, an upper layer, a middle layer and a lower layer, wherein each phase winding occupies one layer in the groove 6, for example, an A phase winding is placed at the upper layer, a B phase winding is placed at the middle layer, and a C phase winding is placed at the lower layer; two phase windings are placed in each slot 6 so that one layer in each slot 6 is left empty as shown in fig. 2, thereby achieving the cooling and ventilating effect. For the motor structure that the armature winding is a three-phase winding and each groove 6 is provided with a layer in an empty state, the number k of the E-shaped iron core segments in the primary iron core 1 is such that (k-1)/3 is an integer greater than 1.

The exciting coil 4 is wound around the primary core 1. Specifically, the exciting coil 4 is wound around k intermediate core arms 11 of the primary core 1.

In the working state, direct current is introduced into the excitation coil 4 to magnetize the primary iron core 1, so that a suspension force with attraction property is generated, and a homopolar and pulse-vibrating magnetic field is generated in an air gap with equal length between the primary iron core 1 and the secondary iron core 2. Three-phase sinusoidal alternating current with certain frequency is introduced into the armature winding 3 to generate a traveling wave magnetic field in an air gap with equal length between the primary iron core 1 and the secondary iron core 2. The armature magnetic field generated by the armature winding 3 interacts with the exciting magnetic field generated by the exciting coil 4, thereby generating thrust.

The ratio of the distance between the adjacent segment cores in the secondary core 2 to the pole pitch of the primary core 1 is preferably 0.8 to 1. It is understood that the ratio of the distance between adjacent segmented cores in the secondary core 2 to the pole pitch of the primary core 1 may also be other values. The distance between adjacent segmented cores in the secondary core 2 refers to the distance between the midpoints of adjacent sides in two adjacent trapezoidal sections. And controlling the distance between adjacent segmented iron cores in the primary iron core 2 according to the polar distance of the primary iron core 1, so that the propelling force and the suspension force generated by the motor reach a desired proportion.

The guide coil 5 is wound around the primary core 1. Specifically, the guidance coil 5 includes two coils, which are wound around k two side core arms 12 of the primary core 1, respectively, for example, one coil is wound around k left side core arms of the primary core 1, and the other coil is wound around k right side core arms of the primary core 1, as shown in fig. 1.

When the primary iron core 1 deviates from the center of the secondary iron core 2, currents with different values are respectively led into the two coils of the guiding coil 5, and because the tail ends of the iron core arms at the two sides in the primary iron core 1 are bent towards the inner side, two guiding forces with different magnitudes and opposite directions (respectively towards the left and the right) can be respectively generated at the left side and the right side of the secondary iron core 2, and finally the resultant force is the guiding force towards the left or the right, so that the primary iron core 1 moves towards the left or the right to return to the position which is vertically aligned with the center of the secondary iron core 2. In this embodiment, the positions of the primary iron core 1 and the secondary iron core 2 may be respectively collected by an auxiliary sensor to detect whether the primary iron core 1 deviates from the center of the secondary iron core 2, and generate a corresponding guiding force when deviating, so that the primary iron core 1 returns.

Simulation analysis and prototype experiments prove that the linear homopolar motor in the embodiment of the invention has the advantages of compact structure, low material consumption, low assembly, disassembly and maintenance cost, high safety, reliability and robustness, good heat dissipation, long service life, integrated propulsion, suspension and guide functions, and is suitable for driving long-stroke linear motion mechanisms such as maglev trains or industrial conveyor belts.

Another embodiment of the present invention provides a method for controlling a linear homopolar motor as in the embodiment shown in fig. 1-3, the method comprising the operations of: direct current is introduced into the excitation coil 4, and three-phase sinusoidal alternating current is introduced into the armature winding 3, so that a homopolar pulsating magnetic field and a traveling wave magnetic field which interact with each other are formed in an air gap between the primary iron core 1 and the secondary iron core 2, thereby generating thrust.

In the embodiment of the present invention, when the primary iron core 1 deviates from the center of the secondary iron core 2, the control method further includes the following operations: according to the deviation between the primary iron core 1 and the secondary iron core 2, currents with corresponding difference values are respectively led into the two coils of the guiding coil 5, so that guiding force for pushing the primary iron core 1 to move towards the direction close to the center of the secondary iron core 2 is generated.

The control method of the linear homopolar motor in this embodiment is the same as the working process of the linear homopolar motor in the embodiment shown in fig. 1-3, and is not described herein again.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A linear homopolar motor is characterized by comprising a primary iron core (1), a secondary iron core (2), an armature winding (3), an excitation coil (4) and a guide coil (5);

the primary iron core (1) is composed ofkThe E-shaped iron cores are sequentially connected to form the iron core,kis an integer of not less than 2, saidkThe E-shaped iron cores are aligned along the connecting direction, the distance between every two adjacent E-shaped iron cores is equal, a groove (6) is formed between middle iron core arms (11) of every two adjacent E-shaped iron cores, and the tail ends of iron core arms (12) on the two sides of each E-shaped iron core are bent towards the inner side direction;

the secondary iron core (2) is composed of a plurality of segmented iron cores, the segmented iron cores are positioned above a middle iron core arm (11) of the primary iron core (1), the distance between every two adjacent segmented iron cores is equal, and a section of air gap with equal length is formed between the secondary iron core (2) and the primary iron core (1);

the armature winding (3) is arranged in the primary core (1)k-1 recess (6); the excitation coil (4) is wound on a middle iron core arm (11) of the primary iron core (1); the guide coil (5) is wound on iron core arms (12) on two sides of the primary iron core (1);

when direct current is introduced into the excitation coil (4), suspension force with an absorption property is generated, and a homopolar and pulse-vibrating magnetic field is generated in an air gap with equal length between the primary iron core (1) and the secondary iron core (2); when three-phase sine alternating current is introduced into the armature winding (3), a traveling wave magnetic field is generated in an air gap with equal length between the primary iron core (1) and the secondary iron core (2), and the homopolar and pulse-vibrating magnetic field and the traveling wave magnetic field interact to generate thrust.

2. A linear homopolar machine according to claim 1, wherein each slot (6) is divided into three layers, the armature winding (3) is a three-phase winding, each phase winding occupies a respective one of the slots (6), and each slot (6) has two of the three-phase windings placed therein.

3. Linear homopolar electric machine according to claim 1, characterized in that the sectional cores of the secondary cores (2) are trapezoidal in cross section.

4. The linear homopolar motor according to claim 1 or 2, wherein the outside edges of the ends of the two side core arms (12) in the E-shaped core are arranged in a unfilled corner structure.

5. Linear homopolar electric machine according to claim 1, characterized in that said guidance coils (5) comprise two coils wound on the two side core arms (12) of said primary core (1), respectively.

6. The linear homopolar machine according to claim 1 or 2, wherein said primary core (1) is formed by transverse lamination of multiple layers of silicon steel sheets.

7. A linear homopolar electrical machine according to claim 1 or 3, wherein the secondary core (2) is formed from an iron casting.

8. Method for controlling a linear homopolar machine according to any one of claims 1 to 7, characterized in that it comprises:

and D, introducing direct current into the excitation coil (4), and introducing three-phase sinusoidal alternating current into the armature winding (3) to form an homopolar magnetic field, a pulsating magnetic field and a traveling wave magnetic field which interact with each other in an air gap between the primary iron core (1) and the secondary iron core (2), so that thrust is generated.

9. The method of claim 8, wherein when the primary core (1) is offset from the center of the secondary core (2), the method further comprises:

and respectively introducing currents with corresponding difference values into the two coils of the guide coil (5) according to the deviation between the primary iron core (1) and the secondary iron core (2) so as to generate a guide force for pushing the primary iron core (1) to move towards the direction close to the center of the secondary iron core (2).