CN217010471U - Novel rotor structure's built-in PMSM - Google Patents

Abstract

The application provides a built-in permanent magnet synchronous motor with a novel rotor structure, which comprises a machine shell, a stator unit and a rotor unit. The rotor unit comprises a high-coercivity V-shaped excitation structure and a low-coercivity V-shaped excitation structure, and an axial asymmetric excitation structure is arranged at a position deviating from a symmetry axis between the high-coercivity V-shaped excitation structure and the low-coercivity V-shaped excitation structure which correspond from inside to outside along the radial direction. Two layers of V-shaped magnets are arranged in the rotor, motor quadrature axis magnetic flux can flow smoothly, motor quadrature axis inductance is increased, and therefore reluctance torque is increased, and the motor can work effectively even under flux weakening control. In addition, since there is an asymmetric excitation structure between two layers of V-shaped excitation structures, the total torque is increased by using the asymmetrically arranged magnets and shifting the phase of the magnetic force torque by more effectively using the reluctance torque.

Description

Novel rotor structure's built-in PMSM

Technical Field

The utility model relates to the technical field of motor manufacturing, in particular to a built-in permanent magnet synchronous motor with a novel rotor structure.

Background

In recent years, in many Electric Vehicles (EVS), an Interior Permanent Magnet Synchronous Machine (IPMSM) is used for driving. An important feature of IPMSM is the ability to drive efficiently from low to high speeds. In the traditional IPMSM, motor quadrature axis current is mainly controlled in a low-speed range, and weak magnetic control is adopted, wherein negative direct current (applied to a rotor and generating a magnetic field opposite to a permanent magnet magnetic field) is mainly used for flowing to a stator at a high speed, so that a wider speed regulation range is realized. However, copper loss and harmonic iron loss due to the negative d-axis current decrease the efficiency of the field weakening control. Further, the torque may be reduced due to irreversible demagnetization of the permanent magnet.

A variable flux motor is an effective solution to this problem. The motor rotor is provided with two types of permanent magnets, namely a high-coercivity magnet and a low-coercivity magnet. In the low speed range, the high coercive force magnet and the low coercive force magnet are magnetized (magnetized state) in the same axis system, and therefore high torque can be obtained. In order to switch from the low-speed range to the high-speed range, a magnetization pulse current is applied to reverse the magnetization direction of the low-coercive-force magnet, and the magnetization direction between the low-coercive-force magnet and the high-coercive-force magnet is reversed (weak magnetic degeneration), so that the high-speed range can be expanded. At present, the mainstream IPMSM motor controls the magnetization direction of a low coercive force magnet by controlling the magnitude of applied magnetization current, thereby realizing the control of different rotating speeds. However, the low coercive force permanent magnet has different magnetization directions at different rotation speeds, which will cause great rotor loss and even irreversible demagnetization of the permanent magnet.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problems, the utility model provides a novel built-in permanent magnet synchronous motor with an asymmetric rotor structure, which can effectively apply flux weakening control and a variable magnetic leakage function to a motor, and has the advantages of saving the loss of rare earth energy, obtaining high torque, expanding a high speed range and the like on the basis, and the specific technical scheme is as follows:

a built-in permanent magnet synchronous motor with a novel rotor structure comprises a shell, a stator unit and a rotor unit, wherein the shell is circular and extends along the axial direction; the stator unit is arranged in the shell, the inner surface of the stator unit is provided with a stator slot, and a winding which is through along the axial direction is arranged in the stator slot; the rotor unit comprises a high-coercivity V-shaped excitation structure and a low-coercivity V-shaped excitation structure which are arranged in a rotor, wherein the rotor is provided with a first V-shaped groove and a second V-shaped groove which are distributed along the circumferential direction from inside to outside along the radial direction, the first V-shaped groove and the second V-shaped groove penetrate through the rotor along the axial direction, the high-coercivity V-shaped excitation structure comprises the first V-shaped groove and a high-coercivity magnet embedded into the first V-shaped groove in an internal mode, and the low-coercivity V-shaped excitation structure comprises the second V-shaped groove and a low-coercivity magnet embedded into the second V-shaped groove in the internal mode; and symmetrical axes of the high-coercivity V-shaped excitation structure and the low-coercivity V-shaped excitation structure which correspond from inside to outside along the radial direction are arranged in the same radial direction.

Further, the high-coercivity magnet is a neodymium magnet, and the low-coercivity magnet is a bonded neodymium iron boron magnet.

Furthermore, an asymmetric excitation structure along the axial direction is arranged at a position deviating from the symmetry axis between the high-coercivity V-shaped excitation structure and the low-coercivity V-shaped excitation structure which correspond from inside to outside along the radial direction.

Further, the asymmetric excitation structure is made of Sm-Fe-N magnets, penetrates through the rotor unit along the axial direction and is embedded into the rotor.

Furthermore, plugging blocks are arranged at two ends of the V shape of the second V-shaped groove.

Further, the block is made of permalloy.

Further, magnetic barriers are respectively arranged at symmetrical positions on the high-coercivity V-shaped excitation structure.

Further, the magnetic barrier is an air gap magnetic barrier.

The utility model has the beneficial effects that:

1. the utility model relates to a built-in permanent magnet synchronous motor with a novel rotor structure, wherein two layers of V-shaped magnets are arranged in a rotor, the motor quadrature axis magnetic flux can flow smoothly, and the motor quadrature axis inductance is increased. Therefore, the reluctance torque is also increased, and it can operate effectively even under the flux-weakening control.

2. The utility model relates to a built-in permanent magnet synchronous motor with a novel rotor structure, wherein a high-coercivity magnet adopts a neodymium magnet, and a low-coercivity magnet adopts a bonded neodymium iron boron magnet. The bonded neodymium iron boron magnet can not generate irreversible demagnetization due to a demagnetization field. The blocking blocks made of permalloy are arranged at the two tail ends of the V shape of the V-shaped groove, the motor torque is effectively improved under the condition of low speed and heavy load through the high magnetic permeability of the permalloy and the saturation magnetic flux density difference between the permalloy and the steel plate, and the high speed range is expanded under the condition of light load.

3. The built-in permanent magnet synchronous motor with the novel rotor structure has an asymmetric excitation structure between two layers of V-shaped excitation structures, and improves the total torque by more effectively utilizing the reluctance torque and adopting the phase positions of asymmetrically arranged magnets and moving magnetic force torque.

4. According to the built-in permanent magnet synchronous motor with the novel rotor structure, magnetic barriers are respectively arranged at the symmetrical positions on the high-coercivity V-shaped excitation structure and the low-coercivity V-shaped excitation structure, the magnetic line trends of the high-coercivity and low-coercivity magnets at different rotating speeds are restrained, a hysteresis eddy current phenomenon is avoided, and the loss of the rotor is effectively reduced.

Drawings

Fig. 1 is a schematic structural diagram of an internal permanent magnet synchronous motor with a novel rotor structure in an embodiment of the present application;

FIG. 2 is a schematic structural view of a rotor according to an embodiment of the present application, including a first V-shaped groove of the rotor and a second V-shaped groove of the rotor;

FIG. 3 is a schematic diagram of a rotor excitation structure in an embodiment of the present application, where the rotor excitation structure includes a high coercivity V-shaped excitation structure, a low coercivity V-shaped excitation structure, and an asymmetric excitation structure;

FIG. 4 is a graph showing the change in magnetic flux density in the example of the present application;

fig. 5 shows the offset angle of the magnetic pole center of the asymmetric structure in the embodiment of the present application.

Wherein: 1. a housing; 2. a stator unit; 201. a winding; 3. a rotor unit; 301. a magnetic barrier; 4. a first V-shaped groove; 5. a second V-shaped groove; 6. an asymmetric excitation structure; 7. a high coercivity V-shaped excitation structure; 8. a low coercive force V-shaped excitation structure; 9. and (6) a plugging block.

Detailed Description

The embodiments will be described in detail below with reference to the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following examples do not represent all embodiments consistent with the present application, but are merely examples of systems and methods consistent with certain aspects of the present application, as detailed in the claims.

The internal permanent magnet synchronous motor with the novel rotor structure shown in fig. 1 comprises a casing 1, a stator unit 2 and a rotor unit 3, wherein the casing 1 is circular and extends along the axial direction, the stator unit 2 is arranged in the casing 1, a stator groove is formed in the inner surface of the stator unit, and a winding 201 which penetrates through the stator groove along the axial direction is arranged in the stator groove. As shown in fig. 1 and 2, the rotor is provided with a first V-shaped groove 4 and a second V-shaped groove 5 which are uniformly distributed along the circumferential direction from inside to outside along the radial direction, and the first V-shaped groove 4 and the second V-shaped groove 5 penetrate through the rotor along the axial direction.

As shown in fig. 3, the high coercive force V-shaped field structure 7 provided in the rotor unit in the radial direction of the rotor includes a first V-shaped groove 4 and a high coercive force magnet made of a neodymium magnet embedded in the built-in first V-shaped groove, and the low coercive force V-shaped field structure 8 includes a second V-shaped groove 5 and a low coercive force magnet made of a bonded neodymium iron boron magnet embedded in the built-in second V-shaped groove. The V-shaped symmetry axes of the high coercivity V-shaped excitation structure 7 and the low coercivity V-shaped excitation structure 8 corresponding from inside to outside in the radial direction are arranged in the same radial direction, that is, the V-shaped structures of the high coercivity V-shaped excitation structure 7 and the low coercivity V-shaped excitation structure 8 are in a left-right symmetrical form with the dotted line symmetry axis in the radial direction of the rotor as shown in fig. 3.

The permanent magnet synchronous motor related to the technical scheme is a 36-slot 6-pole built-in permanent magnet synchronous motor, and therefore 6 first V- shaped grooves 4 and 6 second V-shaped grooves 5 are arranged in the circumferential direction of the rotor. Fig. 1 is a partial schematic view of the machine, whereby only 2 of each of the first V-shaped grooves 4 and the second V-shaped grooves 5 are shown. The flux linkage of the armature winding turns varies in size from two periods, maximum to minimum, each time the rotor rotates one pole. Wherein the magnetic flux emitted by the magnets mounted in the first V-groove 4 and the second V-groove 5 is linked to the winding 201 through an air gap. The winding 201 is a traditional integral-slot concentrated winding, so that winding and installation are facilitated, and the efficiency of the motor is improved. Although the technical scheme adds the rotor unit 3 compared with the prior art, the output torque and the power density of the motor can be obviously improved because the rotor unit 3 reduces the rotor mass and restrains the rotor magnet wires.

As shown in fig. 3, the dashed lines here represent the symmetry axes of the V-shaped structures of the high coercivity V-shaped field structure 7 and the low coercivity V-shaped field structure 8. An asymmetric excitation structure 6 which is shown in fig. 3 and is arranged along the axial direction of the motor rotor is arranged at a position deviating from the symmetrical axis of the V-shaped excitation structure between the high-coercivity V-shaped excitation structure 7 and the low-coercivity V-shaped excitation structure 8 which correspond from inside to outside along the radial direction of the motor rotor. The asymmetrical excitation structure 6 is made of Sm-Fe-N magnets, and the asymmetrical excitation structure adopts a built-in mounting structure, namely the magnets penetrate through the rotor unit along the axial direction of the motor rotor and are embedded into the rotor.

As shown in fig. 3, the second V-shaped groove 5 is provided at both ends of the V-shape with the blocks 9 made of permalloy, which is an alloy of iron and nickel and has a high magnetic permeability. The high speed range can be extended by utilizing the high permeability of permalloy and the difference in saturation magnetic flux density between permalloy and steel sheet. Since the two ends of the second V-shaped groove 5 are provided with the blocking blocks, an air gap is formed between the blocking blocks and the permanent magnets in the V-shaped groove.

Next, the magnetic flux flow in the low-speed and high-speed regions is described. A high torque is required in a low speed range under heavy load, and thus a large amount of magnetic flux is required to flow from the magnet to the stator. Although part of the magnetic flux flows to the permalloy, most of the magnetic flux flows to the stator, and because the permalloy has a low saturation magnetic flux density, the permalloy functions as a magnetic flux mask. Furthermore, since the motor quadrature magnetic circuit is not blocked and reluctance torque can be utilized, the difference in d-axis and motor quadrature inductance is greater than that of a variable leakage flux motor. On the other hand, field weakening control is used to achieve high speed. The magnetic flux is simply reduced by the field weakening control in the conventional IPMSM. However, most of the magnetic flux leaks into the air gap and flows to the stator. In the proposed model, the magnetic flux of the magnet flows to the permalloy, not to the stator, due to its high permeability. Therefore, the magnetic flux may be short-circuited in the rotor, which may extend a high-speed region.

As shown in fig. 5, an asymmetric excitation structure is built in the right side of the d-axis between the double-layer V-shaped excitation structures of the permanent magnet motor rotor. The permanent magnet material selected for the asymmetric excitation structure has higher coercive force so as to avoid the influence of the change of the air gap magnetic field intensity on the magnetization direction of the permanent magnet due to the change of pulse current during speed regulation. And meanwhile, the permanent magnet has better shape freedom degree and higher high-temperature resistance, and the irreversible demagnetization of the permanent magnet is prevented. The magnetization direction of the basic model of the motor is the same as the direction of the d axis. On the other hand, since the magnets are arranged asymmetrically, the magnetic pole center is located at a position deviated from the d-axis direction in the rotor shown in fig. 5, so that the magnetic torque and the reluctance torque are substantially the same in direction, and the motor reluctance torque is effectively utilized to increase the load torque. The d-axis magnetic flux direction of the V-shaped symmetrical permanent magnet is deviated from the position of alpha degrees, and the magnetic flux lines are in a non-excitation condition, wherein the magnetic pole center is deviated from the magnetic pole center of the rotor symmetrical structure. By properly adjusting the offset angle, the amplitude of the fundamental wave generated by the technical scheme can be equal to that of the conventional symmetrical scheme.

When the center of the magnetic pole of the rotor is deviated, the crossed shaft position of the d shaft and the motor is deviated along with the deviation. When the asymmetric excitation structure is added, the magnetic flux generated by the d-axis current flows through the magnet, so that the magnetic resistance increases and the d-axis inductance Ld decreases. Since the magnetic flux generated by the motor quadrature current does not flow through the magnet, the magnetic resistance decreases, and the motor quadrature inductance Lq becomes large. The reluctance torque generated by the rotor is larger than that of the conventional rotor because the reluctance torque is proportional to the inductance difference between the d-axis and the motor intersecting axis.

In IPMSM, field weakening control is generally employed to reduce induced electromotive force in a high-speed range. The magnetic flux caused by the negative armature current and the magnetic flux from the permanent magnet partially cancel each other. Therefore, the magnetic flux connected to the stator can be reduced, and high speed can be achieved. When only the conventional high coercive force magnet is used, the magnetic flux linked to the stator is reduced due to the negative d-axis current, but since the coercive force is large and the degree of reduction is small, as shown in fig. 4, the high coercive force magnet and the low coercive force magnet are used. Neodymium magnets have a high residual magnetic flux density. Therefore, neodymium magnets are used as high coercive force magnets. However, if a neodymium magnet is used as the low coercive force magnet, irreversible demagnetization occurs under flux weakening control. To solve this problem, a bonded neodymium iron boron magnet is used as the low coercive force magnet as a separate member from the stator yoke. In addition, when the pulse current changes, the magnet wires on the rotor side are changed differently, the magnetic lines of the rotor side are adversely affected, and hysteresis and eddy current loss are caused, so that the magnetic barriers 301 formed by air gaps are respectively arranged at the symmetrical positions on the high-coercivity V-shaped excitation structure, and the rotor loss is effectively reduced by adding the air barriers 301. As shown in fig. 2, symmetrical air gaps 301 are formed on the rotor made of silicon steel sheets to symmetrically separate the first V-shaped grooves 4, so that the original complete V-shaped permanent magnet is separated by the air gap magnetic barrier after the permanent magnet is embedded in the first V-shaped groove 4.

The use of bonded neodymium iron boron magnets as the low coercivity magnet instead of neodymium magnets has two major advantages. First, the bonded ndfeb magnet has a higher resistivity than a neodymium magnet because it is a mixture of a neodymium magnet and a polymer, and eddy current loss can be reduced. Second, since the magnetic flux density of the bonded ndfeb magnet is not higher than that of the neodymium magnet, the magnetic flux connected to the stator is small, the induced electromotive force can be suppressed, and flux weakening and speed extension can be effectively achieved.

As shown in fig. 4, when a demagnetization field occurs, the operating point of the neodymium magnet permanent magnet is from a1 to B1, and the bonded neodymium iron boron magnet is from a2 to B2. Next, when the demagnetizing field is removed, it does not return to a1 since the operating point B1 has exceeded the inflection point. However, it moves to another operating point C1 on the B-H characteristic. In other words, irreversible demagnetization of the permanent magnet is caused. On the other hand, since the operation point B2 does not exceed the inflection point, the operation point returns to a 2; i.e. no irreversible magnetization of the permanent magnet occurs. Therefore, the two circles in the first magnetic layer are not affected by irreversible demagnetization caused by a demagnetization field, and the use of the bonded ndfeb magnet is very effective.

The embodiments of the present application have been described in detail, but the present application is only a preferred embodiment of the present application and should not be construed as limiting the scope of the present application. All equivalent changes and modifications made within the scope of the present application shall fall within the scope of the present application.

Claims (8)

1. The utility model provides a novel rotor structure's built-in PMSM, includes casing (1), stator unit (2) and rotor unit (3), its characterized in that:

the shell (1) is circular and extends along the axial direction;

the stator unit (2) is arranged in the shell (1), a stator groove is formed in the inner surface of the stator unit, and a winding (201) which penetrates through the stator groove along the axial direction is arranged in the stator groove;

the rotor unit (3) comprises a high-coercivity V-shaped excitation structure (7) and a low-coercivity V-shaped excitation structure (8) which are arranged in a rotor, wherein the rotor is provided with a first V-shaped groove (4) and a second V-shaped groove (5) which are distributed along the circumferential direction from inside to outside along the radial direction, the first V-shaped groove (4) and the second V-shaped groove (5) penetrate through the rotor along the axial direction, the high-coercivity V-shaped excitation structure (7) comprises the first V-shaped groove (4) and a high-coercivity magnet embedded into the first V-shaped groove (4) in an internal mode, and the low-coercivity V-shaped excitation structure (8) comprises the second V-shaped groove (5) and a low-coercivity magnet embedded into the second V-shaped groove (5) in the internal mode;

and symmetrical axes of the high-coercivity V-shaped excitation structure (7) and the low-coercivity V-shaped excitation structure (8) which correspond from inside to outside along the radial direction are arranged in the same radial direction.

2. The interior permanent magnet synchronous machine of a new rotor structure of claim 1, wherein: the high-coercivity magnet is a neodymium magnet, and the low-coercivity magnet is an adhered neodymium iron boron magnet.

3. The interior permanent magnet synchronous motor of a novel rotor structure according to claim 1, wherein: an axial asymmetric excitation structure (6) is arranged at a position deviating from a symmetry axis between a high coercive force V-shaped excitation structure (7) and a low coercive force V-shaped excitation structure (8) which correspond from inside to outside along the radial direction.

4. The interior permanent magnet synchronous motor of a novel rotor structure according to claim 3, wherein: the asymmetric excitation structure (6) is made of Sm-Fe-N magnets, and the asymmetric excitation structure (6) penetrates through the rotor unit along the axial direction and is embedded into the rotor.

5. The interior permanent magnet synchronous machine of a new rotor structure of claim 1, wherein: and sealing blocks (9) are arranged at the two V-shaped ends of the second V-shaped groove (5).

6. The interior permanent magnet synchronous motor of a novel rotor structure according to claim 5, wherein: the block (9) is made of permalloy.

7. The interior permanent magnet synchronous machine of a novel rotor structure according to any one of claims 1 to 6, wherein: magnetic barriers (301) are respectively arranged at symmetrical positions on the high-coercivity V-shaped excitation structure (7).

8. The interior permanent magnet synchronous motor of a novel rotor structure according to claim 7, wherein: the magnetic barrier (301) is an air gap magnetic barrier.

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