CN111682667A - A 48/8 Bearingless Alternating Pole Permanent Magnet Synchronous Motor - Google Patents

Abstract

The invention discloses a 48/8 bearingless alternating pole permanent magnet synchronous motor, belonging to the technical field of magnetic suspension motors, comprising a stator iron core, a rotor iron core, a permanent magnet, a three-phase torque winding and a suspension winding. The permanent magnets are arranged with the same polarity, and the iron core between the permanent magnets of the rotor is magnetized to the opposite polarity to the permanent magnets. Two sets of windings on the stator core provide torque magnetic field and suspension magnetic field respectively. On the basis of in-depth analysis of the suspension excitation of the motor, a sinusoidal winding method is proposed for the suspension winding structure. When the motor realizes the torque and suspension functions at the same time, the suspension force performance is improved, and the coupling degree of the suspension force in the x and y directions is reduced. Compared with other methods of improving suspension force by adding auxiliary structures, this method has simpler motor structure and less loss.

Description

A 48/8 Bearingless Alternating Pole Permanent Magnet Synchronous Motor

technical field

The invention relates to a bearingless alternating pole permanent magnet synchronous motor, which is suitable for high-speed and high-power motor applications. It belongs to the field of magnetic levitation motors applying bearingless technology.

Background technique

Alternating pole permanent magnet synchronous motor was first proposed in US patent US:4631435[P], and it was further improved around 2000. The permanent magnets of the motor are arranged with the same polarity, and the adjacent rotor cores are magnetized to the other polarity, also known as "iron poles". This type of motor can flexibly adjust the magnetic flux under the iron pole to achieve the purpose of adjusting the air gap magnetic field. Studies have shown that the use of permanent magnets in this type of motor is more economical. In recent years, the alternating pole structure has been used in various types of permanent magnet motors due to its advantages such as less use of permanent magnets and easier field weakening.

The bearingless motor integrates the suspended magnetic bearing winding into the motor stator, which has the advantages of high efficiency, maintenance-free, long service life, and low requirements on the operating environment. The bearingless permanent magnet motor with alternating pole structure can make the suspension force irrelevant to the rotor position angle when the number of motor pole pairs is p≥4, and the trade-off between the torque and suspension performance of the thickness of the permanent magnet does not need to be considered. However, the distribution of the air gap magnetic field of the alternating pole bearingless permanent magnet synchronous motor is more complicated than that of the traditional bearingless permanent magnet synchronous motor.

In view of the above-mentioned problem of the suspension force performance of the alternating pole bearingless permanent magnet synchronous motor, many researchers have proposed different improvement methods. Some researchers compared the effects of concentrated winding and distributed winding, two-phase winding and three-phase winding on the suspension performance of the motor. Some researchers have proposed methods of adding auxiliary poles or adding auxiliary windings in the literature, and they believe that they can achieve better suspension effect and decoupling effect of suspension force in the x and y directions than the traditional winding structure. But both of these methods make the motor structure more complicated and the losses larger.

SUMMARY OF THE INVENTION

The present invention designs a three-phase 48-slot 8-pole alternating-pole bearingless permanent-magnet synchronous motor for the application of the bearingless alternating-pole permanent magnet synchronous motor in the high-speed and low-loss occasions, especially the problems existing in the above-mentioned suspension force performance. For the motor, by optimizing the structure of the motor body, especially the structure design of the suspension winding, the pulsation of the motor suspension force is smaller, the coupling degree in the x and y directions is reduced, and the end is smaller and the loss is low.

In order to achieve the above object, the technical solution of the present invention is as follows: the motor includes a stator core, a rotor core, a permanent magnet, a three-phase torque winding and a suspension winding. The permanent magnets in the rotor can be inserted or built-in. The magnetization directions of the permanent magnets are arranged in the same polarity along the rotor surface, and the iron core part adjacent to the permanent magnets is magnetized to the opposite polarity, which is called "iron pole". Since the permeance of the iron core is much larger than that of the permanent magnet, the magnetic field flux linkage generated by the winding is almost entirely hinged from the iron core. The stator core has 48 slots, with inclined slot design. The three-phase torque winding is designed as a common permanent magnet synchronous motor.

The suspension force of the motor is analyzed. When the number of pole pairs meets certain conditions, the suspension force has nothing to do with the rotor position angle, but in fact, the suspension force fluctuates regularly with the rotor position in each suspension force period, and there is coupling in the x and y directions. Aiming at the above problems, this paper proposes a new method for assigning suspension windings: in one suspension degree of freedom, the suspension winding adopts a concentric sinusoidal winding, and the number of conductors in each slot of the same phase winding is calculated and allocated according to the sinusoidal law, so that the slot The current distribution approximately conforms to the sinusoidal waveform, which is beneficial to weaken the high-order harmonics in the suspended air gap magnetic field, so that the generated suspended magnetomotive force is close to the sinusoidal waveform.

Compared with the prior art, the beneficial effects of the present invention:

1. The motor designed by the present invention can effectively reduce the fluctuation of the motor suspension force, reduce the coupling of the suspension force in the x and y directions, and at the same time, the structural changes to the existing motor are relatively small, and the loss is small.

2. The suspension winding designed in the sinusoidal manner proposed by the present invention can reduce the harmonics of the suspension magnetomotive force and improve the suspension performance of the motor under the condition that the size of the total suspension current remains unchanged. At the same time, the end of the suspension winding of the motor is small, and the loss is small.

Description of drawings

Fig. 1 is the structure diagram of 48/8 bearingless alternating pole permanent magnet synchronous motor of the present invention;

Fig. 2 is the operating principle diagram of the designed alternating pole permanent magnet synchronous motor;

Fig. 3 is the winding development diagram of one-phase suspension winding;

Figure 4 shows the comparison of the air-gap flux density between the sinusoidal winding designed at a certain pole and the traditional concentrated winding.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be pointed out that the technical solution and design principle of the present invention are described in detail below only with an optimized technical solution, but the protection scope of the present invention does not limited to this.

The described embodiment is the preferred embodiment of the present invention, but the present invention is not limited to the above-mentioned embodiment, without departing from the essence of the present invention, any obvious improvement, replacement or All modifications belong to the protection scope of the present invention.

The 48/8 alternating pole bearingless permanent magnet synchronous motor of the present invention is shown in Fig. 1 and Fig. 2, which includes a stator core, a rotor core, permanent magnets, torque windings and suspension windings. in:

The stator iron core has 48 slots, the inclined slot design, and the inclined slot angle is 30°. The motor adopts a double-winding structure, and the torque winding and the suspension winding are wound in the same stator slot. The design and winding method of the torque winding are the same as those of the traditional permanent magnet synchronous motor.

The permanent magnets are interpolated, arranged with the same polarity, and fixed in the rotor core. In order to adapt to high-speed operation, a carbon fiber protective cover should be added outside the permanent magnet and the rotor core. Four permanent magnets are arranged with the same polarity, and the rotor core between adjacent permanent magnets is magnetized to the opposite polarity to the permanent magnets, forming an 8-pole magnetic field. Since the permeance of the iron core is much larger than that of the permanent magnet, the magnetic field flux linkage generated by the winding is almost entirely hinged from the iron core.

The suspension winding is designed as a sinusoidal winding, and the distribution of the number of turns of the suspension winding is calculated according to the pole pitch and the total number of turns of the suspension winding, and the winding is concentric. In the specific example of the present invention, taking the suspension in the y-axis direction as an example, the number of pole pairs of the suspension winding of a three-phase 48-slot 8-pole motor is 1, the pole pitch τ=24, and the slot pitch angle α. The three-phase suspension windings A, B, and C are placed at 120° space intervals, and are designed according to the three-phase 60° phase belt. The phase sequence of the windings is A→-C→B→-A→C→-B, and the coil span is odd. type of concentric structure. Taking phase A as an example, calculate according to the design method of three-phase sinusoidal winding:

Σ=0.831+0.752+0.659+0.556=2.798 (2)

Assuming that the total number of turns of the phase winding is N, the distribution ratio of the number of coil turns is:

The number of turns of the coil in slots 5-28 is:

The number of turns of the coil in slots 6-27 is:

The number of turns of the coil in slots 7-26 is:

The number of turns of the coil in slots 8-25 is:

If the span between 8-25 slots is considered to be relatively small, it can also be allocated according to 3 sets of coils:

Σ=0.831+0.752+0.659=2.242 (7)

Slots 5-28:

Slots 6-27:

Slots 7-26:

The calculation of the number of turns of the B and C-phase windings is similar to that of the A phase. The specific number of turns of the three-phase windings can be fine-tuned according to actual needs and manufacturing convenience. The current required for the suspension force in the x and y directions is transformed into three-phase currents according to formula (11) and flows into the designed windings. The expanded view of one-phase suspension windings is shown in Figure 3.

Among them, i _A , i _B , and i _C are the three-phase suspension winding currents, and i _x and i _y are the currents required for the suspension force in the x-axis and y-axis directions.

The high-order harmonics of the magnetomotive force generated by the suspension winding after the improved structure are reduced and are closer to the sinusoidal distribution; it can be seen from Figure 4 that the magnetic suspension winding air-gap magnetic flux density after the improvement The resulting air gap flux density is more sinusoidal.

Compared with the levitation force generated in one electrical cycle, the levitation force fluctuation generated by the sinusoidal winding method of the suspension winding is significantly improved compared with the concentrated winding, and is also better than that of the three-phase distributed winding. The coupling degree of suspension force in the x and y directions decreases. Therefore, the application of the sinusoidal winding method to the suspension winding can reduce the harmonics of the suspension magnetomotive force and improve the suspension performance of the motor while the total suspension current is unchanged. At the same time, the end of the suspension winding of the motor is relatively small and the loss is low.

The series of detailed descriptions listed above are only specific descriptions for the feasible embodiments of the present invention, and they are not used to limit the protection scope of the present invention. All should be included within the protection scope of the present invention.

Claims (9)

1. a 48/8 bearingless alternating pole permanent magnet synchronous motor, is characterized in that, comprises: stator iron core (1), rotor iron core (2), permanent magnet (3), stator iron core (1) comprises two sets of windings, They are the torque winding (4) and the suspension winding (5) respectively, the permanent magnets (3) are fixed in the rotor core (2) and are arranged with the same polarity, and the rotor cores between adjacent permanent magnets can be magnetized to be the same as the permanent magnets. opposite polarity. 2. A 48/8 bearingless alternating pole permanent magnet synchronous motor according to claim 1, characterized in that, the stator core (1) comprises 48 slots, the inclined slot is designed, the angle of the inclined slot is 30°, and the double The winding structure, that is, the two sets of windings of the torque winding (4) and the suspension winding (5) are wound together in one stator slot. 3. a kind of 48/8 bearingless alternating pole permanent magnet synchronous motor according to claim 1, is characterized in that, the permanent magnet (3) is an in-line or built-in type, and 4 permanent magnets (3) have the same pole The rotor core (2) between adjacent permanent magnets is magnetized to the opposite polarity to that of the permanent magnets, forming an 8-pole magnetic field, and the magnetic field flux linkage generated by the winding can be almost completely hinged from the core. 4. A 48/8 bearingless alternating pole permanent magnet synchronous motor according to claim 1, characterized in that, the permanent magnet (3) is provided with a carbon fiber protective cover. 5. a kind of 48/8 bearingless alternating pole permanent magnet synchronous motor according to claim 1, is characterized in that, described suspension winding (5) is sinusoidal winding, calculate suspension according to suspension winding pole pitch and total number of turns Distribution of winding turns, concentric winding. 6. a kind of 48/8 bearingless alternating pole permanent magnet synchronous motor according to claim 5, is characterized in that, when the y-axis direction is suspended, the suspension winding is designed as follows: The three-phase 48-slot 8-pole motor has a suspended winding pole pair number of 1, a pole pitch τ=24, and a slot pitch angle α. The three-phase suspension windings A, B, and C are designed according to the three-phase 60° phase belt, and the coil span is For odd-numbered concentric structures, taking phase A as an example, calculate the distribution of winding turns according to the design method of three-phase sinusoidal windings:

Σ=0.831+0.752+0.659+0.556=2.798 (2) Assuming that the total number of turns of the phase winding is N, the distribution ratio of the number of turns of each coil is: Slots 5-28:

Slots 6-27:

Slots 7-26:

Slots 8-25:

7. a kind of 48/8 bearingless alternating pole permanent magnet synchronous motor according to claim 6, is characterized in that, also comprises: also can be distributed according to following 3 groups of coils: Σ=0.831+0.752+0.659=2.242 (7) Slots 5-28:

Slots 6-27:

Slots 7-26:

The calculation of the number of turns of the B and C phase windings is similar to that of the A phase. 8. A 48/8 bearingless alternating pole permanent magnet synchronous motor according to claim 6 or 7, characterized in that, when levitating in the x-axis direction, the suspension winding design is the same as the y-axis levitating. 9. A kind of 48/8 bearingless alternating pole permanent magnet synchronous motor according to claim 8, characterized in that the current required for the suspension force in the x and y directions is converted into a three-phase current according to the following formula (11). Design winding:

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