Structure for weakening counter electromotive force harmonic waves of permanent magnet synchronous motor winding

Abstract

The utility model discloses a structure for weakening counter electromotive force harmonic waves of a permanent magnet synchronous motor winding, which comprises a rotor iron core, permanent magnet grooves and additional grooves are arranged in the rotor iron core, and permanent magnets are arranged in the permanent magnet grooves; the additional grooves are connected with one ends, close to the outer surface of the rotor core, of the permanent magnet grooves, and extend towards the magnetic pole centers of the permanent magnets; the size of the additional groove is gradually reduced from the position close to the permanent magnet to the position close to the center of the magnetic pole. According to the utility model, the additional grooves are additionally arranged on the basis of the permanent magnet grooves in the existing rotor iron core, the additional grooves are connected with the end parts, close to the outer surface of the rotor, of the permanent magnet grooves and extend towards the centers of the magnetic poles, and the widths of the additional grooves are gradually reduced from the positions close to the permanent magnets to the positions close to the centers of the magnetic poles; by designing the structure, the effective air gap length near the end part of the magnetic pole area can be increased, and the effective air gap length of the magnetic pole center area cannot be changed, so that harmonic waves in air gap flux density distribution can be weakened.

Description

Technical Field

[0001] This utility model relates to the field of motors, specifically a structure for reducing the harmonics of the back electromotive force of a permanent magnet synchronous motor winding. Background Technology

[0002] Unlike traditional electrically excited motors (such as asynchronous motors), permanent magnet synchronous motors rely on permanent magnets to generate an excitation magnetic field.

[0003] In addition, among the many types of permanent magnet synchronous motors, the built-in permanent magnet synchronous motor, in which the permanent magnet is placed inside the rotor core, has high power density and high mechanical strength, and is widely used.

[0004] However, without considering the stator slots, the no-load air gap magnetic field of the built-in permanent magnet synchronous motor is close to a rectangular distribution, and the harmonic content of the air gap magnetic flux density is much higher than that of an electrically excited motor of the same capacity. This leads to an increase in the harmonic content of the winding back electromotive force, which in turn causes the harmonic content of the winding current to be too high when the motor is under load, causing fluctuations in the electromagnetic torque and speed of the motor, which seriously affects the operating performance of the motor.

[0005] There are two traditional approaches to solving this problem:

[0006] 1. The stator skewed slot structure commonly used in electrically excited motors is adopted. However, the stator skewed slot structure increases the assembly difficulty of the stator core and windings. In addition, for motors with a large outer diameter and short axial length, the axial length of the stator core is short. If the stator skewed slot structure is adopted, the tilt angle of the stator slot along the axial direction will be too large, making the assembly of the windings very difficult. Therefore, motors with this structure are usually difficult to adopt the stator skewed slot structure.

[0007] 2. Employing a non-uniform air gap structure reduces the harmonic content of the air gap magnetic flux density, such as... Figure 2 As shown, in the non-uniform air gap structure, the air gap at the center of each magnetic pole is shorter, while the air gap at the edge of the magnetic pole and between adjacent magnetic poles is longer. In this way, without considering the stator slots, an approximately sinusoidal distribution of air gap magnetic flux density can be obtained, and the harmonic content of the air gap magnetic flux density is suppressed.

[0008] As one of the advantages of built-in permanent magnet synchronous motors, the permanent magnets built into the rotor core make the equivalent air gap length of the direct axis (at the center of the magnetic pole) greater than that of the quadrature axis (at the center of the region between adjacent magnetic poles). Therefore, its direct axis inductance is significantly smaller than that of the quadrature axis inductance, and it has a significant salient pole effect, which will generate additional magnetic reluctance power and increase the maximum output power of the motor.

[0009] However, when adopting Figure 2When the uneven air gap is shown, the air gap length at the cross axis increases, the cross axis inductance decreases, the difference between the direct axis inductance and the cross axis inductance also decreases, the reluctance power and the maximum power that can be output by the motor also decrease, and the performance of the motor is greatly affected. Content of the utility model

[0010] The utility model discloses a structure for weakening the back electromotive force harmonic of the winding of a permanent magnet synchronous motor to solve the above problems existing in the prior art.

[0011] Technical scheme: a structure for weakening the back electromotive force harmonic of the winding of a permanent magnet synchronous motor, comprising:

[0012] A rotor core is provided with a permanent magnet slot and an additional slot, and the permanent magnet slot is provided with a permanent magnet;

[0013] The additional slot is connected to one end of the permanent magnet slot close to the outer surface of the rotor core and extends to the center of the magnetic pole of the permanent magnet; the size of the additional slot gradually decreases from the position close to the permanent magnet to the position close to the center of the magnetic pole.

[0014] The utility model adds an additional slot to the permanent magnet slot in the existing rotor core, the additional slot is connected to the end of the permanent magnet slot close to the outer surface of the rotor and extends to the center of the magnetic pole, and the width of the additional slot gradually decreases from the position close to the permanent magnet to the position close to the center of the magnetic pole; by designing the structure, the effective air gap length near the end of the magnetic pole region is increased, and the effective air gap length of the center region of the magnetic pole does not change, so that the harmonic in the air gap magnetic density distribution can be weakened.

[0015] After the rotor with the additional slot in the rotor core is used, the harmonic content in the back electromotive force of the winding of the permanent magnet synchronous motor is significantly reduced, and the difference between the direct axis inductance and the cross axis inductance of the motor is not reduced, so that the maximum power output by the motor can be guaranteed to be high.

[0016] In a further embodiment, the permanent magnet slot is designed in multiple groups, and each group includes two mirror image slots.

[0017] The two slots have a predetermined distance.

[0018] In a further embodiment, the extension lines of the two slots have an intersection point.

[0019] The end of the two slots close to the intersection point is close to the center of the rotor core.

[0020] The end of the two slots away from the intersection point is close to the outer surface of the rotor core.

[0021] In a further embodiment, the permanent magnet slots are distributed in a circumferential array along the rotor core.

[0022] In a further embodiment, the rotor core is sleeved with a stator core on the outer surface.

[0023] The stator core is internally provided with a plurality of windings.

[0024] In a further embodiment, the rotor core outer surface and the stator core inner surface form an air gap, and the air gap is uniform.

[0025] In a further embodiment, the stator core is internally provided with a plurality of winding slots matched with the windings, and the winding slots are in communication with the air gap.

[0026] Beneficial effects: The utility model discloses a structure of weakening permanent magnet synchronous motor winding counter electromotive force harmonic, the utility model adds additional slot on the basis of the permanent magnet slot in the existing rotor core, and the additional slot is connected with the end portion of permanent magnet slot close to the outer surface of rotor, extends to the magnetic pole center, and the width of the additional slot gradually reduces from close to the permanent magnet to close to the magnetic pole center, and the effective air gap length near the end portion of magnetic pole area is increased through the design of the structure, and the effective air gap length of the magnetic pole center area does not change, so that the harmonic in air gap magnetic density distribution can be weakened.

[0027] After adopting the rotor with the additional slot in the rotor core, the harmonic content in the winding counter electromotive force of the permanent magnet synchronous motor is significantly reduced, and the difference of the direct axis inductance and the cross axis inductance of the motor is not reduced, so that the maximum power output of the motor can be guaranteed to be high. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is the structure schematic diagram of the utility model.

[0029] Figure 2 It is the uneven air gap schematic diagram in the prior art.

[0030] Figure 3 It is the air gap magnetic density distribution schematic diagram of the motor.

[0031] Figure 3 (a) is the magnetic density distribution schematic diagram of the uniform air gap motor.

[0032] Figure 3 (b) is the magnetic density distribution schematic diagram of the motor with additional slot.

[0033] Figure 4 It is the winding counter electromotive force schematic diagram of the motor.

[0034] Figure 4 (a) is the winding counter electromotive force schematic diagram of the uniform air gap motor.

[0035] Figure 4 (b) is the winding counter electromotive force schematic diagram of the motor with additional slot.

[0036] Reference signs are:

[0037] 1, stator core; 2, winding; 3, rotor core; 4, permanent magnet;

[0038] 51, permanent magnet slot; 52, additional slot. DETAILED DESCRIPTION

[0039] The application relates to a structure for weakening the back electromotive force harmonic of a permanent magnet synchronous motor winding, which is explained in detail below through a specific embodiment.

[0040] A structure for weakening the back electromotive force harmonic of a permanent magnet synchronous motor winding is shown in the accompanying drawings, which comprises: Figure 1

[0041] A rotor core, permanent magnet slots and additional slots are formed in the rotor core, and permanent magnets are arranged in the permanent magnet slots.

[0042] The additional slots are connected to one end of the permanent magnet slots close to the outer surface of the rotor core and extend to the center of the magnetic pole of the permanent magnet; the size of the additional slots gradually decreases from the position close to the permanent magnet to the position close to the center of the magnetic pole.

[0043] The utility model adds additional slots on the basis of the permanent magnet slots in the existing rotor core, the additional slots are connected to the end part close to the outer surface of the rotor and extend to the center of the magnetic pole, the width of the additional slots gradually decreases from the position close to the permanent magnet to the position close to the center of the magnetic pole, the structure can increase the effective air gap length near the end part of the magnetic pole region, and the effective air gap length of the center region of the magnetic pole does not change, so that the harmonic in the air gap magnetic density distribution can be weakened.

[0044] After the rotor with the additional slots in the rotor core is adopted, the harmonic content in the back electromotive force of the winding of the permanent magnet synchronous motor is significantly reduced, and the difference between the direct-axis inductance and the quadrature-axis inductance of the motor is not reduced, so that the maximum power output of the motor can be guaranteed to be high.

[0045] The permanent magnet slots are designed in multiple groups, and each group comprises two mirror image slots.

[0046] The two slots have a predetermined distance.

[0047] The extension lines of the two slots have an intersection point.

[0048] One end of the two slots close to the intersection point is close to the center of the rotor core.

[0049] One end of the two slots away from the intersection point is close to the outer surface of the rotor core.

[0050] The permanent magnet slots are distributed in a circumferential array along the rotor core. ​

[0051] The rotor core is sleeved with a stator core on the outer surface.

[0052] The stator core is internally provided with a plurality of windings.

[0053] The outer surface of the rotor core and the inner surface of the stator core form an air gap, and the air gap is uniform.

[0054] The stator core is internally provided with a plurality of winding slots matched with the windings, and the winding slots are communicated with the air gap.

[0055] As can be seen from Figure 3 , after the additional slot is added inside the rotor core, the magnetic circuit structure of the motor is changed, compared with the original motor model with uniform air gap, after the structure of the application is applied, the air gap magnetic flux density distribution of the motor is closer to the sinusoidal distribution.

[0056] The air gap magnetic flux density waveforms in Figure 3 are analyzed respectively, Figure 3 the fundamental wave amplitude of the air gap magnetic flux density of the original model (a) is 1.089T, and the harmonic content is 29.75%, while Figure 3 the fundamental wave amplitude of the air gap magnetic flux density of the improved model (b) is 1.059T, and the harmonic content is 25.17%; it can be seen that after the structure of the application is applied, the fundamental wave of the air gap magnetic flux density is slightly reduced, but the harmonic content is significantly reduced.

[0057] It can be further seen from Figure 4 that after the additional slot is added inside the rotor core, the winding back electromotive force waveform of the motor is also closer to the sinusoidal distribution.

[0058] The winding back electromotive force waveforms in Figure 4 are analyzed respectively, Figure 4 the fundamental wave amplitude of the winding back electromotive force of the original model (a) is 537.3V, and the harmonic content is 4.64%, while Figure 4 the fundamental wave amplitude of the winding back electromotive force of the improved model (b) is 522.3V, and the harmonic content is 2.41%; it can be seen that after the structure of the application is applied, the fundamental wave of the winding back electromotive force is slightly reduced, but the harmonic content is also significantly reduced, which is more conducive to the stable operation of the motor.

[0059] Working principle: On the basis of the existing permanent magnet slot inside the rotor core, an additional slot is added, which is connected to the end of the permanent magnet slot close to the outer surface of the rotor and extends to the center of the magnetic pole. The width of the additional slot gradually decreases from the position close to the permanent magnet to the position close to the center of the magnetic pole. By designing this structure, the effective air gap length near the end of the magnetic pole region is increased, while the effective air gap length of the center region of the magnetic pole does not change. In this way, the harmonics in the air gap magnetic flux density distribution can be weakened.

[0060] The preferred embodiments of the present application are described in detail above with reference to the drawings, but the present application is not limited to the specific details of the above-described embodiments. Within the technical concept of the present application, various equivalent transformations of the technical solutions of the present application can be made, and these equivalent transformations all belong to the protection scope of the present application.

Claims

1. A structure for weakening back electromotive force harmonics of a winding of a permanent magnet synchronous motor, characterized by, The application relates to a rotor core, which comprises a permanent magnet slot and an additional slot, the permanent magnet slot being provided with a permanent magnet. The additional slot is connected with the permanent magnet slot at one end close to the outer surface of the rotor core and extends to the center of the magnetic pole of the permanent magnet. The size of the additional slot gradually decreases from the position close to the permanent magnet to the position close to the center of the magnetic pole. The permanent magnet slot is designed in multiple groups, each group comprising two mirror-image slots.

2. The structure for weakening the back electromotive force harmonics of the winding of a permanent magnet synchronous motor according to claim 1, characterized in that: The two slots have a predetermined distance. The extension lines of the two slots have an intersection point.

3. The structure for weakening the back electromotive force harmonics of the winding of a permanent magnet synchronous motor according to claim 2, characterized in that: The two slots are close to the center of the rotor core at one end close to the intersection point. The two slots are close to the outer surface of the rotor core at one end far from the intersection point. The permanent magnet slots are distributed in a circular array along the rotor core.

4. The structure for weakening the back electromotive force harmonics of the winding of a permanent magnet synchronous motor according to claim 1, characterized in that: A stator core is sleeved on the outer surface of the rotor core.

5. The structure for weakening the back electromotive force harmonics of the winding of a permanent magnet synchronous motor according to claim 1, characterized in that: The stator core is provided with multiple windings. The outer surface of the rotor core and the inner surface of the stator core form an air gap, which is uniform.

6. The structure for weakening the back electromotive force harmonics of the winding of a permanent magnet synchronous motor according to claim 5, characterized in that: The stator core is provided with multiple groups of winding slots matched with the windings, and the winding slots are communicated with the air gap.

7. The structure for weakening the back electromotive force harmonics of the winding of a permanent magnet synchronous motor according to claim 6, characterized in that: ​

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