CN110994840A

CN110994840A - Synchronous motor with permanent magnet reluctance hybrid rotor structure

Info

Publication number: CN110994840A
Application number: CN201911301658.5A
Authority: CN
Inventors: 孔晓光; 梁文星; 徐鸿; 刘春浩
Original assignee: Shenyang University of Chemical Technology
Current assignee: Shenyang University of Chemical Technology
Priority date: 2019-12-17
Filing date: 2019-12-17
Publication date: 2020-04-10

Abstract

A synchronous motor with a permanent magnet reluctance hybrid rotor structure relates to a motor, and comprises an outer permanent magnet rotor (1), an inner permanent magnet auxiliary type synchronous reluctance rotor (2), a middle stator (3) and a magnetism isolating ring (4); a novel Halbach permanent magnet is arranged on the outer rotor (1); the inner side and the outer side of the middle stator (3) are grooved, and sinusoidal windings are wound on the grooves; the permanent magnets of the inner rotor (2) are placed asymmetrically. The sinusoidal winding and the novel Halbach permanent magnet can effectively weaken harmonic waves in an air gap and improve the sine property of a waveform, the asymmetric arrangement mode of the inner rotor permanent magnet can fully utilize a permanent magnet torque component and a reluctance torque component in an inner motor, the torque density of the motor is improved, and meanwhile, the overall volume of the motor can be effectively reduced by the arrangement mode of the outer permanent magnet inner reluctance rotor.

Description

Synchronous motor with permanent magnet reluctance hybrid rotor structure

Technical Field

The invention relates to a motor, in particular to a synchronous motor with a permanent magnet reluctance hybrid rotor structure.

Background

The permanent magnet synchronous motor has the advantages of superior performance, good stability, rapid development in recent years, simple structure, high torque density, high efficiency and high power factor. But the permanent magnet synchronous motor also has the defect of difficult field weakening, and the synchronous reluctance motor has high salient pole ratio and wide field weakening range, thereby well making up the defects of the permanent magnet motor.

The permanent magnet auxiliary type synchronous reluctance motor belongs to a salient pole type motor, the torque density of the traditional synchronous reluctance motor is improved due to the fact that the salient pole ratio is increased, the electromagnetic torque of the motor contains a permanent magnet torque component and a reluctance torque component, and the maximum value exists when the current angle is 0 degree and 45 degrees respectively. The maximum value of the resultant torque is less than the algebraic sum of the maximum values of the permanent magnet torque and the reluctance torque, making them underutilized.

Therefore, it is necessary to improve the torque density of the motor and improve the operation efficiency by making full use of these two torque components. The internal space of the permanent magnet synchronous motor is necessary to be fully utilized, so that the cost can be reduced, and the comprehensive performance of the motor can be improved.

Disclosure of Invention

The invention aims to provide a synchronous motor with a permanent magnet reluctance hybrid rotor structure, which makes full use of the space of an inner cavity of a stator, reduces the volume of the motor, reduces the cost, improves the overall operation efficiency of a system and improves the torque density of the motor.

The purpose of the invention is realized by the following technical scheme:

a synchronous motor with a permanent magnet reluctance hybrid rotor structure comprises an outer rotor, an inner rotor and a stator; the stator is positioned between the outer rotor and the inner rotor; the outer rotor is attached with a Halbach permanent magnet structure, and each permanent magnet in each pole is in a convex shape; the inner rotor is a synchronous reluctance rotor with equal air gap width, and the permanent magnets are asymmetrically placed in each layer of magnetic barriers of the synchronous reluctance rotor; the inner surface and the outer surface of the middle stator are evenly grooved, the magnetic isolation ring is embedded in the middle of the stator, and a set of three-phase double-layer concentric sine winding is respectively embedded in the grooves on the inner surface and the outer surface of the stator to form the total stator winding of the motor.

The Halbach permanent magnet on the outer permanent magnet rotor adopts a parallel magnetizing mode, the outer rotor is of a surface-mounted structure, each permanent magnet is an area to form a plurality of areas, and the magnetizing directions from the two sides of each permanent magnet to the middle of each permanent magnet gradually transition from the tangential direction to the radial direction.

When the inner rotor permanent magnet is not arranged, the magnetic conduction layer and the non-magnetic conduction layer of the inner magnetic resistance rotor both adopt a U-shaped structure, wherein the non-magnetic conduction layer is air; the permanent magnets are embedded into two sides of the non-magnetic conductive layer and are placed in an asymmetric mode.

The synchronous motor with the permanent magnet reluctance hybrid rotor structure is divided into an inner motor and an outer motor by the magnetism isolating ring.

The synchronous motor with the permanent magnet reluctance hybrid rotor structure is characterized in that the outer rotor is of a cup-shaped structure, one side of the outer rotor is connected with a bearing, and the inner rotor and the outer rotor are coaxial.

The invention has the advantages and effects that:

1. the invention provides a synchronous motor with a permanent magnet reluctance hybrid rotor structure. The inner rotor asymmetrically puts the permanent magnet in the magnetic barrier on the basis of the synchronous reluctance rotor with the U-shaped magnetic barrier, which is beneficial to improving the utilization rate of the permanent magnet torque and the reluctance torque. The inner surface and the outer surface of the middle stator are uniformly grooved, and the magnetism isolating ring is inserted in the middle of the stator, so that the magnetic fields of an inner motor formed by the inner stator and the inner rotor and an outer motor formed by the outer stator and the outer rotor are mutually independent and are convenient to control. The windings on the inner side and the outer side of the stator are three-phase double-layer concentric sinusoidal windings, the slot filling rate of each slot is the same, and the space of the stator slot is fully utilized. In order to ensure the normal rotation of the rotor, the outer rotor is of a cup-shaped structure and is connected with the bearing, and the inner rotor and the outer rotor are coaxially connected.

2. The motor provided by the invention is a double-rotor single-stator motor, the inner rotor is a permanent magnet auxiliary type synchronous reluctance rotor (the permanent magnet is neodymium iron boron or common ferrite), the problem that the torque of the pure synchronous reluctance rotor is insufficient is solved, the outer rotor is a novel Halbach surface-mounted rotor, the largest advantage is that the larger inner cavity space of the motor stator is fully utilized, the integral volume of the motor is reduced, the torque density is improved, the cost is saved, and the advantage of the motor in a multi-pole motor is more obvious. Compared with the inner rotor which is a permanent magnet rotor, the outer rotor is a permanent magnet rotor, and because the motor rotor is subjected to centrifugal force when rotating, and the permanent magnets are attached to the surface of the rotor, if effective protective measures are not provided, the permanent magnets on the inner rotor have the risk of flying out when rotating at high speed; and the outer rotor motor greatly reduces the risk.

3. Another benefit of the reluctance rotor of the present invention being inside and the permanent magnet rotor outside is the heat dissipation aspect of the motor. Because of the effect of the air magnetic barrier of the reluctance rotor, the ventilation performance is good, the heat generated on the inner side of the motor is easy to dissipate, and because the outer side of the permanent magnet outer rotor is in contact with air, the heat dissipation is easy, and the problem that the heat dissipation of the traditional inner permanent magnet rotor is difficult is solved. Meanwhile, the three-phase double-layer concentric sinusoidal winding of the stator has a better effect of reducing temperature rise compared with the traditional lap winding.

4. The U-shaped magnetic barrier of the inner rotor is equivalent to increase the quadrature axis magnetic resistance, the magnetic barrier is made into a structure with two narrow ends and a wide middle part, the modulation effect on a magnetic field is better, the permanent magnet is placed on the shoulder part of the magnetic barrier, the permanent magnet torque and the magnetic resistance torque can be fully utilized, the overall performance of the motor is improved, meanwhile, the mechanical strength of a rotor punching sheet is considered, the magnetic rib is added between the magnetic barriers of the 2 nd layer and the 3 rd layer, and the arrangement of the novel Halbach permanent magnet and the three-phase double-layer concentric sine winding can optimize the magnetic density waveform and the potential waveform and weaken the harmonic wave.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic view of the magnetization direction of the inner rotor structure and the magnets when they are asymmetrically placed according to the present invention;

FIG. 3 is a schematic diagram of the structure of each pole of the inner rotor;

fig. 4 is a schematic diagram of each pole of permanent magnet of the outer rotor and the magnetization direction thereof.

The figure includes: 1. the magnetic field generator comprises an outer rotor, 2. an inner rotor, 2-1. a magnetic conduction layer, 2-2. a non-magnetic conduction layer, 2-3. magnetic ribs, 3. a stator, 4. a magnetism isolating ring, 5. a stator winding, 6. an outer rotor permanent magnet and 7. an inner rotor permanent magnet.

Detailed Description

The present invention will be described in detail with reference to the embodiments shown in the drawings.

The invention relates to a synchronous motor with a permanent magnet reluctance hybrid rotor structure, which consists of an outer rotor, an inner rotor and a stator; the stator is positioned between the outer rotor and the inner rotor; the novel Halbach permanent magnet structure is attached to the outer rotor, for convenient production, the pole arc coefficients of all the permanent magnets are the same, each permanent magnet is in a convex shape, the direction of a synthesized magnetic field between every two convex magnets is positioned between the left permanent magnet and the right permanent magnet, so that the total magnetic field is closer to sine under the condition of the same number of the permanent magnets, and the permanent magnet material is fully utilized. The inner rotor is a synchronous reluctance rotor with equal magnetic barrier width, the magnetic barrier is U-shaped, the magnetic conduction layer accounts for 48% of the total sum of the magnetic conduction layer and the magnetic barrier, the thickness of two ends of the magnetic barrier under each pole is thinner than that of the middle part, namely the width of the magnetic conduction layer at two ends is thicker than that of the magnetic conduction layer at the middle part, the effect of the magnetic barrier is that more magnetic flux flows through the magnetic conduction layers at two sides and less magnetic flux flows through the middle part, the magnetic flux path is limited, and the torque pulsation is reduced. The number of magnetic barrier layers is determined by

Wherein

The number of stator slots per pole pair,

the number of separation points per pole pair. Such as a 4-pole 36-slot machine, the number of stator slots per pole pair

Then, then

Or

I.e., the separation point per pole is 7 or 11, i.e., the number of magnetic barriers per pole is 3 or 5, and the number of magnetic barriers is selected to be 3 in order to reduce the manufacturing cost. With rotor punching of each pole

The axis is a symmetry axis, the radians of every two separated points are the same, and the angles from the two ends of each layer of magnetic barriers to the symmetry axis can be calculated to be 25.71 degrees, 51.43 degrees and 77.14 degrees respectively. In order to improve the torque density of the traditional synchronous reluctance motor, the permanent magnets are added in the magnetic barriers and are asymmetrically placed, because the current angle of the maximum value of the permanent magnet torque is equal to or larger than 0 degrees, the current angle of the maximum value of the reluctance torque is smaller than 45 degrees, the permanent magnets are asymmetrically placed, so that the maximum values of the permanent magnet torque and the reluctance torque can be at the same current angle or similar current angles, and the integral torque density is improved. The inner surface and the outer surface of the middle stator are evenly grooved, in order to reduce mutual interference of magnetic fields of the inner motor and the outer motor, the magnetic isolation ring is embedded in the middle of the stator, and the motor can be equivalent to the inner motor and the outer motor, so that analysis is convenient. A set of three-phase double-layer concentric sine windings are respectively embedded in the inner surface groove and the outer surface groove of the stator to form a total stator winding of the motor. The Halbach permanent magnet on the outer permanent magnet rotor adopts a parallel magnetizing mode, the rotor is of a surface-mounted structure, each permanent magnet is an area to form a plurality of areas, and the included angle between the magnetization direction of the permanent magnet under each pole and the horizontal direction is gradually increased from two sides to the middle. The stator slot is wound with a three-phase double-layer concentric sinusoidal winding, and compared with the traditional three-phase double-layer lap winding, the stator slot can reduce loss, improve the efficiency of the motor, reduce the harmonic content of the magnetic potential of the winding, and improve the coefficient of a fundamental wave winding, thereby reducing the cost of the motor. Meanwhile, in order to ensure that the slot filling rate in the inner slot and the outer slot of the middle stator is not changed, the space of the stator slot is fully utilized, and the number of the conductors on the upper layer and the lower layer of each slot is correspondingly adjusted on the basis of unequal-turn sinusoidal windings.

Example 1

Fig. 1 is a schematic structural diagram of a synchronous motor with a permanent magnet reluctance hybrid rotor structure. The motor is composed of an outer rotor 1, an inner rotor 2 and a stator 3, wherein the stator 3 is positioned between the outer rotor 1 and the inner rotor 2. The inner surface and the outer surface of the stator 3 are uniformly grooved, a set of three-phase double-layer concentric sine winding is embedded in the inner groove and the outer groove of the stator 3 for improving the air gap flux density and the sine property of the back electromotive force waveform, the groove filling rate of each groove on the inner surface or the outer surface of the stator is the same for improving the utilization rate of the stator groove, and simultaneously, the inner groove and the outer groove of the stator are of a skewed slot structure for further weakening the tooth harmonic wave. The basic wave in the air gap flux density waveform of the traditional permanent magnet motor is low in occupied ratio and more in harmonic wave, Halbach permanent magnets are attached to the surface of an outer rotor 1 of the motor, each permanent magnet is in a convex shape, and the flux density of an outer rotor permanent magnet 6 in an air gap is closer to sine through magnetic field superposition. The common synchronous reluctance rotor has lower torque density, and the permanent magnets are asymmetrically embedded at the bottom and two sides of the non-magnetic conductive layer 2-2, so that the torque density is improved, and the permanent magnet torque and the reluctance torque are fully utilized. Because the inner rotor and the outer rotor are provided with the permanent magnets, in order to ensure that the magnetic fields of the inner motor and the outer motor do not interfere with each other, the yoke part of the stator 3 is provided with the magnetism isolating ring 4, so that the magnetic fields of the inner motor and the outer motor do not interfere with each other, the analysis is convenient, and the control of the motor is simpler. The structure of the inner magnetic resistance and the outer permanent magnet enables the size of the motor to be reduced, and the overall utilization rate of materials to be high.

Compared with a permanent magnet motor, the synchronous reluctance motor has the advantages of wide speed regulation range, high overload capacity of the motor, expansion of constant power range and contribution to heat dissipation. Fig. 2 is a schematic view of the magnetization direction of the inner rotor structure and the asymmetric arrangement of the magnets. The thickness of the lower magnetic conduction layer 2-1 of each pole of the inner rotor 2 has wider two ends and narrower middle, so that the magnetic fluxes at the two sides are more than the magnetic flux in the middle, and the overall performance of the motor is improved. In view of the mechanical strength of the rotor, magnetic ribs 2-3 are distributed between the magnetically permeable layer 2-1 and the non-magnetically permeable layer 2-2. The permanent magnets are embedded in the non-magnetic conductive layer 2-2 (magnetic barrier) and are asymmetrically embedded, so that the defect of low torque density in the traditional situation is overcome, the efficiency is improved, and the advantages of the reluctance motor are reserved. The maximum values of the permanent magnet torque component and the reluctance torque component are respectively reached at the current angle of 0 degree and 45 degrees, the maximum values of the permanent magnet torque component and the reluctance torque component can be reached at the same current angle or the similar current angle by the placement mode of the permanent magnet, and the utilization rate of the two types of torque is improved.

Fig. 3 is a schematic diagram of the structure of each pole of the inner rotor. The non-magnetic conductive layer 2-2 (magnetic barriers) is of a U-shaped structure, the number of the magnetic barriers is 3, and the widths of two adjacent magnetic barriers are equal. Considering the saturation of the stator and the rotor, the ratio of the total width of the magnetic conduction layers to the sum of the widths of the magnetic conduction layers and the non-magnetic conduction layers is influenced by factors such as the width of a stator slot, 48% is taken, the thickness of two ends of each layer of magnetic barrier is thinner than the thickness of the middle part, namely the width of the magnetic conduction layers at two ends is thicker than that of the magnetic conduction layer at the middle part, the magnetic flux flowing through the magnetic conduction layers at two sides is more and less, the magnetic flux path is limited, and the torque pulsation is reduced. The number of magnetic barrier layers is determined by

Wherein

The number of stator slots per pole pair,

Then, then

Or

The axis is a symmetry axis, the radians between every two separated points are the same, and the angles from the two ends of each layer of magnetic barrier to the symmetry axis can be calculated to be 25.71 degrees, 51.43 degrees and 77.14 degrees respectively.

Fig. 4 is a schematic diagram of each pole of permanent magnet of the outer rotor and the magnetization direction thereof. The Halbach array can improve the torque density of the motor and improve the sine of the air gap flux density. In order to improve the utilization rate of the permanent magnets, each pole of permanent magnet adopts an 8-segment structure, and each permanent magnet is respectively magnetized. The included angle between the magnetization direction of the permanent magnet under each pole and the horizontal direction is gradually increased from two sides to the middle. Every permanent magnet is "protruding" style of calligraphy structure, and the harmonic in the air gap can be weakened more effectively to novel Halbach permanent magnet, improves the sine nature of wave form to can also further reduce the tooth's socket torque, reduce torque ripple.

Claims

1. A synchronous motor with a permanent magnet reluctance hybrid rotor structure is characterized in that the motor comprises an outer rotor (1), an inner rotor (2) and a stator (3); the stator (3) is positioned between the outer rotor (1) and the inner rotor (2); a Halbach permanent magnet structure is attached to the outer rotor (1), and each permanent magnet in each pole is in a convex shape; the inner rotor (2) is a synchronous reluctance rotor with equal air gap width, and the permanent magnets (7) are asymmetrically placed in each layer of magnetic barriers of the synchronous reluctance rotor; the inner surface and the outer surface of the middle stator (3) are evenly grooved, the middle of the stator is embedded with a magnetic isolation ring (4), and the inner surface and the outer surface of the stator are respectively embedded with a set of three-phase double-layer concentric sine windings to form a total stator winding (5) of the motor.

2. The synchronous motor with the permanent magnet reluctance hybrid rotor structure according to claim 1, wherein Halbach permanent magnets on the outer permanent magnet rotor (1) are magnetized in parallel, the outer rotor (1) is of a surface-mounted structure, each permanent magnet is an area to form a plurality of areas, and the magnetizing directions from two sides to the middle of each permanent magnet gradually transition from tangential to radial.

3. A synchronous machine with a permanent magnet reluctance hybrid rotor structure according to claim 1, wherein when the inner rotor permanent magnet (7) is not provided, the magnetic conduction layer (2-1) and the non-magnetic conduction layer (2-2) of the inner reluctance rotor both adopt a "U" shaped structure, wherein the non-magnetic conduction layer (2-2) is air; the permanent magnets are embedded into two sides of the non-magnetic conductive layer (2-2) and are placed in an asymmetric mode.

4. A synchronous machine with a hybrid rotor structure of permanent magnet reluctance according to claim 1, characterized in that the magnetism isolating ring (4) divides it into an inner machine and an outer machine.

5. A synchronous machine with a hybrid rotor structure of permanent magnet reluctance according to claim 1, characterized in that said outer rotor (1) is of cup-shaped configuration and is connected to a bearing on one side, with the inner and outer rotors coaxial.