A magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor and its working method

Abstract

The present invention discloses a magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor and a working method thereof. The stator of the present invention is provided with six stator cores evenly distributed along the circumferential direction, and two rectangular slots are provided on the inner arc surface of each stator core. Each stator core is provided with an integrally formed pole shoe at a position close to the inner arc surface on both sides, and the pole shoe is in a pointed shape; the rotor is provided with four rotor cores evenly distributed along the circumferential direction, and a permanent magnet is provided between each two adjacent rotor cores, and two arc slots are provided on the outer arc surface of each rotor core. The cross section of the permanent magnet is trapezoidal, and the outer arc surface of each rotor core and the outer arc surface of each permanent magnet form a cylindrical surface. The magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor with a specific structure proposed by the present invention can realize the work of transporting liquids, and the permanent magnet synchronous motor with a specific structure used in the present invention has less magnetic leakage phenomenon.

Description

Technical Field

[0001] The present invention belongs to the technical field of permanent magnet synchronous motors, and in particular relates to a magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor and a working method thereof. Background Art

[0002] Magnetic levitation centrifugal pumps use magnetic levitation technology to suspend the rotating parts in a contactless state. Compared with the mechanical bearings of traditional centrifugal pumps, this design eliminates mechanical friction, reduces energy loss, and improves efficiency. In addition, since magnetic levitation centrifugal pumps do not require mechanical seals, the risk of leakage is reduced. This is especially true when handling toxic, corrosive, or expensive liquids, preventing damage to the environment and equipment caused by liquid leakage. Existing magnetic levitation centrifugal pumps are mainly driven by brushless DC motors. However, when the load is too large or the rated speed is exceeded for a long time, the motor life is easily shortened. Permanent magnet synchronous motors have advantages such as high power density and good speed regulation performance. They are used to drive magnetic levitation centrifugal pumps. Compared with brushless DC motors, permanent magnet synchronous motors eliminate the losses in traditional mechanical transmission and have a long life. However, existing permanent magnet synchronous motors have a relatively serious magnetic leakage phenomenon. The occurrence of magnetic leakage can reduce the output torque of the magnetic levitation centrifugal pump, reduce load capacity, reduce output efficiency, and increase losses. Magnetic leakage can also cause motor overheating and shorten the service life. Therefore, it is necessary to design a magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor with less magnetic leakage. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor and a working method thereof.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention discloses a magnetic suspension centrifugal pump driven by a permanent magnet synchronous motor, comprising a stator, a pump body and a rotor.

[0006] The stator includes a base, a winding coil group, a stator core, and a fixed base. The fixed base is coaxial with the base and spaced apart from each other. Six stator cores evenly distributed along the circumference are fixed to the base. Six through slots evenly distributed along the circumference are provided on the inner arc surface of the fixed base, and each stator core is embedded in a through slot at the end away from the base. A winding coil group is wound around each stator core between the fixed base and the base, and the winding coil group consists of winding coil 1 and winding coil 2. Two symmetrically arranged rectangular slots are provided on the inner arc surface of each stator core. Each stator core is provided with an integrally formed pole shoe near the inner arc surface on both sides, and the pole shoe is pointed. Winding coil 1 is wound around the end of the stator core near the base and is a driving coil. Winding coil 2 is wound around the end of the stator core near the rotor and is a suspension coil. The winding coil group on each of the two oppositely arranged stator cores constitutes a winding group.

[0007] The pump body includes a casing, a rotor seat, an impeller, a flange, an end cover, and a top seat. The fixed seat and base are both fixed in the casing; the top seat is fixed to the fixed seat, sealing the stator in the casing, and the top seat is provided with an output flow channel that communicates with the inner cavity of the top seat; the rotor seat is fixed in the top seat and is located at the center of the fixed seat; the end cover is fixed to the top seat, and the input flow channel opened in the middle communicates with the inner cavity of the top seat, and the flange is fixed to the end cover.

[0008] The rotor is placed in the rotor base, and includes a permanent magnet, a rotor core and a magnetic disk; the magnetic disk is arranged in the rotor base, and four rotor cores arranged equidistantly along the circumferential direction are fixed on the magnetic disk, and a permanent magnet is provided between each two adjacent rotor cores; two symmetrically arranged arc grooves are provided on the outer arc surface of each rotor core, and grooves are provided on the two side rectangular surfaces of each rotor core, and notches are provided at the outer positions of the two side rectangular surfaces of each permanent magnet, and the two sides of each permanent magnet are embedded in the adjacent grooves on the two adjacent rotor cores and fixed to the corresponding grooves; the impeller is arranged in the inner cavity of the top seat and is fixed to the end of each rotor core away from the magnetic disk; wherein the cross-section of the permanent magnet is trapezoidal, and the outer arc surface of each rotor core and the outer arc surface of each permanent magnet form a cylindrical surface.

[0009] Preferably, an isolation pad is fixed on the stator core between the first winding coil and the second winding coil.

[0010] Preferably, the rotor core and the permanent magnet are further fixed by epoxy resin sealing.

[0011] Preferably, a triangular hole is opened at the center of the top surface of the rotor core.

[0012] Preferably, three Hall angle sensors evenly distributed along the circumference and three eddy current displacement sensors evenly distributed along the circumference are fixed in the housing.

[0013] Preferably, the process of selecting the stator core structure is as follows: setting a value range of the stator core cross-sectional area, the pole shoe slope, and the pole shoe length, and selecting multiple nodes within the value range of the stator core cross-sectional area, the pole shoe slope, and the pole shoe length; combining the nodes selected within the value range of the stator core cross-sectional area, the pole shoe slope, and the pole shoe length using an orthogonal test method to obtain each experimental combination one; using each experimental combination one to perform a simulation experiment using the electromagnetic simulation software Maxwell to obtain a magnetic induction intensity cloud map at the stator core, a magnetic line distribution cloud map at the pole shoe, and an air gap magnetic flux waveform for each experimental combination under a preset maximum power; and then selecting an experimental combination one in which the magnetic induction intensity of the stator core does not exceed the magnetic flux saturation value of the stator core, and the air gap harmonic distortion rate and the magnetic leakage phenomenon at the pole shoe are within the preset selection range one.

[0014] Preferably, the size selection process of the permanent magnet is as follows: assuming that the inner width of the permanent magnet is L1, and the outer width at the slot position is L2, the slot size and the cross-sectional area of ​​the permanent magnet remain unchanged, setting the ratio range of L1 and L2, and selecting n ratios on average within the ratio range, and n≥5, using the selected n ratios to perform simulation experiments through the electromagnetic simulation software Maxwell to obtain the cogging torque and electromagnetic torque simulation results under the n ratios, and then selecting the ratio corresponding to the optimal simulation result among the n simulation results, and selecting m ratios on average within the range between two ratios adjacent to the ratio, and m>n, using the selected m ratios to perform simulation experiments through the electromagnetic simulation software Maxwell to obtain the cogging torque and electromagnetic torque simulation results under the m ratios, and then selecting the ratio of the optimal simulation result among the m simulation results, which is the optimal ratio of L1 to L2.

[0015] Preferably, the size selection process of the circular arc slot and the rectangular slot is as follows: setting the value ranges of the circular arc slot diameter R, the aspect ratio of the rectangular slot, the angle A between the two circular arc slots on the rotor core, and the angle between the two rectangular slots on the stator core, and selecting multiple nodes within the value ranges of the circular arc slot diameter R, the aspect ratio of the rectangular slot, the angle A between the two circular arc slots on the rotor core, and the angle between the two rectangular slots on the stator core, and using the orthogonal test method to combine the multiple nodes selected within the value ranges of the circular arc slot diameter R, the aspect ratio of the rectangular slot, the angle A between the two circular arc slots on the rotor core, and the angle between the two rectangular slots on the stator core to obtain each experimental combination two, using each experimental combination two to perform simulation experiments using the electromagnetic simulation software Maxwell to obtain the electromagnetic torque data graph and the magnetic circuit distribution cloud graph under each experimental combination two, and selecting the experimental combination two whose electromagnetic torque mean, torque fluctuation, and permanent magnet leakage phenomenon are within the preset selection range two.

[0016] The present invention provides a working method of a magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor, as follows:

[0017] The winding coils 1 of the three groups of windings are connected to the U phase, V phase and W phase of a three-phase AC power supply respectively, and the winding coils 2 of the three groups of windings are connected to the U phase, V phase and W phase of another three-phase AC power supply respectively, the output flow channel of the top seat is fixed and connected to the delivery pipe, and the input flow channel of the end cover is immersed below the liquid level of the liquid to be transported; each winding coil 1 and each winding coil 2 are energized, and each winding coil 2 generates an excitation suspension magnetic field, which interacts with the magnetic field of the magnetic disk, so that the magnetic disk drives each permanent magnet, each rotor core and impeller to suspend, and at the same time, each winding coil 1 generates an excitation drive magnetic field, which interacts with the magnetic field of each permanent magnet, drives each permanent magnet to drive the magnetic disk, impeller and each rotor core to rotate, and the rotating impeller introduces the liquid to be transported from the input flow channel of the end cover into the impeller, and transports the liquid to be transported from the output flow channel of the top seat to the delivery pipe;

[0018] Among them, the pole shoes provided on the stator core increase the air gap, thereby reducing the harmonic distortion rate of the air gap magnetic flux waveform, and improving the stability of the magnetic levitation centrifugal pump during operation. In addition, due to the pointed shape of the pole shoes, the cross-sectional area of ​​the pole shoes is reduced, thereby increasing the magnetic resistance of the pole shoes and reducing the magnetic flux passing through. At the same time, the rectangular slots opened on the stator core adjust the magnetic circuit distribution, thereby reducing the phenomenon that the magnetic lines of force generated by the winding coil group do not pass through the air gap but close themselves at the pole shoes. In addition, the cross-sectional shape of the permanent magnet is trapezoidal, and no rotor core is provided between the outer arc surface of the permanent magnet and the air gap, so that the magnetic lines of force generated at the outer arc surface of the permanent magnet directly pass through the air gap to form a closed magnetic circuit with the magnetic lines of force generated by the winding coil group, and the closed path of the magnetic lines of force is shortened. The arc slots and the rectangular slots work together to reduce the phenomenon that the permanent magnet generates a closed magnetic circuit between the adjacent rotor core and the opposite stator core.

[0019] The present invention has the following beneficial effects:

[0020] 1. The magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor with a specific structure proposed in the present invention can realize the liquid transportation work, and the permanent magnet synchronous motor with a specific structure used in the present invention is improved on the basis of the structure of the traditional permanent magnet synchronous motor, so that the leakage magnetic phenomenon is reduced, the output torque, load capacity and output efficiency are increased, the loss is reduced, and the service life is increased. Specifically, the present invention achieves optimized adjustment of the entire magnetic circuit distribution through the arc grooves opened on each stator core and the rectangular grooves opened on each rotor core, thereby reducing magnetic leakage, improving the utilization rate of permanent magnets, and thus improving the electromagnetic torque, thereby improving the output torque and load capacity, improving output efficiency, reducing losses, and increasing service life. It also weakens the cogging torque between the stator and the rotor, improves the stability of the rotor operation, and thus improves the accuracy of the control of the magnetic levitation centrifugal pump; further, the present invention uses trapezoidal permanent magnets to replace traditional rectangular permanent magnets, and makes the outer arc surface of the trapezoidal permanent magnet directly contact the air gap, shortening the closed path of the magnetic line of force, reducing the loss of the magnetic line of force, further improving the utilization rate of the permanent magnet, improving the electromagnetic torque, and improving the output torque and load capacity. At the same time, the use of trapezoidal permanent magnets also optimizes the magnetic circuit distribution, avoiding the occurrence of fluctuations caused by the local magnetic induction intensity of the rotor core far exceeding the magnetic density saturation value of the material.

[0021] 2. The present invention increases the air gap between the rotor and the stator by arranging pole shoes on each stator core, thereby reducing the harmonic distortion rate of the air gap magnetic flux waveform, thereby improving the stability of the magnetic levitation centrifugal pump during operation. The pole shoes in the present invention are shaped into pointed corners, which reduces the cross-sectional area of ​​the pole shoes, thereby increasing the magnetic resistance of the pole shoes and reducing the magnetic flux passing through. At the same time, due to the adjustment of the magnetic circuit distribution by the rectangular slots on the corresponding stator cores, the magnetic lines of force generated by the coil pass through the air gap and close with the magnetic lines of force generated by the permanent magnet or the magnetic disk, and the phenomenon that the magnetic lines of force generated by the coil do not pass through the air gap but close themselves at the pole shoes is reduced. While improving the operating stability of the magnetic levitation centrifugal pump, the leakage magnetic phenomenon is further reduced.

[0022] 3. In the present invention, the rotor core and the permanent magnet are fixed by inlaying, and a glue-filling packaging process is adopted, which increases the overall mechanical strength of the rotor, effectively reduces the vibration generated during operation, avoids the occurrence of resonance, and reduces the noise level. In addition, the present invention uses epoxy resin with high thermal conductivity, which improves the heat dissipation capacity of the rotor after glue sealing, further extending the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a sectional view of the three-dimensional structure of the present invention;

[0024] Figure 2 Schematic diagram of the structure of the stator and rotor in the present invention;

[0025] Figure 3 Schematic diagram of the structure of the rotor base, stator core and rotor in the present invention;

[0026] Figure 4 Schematic diagram of the structure of the rotor and impeller in the present invention;

[0027] Figure 5 Schematic diagram of the magnetization direction of the permanent magnet in the present invention;

[0028] Figure 6 Schematic diagram of the structure of the permanent magnet in the present invention;

[0029] Figure 7 Schematic diagram of the structure of the rotor core in the present invention;

[0030] Figure 8 It is a structural diagram of the driving structure in the conventional structure;

[0031] Figure 9 Schematic diagram of the driving structure of the present invention;

[0032] Figure 10 A comparison chart of the cogging torque data of the present invention and the conventional structure;

[0033] Figure 11 This is a comparison chart of electromagnetic torque data between the present invention and conventional structures. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings.

[0035] like Figure 1 、 Figure 2 、 Figure 3 and Figure 4As shown, the present invention is a magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor, comprising a stator, a pump body and a rotor. The stator comprises a base 2, a winding coil group, a stator core 8 and a fixed seat 9. The fixed seat 9 is coaxial with the base 2 and is spaced apart from each other; six stator cores 8 evenly distributed along the circumference are fixed on the base 2; six through slots evenly distributed along the circumference are provided on the inner arc surface of the fixed seat 9, and each stator core 8 is embedded in a through slot at one end away from the base 2; a winding coil group is wound around each stator core 8 between the fixed seat 9 and the base 2, and the winding coil group consists of a winding coil 1 3 and a winding coil 2 4; two symmetrically arranged rectangular slots 801 are provided on the inner arc surface of each stator core 8, and an integrally formed pole shoe 802 is provided on both sides of each stator core 8 near the inner arc surface, and the pole shoe 802 is pointed; wherein, the winding coil 1 3 is wound around the stator core 8 close to the inner arc surface. One end near the base 2 is the drive coil, and the winding coil 2 4 is wound on the end of the stator core 8 near the rotor, which is a suspension coil. The winding coil group on each of the two oppositely arranged stator cores 8 is a winding group; the pole shoe 802 is used to increase the air gap, reduce the harmonic distortion rate of the air gap magnetic flux waveform, and improve the stability of the magnetic levitation centrifugal pump during operation. The pole shoe 802 is set to a pointed shape to reduce the cross-sectional area of ​​the pole shoe 802, increase the magnetic resistance of the pole shoe 802, and reduce the magnetic flux passing through the pole shoe 802. In addition, the rectangular slot 801 is used to adjust the magnetic circuit distribution, reduce the phenomenon that the magnetic lines of force generated by the winding coil group on the corresponding stator core 8 do not pass through the air gap but pass through the pole shoe and close themselves, and reduce the leakage magnetic phenomenon at the pole shoe.

[0036] The pump body includes a casing 1, a rotor seat 7, an impeller 12, a flange 13, an end cover 14, and a top seat 15. The fixed seat 9 and base 2 are both fixed within the casing 1; the top seat 15 is fixed to the fixed seat 9, sealing the stator within the casing 1. The top seat 15 has an output flow channel that communicates with the inner cavity of the top seat 15; the rotor seat 7 is fixed within the top seat 15 and is located at the center of the fixed seat 9; the end cover 14 is fixed to the top seat 15, and the input flow channel opened in the middle communicates with the inner cavity of the top seat 15. The flange 13 is fixed to the end cover 14.

[0037] The rotor is placed in the rotor seat 7, and includes a permanent magnet 5, a rotor core 6 and a magnetic disk 11; the magnetic disk 11 is arranged in the rotor seat 7, and four rotor cores 6 arranged equidistantly along the circumferential direction are fixed on the magnetic disk 11, and a permanent magnet 5 is arranged between each two adjacent rotor cores 6; two symmetrically arranged arc grooves 602 are provided on the outer arc surface of each rotor core 6, and grooves are provided on the two side rectangular surfaces of each rotor core 6, and notches are provided on the outer positions of the two side rectangular surfaces of each permanent magnet 5, and the two sides of each permanent magnet 5 are embedded in the adjacent grooves on the two adjacent rotor cores 6 and fixed to the corresponding grooves. The impeller 12 is arranged in the inner cavity of the top seat 15, and is fixed to the end of each rotor core 6 away from the magnetic disk 11. Among them, the cross section of the permanent magnet 5 is trapezoidal, and the outer arc surface of each rotor core 6 and the outer arc surface of each permanent magnet 5 form a cylindrical surface. The magnetization direction of the permanent magnet 5 is tangential to the outer arc surface, such as Figure 5 As shown; compared with conventional rectangular permanent magnets with the same cross-sectional area, all the magnetic lines of force generated by the outer side surface of the rectangular permanent magnet facing away from the rotation center need to pass through the rotor core, and then pass through the air gap to form a closed magnetic circuit with the magnetic lines of force generated by the coil, while the rotor core 6 is not provided between the outer arc surface of the trapezoidal permanent magnet and the air gap, so that the magnetic lines of force generated by the outer arc surface of the trapezoidal permanent magnet do not pass through the rotor core 6 but directly pass through the air gap to form a closed magnetic circuit with the magnetic lines of force generated by the winding coil group, shortening the closed path of the magnetic lines of force, reducing losses, and improving the utilization rate of the permanent magnet. At the same time, the magnetic circuit distribution is optimized, avoiding the occurrence of fluctuations caused by the local magnetic induction intensity of the rotor core far exceeding the magnetic density saturation value of the material; in addition, the arc groove 602 and the rectangular groove 801 work together to adjust the distribution of the entire magnetic circuit, reducing the phenomenon of the permanent magnet generating a closed magnetic circuit in the adjacent rotor core and the opposite stator core 8, and further reducing the leakage magnetic phenomenon.

[0038] As a preferred embodiment, an isolation pad 10 is fixed on the stator core 8 between the winding coil 1 3 and the winding coil 2 4 . The isolation pad 10 is used to isolate the winding coil 1 3 from the winding coil 2 4 .

[0039] As a preferred embodiment, the rotor core 6 and the permanent magnet 5 are also fixed by epoxy resin sealing, which increases the overall mechanical strength of the rotor, effectively reduces the vibration generated during operation, avoids the occurrence of resonance, and reduces the noise level. In addition, epoxy resin is non-toxic and has high thermal conductivity, which improves the heat dissipation capacity of the rotor after sealing and extends the service life of the magnetic levitation pump.

[0040] As a preferred embodiment, a triangular hole 601 is opened at the center of the top surface of the rotor core 6. The triangular hole 601 is used to position the rotor core 6 when fixing the rotor core 6.

[0041] As a preferred embodiment, three Hall angle sensors and three eddy current displacement sensors evenly distributed along the circumference are fixed in the shell 1. The Hall angle sensor is used to detect the rotational speed of the rotor, and the eddy current displacement sensor is used to detect the radial displacement of the rotor. The stator current is then adjusted according to the rotational speed and radial displacement of the rotor to maintain a stable suspension state of the rotor.

[0042] As a preferred embodiment, when the operating power is increased (the coil current is increased), the magnetic induction intensity inside the stator core 8 will increase accordingly. When the magnetic induction intensity inside the stator core 8 exceeds the magnetic flux saturation value of the stator core 8, the magnetic resistance of the stator core 8 will increase rapidly, thereby increasing power consumption. The size of the cross-sectional area of ​​the stator core 8 will directly affect the size of the magnetic flux saturation value of the stator core 8, thereby affecting the size of the magnetic resistance of the stator core 8. Therefore, it is necessary to select the structure of the stator core 8. At the same time, when the pole shoe is too long, the magnetic lines of force of the permanent magnet will close automatically through the pole shoe, thereby causing magnetic leakage and reducing the working efficiency of the magnetic levitation centrifugal pump. Therefore, when selecting the structure of the stator core 8, attention should also be paid to the shape and size of the pole shoe 802. The selection process of the stator core 8 structure is: setting the cross-sectional area of ​​the stator core 8, The range of values ​​of the slope of the pole shoe 802 and the length of the pole shoe 802 is selected, and multiple nodes are selected within the range of values ​​of the cross-sectional area of ​​the stator core 8, the slope of the pole shoe 802 and the length of the pole shoe 802. The orthogonal test method is used to combine the nodes selected within the range of values ​​of the cross-sectional area of ​​the stator core 8, the slope of the pole shoe 802 and the length of the pole shoe 802 to obtain each experimental combination one. The electromagnetic simulation software Maxwell is used to perform simulation experiments to obtain the magnetic induction intensity cloud map at the stator core 8, the magnetic line distribution cloud map at the pole shoe 802 and the air gap magnetic flux waveform of each experimental combination under maximum power. Then, an experimental combination one is selected in which the magnetic induction intensity of the stator core 8 does not exceed the magnetic flux saturation value of the stator core 8, and the leakage magnetic phenomenon at the pole shoe 802 and the air gap harmonic distortion rate are within the preset selection range one.

[0043] As a preferred embodiment, the magnetic field density and magnetic field distribution of the permanent magnet are related to the shape of the permanent magnet. In order to have a better permanent magnet magnetic field distribution, the size of the permanent magnet 5 needs to be selected. The size selection process of the permanent magnet 5 is as follows: Figure 6As shown, the inner width of the permanent magnet 5 is L1, the outer width at the slot position is L2, the slot size and the cross-sectional area of ​​the permanent magnet 5 remain unchanged, set the ratio range of L1 to L2, select n ratios on average within the ratio range, and n ≥ 5, use the selected n ratios to perform simulation experiments through the electromagnetic simulation software Maxwell, obtain the cogging torque and electromagnetic torque simulation results under n ratios, then select the ratio corresponding to the optimal simulation result from the n simulation results, and select m ratios on average within the range between the two ratios adjacent to the ratio, and m> n, use the selected m ratios to perform simulation experiments through the electromagnetic simulation software Maxwell, A simulation experiment is performed using Maxwell software to obtain simulation results of the cogging torque and electromagnetic torque under m ratios. Then, the ratio of the optimal simulation result among the m simulation results is selected, which is the optimal ratio of L1 to L2. In addition, before selecting the size of the permanent magnet 5, under the premise of ensuring the fixing strength of the permanent magnet 5 and the two adjacent rotor cores 6, the width L3 of the slot is reduced as much as possible to increase the contact area between the outer arc surface of the permanent magnet and the air gap, reduce the number of magnetic lines of force generated at the outer position of the permanent magnet passing through the rotor core 6, and further improve the utilization rate of the permanent magnet. In this embodiment, the ratio of L1 to L2 is set in the range of 1.1 to 1.5.

[0044] As a preferred embodiment, the size selection process of the arc groove 602 and the rectangular groove 801 is as follows: Figure 7 As shown, the value ranges of the diameter R of the arc groove 602, the aspect ratio of the rectangular groove 801, the angle A between the two arc grooves 602 on the rotor core 6 (the central angle on the circumference of the circle passing through the two arc grooves 602 and with the rotor base 7 as the center), and the angle between the two rectangular grooves 801 on the stator core 8 (the central angle on the circumference of the circle passing through the two rectangular grooves 801 and with the rotor base 7 as the center) are set, and multiple nodes are selected within the value ranges of the diameter R of the arc groove 602, the aspect ratio of the rectangular groove 801, the angle A between the two arc grooves 602 on the rotor core 6, and the angle between the two rectangular grooves 801 on the stator core 8. The orthogonal test is used to determine the value range of the diameter R of the arc groove 602, the aspect ratio of the rectangular groove 801, the angle A between the two arc grooves 602 on the rotor core 6, and the angle The experimental method combines multiple nodes selected within the value range of the arc slot 602 diameter R, the aspect ratio of the rectangular slot 801, the angle A between the two arc slots 602 on the rotor core 6, and the angle between the two rectangular slots 801 on the stator core 8 to obtain each experimental combination two. Each experimental combination two is used to perform simulation experiments using the electromagnetic simulation software Maxwell to obtain the electromagnetic torque data graph and magnetic circuit distribution cloud graph under each experimental combination two. The experimental combination two whose electromagnetic torque mean value, torque fluctuation (the difference between the maximum electromagnetic torque and the minimum electromagnetic torque) and permanent magnet leakage phenomenon are within the preset selection range two is selected.

[0045] The present invention provides a working method of a magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor, as follows:

[0046] The winding coils 1 (3) of the three winding groups are connected to the U phase, V phase and W phase of a three-phase AC power supply respectively, and the winding coils 2 (4) of the three winding groups are connected to the U phase, V phase and W phase of another three-phase AC power supply respectively. The output flow channel of the top seat 15 is fixed and connected to the delivery pipe, and the input flow channel of the end cover 14 is immersed below the liquid level to be delivered; each winding coil 1 (3) and each winding coil 2 (4) are energized, and each winding coil 2 (4) generates an excitation suspension magnetic field, which mainly interacts with the magnetic field of the disk 11. The magnetic disk 11 drives each permanent magnet 5, each rotor core 6 and the impeller 12 to suspend, and at the same time each winding coil 3 generates an excitation driving magnetic field. The excitation driving magnetic field mainly interacts with the magnetic field of each permanent magnet 5, driving each permanent magnet 5 to drive the magnetic disk 11, the impeller 12 and each rotor core 6 to rotate. The rotating impeller 12 introduces the liquid to be transported from the input flow channel of the end cover 14 into the impeller 12, and transports the liquid to be transported from the output flow channel of the top seat 15 to the delivery pipe, thereby realizing the liquid transportation work.

[0047] Among them, the pole shoe 802 provided on the stator core 8 increases the air gap, thereby reducing the harmonic distortion rate of the air gap magnetic flux waveform, and improving the stability of the magnetic levitation centrifugal pump during operation. In addition, since the shape of the pole shoe 802 is pointed, the cross-sectional area of ​​the pole shoe 802 is reduced, thereby increasing the magnetic resistance of the pole shoe 802 and reducing the magnetic flux passing through. At the same time, the rectangular slot 80 opened on the stator core 8 adjusts the magnetic circuit distribution, so that the magnetic lines of force generated by the winding coil group pass through the air gap and close with the magnetic lines of force generated by the permanent magnet or disk, and the phenomenon that the magnetic lines of force generated by the winding coil group do not pass through the air gap but close themselves at the pole shoe is reduced, thereby reducing the leakage magnetic phenomenon. In addition, the cross-sectional area of ​​the permanent magnet 5 is The shape is trapezoidal, and the rotor core 6 is not arranged between the outer arc surface of the permanent magnet 5 and the air gap, so that the magnetic lines of force generated by the outer arc surface of the permanent magnet directly pass through the air gap and form a closed magnetic circuit with the magnetic lines of force generated by the winding coil group. The closed path of the magnetic lines of force is shortened, which reduces the loss and improves the utilization rate of the permanent magnet. At the same time, the magnetic field distribution of the entire magnetic circuit is optimized, avoiding the fluctuation phenomenon caused by the local magnetic induction intensity of the rotor core far exceeding the magnetic density saturation value of the material. The arc groove 602 and the rectangular groove 801 work together to further optimize and adjust the distribution of the entire magnetic circuit, so that the phenomenon of the permanent magnet generating a closed magnetic circuit in the adjacent rotor core and the opposite stator core 8 is reduced, further reducing the leakage magnetic phenomenon.

[0048] In order to demonstrate the optimization effect of the present invention relative to the conventional permanent magnet synchronous motor driven magnetic levitation centrifugal pump (denoted as conventional structure), the driving structure of the present invention (rotor and stator parts) and the driving structure of the conventional structure were simulated using the electromagnetic simulation software Maxwell, wherein, Figure 8 and Figure 9As shown, there are schematic diagrams of the drive structure of the conventional structure and the drive structure of the present invention, respectively. In the conventional structure, the permanent magnet adopts a rectangular permanent magnet, the rotor core adopts an integrated structure, and no slots are provided on the rotor core and the stator core. When the simulation experiment is carried out, the main body size of the drive structure of the present invention is consistent with the main body size of the drive structure of the conventional structure, and the cross-sectional area of ​​the trapezoidal permanent magnet in the present invention is equal to the cross-sectional area of ​​the rectangular permanent magnet. The simulation parameters are consistent, and the simulation experiment results are as follows:

[0049] like Figure 10 As shown in the figure, a comparison chart of the cogging torque data of the present invention and the conventional structure shows that the peak-to-peak value of the cogging torque of the present invention is 231mN·m, and the peak-to-peak value of the cogging torque of the conventional structure is 589mN·m. Compared with the conventional structure, the cogging torque of the present invention is reduced by 61%. The lower cogging torque can not only reduce the fluctuation during operation, but also reduce the control difficulty of the magnetic levitation centrifugal pump and improve the control accuracy of the magnetic levitation centrifugal pump.

[0050] like Figure 11 As shown in the figure, it is a comparison diagram of the electromagnetic torque data of the present invention and the conventional structure. It can be seen that the mean electromagnetic torque of the present invention is 1.16N·m, and the torque fluctuation is 0.37N·m. The mean electromagnetic torque of the conventional structure is 0.98N·m, and the torque fluctuation is 0.59N·m. Compared with the conventional structure, the mean electromagnetic torque of the present invention is increased by 18%, and the torque fluctuation is reduced by 37%. It can be seen that the present invention has obvious effects in improving the torque mean and reducing the torque fluctuation.

Claims

1. A magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor, comprising a stator, a pump body and a rotor, characterized in that: The stator comprises a base, a winding coil group, a stator iron core and a fixed base; the fixed base is coaxial with the base and is set at an upper and lower interval; six stator iron cores evenly distributed along the circumference are fixed on the base; six through slots evenly distributed along the circumference are opened on the inner arc surface of the fixed base, and each stator iron core is embedded in a through slot at one end away from the base; a winding coil group is wound around the position between the fixed base and the base on each stator iron core, and the winding coil group consists of winding coil one and winding coil two; two rectangular slots are symmetrically arranged on the inner arc surface of each stator iron core, and each stator iron core is provided with an integrally formed pole shoe at a position near the inner arc surface on both sides, and the pole shoe is pointed; wherein, winding coil one is wound on one end of the stator iron core close to the base, which is a driving coil, and winding coil two is wound on one end of the stator iron core close to the rotor, which is a suspension coil, and the winding coil group on each of the two relatively arranged stator iron cores is a group of windings; The pump body includes a casing, a rotor seat, an impeller, a flange, an end cover and a top seat; the fixed seat and the base are both fixed in the casing; the top seat is fixed on the fixed seat to seal the stator in the casing, and the top seat is provided with an output flow channel, which is connected to the inner cavity of the top seat; the rotor seat is fixed in the top seat and is located at the center of the fixed seat; the end cover is fixed on the top seat, and the input flow channel opened in the middle is connected to the inner cavity of the top seat, and the flange is fixed to the end cover; The rotor is placed in the rotor seat, including a permanent magnet, a rotor core and a magnetic disk; the magnetic disk is arranged in the rotor seat, and four rotor cores arranged equidistantly along the circumferential direction are fixed on the magnetic disk, and a permanent magnet is provided between each two adjacent rotor cores; two symmetrically arranged arc grooves are provided on the outer arc surface of each rotor core, and grooves are provided on the two side rectangular surfaces of each rotor core, and notches are provided on the outer positions of the two side rectangular surfaces of each permanent magnet, and the two sides of each permanent magnet are embedded in the adjacent grooves on the two adjacent rotor cores and fixed to the corresponding grooves; the impeller is arranged in the inner cavity of the top seat and is fixed to the end of each rotor core away from the magnetic disk; wherein the cross section of the permanent magnet is trapezoidal, and the outer arc surface of each rotor core and the outer arc surface of each permanent magnet form a cylindrical surface; The stator core structure selection process is as follows: setting a value range of the stator core cross-sectional area, the pole shoe slope, and the pole shoe length, and selecting multiple nodes within the value range of the stator core cross-sectional area, the pole shoe slope, and the pole shoe length, using an orthogonal test method to combine the nodes selected within the value range of the stator core cross-sectional area, the pole shoe slope, and the pole shoe length to obtain each experimental combination one, using each experimental combination one to perform a simulation experiment using electromagnetic simulation software Maxwell to obtain a magnetic induction intensity cloud map at the stator core, a magnetic line distribution cloud map at the pole shoe, and an air gap magnetic flux waveform for each experimental combination under a preset maximum power, and then selecting an experimental combination one in which the magnetic induction intensity of the stator core does not exceed the magnetic flux saturation value of the stator core, and the air gap harmonic distortion rate and the magnetic leakage phenomenon at the pole shoe are within the preset selection range one; The size selection process of the permanent magnet is as follows: assuming that the inner width of the permanent magnet is L1 and the outer width at the slot position is L2, the slot size and the cross-sectional area of ​​the permanent magnet remain unchanged, setting the ratio range of L1 to L2, selecting n ratios on average within the ratio range, and n≥5, using the selected n ratios to perform simulation experiments using electromagnetic simulation software Maxwell, obtaining cogging torque and electromagnetic torque simulation results under the n ratios, then selecting the ratio corresponding to the optimal simulation result among the n simulation results, and averaging m ratios within the range between two ratios adjacent to the ratio, and m>n, using the selected m ratios to perform simulation experiments using electromagnetic simulation software Maxwell, obtaining cogging torque and electromagnetic torque simulation results under the m ratios, and then selecting the ratio of the optimal simulation result among the m simulation results, which is the optimal ratio of L1 to L2.

2. A magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor according to claim 1, characterized in that: An isolation pad is fixed on the stator core at a position between the first winding coil and the second winding coil.

3. The magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor according to claim 1, characterized in that: The rotor core and the permanent magnet are also fixed by epoxy resin sealing.

4. The magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor according to claim 1, characterized in that: A triangular hole is provided at the center of the top surface of the rotor core.

5. The magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor according to claim 1, characterized in that: Three Hall angle sensors evenly distributed along the circumference and three eddy current displacement sensors evenly distributed along the circumference are fixed in the shell.

6. The magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor according to claim 1, characterized in that: The size selection process of the circular arc slot and the rectangular slot is as follows: setting the value ranges of the circular arc slot diameter R, the aspect ratio of the rectangular slot, the angle A between the two circular arc slots on the rotor core, and the angle between the two rectangular slots on the stator core, and selecting multiple nodes within the value ranges of the circular arc slot diameter R, the aspect ratio of the rectangular slot, the angle A between the two circular arc slots on the rotor core, and the angle between the two rectangular slots on the stator core, using the orthogonal test method to combine the multiple nodes selected within the value ranges of the circular arc slot diameter R, the aspect ratio of the rectangular slot, the angle A between the two circular arc slots on the rotor core, and the angle between the two rectangular slots on the stator core to obtain each experimental combination two, using each experimental combination two to perform simulation experiments using the electromagnetic simulation software Maxwell to obtain the electromagnetic torque data graph and the magnetic circuit distribution cloud graph under each experimental combination two, and selecting the experimental combination two whose electromagnetic torque mean value, torque fluctuation, and permanent magnet leakage phenomenon are within the preset selection range two.

7. A method for operating a magnetic levitation centrifugal pump driven by a permanent magnet synchronous motor according to any one of claims 1 to 6, characterized in that: The details are as follows: The winding coils 1 of the three groups of windings are connected to the U phase, V phase and W phase of a three-phase AC power supply respectively, and the winding coils 2 of the three groups of windings are connected to the U phase, V phase and W phase of another three-phase AC power supply respectively, the output flow channel of the top seat is fixed and connected to the delivery pipe, and the input flow channel of the end cover is immersed below the liquid level of the liquid to be transported; each winding coil 1 and each winding coil 2 are energized, and each winding coil 2 generates an excitation suspension magnetic field, which interacts with the magnetic field of the magnetic disk, so that the magnetic disk drives each permanent magnet, each rotor core and impeller to suspend, and at the same time, each winding coil 1 generates an excitation drive magnetic field, which interacts with the magnetic field of each permanent magnet, drives each permanent magnet to drive the magnetic disk, impeller and each rotor core to rotate, and the rotating impeller introduces the liquid to be transported from the input flow channel of the end cover into the impeller, and transports the liquid to be transported from the output flow channel of the top seat to the delivery pipe; Among them, the pole shoes provided on the stator core increase the air gap, thereby reducing the harmonic distortion rate of the air gap magnetic flux waveform, and improving the stability of the magnetic levitation centrifugal pump during operation. In addition, due to the pointed shape of the pole shoes, the cross-sectional area of ​​the pole shoes is reduced, thereby increasing the magnetic resistance of the pole shoes and reducing the magnetic flux passing through. At the same time, the rectangular slots opened on the stator core adjust the magnetic circuit distribution, thereby reducing the phenomenon that the magnetic lines of force generated by the winding coil group do not pass through the air gap but close themselves at the pole shoes. In addition, the cross-sectional shape of the permanent magnet is trapezoidal, and no rotor core is provided between the outer arc surface of the permanent magnet and the air gap, so that the magnetic lines of force generated at the outer arc surface of the permanent magnet directly pass through the air gap to form a closed magnetic circuit with the magnetic lines of force generated by the winding coil group, and the closed path of the magnetic lines of force is shortened. The arc slots and the rectangular slots work together to reduce the phenomenon that the permanent magnet generates a closed magnetic circuit between the adjacent rotor core and the opposite stator core.

Images