Three-winding three-phase variable speed magnetic suspension asynchronous motor

Abstract

The application discloses a three-winding three-phase variable-speed magnetic suspension asynchronous motor, which comprises a three-winding stator and a fixed-pole rotor. The three-winding stator comprises a stator core and a stator winding, wherein the stator core is made of silicon steel sheets, and the stator winding is composed of a torque winding, a suspension force winding and a speed regulating winding. The suspension force winding is embedded in the inner layer of the stator slot, and the torque winding and the speed regulating winding are embedded in the outer layer of the stator slot in a phase-to-phase distribution mode. The fixed-pole rotor comprises a rotor core and a plurality of insulated rotor coils, wherein the rotor core is made of silicon steel sheets, and the insulated coils are wound in a special structure to form a closed loop and are sequentially embedded in the rotor slot. The rotor coil with a special connection mode is used to replace the traditional squirrel-cage rotor, so that the defects of the traditional speed regulating method of the magnetic suspension asynchronous motor, such as high cost, complex technology and harmonic generation of a frequency converter, can be effectively solved, and the problem of the induced current of the suspension force winding is considered.

Description

Technical Field

[0001] This invention belongs to the technical field of electrical drive control equipment, and in particular to a novel three-winding three-phase variable voltage speed regulating magnetic levitation asynchronous motor. Background Technology

[0002] With the increasing demands of modern industrial production, electric motors are constantly developing and improving, resulting in a growing variety of types. Magnetic levitation asynchronous motors, as a relatively new type of motor that has emerged in recent decades, not only possess the advantages of induction motors—simple structure, reliable operation, low cost, and convenient maintenance—but also combine the frictionless, wear-free, pollution-free, and long-lasting characteristics of magnetic levitation motors. Therefore, they have profound research value in sterile and high-speed applications such as artificial heart pumps and flywheel energy storage.

[0003] To meet practical operational needs and achieve various speed requirements, motor speed regulation has always been a core research focus. Similar to traditional asynchronous motors, common speed regulation methods for magnetic levitation asynchronous motors include pole-changing speed regulation, frequency conversion speed regulation, rotor series resistance, and stator voltage variation speed regulation. Chinese patent authorization number ZL202011015815.9, entitled "A Pole-Changing Speed-Regulating Wound-Rotor Magnetic Levitation Asynchronous Motor," achieves speed regulation by changing the number of pole pairs in the torque winding. However, its principle involves switching between 1, 2, and 3 pole pairs in the torque winding to achieve speed regulation. Therefore, the motor proposed in this patent only has three fixed speeds, failing to meet the requirements for stepless speed regulation. Chinese patent application number ZL201510461711.3, entitled "An Unbalanced Vibration Control System for Magnetic Levitation Asynchronous Motor Based on Current Compensation," feeds the three-phase current output from the random displacement control inverse system into the three-phase magnetic levitation control winding of the magnetic levitation asynchronous motor, adjusting the motor speed by changing the current frequency. However, commonly used frequency converters are very expensive and increase the complexity of the control system. Furthermore, the PWM wave output by the frequency converter causes the motor to overheat and shorten its lifespan. While rotor resistance speed regulation has advantages such as lower technical requirements, ease of use, low equipment cost, and no electromagnetic harmonic interference, its mechanical properties are relatively rigid, and it can only be applied to wound rotors, resulting in a very limited speed regulation range. At the same time, the added slip power during speed regulation is entirely converted into heat loss in the form of the series resistor, leading to lower efficiency. Besides the above speed regulation methods, the traditional variable stator voltage speed regulation method has simple circuitry, small device size, and low price, but it increases slip loss during speed regulation, and because the stator has only one winding, the speed regulation range is also very limited.

[0004] Besides speed regulation issues, magnetic levitation asynchronous motors also suffer from induced current in the levitation winding. Traditional squirrel-cage rotors are connected at both ends by short-circuit rings, resulting in a short-circuit structure for the entire rotor. Therefore, it can sense the stator magnetic field under any number of pole pairs, ultimately causing the induced current in the levitation winding to affect the motor's torque and speed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a three-winding, three-phase variable-voltage speed-regulating magnetic levitation asynchronous motor. The motor stator employs a three-winding structure, including a torque winding, a levitation force winding, and a speed-regulating winding. The motor rotor adopts a fixed-pole structure, replacing the traditional squirrel-cage rotor with rotor coils using a special connection method. This effectively solves the drawbacks of traditional speed regulation methods for magnetic levitation asynchronous motors, such as high cost of frequency converters, complex technology, and harmonic generation, while also considering the induced current problem of the levitation force winding.

[0006] The technical solution adopted in this invention is as follows:

[0007] A three-winding, three-phase variable-voltage speed-regulating magnetic levitation asynchronous motor comprises, from the outside to the inside in the radial direction, a stator core, a rotor core, and a shaft; the stator slots of the stator core are provided with torque windings, speed-regulating windings, and levitation force windings; the rotor slots of the rotor core are connected by rotor coils with a fixed pole structure; and an air gap exists between the stator core and the rotor core.

[0008] Furthermore, the stator core is made of stacked silicon steel sheets and adopts an open slot structure with 36 stator slots.

[0009] Furthermore, the rotor core is made of stacked silicon steel sheets and adopts an open slot structure with 24 rotor slots.

[0010] Furthermore, the stator slots are divided into an inner layer and an outer layer radially from the inside out. A set of 2-pole levitation windings is embedded in the inner layer of the stator slots, filling all 36 stator slots. A set of 1-pole torque windings and a set of 3-pole speed regulating windings are embedded in the outer layer of the stator slots.

[0011] Furthermore, the torque winding and the speed regulating winding are distributed alternately in the stator slots, each occupying 18 stator slots.

[0012] Furthermore, taking the rotor shaft center as the central symmetry point, the four centrally symmetrical rotor slots are divided into a group, for a total of 6 groups, and a set of rotor coils with fixed pole structure are embedded in each group of rotor slots.

[0013] Furthermore, the rotor coil comprises 8 segments, of which 4 segments are placed axially and the other 4 segments are placed radially, and are connected sequentially in the order of "axial-radial-axial-radial" to form a closed loop.

[0014] Furthermore, a voltage is applied to the torque winding, generating a single-pole rotating magnetic field on the outside of the stator; the axial guide bars in the rotor slots cut the rotating magnetic field relative to each other, and at the same time, an induced current is generated in the closed rotor guide bars. The rotor induced current generates a Lorentz force in the rotating magnetic field, which in turn generates an electromagnetic torque acting on the rotor guide bars, driving the motor rotor to rotate.

[0015] Furthermore, applying voltage to the speed regulating winding generates a three-pole rotating magnetic field on the outside of the stator, producing electromagnetic torque. Further, applying voltage to the levitation winding generates a two-pole rotating magnetic field on the inside of the stator, which interacts with the magnetic fields of the torque winding and the speed regulating winding to produce two Maxwell unbalanced magnetic pulls, which superimpose to form a levitation force acting on the rotor.

[0016] The beneficial effects of this invention are:

[0017] 1. This invention designs a fixed-pole structure rotor that can sense the torque winding of one pair of poles and the speed-regulating winding of three pairs of poles, but cannot sense the levitation force winding of two pairs of poles. This solves the problem of levitation force winding induced current generated by traditional squirrel-cage rotors, which affects the torque and speed of the motor.

[0018] 2. This invention adds an extra speed-regulating winding to the traditional magnetic levitation asynchronous motor and designs its winding distribution in relation to the torque winding and levitation force winding. By changing the voltage of the speed-regulating winding, the motor speed is adjusted, overcoming the shortcomings of traditional speed regulation methods such as the high cost of frequency converters, harmonic generation, and limited speed regulation range.

[0019] 3. This invention achieves motor torque and levitation force control simultaneously by directly changing the voltage of the torque winding, speed regulating winding and levitation force winding, thus simplifying the control system of traditional magnetic levitation asynchronous motors. Attached Figure Description

[0020] Figure 1 This is a diagram of the stator core of the present invention.

[0021] Figure 2 This is a diagram of the rotor core of the present invention.

[0022] Figure 3 This is the torque winding wiring diagram of the present invention.

[0023] Figure 4 This is the wiring diagram of the speed regulating winding of the present invention.

[0024] Figure 5 This is the wiring diagram of the levitation winding of the present invention.

[0025] Figure 6 This is a structural diagram of the rotor coil of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0027] This application designs a three-winding, three-phase variable-voltage speed-regulating magnetic levitation asynchronous motor, which consists of a motor stator core, torque winding, speed-regulating winding, levitation force winding, rotor core, fixed-pole rotor coil, and shaft, arranged radially from the outside to the inside. There is an air gap between the stator core and the rotor core.

[0028] like Figure 1 The stator core of a three-winding, three-phase variable-speed magnetic levitation asynchronous motor shown is made of stacked silicon steel sheets of model DW465-50. It adopts an open slot structure with a total of 36 stator slots. Each stator slot is divided into inner and outer layers radially from the inside out. Among them, slots numbered 1-36 are the inner layer of stator slots, and slots numbered 37-72 are the outer layer of stator slots.

[0029] like Figure 2 The rotor core of a three-winding, three-phase variable-speed magnetic levitation asynchronous motor shown is made of stacked silicon steel sheets of model DW465-50. It adopts an open slot structure and has a total of 24 rotor slots, each of which is numbered 73-96.

[0030] like Figure 3 The torque winding of a three-winding, three-phase variable-speed magnetic levitation asynchronous motor is shown. Winding A1 is embedded in the inner layers of stator slots 35, 5, 11, 17, 23, and 29; winding B1 is embedded in the inner layers of stator slots 1, 7, 13, 19, 25, and 31; and winding C1 is embedded in the inner layers of stator slots 3, 9, 15, 21, 27, and 33. A1, B1, and C1 are connected to a three-phase voltage source for the torque winding.

[0031] like Figure 4 The speed-regulating winding of a three-winding, three-phase variable-speed magnetic levitation asynchronous motor is shown. Winding A2 is embedded in the inner layer of stator slots 36, 2, 4, 18, 20, and 22; winding B2 is embedded in the inner layer of stator slots 6, 8, 10, 24, 26, and 28; and winding C2 is embedded in the inner layer of stator slots 12, 14, 16, 30, 32, and 34. A2, B2, and C2 are connected to the three-phase voltage source of the speed-regulating winding.

[0032] like Figure 5The levitation force winding of a three-winding, three-phase variable-speed magnetic levitation asynchronous motor is shown. Winding A3 is embedded in the outer layer of stator slots 43, 44, 45, 52, 53, 54, 61, 62, 63, 70, 71, and 72. Winding B3 is embedded in the outer layer of stator slots 40, 41, 42, 49, 50, 51, 58, 59, 60, 67, 68, and 69. Winding C3 is embedded in the outer layer of stator slots 37, 38, 39, 46, 47, 48, 55, 56, 57, 64, 65, and 66. Windings A3, B3, and C3 are connected to a three-phase voltage source for the levitation force winding.

[0033] The four centrally symmetrical rotor slots are divided into six groups, each group consisting of slots 73, 79, 85, 91; 74, 80, 86, 92; 75, 81, 87, 93; 76, 82, 88, 94; 77, 83, 89, 95; and 78, 84, 90, 96. Each group of rotor slots contains a set of fixed-pole rotor coils. Each set of rotor coils comprises eight segments, four axially positioned and four radially positioned, connected sequentially in a "axial-radial-axial-radial" order to form a closed loop. The rotor coil structure is as follows: Figure 6 As shown. Taking rotor slots numbered 73, 79, 85, and 91 as an example, "73 and 79" and "85 and 91" are radially connected on one end face of the rotor core; "91 and 73" and "85 and 79" are radially connected on the other end face of the rotor core; they are axially connected within the same stator slot; thus forming a "shaft-radial-shaft-radial" connection method.

[0034] The rotation principle is as follows: When a rated current is applied to the torque winding, a single-pole rotating magnetic field is generated in the inner layer of the stator. The axial guide bars in the rotor slots cut the rotating magnetic field relative to each other, inducing a current in the closed rotor bars. This induced current further generates a Lorentz force in the rotating magnetic field, which in turn generates an electromagnetic torque acting on the rotor bars, driving the motor rotor to rotate.

[0035] The principle of levitation is as follows: When a voltage is applied to the levitation force winding, a two-pair rotating magnetic field is generated on the outer layer of the stator. This magnetic field has a pole number that differs by 1 from the one-pair magnetic field generated by the torque winding. The two interact to generate Maxwell's unbalanced magnetic pull. Based on the dot product and cross product principles of vectors, the current of the main control levitation force winding is decomposed into the d and q axes. The motor is levitation is achieved by changing the currents on the d and q axes.

[0036] The speed control principle is as follows: applying voltage to the speed control winding generates a three-pair magnetic field in the inner layer of the stator. This magnetic field, according to the principle of rotation, produces an electromagnetic torque acting on the rotor bars. This torque cancels out the electromagnetic torque generated by the torque winding, thus affecting the motor speed. By calculating the specific relationship between the speed control winding current and the speed, the speed can be precisely controlled.

[0037] In single-pole and triple-pole magnetic fields, the induced currents at locations 180° apart in spatial distribution have the same direction, while in double-pole magnetic fields, the induced currents at locations 180° apart in spatial distribution have opposite directions. Therefore, the induced currents generated by single-pole and double-pole magnetic fields can form a loop within the fixed-pole rotor coils, while the induced current generated by double-pole magnetic fields cannot. Thus, the fixed-pole rotor structure described above can only induce torque windings of single-pole and speed-regulating windings of triple-pole.

[0038] Specific Implementation Cases

[0039] In the implementation case, a three-winding magnetic levitation motor with a rated power of 2kW was selected for testing. The motor dimensions are as follows: stator outer diameter is 128mm, stator inner diameter is 65mm, rotor outer diameter is 64.5mm, rotor inner diameter is 20.5mm, and core length is 80mm.

[0040] First, the torque winding voltage was kept constant. The speed regulating winding voltage was then decreased in 10V increments starting from 220V: 220V, 190V, 180V, 170V, 160V, 150V, 140V, and 130V. The measured motor speeds were 1193.4 rpm, 1205.3 rpm, 1219.3 rpm, 1235.7 rpm, 1255.6 rpm, 1280.4 rpm, 1312.9 rpm, 1360.0 rpm, and 1448.7 rpm, respectively. Next, the least squares method was used to fit the above nine sets of data, and the approximate functional relationship between the speed regulating winding voltage and the motor speed was obtained as follows:

[0041] n=0.09752U S-R 2 -42.78U S-R +5894,1200 <n≤1500 (1)

[0042] Next, the speed regulating winding voltage was kept constant, while the torque winding voltage decreased in 10V increments starting from 220V: 220V, 190V, 180V, 170V, 160V, 150V, 140V, and 130V. The measured motor speeds were 1193.4 rpm, 1167.8 rpm, 1143.6 rpm, 1120.4 rpm, 1097.9 rpm, 1075.7 rpm, 1053.7 rpm, 1031.6 rpm, and 1009.3 rpm, respectively. Using the least squares method to fit these nine sets of data, the approximate functional relationship between the torque winding voltage and the motor speed was obtained as follows:

[0043] n = 3.685U T +376.6,1000 <n≤1200 (2)

[0044] Where n is the motor speed, u T For the torque winding voltage, u S-R This is the voltage of the speed regulating winding.

[0045] Based on the above functional relationship, variable voltage speed regulation of the magnetic levitation asynchronous motor can be achieved within the range of 1000rpm to 1500rpm.

[0046] Establish the inductance matrix equation for a three-winding magnetic levitation motor:

[0047]

[0048] Where Ψ represents magnetic flux linkage, i represents current, L represents self-inductance, M represents mutual inductance, 1 represents stator, 2 represents rotor, T represents torque winding, SR represents speed regulating winding, and S represents levitation winding. Example: Ψ T1 Ψ represents the stator flux linkage of the torque winding. S-R2 L represents the rotor flux linkage of the speed regulating winding. T1 M represents the stator self-inductance of the torque winding. T1S-R1 This represents the mutual inductance between the torque winding stator and the torque winding rotor.

[0049] Establish the rotor voltage equation for the torque winding:

[0050]

[0051] Among them, u T2d and u T2q These are the components of the rotor voltage of the torque winding on the d and q axes, respectively. T2d and i T2q These are the components of the rotor current of the torque winding on the d and q axes, respectively. T2d and Ψ T2q These are the components of the rotor flux linkage of the torque winding on the d and q axes, respectively, R r For rotor resistance, ω r ω is the rotor angular velocity. T denoted as angular velocity of the torque winding, and p is the differential symbol.

[0052] Establish the rotor voltage equation for the speed regulating winding:

[0053]

[0054] Among them, u S-R2d and u S-R2q These are the components of the rotor voltage of the speed regulating winding on the d and q axes, respectively. S-R2d and i S-R2q These are the components of the rotor current of the speed regulating winding on the d and q axes, respectively. S-R2d and ΨS-R2q These are the components of the rotor flux linkage of the speed regulating winding on the d and q axes, respectively, ω S-R This refers to the angular velocity of the speed-regulating winding.

[0055] The rotor magnetic field orientation method is adopted, namely

[0056]

[0057]

[0058] Substituting equations (3), (6), and (7) into equations (4) and (5), we obtain:

[0059]

[0060]

[0061] Further simplification yields

[0062]

[0063] Construct the levitation force equation for a three-winding magnetic levitation motor:

[0064]

[0065] Among them, f xT and f yT These are the components of the levitation force generated by the torque winding on the x and y axes, respectively, f. xS-R and f yS-R These are the components of the levitation force generated by the speed-regulating winding on the x and y axes, respectively, i S1d and i S1q These are the components of the stator current of the levitation winding on the d and q axes, respectively, i T1d and i T1q These are the components of the stator current of the torque winding on the d and q axes, respectively, i S-R1d and i S-R1q These represent the components of the stator current of the speed regulating winding on the d and q axes, respectively, and K... mT and K mS-R These are two constants.

[0066] According to equations (10) and (11), by adjusting i T1d and i S-R1d Maintaining the magnetic flux Ψ of the two rotors T2 and Ψ S-R2 Unchanged, by adjusting i S1d and i S1q This allows for simultaneous control of the torque and levitation force of a three-winding magnetic levitation motor.

[0067] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made based on the principles and design ideas disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A three-winding, three-phase variable-voltage speed-regulating magnetic levitation asynchronous motor, characterized in that: The components, arranged radially from the outside to the inside, are a motor stator core, a rotor core, and a shaft. The stator slots of the motor stator core are equipped with torque windings, speed-regulating windings, and levitation windings. The rotor slots of the rotor core are connected by rotor coils with a fixed pole structure. An air gap exists between the stator core and the rotor core. The stator slots are divided into an inner layer and an outer layer radially from the inside out. A set of 2-pole levitation windings is embedded in the inner layer of the stator slots, filling all 36 stator slots. A set of 1-pole torque windings and a set of 3-pole speed regulating windings are embedded in the outer layer of the stator slots. The torque winding and the speed regulating winding are distributed alternately in the stator slots, each occupying 18 stator slots; With the rotor shaft center as the central symmetry point, the four centrally symmetrical rotor slots are divided into a group, for a total of 6 groups. A set of rotor coils with fixed pole structure is embedded in each group of rotor slots. The rotor coil comprises 8 segments, of which 4 segments are placed axially and the other 4 segments are placed radially, and are connected sequentially in the order of "axial-radial-axial-radial" to form a closed loop; When the rated current is applied to the torque winding, a single-pole rotating magnetic field is generated in the inner layer of the stator. When voltage is applied to the levitation winding, a two-pair rotating magnetic field is generated in the outer layer of the stator; when voltage is applied to the speed regulating winding, a three-pair magnetic field is generated in the inner layer of the stator. In a 1-pole rotating magnetic field and a 3-pole rotating magnetic field, the induced currents at locations 180° apart in spatial distribution have the same direction, while in a 2-pole rotating magnetic field, the induced currents at locations 180° apart in spatial distribution have opposite directions. Therefore, the induced currents generated by the 1-pole and 3-pole rotating magnetic fields can form a loop within the rotor coil of the fixed-pole structure, while the induced currents generated by the 2-pole rotating magnetic field cannot form a loop. Thus, the fixed-pole rotor can only sense the torque winding of the 1-pole structure and the speed-regulating winding of the 3-pole structure, and cannot sense the levitation winding of the 2-pole structure, thus suppressing the influence of the induced current of the levitation winding on torque and speed. Simultaneous control of motor torque and levitation force is achieved by directly changing the voltage of the torque winding, speed regulating winding, and levitation force winding.

2. The three-winding, three-phase variable-voltage speed-regulating magnetic levitation asynchronous motor according to claim 1, characterized in that: The stator core is made of stacked silicon steel sheets and adopts an open slot structure with 36 stator slots.

3. The three-winding, three-phase variable-voltage speed-regulating magnetic levitation asynchronous motor according to claim 1, characterized in that: The rotor core is made of stacked silicon steel sheets and has an open slot structure with 24 rotor slots.

4. A three-winding, three-phase variable-voltage speed-regulating magnetic levitation asynchronous motor according to claim 1 or 2, characterized in that: A voltage is applied to the torque winding, generating a single-pole rotating magnetic field on the outside of the stator. The axial guide bars in the rotor slots cut the rotating magnetic field relative to each other, and at the same time, an induced current is generated in the closed rotor guide bars. The induced current in the rotor generates a Lorentz force in the rotating magnetic field, which in turn generates an electromagnetic torque acting on the rotor guide bars, driving the motor rotor to rotate.

5. A three-winding, three-phase variable-voltage speed-regulating magnetic levitation asynchronous motor according to claim 4, characterized in that: Applying voltage to the speed regulating winding generates a three-pole rotating magnetic field on the outside of the stator, producing electromagnetic torque.

6. A three-winding, three-phase variable-voltage speed-regulating magnetic levitation asynchronous motor according to claim 4, characterized in that: When a voltage is applied to the levitation winding, a two-pole rotating magnetic field is generated inside the stator. This magnetic field interacts with the magnetic fields of the torque winding and the speed regulating winding, generating two Maxwell unbalanced magnetic pulls. Their superposition forms the levitation force acting on the rotor.

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