A rotor core, a permanent magnet motor, and a variable frequency compressor

Abstract

This invention provides a rotor core, a permanent magnet motor, and a variable frequency compressor, relating to the field of motor and compressor design and manufacturing technology. The rotor core includes uniformly distributed permanent magnet slots, with grooves between adjacent slots. Each groove extends inward along the radial direction of the rotor core, and a parallel magnetic bridge is provided between the groove and the slot. Symmetrically distributed first, second, and third magnetic barrier slots are provided on both sides of the top of each slot. The outer side of the rotor core above the magnetic barrier slots includes a first and second circular arc, with the second arc intersecting the side of the groove. Permanent magnets with alternating magnetic properties are embedded in each slot. In this invention, the outer radius Rr of the rotor core, the distance ho from the midpoint of the bottom of the permanent magnet slot to the center point of the rotor core, and the thickness hm of the permanent magnet satisfy 2 < (Rr - ho) / hm ≤ 3.4. Furthermore, by reasonably setting the position and size of the magnetic barrier slots, the magnetic circuit distribution can be changed, leakage flux reduced, the power density of the motor increased, and the electromagnetic vibration noise of the motor and compressor reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of compressor design and manufacturing, in particular, especially relates to a rotor core, a permanent magnet motor and a variable frequency compressor. BACKGROUND

[0002] The variable frequency compressor is configured with a frequency converter and a rare earth permanent magnet motor, which can dynamically and steplessly adjust the operating speed, can operate at a speed higher than the rated speed in the initial start-up period after temperature setting, realizes rapid refrigeration or heating, and operates at low frequency, low power consumption, low power, low noise when reaching the set temperature, is high in energy efficiency, and is far higher in comprehensive energy efficiency ratio than the fixed frequency compressor. At present, the variable frequency compressor has become the mainstream of household or commercial refrigeration and heating equipment due to its advantages of comfort, energy saving and reliability.

[0003] The motor as the driving power source of the compressor is an important component of the compressor product, and the performance of the motor directly affects the overall performance of the compressor and the customer experience. In recent years, with the development of power electronic devices and control strategy control algorithm, the variable frequency rare earth permanent magnet motor gradually replaces the fixed frequency product using an induction motor. Compared with the induction motor and the electrically excited synchronous motor, the permanent magnet motor can maintain high efficiency and power factor under different loads, is low in energy consumption, small in size and light in weight under the same power, and can realize rapid response and precise control by matching the frequency converter.

[0004] The rare earth permanent magnet motor is often high in cost, and related technical means need to be adopted to increase the power density while ensuring excellent performance and reduce the cost. The permanent magnet motor using fractional slot concentrated winding is widely applied because it can reduce the end length, reduce the copper loss, and can be mass-produced with high manufacturing efficiency. However, a large number of useless harmonics exist in the motor, which brings about large motor torque ripple, obvious vibration and noise and other problems.

[0005] The present application provides a rotor core, a permanent magnet motor and a variable frequency compressor to increase the power density, reduce the cost, and reduce the vibration and noise of the motor and the compressor. SUMMARY

[0006] The rare earth permanent magnet motor is high in cost, and a large number of useless harmonics exist in the motor after using fractional slot concentrated winding, which brings about large motor torque ripple, obvious vibration and noise and other technical problems, and the present application provides a rotor core, a permanent magnet motor and a variable frequency compressor. The present application reasonably sets the positions and sizes of the first magnetic barrier slot, the second magnetic barrier slot and the third magnetic barrier slot on the basis of limiting the maximum vertical distance from the top of the permanent magnet slot to the outside of the rotor core, and sets the grooves between the first arc, the second arc outside the rotor core and the permanent magnet slot, so as to reduce the magnetic flux leakage, improve the magnetic field distribution and reduce the vibration and noise.

[0007] The technical means adopted by the present application are as follows:

[0008] A rotor core with an outer radius Rr, the rotor core comprising uniformly distributed permanent magnet grooves, the distance from the bottom midpoint of the permanent magnet groove to the center point of the rotor core being ho, and a magnetically alternating permanent magnet being embedded in each of the permanent magnet grooves, the thickness of the permanent magnet being hm, the outer radius Rr of the rotor core, the distance ho from the bottom midpoint of the permanent magnet groove to the center point of the rotor core, and the thickness hm of the permanent magnet satisfying 2 < (Rr-ho) / hm ≤ 3.4.

[0009] The top of each of the permanent magnet grooves is provided with symmetrically distributed first, second, and third magnetic barrier grooves.

[0010] The distance from the top of the first magnetic barrier groove to the permanent magnet groove is h1, and the distance from the side of the first magnetic barrier groove to the permanent magnet groove is L1, and the width of the first magnetic barrier groove is w1; the distance from the top of the second magnetic barrier groove to the permanent magnet groove is h2, and the distance from the first magnetic barrier groove to the second magnetic barrier groove is L2, and the width of the second magnetic barrier groove is w2; the distance from the top of the third magnetic barrier groove to the permanent magnet groove is h3, and the distance from the second magnetic barrier groove to the third magnetic barrier groove is L3, and the width of the third magnetic barrier groove is w3.

[0011] The top of each of the first, second, and third magnetic barrier grooves is a circular arc, and the radius of the circular arc is Rk.

[0012] Each of the size relationships satisfies 0.45mm ≤ h1 < h2 < h3 ≤ 1.3mm; 2mm ≤ L1 < L2 < L3 ≤ 5mm; 2.55h1 ≤ w1 ≤ 3.5h1; w3 = w2 < L1, h1 < Rr-Rk ≤ h3.

[0013] Further, each edge intersection of all the magnetic barrier grooves is chamfered by 0.2mm.

[0014] Further, the outer side of the rotor core above the magnetic barrier grooves comprises a first circular arc and a second circular arc.

[0015] The center of the first circular arc O1 is at the center of the rotor core, and the central angle δ satisfies 20° ≤ δ ≤ 30°.

[0016] The center of the second circular arc O2 deviates from the center of the first circular arc O1, and the radius Rc of the second circular arc satisfies Rr-25.7mm ≤ Rc ≤ Rr-22.6mm.

[0017] Further, the number of the permanent magnets is p, the number of the stator slots outside the rotor core is Z, and the number of the symmetric windings embedded in the stator core is m, wherein p, m, and Z satisfy p = (2 Z) / m.

[0018] Further, a groove is arranged between two adjacent permanent magnet grooves, and each groove extends inward along the radial direction of the rotor core;

[0019] The second arc intersects with the side of the groove to form a first chamfer, and the side of the groove intersects with the bottom of the groove to form a second chamfer.

[0020] The angle between the bottom of the groove and the bottom of the permanent magnet groove is θ, and θ and the number of permanent magnet grooves p satisfy: θ = 180° (1-1 / p).

[0021] Further, the groove and the side of the permanent magnet groove form a parallel magnetic bridge, and the width of the parallel magnetic bridge is wb, wb, Rr and Rk satisfy: wb = Rr-Rk.

[0022] Further, the directions of the magnetic fields of adjacent permanent magnets are the same and opposite to the radial direction of the rotor core, respectively.

[0023] The permanent magnet has a rectangular shape.

[0024] The thickness of the permanent magnet is hm, and hm and w1 satisfy: w1 < hm ≤ 3mm.

[0025] The width of the permanent magnet is wm, the width of the permanent magnet groove is wc, and the relationship between wm, wc and the dimensions of the magnetic barrier groove satisfies: L1+L2+L3+w1+w2+w3 < (wc-0.1mm) / 2 = wm / 2.

[0026] The application also includes a permanent magnet motor comprising the rotor core.

[0027] The application also includes a variable frequency compressor comprising the permanent magnet motor.

[0028] Compared with the prior art, the application has the following advantages:

[0029] 1. On the basis of determining the distance ho between the midpoint of the bottom of the permanent magnet groove and the center point of the rotor core, the thickness hm of the permanent magnet, the outer radius Rr of the rotor core, and the relationship between the distance ho and the center point of the rotor core, the positions and sizes of the first magnetic barrier groove, the second magnetic barrier groove and the third magnetic barrier groove symmetrically distributed on both sides of the top of the permanent magnet groove are limited to change the magnetic path, improve the magnetic field distribution, increase the effective value of the no-load back electromotive force, reduce the power density, improve the efficiency of the motor and the compressor system, reduce the harmonics, and reduce the vibration noise.

[0030] 2. By arranging the first arc with the center at the center of the rotor core, the second arc with the center deviating from the center of the rotor core, and the groove between the permanent magnet grooves on the outer circle of the rotor, and making relevant limitations, the back electromotive force waveform can be improved, the magnetic flux leakage can be reduced, and the power density can be further increased.

[0031] 3. By limiting the width, thickness, shape, magnetization direction of the permanent magnet, the cost of the motor can be reduced on the basis of ensuring electromagnetic performance.

[0032] 4. On the basis of the original stator refrigerant flow channel, the first magnetic barrier groove, the second magnetic barrier groove, the third magnetic barrier groove and the groove opened by the application can further increase the refrigerant flow area inside the compressor, improve temperature rise, reduce loss and increase efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0034] Figure 1 It is a structural schematic diagram of the rotor core of the present application.

[0035] Figure 2 It is Figure 1 the enlarged view of A in the middle.

[0036] Figure 3 It is Figure 1 the enlarged view of B in the middle.

[0037] Figure 4 It is Figure 1 the enlarged view of C in the middle.

[0038] Figure 5 It is a structural schematic diagram of the permanent magnet motor in the present application.

[0039] Figure 6 It is a comparison diagram of the effective value of the no-load back electromotive force of the rotor core of the present application and the prior art.

[0040] Figure 7 It is a comparison diagram of the efficiency of the rotor core of the present application and the prior art at the rated point.

[0041] Figure 8 It is a comparison diagram of the radiation sound power of the rotor core of the present application and the prior art.

[0042] Figure 9 It is a comparison diagram of the radiation sound power of the rotor core of the present application and the prior art at 24 times frequency.

[0043] In the figure: 1, permanent magnet motor; 11, stator core; 111, stator slot; 12, rotor core; 121, permanent magnet slot; 122, permanent magnet; 123, first magnetic barrier slot; 124, second magnetic barrier slot; 125, third magnetic barrier slot; 126, groove; 127, parallel magnetic bridge; 128, first circular arc; 129, second circular arc; 130, first chamfer; 131, second chamfer. DETAILED DESCRIPTION

[0044] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0045] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0046] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form, unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a reference to the presence of a feature, step, operation, device, component and / or combinations thereof.

[0047] Unless specifically stated otherwise, the relative arrangement of components and steps, numerical expressions, and numerical values set forth in the various embodiments described herein are not limiting. It should be understood that the various parts shown in the drawings are not necessarily drawn to scale in proportion. The technology, methods and devices known to those skilled in the relevant art can not be discussed in detail, but should be considered as part of the specification. In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, and not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0048] As Figures 1-5As shown, the application provides a rotor core and a permanent magnet motor. The permanent magnet motor 1 comprises a stator core 11, a stator slot 111 inside the stator core, a rotor core 12, an outer radius of the rotor core 12 is Rr, which comprises uniformly distributed permanent magnet slots 121, a distance from a bottom midpoint of the permanent magnet slot 121 to a center point of the rotor core 12 is ho, a magnetically alternating permanent magnet 122 is embedded in each permanent magnet slot 121, a thickness of the permanent magnet 122 is hm, and a relationship 2<(Rr-ho) / hm≤3.4 is satisfied; a first magnetic barrier slot 123, a second magnetic barrier slot 124 and a third magnetic barrier slot 125 are symmetrically arranged on both sides of a top of the permanent magnet slot 121, a distance from the first magnetic barrier slot 123 to the top of the permanent magnet slot 121 is h1, a distance from the first magnetic barrier slot 123 to a side of the permanent magnet slot 121 is L1, a width of the first magnetic barrier slot 123 is w1, a distance from the second magnetic barrier slot 124 to the top of the permanent magnet slot 121 is h2, a distance from the second magnetic barrier slot 124 to the first magnetic barrier slot 123 is L2, and a width of the second magnetic barrier slot 124 is w2; a distance from the third magnetic barrier slot 125 to the top of the permanent magnet slot 121 is h3, a distance from the third magnetic barrier slot 125 to the second magnetic barrier slot 124 is L3, and a width of the third magnetic barrier slot 125 is w3; the top of the first magnetic barrier slot 123, the top of the second magnetic barrier slot 124 and the top of the third magnetic barrier slot 125 are all circular arcs, and a radius of the top circular arc is Rk. The size relationship satisfies 0.45mm≤h1<h2<h3≤1.3mm, 2mm≤L1<L2<L3≤5mm, 2.55h1≤w1≤3.5h1, w3=w2<L1, and h1<Rr-Rk≤h3. On the premise of ensuring the mechanical strength of the rotor core 12, the magnetic circuit direction can be changed, the magnetic field distribution can be improved, the effective value of the no-load back electromotive force can be increased, the power density can be reduced, the harmonics can be reduced, and the electromagnetic vibration noise can be reduced. In the embodiment, Rr=42.8mm, ho=34.6mm, hm=2.5mm, (Rr-ho) / hm=3.28, and the relationship 2<(Rr-ho) / hm≤3.4 is satisfied; in the embodiment, h1=0.5mm, h2=0.8mm, h3=1.2mm, and the relationship 0.45mm≤h1<h2<h3≤1.3mm is satisfied; in the embodiment, L1=2.7mm, L2=3.7mm, L3=4.3mm, and the relationship 2mm≤L1<L2<L3≤5mm is satisfied; in the embodiment, w1=1.4mm, and the relationship 2.55h1=1.275mm≤w1=1.4mm≤3.5h1=1.75mm is satisfied; in the embodiment, w2=w3=1mm, and the relationship w3=w2<L1 is satisfied; in the embodiment, Rk=42.2mm, h1=0.5mm, and h3=1.2mm, and the relationship h1<Rr-Rk=0.6mm≤h3 is satisfied.

[0049] Preferably, in the limited rotor core space, in order to reduce the mold cost and further improve the magnetic field direction, a 0.2mm chamfer is arranged at each edge intersection of all magnetic barrier slots.

[0050] Preferably, the outer side of the rotor core 12 above each magnetic barrier slot comprises a first circular arc 128 and a second circular arc 129, the center O1 of the first circular arc 128 is at the center of the rotor core 12, and the central angle δ satisfies: 20°≤δ≤30°; the center O2 of the second circular arc 129 deviates from the center O1 of the first circular arc 128, and the radius Rc of the second circular arc 129 satisfies: Rr-25.7mm≤Rc≤Rr-22.6mm. By setting the segmented circular arc, the air gap between the rotor core 12 and the stator core 11 can be made uneven, the magnetic flux distribution can be improved, some adverse harmonics can be weakened, and the motor performance can be improved.

[0051] Preferably, in order to ensure that the concentrated winding is embedded in the stator slot 111 in the stator core 11 to achieve the reduction of the end length, reduce the copper loss, improve the degree of mass production, and improve the manufacturing efficiency, the number p of permanent magnets 122, the number Z of stator slots 111 of the stator core 11 outside the rotor core 12, and the number m of symmetrical winding phases embedded in the stator core 11 satisfy: p=(2 Z) / m. In the embodiment, the number p of permanent magnets 122 is 6, the number Z of stator slots 111 is 9, and the number m of symmetrical winding phases is 3, so that p=(2 Z) / m is satisfied.

[0052] Preferably, in order to reduce the leakage magnetic flux between the permanent magnets 122, a groove 126 is arranged between the two adjacent permanent magnet slots 121, and each groove 126 extends inward along the radial direction of the rotor core 12; in order to avoid magnetic field distortion and further improve the magnetic field, the second circular arc 129 intersects with the side of the groove 126 to form a first chamfer 130, and the side of the groove 126 intersects with the bottom of the groove 126 to form a second chamfer 131; in order to achieve a reasonable value of the cross-axis inductance, increase the refrigerant flow area to improve the temperature rise and efficiency, and improve the demagnetization resistance of the permanent magnet 122, the angle θ between the bottom of the groove 126 and the bottom of the permanent magnet slot 121 and the number p of permanent magnet slots 121 satisfy: θ=180° (1-1 / p). In the embodiment, θ=180° (1-1 / 6)=150°.

[0053] Preferably, in order to further reduce the leakage magnetic flux, the groove 126 and the side of the permanent magnet slot 121 form a parallel magnetic flux bridge 127, in order to enhance the effect of reducing the leakage magnetic flux, the magnetic field of the parallel magnetic flux bridge 127 needs to be highly saturated, and the width wb of the parallel magnetic flux bridge 127 needs to satisfy: wb=Rr-Rk, so as to ensure that the parallel magnetic flux bridge 127 is not affected by the interference and centrifugal force during the rotation.

[0054] Preferably, the magnetic field direction of the adjacent permanent magnet 122 is the same as and opposite to the radial direction of the rotor core 12 respectively, and the permanent magnet 122 is rectangular in shape for easy installation and reduced processing cost, the thickness hm of the permanent magnet 122 and the width w1 of the first magnetic barrier slot 123 satisfy: w1 < hm ≤ 3 mm, the width wm of the permanent magnet 122 and the width wc of the permanent magnet slot 121 and the sizes of the first magnetic barrier slot 123, the second magnetic barrier slot 124 and the third magnetic barrier slot 125 satisfy: L1 + L2 + L3 + w1 + w2 + w3 < (wc-0.1 mm) / 2 = wm / 2. By limiting the width, thickness, shape and magnetizing direction of the permanent magnet 122, a reasonable pole arc coefficient can be ensured, the use amount of the permanent magnet 122 is reduced, and the motor cost is reduced on the basis of ensuring electromagnetic performance.

[0055] It should be noted that the "prior art" appearing below specifically refers to the case where the outer radius of the rotor core 12 is Rr, the distance from the bottom midpoint of the permanent magnet slot 121 to the center point of the rotor core 12 is ho, the thickness of the permanent magnet 122 is hm, and 2 < (Rr-ho) / hm ≤ 3.4 is satisfied, and the first magnetic barrier slot 123, the second magnetic barrier slot 124 and the third magnetic barrier slot 125 are not provided. The size, residual magnetism, magnetizing method and coercive force of the permanent magnet of the "prior art" are consistent with those of the present application.

[0056] As shown in Figure 6 the contrast diagram of the no-load back electromotive force effective value of the rotor core adopting the present application and the prior art at a speed of 1000 rpm is shown. The no-load back electromotive force of the rotor core adopting the present application is increased by 2.35% compared with the prior art, i.e. under the condition that the motor has not entered the field weakening and the magnetic circuit has not been saturated, the current is reduced by the same amount, and the copper loss at low speed is reduced. The purpose of reducing the leakage magnetic between the permanent magnets 122 and increasing the power density is achieved.

[0057] As shown in Figure 7 the efficiency contrast diagram of the compressor at the rated point (load torque 29.1 Nm, speed 3600 rpm) is shown. As can be seen from Figure 7 , the efficiency of the rotor core adopting the present application is improved.

[0058] As shown in Figures 8-9 the radiation sound power contrast diagram of the rotor core adopting the present application and the prior art at high speed and under a load torque of 17.43 Nm, and the radiation sound power contrast diagram of the rotor core adopting the present application and the prior art at 24 times the frequency are shown.

[0059] During the high-speed operation of the compressor, the requirement for vibration and noise is high, and from Figure 8It can be seen that, for the compressor high-speed operation process, at different rotating speeds, the rotor core of the embodiment of the application has different degrees of reduction in the radiation sound power compared with the prior art, and at higher rotating speeds, the radiation sound power is reduced more significantly. At the three rotating speeds, the radiation sound power is reduced by 2.40%, 7.34%, and 9.07% respectively, proving the effectiveness of the rotor core of the application.

[0060] For the 24 times mechanical rotation frequency noise which is relatively sensitive to human ears, from Figure 9 It can be seen that, for the compressor high-speed operation process, at different rotating speeds, the rotor core of the embodiment of the application has different degrees of reduction in the radiation sound power compared with the prior art, and at higher rotating speeds, the radiation sound power is reduced more significantly. At the three rotating speeds, the radiation sound power is reduced by 2.40%, 7.34%, and 9.07% respectively, proving the effectiveness of the rotor core of the application.

[0061] The application provides a permanent magnet motor, which adopts the rotor core 12.

[0062] The application also provides a variable frequency compressor, which adopts the permanent magnet motor 1, wherein other structures and operations of the permanent magnet motor and the variable frequency compressor are known to those skilled in the art, and will not be described in detail.

[0063] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A rotor core characterized by, The outer radius of the rotor core is Rr, the rotor core comprises uniformly distributed permanent magnet grooves, the distance from the bottom midpoint of the permanent magnet groove to the center point of the rotor core is ho, each of the permanent magnet grooves is embedded with magnetically alternating permanent magnets, the thickness of the permanent magnets is hm, and Rr, ho and hm satisfy 2<(Rr-ho) / hm≤3.4; Each of the two sides of the top of the permanent magnet groove is provided with symmetrically distributed first, second and third magnetic barrier grooves, which are arranged from the edge to the center in sequence; The distance from the first magnetic barrier groove to the top of the permanent magnet groove is h1, the distance from the first magnetic barrier groove to the side of the permanent magnet groove is L1, and the width of the first magnetic barrier groove is w1; the distance from the second magnetic barrier groove to the top of the permanent magnet groove is h2, the distance from the second magnetic barrier groove to the first magnetic barrier groove is L2, and the width of the second magnetic barrier groove is w2; the distance from the third magnetic barrier groove to the top of the permanent magnet groove is h3, the distance from the third magnetic barrier groove to the second magnetic barrier groove is L3, and the width of the third magnetic barrier groove is w3; The top of the first, second and third magnetic barrier grooves is located on the same circular arc, and the radius of the circular arc is Rk; Each of the size relationships satisfies 0.45mm≤h1<h2<h3≤1.3mm, 2mm≤L1<L2<L3≤5mm, 2.55h1≤w1≤3.5h1, w3=w2<L1, and h1<Rr-Rk≤h3.

2. The rotor core according to claim 1, characterized by Each edge intersection of all the magnetic barrier grooves is chamfered by 0.2mm.

3. The rotor core according to claim 1, characterized by The outer side of the rotor core above the magnetic barrier grooves comprises a first circular arc and a second circular arc; The center of the first circular arc O1 is at the center of the rotor core, and the occupied central angle δ satisfies 20°≤δ≤30°; The center of the second circular arc O2 deviates from the center O1 of the first circular arc, and the radius Rc of the second circular arc satisfies Rr-25.7mm≤Rc≤Rr-22.6mm.

4. The rotor core according to claim 3, characterized by The number of the permanent magnets is p, the number of the stator slots outside the rotor core is Z, and the number of the symmetric winding phases embedded in the stator core is m, wherein p, m and Z satisfy: p=(2 Z) / m.

5. The rotor core according to claim 4, characterized by A groove is arranged between two adjacent permanent magnet grooves, and each groove extends inward along the radial direction of the rotor core; The second circular arc intersects with the side of the groove to form a first chamfer, and the side of the groove intersects with the bottom of the groove to form a second chamfer; The angle between the groove bottom edge and the permanent magnet slot bottom edge is θ, and θ and the number of permanent magnet slots p satisfy: θ = 180° (1-1 / p).

6. The rotor core according to claim 5, characterized by The groove and the side of the permanent magnet groove form a parallel magnetic bridge, and the width of the parallel magnetic bridge is wb, wb, Rr and Rk satisfy wb=Rr-Rk.

7. The rotor core according to claim 1, characterized by The directions of the magnetic fields of adjacent permanent magnets are the same and opposite to the radial direction of the rotor core, respectively; The permanent magnet is rectangular in shape; The thickness of the permanent magnet is hm, and hm and w1 satisfy w1<hm≤3mm; The width of the permanent magnet is wm, the width of the permanent magnet groove is wc, and the relationship between wm, wc and the size of the magnetic barrier groove satisfies L1+L2+L3+w1+w2+w3<(wc-0.1mm) / 2=wm / 2.

8. A permanent magnet electric machine characterized by, The rotor core comprises the rotor core according to any one of claims 1-7.

9. A variable frequency compressor characterized by, The permanent magnet motor comprises the rotor core according to claim 8.

Images