CN107370268A - Permanent magnet rotor with low magnetic loss risk and asynchronous starting permanent magnet synchronous motor - Google Patents

Abstract

The invention discloses a permanent magnet rotor with low magnetic loss risk and an asynchronous starting permanent magnet synchronous motor. The permanent magnet rotor with the low magnetic loss risk comprises a rotor iron core and a permanent magnet, and is characterized in that the end part of the permanent magnet is polygonal in cross section, the whole cross section of the permanent magnet is in an axisymmetric structure, and a symmetry axis is a central line perpendicular to the magnetization direction of the permanent magnet. The demagnetization resistance of the permanent magnet in the asynchronous starting permanent magnet synchronous motor can be improved on the premise of keeping the performance of the motor.

Description

Permanent magnet rotor and asynchronous start permanent magnet synchronous motor with low risk of loss of magnetism

technical field

The invention belongs to the field of motors, and in particular relates to a permanent magnet rotor with low risk of loss of magnetism and an asynchronous start permanent magnet synchronous motor.

Background technique

Structurally, the asynchronous start permanent magnet synchronous motor can be regarded as a permanent magnet placed inside the rotor core of a traditional asynchronous motor. The motor relies on the asynchronous torque generated by the cage winding on the outer surface of the rotor to realize self-starting. When the motor runs stably at synchronous speed, the cage winding no longer works, and the motor operates by the interaction between the stator magnetic field and the rotor permanent magnetic field. Compared with traditional asynchronous motors, asynchronous start permanent magnet synchronous motors have outstanding advantages such as high efficiency, high power factor and wide economical operating range.

Similar to other types of permanent magnet motors, the demagnetization of the permanent magnets in the asynchronous start permanent magnet synchronous motor will seriously affect the operating performance of the motor. How to reduce the risk of demagnetization of asynchronously started permanent magnet synchronous motors will help to further promote the popularization and application of this type of motors and improve energy efficiency.

Contents of the invention

In order to solve the deficiencies of the prior art, the first object of the present invention is to provide a permanent magnet rotor with low risk of demagnetization, which can improve the anti-demagnetization resistance of the permanent magnets in the asynchronous start permanent magnet synchronous motor under the premise of maintaining the performance of the motor ability.

The first object of the present invention is to provide a permanent magnet rotor with low risk of loss of magnetism, which includes a rotor core and a permanent magnet, the cross-sectional shape of the end of the permanent magnet is polygonal, and the entire cross-section of the permanent magnet is an axisymmetric structure , the axis of symmetry is the centerline perpendicular to the magnetization direction of the permanent magnet.

Further, the polygon is an isosceles trapezoid.

Further, when the polygon is an isosceles trapezoid, the waist length of the isosceles trapezoid is times the width of the end of the permanent magnet along the magnetization direction of the permanent magnet.

The cross-sectional shape of the end of the permanent magnet of the present invention is a polygon, and the corners that are prone to demagnetization of the permanent magnet are cut off, so that the permanent magnet does not have an end corner area, which can effectively reduce the degree of distortion of the magnetic force lines at the end of the permanent magnet. The minimum working point of the end area of the permanent magnet is increased, the probability of demagnetization of the permanent magnet is reduced, and the anti-demagnetization ability of the permanent magnet is improved.

The waist length of an isosceles trapezoid is times the width of the end of the permanent magnet along the magnetization direction of the permanent magnet, the main purpose is to cut off the corners of the permanent magnet that are prone to demagnetization, and also to facilitate the processing of the permanent magnet. In addition, for different motors, according to the specific structural parameters of the motor, the finite element method can be used to optimize the calculation and analysis of the waist length of the isosceles trapezoid, and obtain the waist of the isosceles trapezoid with the strongest anti-demagnetization ability suitable for a specific motor. long value.

It should be noted that, besides the isosceles trapezoid, the polygonal cross-sectional shape of the end of the permanent magnet may also be a hexagon with two parallel bases.

Further, the outer surface of the rotor core has a plurality of rotor slots.

Further, at least one permanent magnet slot is arranged inside the rotor core, and one or more permanent magnets are arranged in each permanent magnet slot.

Further, the size of the permanent magnet matches the size of the permanent magnet slot.

Further, when a plurality of permanent magnet slots are provided inside the rotor core, the permanent magnet slots are arranged in a "W" shape.

It should be noted that when multiple permanent magnet slots are provided inside the rotor core, they can also be arranged in various other forms.

Further, the rotor core is cylindrical and is processed by a plurality of stacked silicon steel sheets.

The second object of the present invention is to provide an asynchronous start permanent magnet synchronous motor.

The second object of the present invention provides a kind of asynchronous start permanent magnet synchronous motor, comprising:

stator, and

In the permanent magnet rotor mentioned above, the permanent magnet rotor is rotatably arranged in the stator, and is spaced apart from the stator by a distance.

Further, the stator includes a cylindrical stator core, a plurality of stator teeth extending inwardly along the radial direction of the stator, stator slots distributed between the plurality of stator teeth, and a stator winding around the stator. Coils with teeth to generate a rotating magnetic field.

Compared with prior art, the beneficial effect of the present invention is:

(1) In the asynchronous starting permanent magnet synchronous motor, the permanent magnet is located inside the rotor core. Under the action of a strong demagnetizing magnetic field, if the cross-sectional shape of the permanent magnet is a traditional rectangle, the corner area of the permanent magnet is prone to irreversible demagnetization . Moreover, under the action of a strong demagnetizing magnetic field, the demagnetizing region will further expand. In the present invention, the shape of the section of the end of the permanent magnet is polygonal, which effectively reduces the probability of irreversible demagnetization at the end of the permanent magnet and improves the operation stability of the asynchronously started permanent magnet synchronous motor.

(2) The present invention effectively improves the anti-demagnetization ability of this type of motor by changing the shape of the permanent magnet inside the rotor iron core of an asynchronous start permanent magnet synchronous motor, which is conducive to the stable operation of this type of motor. This motor of the present invention is easy to implement and The effect is remarkable; and the invention only changes the shape of the end of the permanent magnet, and the other structural parameters of the motor do not change, so the influence on the performance of the motor is small.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application, and do not constitute improper limitations to the present application.

Fig. 1 is a schematic view of the rotor structure with a traditional rectangular permanent magnet;

Fig. 2 is the distribution diagram of the magnetic lines of force inside the motor with the traditional rectangular permanent magnet rotor;

Fig. 3 is a structural schematic diagram of a permanent magnet rotor with low risk of demagnetization according to the present invention;

Fig. 4 is a schematic view of a permanent magnet whose end section shape is polygonal according to the present invention;

Fig. 5 is a graph comparing the change curves of the minimum working point of the traditional rectangular permanent magnet and the permanent magnet of the present invention.

Among them, 1-rotor core, 2-permanent magnet, 3-rotor slot, 4-permanent magnet slot.

detailed description

It should be pointed out that the following detailed description is exemplary and intended to provide further explanation to the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

Fig. 1 is a schematic diagram of the structure of a rotor with a traditional rectangular permanent magnet.

As shown in FIG. 1 , a rotor with a traditional rectangular permanent magnet includes: a rotor core 1 , on which a rotor slot 3 and a permanent magnet slot 4 are opened, and a permanent magnet 2 is arranged in the permanent magnet slot 4 . Wherein, the cross section of the permanent magnet 2 is rectangular.

When the speed of the asynchronously started permanent magnet synchronous motor is fixed at a constant value close to the synchronous speed, when the permanent magnet with the traditional rectangular cross-section shape is used, when the most serious demagnetization operating point of the motor occurs, the distribution diagram of the magnetic force lines inside the motor is shown in Figure 2 shown.

It can be seen from Figure 2 that the distribution of magnetic force lines in most areas of the permanent magnet (near the middle of the permanent magnet) is uniform and consistent with the magnetization direction of the permanent magnet, indicating that the magnetic density of each point of the permanent magnet in this area The size and direction are consistent, and the probability of demagnetization is very small; while at the end of the permanent magnet, the magnetic force line is distorted, and the direction is no longer consistent with the magnetization direction of the permanent magnet, especially at the corner position of the end of the permanent magnet , the direction of the magnetic field line deviates more from the magnetization direction of the permanent magnet, and the operating points of each point in these areas are lower, and demagnetization is more likely to occur.

To sum up, when using the traditional permanent magnet with rectangular cross-section, in the corner area of the end of the permanent magnet, the working point of each point of the permanent magnet is relatively low. , irreversible demagnetization will occur;

When using a traditional rectangular cross-section permanent magnet, under the action of a strong demagnetization magnetic field, the corner area of the permanent magnet is prone to irreversible demagnetization, and under the action of the demagnetization magnetic field, the area of the irreversible demagnetization area will further expand, resulting in a decline in the performance of the motor .

Therefore, in order to improve the anti-demagnetization ability of the asynchronously started permanent magnet synchronous motor, the present invention provides a permanent magnet rotor with low risk of demagnetization.

As shown in Figure 3, a permanent magnet rotor with low risk of loss of magnetism according to the present invention includes a rotor core 1 and a permanent magnet 2, the cross-sectional shape of the end of the permanent magnet 2 is polygonal, and the permanent magnet 2 is completely The cross-section is an axisymmetric structure, and the symmetry axis is the center line perpendicular to the magnetization direction of the permanent magnet.

Wherein, the outer surface of the rotor core 1 has a plurality of rotor slots 3 .

In a specific implementation process, at least one permanent magnet slot 4 is arranged inside the rotor core 1 , and one or more permanent magnets 2 are arranged in each permanent magnet slot 4 .

In a specific implementation process, the size of the permanent magnet 2 matches the size of the permanent magnet slot 4 .

When a plurality of permanent magnet slots are provided inside the rotor core, the permanent magnet slots are arranged in a "W" shape.

It should be noted that when multiple permanent magnet slots are provided inside the rotor core, they can also be arranged in various other forms.

Wherein, the rotor core 1 has a cylindrical shape and is processed by a plurality of stacked silicon steel sheets.

As shown in Figure 4, taking the cross-sectional shape of the end of the permanent magnet as an isosceles trapezoid as an example:

h _m - the thickness of the permanent magnet along the magnetization direction, l ₁ - the distance between the points a ₁ ~ a ₄ in Figure 4 and the end of the permanent magnet, l ₂ - the distance between the points b ₁ ~ b ₄ in Figure 4 and the permanent magnet ( Bottom) The distance between the surfaces.

Wherein, the distance l ₁ between points a ₁ ~ a ₄ and the end of the permanent magnet = h _m /3, and the distance between b ₁ ~ b ₄ and the upper (lower) surface of the permanent magnet l ₂ = h _m /3 .

At this time, the waist length of the isosceles trapezoid is times the width of the end of the permanent magnet along the magnetization direction of the permanent magnet.

The cross-sectional shape of the end of the permanent magnet of the present invention is a polygon, and the corners that are prone to demagnetization of the permanent magnet are cut off, so that the permanent magnet does not have an end corner area, which can effectively reduce the degree of distortion of the magnetic force lines at the end of the permanent magnet. The minimum working point of the end area of the permanent magnet is increased, the probability of demagnetization of the permanent magnet is reduced, and the anti-demagnetization ability of the permanent magnet is improved.

The waist length of an isosceles trapezoid is times the width of the end of the permanent magnet along the magnetization direction of the permanent magnet, the main purpose is to cut off the corners of the permanent magnet that are prone to demagnetization, and also to facilitate the processing of the permanent magnet. In addition, for different motors, the finite element method can be used to optimize the calculation and analysis of the values of l ₁ and l ₂ according to the specific structural parameters of the motor, and obtain the values of l ₁ and l ₂ with the strongest anti-demagnetization ability suitable for specific motors value.

It should be noted that, besides the isosceles trapezoid, the polygonal cross-sectional shape of the end of the permanent magnet may also be a hexagon with two parallel bases.

Specifically, for different motors, according to the specific structural parameters of the motor, the finite element method can be used to optimize calculation and analysis of each side length of the polygon to obtain the value of the side length with the strongest anti-demagnetization ability suitable for a specific motor.

The end of the permanent magnet of the present invention does not have end corner areas, which can effectively reduce the degree of distortion of the magnetic field lines at the end of the permanent magnet, increase the minimum working point of the end area of the permanent magnet, reduce the probability of demagnetization of the permanent magnet, and improve The resistance to demagnetization of permanent magnets.

Fig. 5 is the change curve of the minimum operating point of the permanent magnet when the speed of an asynchronous permanent magnet synchronous motor is fixed at a constant value close to the synchronous speed, and the traditional rectangular permanent magnet and the permanent magnet whose end section shape is polygonal are respectively used. The curve shows the minimum value of the working points of all the permanent magnets at each moment. For an asynchronous start permanent magnet synchronous motor, when the motor is started to a speed close to the synchronous speed, the demagnetization magnetic field strength in the motor is the largest, so the most serious demagnetization operating point of the motor can be obtained by using this calculation method (under the action of the strongest demagnetization magnetic field, The minimum value of the working point of each point on all permanent magnets), that is, the minimum value of the corresponding curve in the figure.

It can be seen from Figure 5 that the most serious demagnetization operating point of the motor is -1.18T when using a permanent magnet with a rectangular cross section, and -0.33T when using a permanent magnet with a polygonal end section shape ; The most serious demagnetization operating point when using a permanent magnet with a polygonal end section shape is much higher than when using a rectangular section permanent magnet. Therefore, when the permanent magnet whose end section is polygonal is used, the risk of demagnetization of the permanent magnet is greatly reduced, and the reliability of the motor operation will be effectively improved.

What the present invention changes is only the end shape of the permanent magnet and when the shape of the permanent magnet is changed, it is carried out on a section perpendicular to the axial direction of the motor. The effect of the changes made in this application is: the cross-sectional shape of the permanent magnet perpendicular to the motor axis is changed, and the shape of the permanent magnet along the axial direction is consistent; and only the shape of the end of the permanent magnet is changed, which has little impact on the performance of the motor .

Based on the permanent magnet rotor shown in FIG. 3 , the present invention also provides an asynchronous start permanent magnet synchronous motor.

A kind of asynchronous starting permanent magnet synchronous motor of the present invention comprises:

stator, and

As shown in FIG. 3 , the permanent magnet rotor is rotatably arranged in the stator and is spaced apart from the stator by a distance.

Wherein, the stator includes a cylindrical stator core, a plurality of stator teeth extending inwardly along the radial direction of the stator, stator slots distributed between the plurality of stator teeth, and winding the stator teeth A coil that generates a rotating magnetic field.

The working principle of a kind of asynchronous start permanent magnet synchronous motor of the present invention is:

In the asynchronous starting permanent magnet synchronous motor, the permanent magnet is located inside the rotor core. Under the action of a strong demagnetizing magnetic field, if the cross-sectional shape of the permanent magnet is a traditional rectangle, the corner area of the permanent magnet is prone to irreversible demagnetization. Moreover, under the action of a strong demagnetizing magnetic field, the demagnetizing region will further expand. In the present invention, the shape of the section of the end of the permanent magnet is polygonal, which effectively reduces the probability of irreversible demagnetization at the end of the permanent magnet and improves the operation stability of the asynchronously started permanent magnet synchronous motor.

The invention effectively improves the anti-demagnetization ability of this type of motor by changing the shape of the permanent magnet inside the rotor iron core of the asynchronous start permanent magnet synchronous motor, which is beneficial to the stable operation of the type of motor. The motor of the invention is easy to implement and has a significant effect; Moreover, the present invention only changes the shape of the end of the permanent magnet, and does not change other structural parameters of the motor, which has little influence on the performance of the motor.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (10)

1. A permanent magnet rotor with low risk of loss of magnetism, which includes a rotor core and a permanent magnet, characterized in that the cross-sectional shape of the end of the permanent magnet is polygonal, and the entire cross-section of the permanent magnet is an axisymmetric structure, symmetrical The axis is the centerline perpendicular to the magnetization direction of the permanent magnet. 2. A permanent magnet rotor with low risk of loss of magnetism according to claim 1, wherein the polygon is an isosceles trapezoid. 3. A permanent magnet rotor with low risk of loss of magnetism as claimed in claim 2, wherein when the polygon is an isosceles trapezoid, the waist length of the isosceles trapezoid is times the width of the end of the permanent magnet along the magnetization direction of the permanent magnet. 4. A permanent magnet rotor with low risk of loss of magnetism according to claim 1 or 2, characterized in that the outer surface of the rotor core has a plurality of rotor slots. 5. A permanent magnet rotor with low risk of loss of magnetism as claimed in claim 1 or 2, characterized in that at least one permanent magnet slot is provided inside the rotor core, and each permanent magnet slot is provided with There are one or more permanent magnets. 6. A permanent magnet rotor with low risk of loss of magnetism as claimed in claim 5, characterized in that the size of the permanent magnets matches the size of the permanent magnet slots. 7. A permanent magnet rotor with low risk of loss of magnetism according to claim 5, characterized in that, when a plurality of permanent magnet slots are arranged inside the rotor core, the permanent magnet slots are in the shape of "W" shape arrangement. 8 . The permanent magnet rotor with low risk of loss of magnetism according to claim 1 , wherein the rotor core is cylindrical and is processed by a plurality of stacked silicon steel sheets. 9. An asynchronous start permanent magnet synchronous motor, characterized in that, comprising: stator, and The permanent magnet rotor with low risk of loss of magnetization according to any one of claims 1-8, wherein the permanent magnet rotor is rotatably arranged in the stator and is spaced apart from the stator by a distance. 10. The asynchronous start permanent magnet synchronous motor as claimed in claim 9, wherein the stator comprises a cylindrical stator core, a plurality of stator teeth extending inwardly along the radial direction of the stator, Stator slots distributed between the plurality of stator teeth and coils wound around the stator teeth to generate a rotating magnetic field.