A dual-stator axial flux motor

Abstract

The application discloses a double-stator axial flux motor, which comprises a stator with a stator winding, the stator winding generates magnetic field harmonics, the magnetic field harmonics include target harmonics and fundamental waves, the stator is two, the stator winding, the magnetic field harmonics, the target harmonics and the fundamental waves are two; in the two stators, the second stator is forward by alpha degrees along the rotation direction of the axial flux motor relative to the first stator, and the current initial phase angle of the second stator lags the current initial phase angle of the first stator by theta degrees, so that the two target harmonics are offset, and the amplitude of the two fundamental waves remains unchanged. In the method of the application, additional adjusting components are not introduced, and the purpose of weakening the target harmonics can be achieved only by changing the relative position of the stator and the initial phase angle of the stator, which is simple and easy to implement.

Description

Technical Field

[0001] This invention relates to the field of axial flux motor technology, and more specifically, to a dual-stator axial flux motor. Background Technology

[0002] Concentrated-winding axial flux motors have advantages such as simple manufacturing process, high power and torque density, low cogging torque, small end cap size, and low copper wire consumption, thus gaining widespread application. However, compared with traditional distributed windings, concentrated windings generate abundant magnetic field harmonics after current is applied. These harmonics, especially low-order harmonics, increase eddy current losses, core losses, and vibration and noise, severely affecting motor performance. The same drawbacks exist for dual-stator axial flux motors. Summary of the Invention

[0003] The purpose of this invention is to design a dual-stator axial flux motor that can reduce target harmonics while maintaining the amplitude of the fundamental frequency. To achieve the above objective, this invention provides the following technical solution:

[0004] A dual-stator axial flux motor includes a stator with stator windings that generate magnetic field harmonics, the magnetic field harmonics including target harmonics and fundamental harmonics. The stator has two stators, and there are two stator windings, two magnetic field harmonics, two target harmonics, and two fundamental harmonics.

[0005] In the two stators, the second stator is forward by α degrees relative to the first stator along the rotation direction of the axial flux motor, and the initial phase angle of the current in the second stator lags behind the initial phase angle of the current in the first stator by θ degrees, so that the two target harmonics cancel each other out and the amplitudes of the two fundamental waves remain unchanged.

[0006] Preferably, when the rotation direction of the target harmonic is the same as the rotation direction of the axial flux motor, α = α1 = 180 / (np), θ = θ1 = pα, where n is the spatial order of the target harmonic and p is the spatial order of the fundamental wave.

[0007] Preferably, when the rotation direction of the target harmonic is opposite to the rotation direction of the axial flux motor, α = α2 = 180 / (np), θ = θ2 = pα, where n is the spatial order of the target harmonic and p is the spatial order of the fundamental wave.

[0008] Preferably, n is obtained by simulation software, and p is equal to the number of pole pairs of the axial flux motor.

[0009] Preferably, the axial flux motor is a six-phase axial flux motor.

[0010] Preferably, the axial flux motor is a 18-slot 16-pole motor, in which the second stator is 10 degrees ahead of the first stator along the rotation direction of the axial flux motor, and the current initial phase angle of the second stator lags behind the current initial phase angle of the first stator by 80 degrees.

[0011] Preferably, the axial flux motor further comprises a power supply system, which comprises a power supply bus line, a first power supply branch line and a second power supply branch line, the second stator winding is connected to the power supply bus line through the second power supply branch line, and the first stator winding is connected to the power supply bus line through the first power supply branch line.

[0012] The first control switch is connected in series on the first power supply branch line, and the second control switch is connected in series on the second power supply branch line.

[0013] Preferably, a time delay device is further connected in series on the second power supply branch line, and the time delay device acts on the second control switch.

[0014] The magnetic field harmonics are all vectors, which have direction and magnitude. The direction of the magnetic field harmonics is related to the relative position of the stators and the current initial phase angle of the stators. The present application sets up a double-stator axial flux motor according to these factors, in which the second stator is a degrees ahead of the first stator along the rotation direction of the axial flux motor, and the current initial phase angle of the second stator lags behind the current initial phase angle of the first stator by θ degrees, so that the two target harmonics cancel each other out, and the amplitudes of the two fundamental waves remain unchanged.

[0015] In the method of the present application, no additional adjusting components are introduced, and the purpose of weakening the target harmonics can be achieved only by changing the relative position of the stators and the initial phase angle of the stators, which is simple and easy to implement. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the scheme in the embodiments of the present application, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.

[0017] Figure 1 The double-stator structure schematic diagram of the axial flux motor provided for a specific embodiment of the present application;

[0018] Figure 2 The schematic diagram of one stator rotating a degrees relative to the other stator provided for a specific embodiment of the present application;

[0019] Figure 3 A circuit diagram of a power supply system provided for a specific embodiment of the present application;

[0020] Figure 4 A comparison diagram of magnetic field harmonics formed by an 18-slot 16-pole axial flux motor and magnetic field harmonics formed by a conventional scheme provided for a specific embodiment of the present application.

[0021] Wherein, 1 is a stator, 1-1 is a stator winding, and 2 is a rotor. DETAILED DESCRIPTION

[0022] The present application discloses a double-stator axial flux motor which can weaken target harmonics while keeping the amplitude of fundamental waves unchanged.

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0024] The present application discloses a double-stator axial flux motor, which comprises a stator having a stator winding. Under the condition of energization, the stator winding generates magnetic field harmonics. The magnetic field harmonics include target harmonics and fundamental waves. The target harmonics are waves causing the vibration of the axial flux motor, and thus need to be eliminated. The fundamental waves are useful waves, and thus need to be kept. The axial flux motor in the present application comprises two stators which have the same structure. If the stators are two, the corresponding stator windings, magnetic field harmonics, target harmonics and fundamental waves are also two.

[0025] Please refer to the accompanying drawings Figure 1 , the accompanying drawings Figure 1 is a schematic diagram of a double-stator structure of an axial flux motor, and in the accompanying drawings Figure 1 , the rotor 2 is arranged between the two stators 1.

[0026] The magnetic field harmonics are all vectors, having direction and size. The direction of the magnetic field harmonics is related to the relative position of the stator and the initial phase angle of the current of the stator. The present application sets up a double-stator axial flux motor according to these factors, in which the second stator is forward by α degrees along the rotation direction of the axial flux motor relative to the first stator, and the initial phase angle of the current of the second stator lags behind the initial phase angle of the current of the first stator by θ degrees, so that the two target harmonics cancel each other out, and the amplitudes of the two fundamental waves remain unchanged.

[0027] The method in this invention does not require the introduction of additional adjustment components. The purpose of weakening the target harmonics can be achieved simply by changing the relative position of the stator and changing the initial phase angle of the stator. It is simple to operate and easy to implement.

[0028] When energized, the stator windings corresponding to the two stators will each generate their respective target harmonics. If one of the stators rotates by α degrees along the rotation direction of the axial flux motor and about its axis, then the vector angle of the magnetic field harmonic corresponding to that stator will rotate by x times α degrees along the rotation direction of the axial flux motor, where x is the spatial order of the magnetic field harmonic. Please refer to the appendix. Figure 2 , attached Figure 2 A schematic diagram is shown showing one stator winding rotating α degrees relative to another stator winding in the direction of rotation of the axial flux motor. (Attached) Figure 2 The two 1-1 in the middle represent two stator windings respectively.

[0029] The rotation direction of the target harmonic is either the same as or opposite to the rotation direction of the axial flux motor. For a specific model of axial flux motor, the rotation direction of both the target harmonic and the axial flux motor is fixed. It should be noted that the rotation direction of the fundamental wave determines the rotation direction of the axial flux motor; that is, the rotation direction of the fundamental wave is always the same as the rotation direction of the axial flux motor.

[0030] When the rotation direction of the target harmonic is the same as the rotation direction of the motor shaft of the axial flux motor, if the initial phase angle of the current of one of the stators lags by θ degrees, then the vector angle of the target harmonic corresponding to that stator will rotate by θ degrees in the opposite direction to the rotation direction of the axial flux motor.

[0031] When the rotation direction of the target harmonic is opposite to the rotation direction of the motor shaft of the axial flux motor, if the initial phase angle of the current of one of the stators lags by θ degrees, then the vector angle of the target harmonic corresponding to that stator will rotate by θ degrees in the same direction as the rotation direction of the axial flux motor.

[0032] Since the rotation direction of the fundamental wave is always the same as the rotation direction of the axial flux motor, under any circumstances, if the initial phase angle of the current in one of the stators lags by θ degrees, then the vector angle of the target harmonic corresponding to that stator will rotate by θ degrees in the same direction as the rotation direction of the axial flux motor.

[0033] One objective of this invention is to ensure that the target harmonics of the two stators cancel each other out, which requires ensuring that the vector angle between the two target harmonics is 180 degrees. Another objective of this invention is to ensure that the amplitude of the fundamental waves of the two stators remains constant, which requires ensuring that the vector angle between the two fundamental waves is 0 degrees.

[0034] According to the above principle, when the rotating direction of the target harmonic is the same as the rotating direction of the axial flux motor: the second stator of the two stators is rotated by an angle of a1 degrees along the rotating direction of the axial flux motor relative to the first stator, then the vector angle of the target harmonic of the second stator is rotated by an angle of n a1 degrees towards the rotating direction of the axial flux motor, n is the spatial order of the target harmonic. At the same time, the initial phase angle of the current of the second stator is lagged by an angle of θ1 relative to the initial phase angle of the current of the first stator, that is, the vector angle of the target harmonic of the second stator is rotated by an angle of θ1 towards the direction opposite to the rotating direction of the axial flux motor. If the vector included angle of the two target harmonics is 180 degrees, then the first calculation formula n a1- θ1 = 180 degrees is met.

[0035] For the fundamental wave, the second stator of the two stators is rotated by an angle of a1 degrees along the rotating direction of the axial flux motor relative to the first stator, then the vector angle of the fundamental wave of the second stator is rotated by an angle of p a1 degrees towards the rotating direction of the axial flux motor, p is the spatial order of the fundamental wave. At the same time, the initial phase angle of the current of the second stator is lagged by an angle of θ1 relative to the initial phase angle of the current of the first stator, that is, the vector angle of the fundamental wave of the second stator is rotated by an angle of θ1 towards the direction opposite to the rotating direction of the axial flux motor. If the vector included angle of the two fundamental waves is 0°, then the second calculation formula p a1- θ1 = 0 is met.

[0036] Combined with the first calculation formula and the second calculation formula, it can be deduced that a1 = 180 / (n-p), θ1 = p a1. When the rotating direction of the target harmonic is the same as the rotating direction of the axial flux motor, the second stator is rotated by an angle of a1 degrees towards the same direction as the axial flux motor relative to the first stator, and at the same time, the initial phase angle of the current of the second stator is lagged by an angle of θ1 degrees relative to the initial phase angle of the current of the first stator, so that the two target harmonics can be cancelled out, and the amplitudes of the two fundamental waves remain unchanged.

[0037] When the rotating direction of the target harmonic is opposite to the rotating direction of the axial flux motor: the second stator of the two stators is rotated by an angle of a2 degrees along the rotating direction of the axial flux motor relative to the first stator, then the vector angle of the target harmonic of the second stator is rotated by an angle of n a2 degrees towards the rotating direction of the axial flux motor, n is the spatial order of the target harmonic. At the same time, the initial phase angle of the current of the second stator is lagged by an angle of θ2 relative to the initial phase angle of the current of the first stator, that is, the vector angle of the target harmonic of the second stator is rotated by an angle of θ2 towards the same direction as the rotating direction of the axial flux motor. If the vector included angle of the two target harmonics is 180 degrees, then the third calculation formula n a2+ θ2 = 180 degrees is met.

[0038] For the fundamental wave, if the second stator is rotated by α2 degrees relative to the first stator along the rotation direction of the axial flux motor, then the vector angle of the fundamental wave in the second stator is rotated by pα2 degrees in the same direction as the rotation of the axial flux motor, where p is the spatial order of the fundamental wave. Simultaneously, the initial phase angle of the current in the second stator lags behind the initial phase angle of the current in the first stator by θ2, meaning the vector angle of the fundamental wave in the second stator is rotated by θ2 in the same direction as the rotation of the axial flux motor. To make the vector angle between the two fundamental waves 0 degrees, the fourth calculation formula must be satisfied: pα2 - θ2 = 0.

[0039] Combining the third and fourth calculation formulas, we can deduce: α2 = 180 / (n+p), θ2 = pα2. When the rotation direction of the target harmonic is the same as the rotation direction of the axial flux motor, the second stator is rotated α2 degrees relative to the first stator in the same direction as the axial flux motor. At the same time, it is ensured that the initial phase angle of the current in the second stator lags behind the initial phase angle of the current in the first stator by θ2 degrees. In this way, it can be ensured that the two target harmonics cancel each other out, while keeping the amplitude of the two fundamental waves unchanged.

[0040] It should be noted that the spatial order n of the target harmonic is obtained through prior software simulation of the axial flux motor. The spatial order p of the fundamental wave is equal to the number of pole pairs of the axial flux motor. The number of pole pairs is fixed for the same model of axial flux motor.

[0041] In a specific embodiment of the present invention, the axial flux motor is designed as a six-phase axial flux motor. That is, the stator windings of both stators of the axial flux motor are three-phase windings. For an 18-slot, 16-pole six-phase axial flux motor, the spatial order n of the target harmonic is 10, and the spatial order p of the fundamental wave is 8. Furthermore, the rotation direction of the target harmonic is opposite to the rotation direction of the axial flux motor. In this axial flux motor, one stator is rotated α2 relative to the other stator in the rotation direction of the axial flux motor, causing the initial phase angle of the stator current to lag by θ2. According to the third and fourth calculation formulas, α2 = 10, θ2 = 80°.

[0042] Please refer to the attached document. Figure 4 , attached Figure 4 A comparison diagram of magnetic field harmonics after adopting this design for an 18-slot, 16-pole, six-phase flux motor and the flux harmonics in a traditional design is shown in the attached diagram. Figure 4 It can be seen that the amplitude of the 10th order magnetic flux density of the target harmonic is greatly weakened, while the amplitude of the fundamental magnetic flux density (8th order) remains basically unchanged. This indicates that the use of this method can effectively weaken specific target harmonics while keeping the fundamental amplitude basically unchanged.

[0043] Next, the power supply circuit is introduced: the present application controls the initial phase angle of the current of the two stator windings by means of time-delay power supply. The two stator windings are supplied by the same power source. The power supply circuit comprises a power supply bus circuit, a first power supply branch circuit and a second power supply branch circuit. The first stator winding is connected to the power supply bus circuit through the first power supply branch circuit, and the second stator winding is connected to the power supply bus circuit through the second power supply branch circuit. Moreover, the present application further connects a first control switch in series on the first power supply branch circuit, and connects a second control switch in series on the second power supply branch circuit. By controlling the first control switch and the second control switch through software, the initial phase angle of the current of the second stator winding can be made to lag behind the initial phase angle of the current of the first stator winding.

[0044] The control generator sends switch commands to the first control switch and the second control switch. In order to facilitate operation, the present application connects a time-delay device in series on the second power supply branch circuit, which acts on the second control switch. After the control signal generator sends the opening command to the first control switch and the second control switch, the first control switch will be closed, thereby supplying power to the first stator winding. As for the second power supply branch circuit, the time-delay device will delay the sending of the opening command, and after a predetermined time delay, the time-delay device will send the opening command to the second control switch, and the second control switch will be closed, thereby realizing time-delay power supply to the second stator winding. If the initial phase angle of the current of the second stator winding is to lag behind by θ, the time required for time-delay power supply is calculated in advance, and the time is input to the time-delay device.

[0045] Please refer to the accompanying drawings Figure 3 , the accompanying drawings Figure 3 is a power supply circuit diagram, and the accompanying drawings Figure 3 connects a time-delay device in series on the second power supply branch circuit, thereby realizing time-delay power supply to the second stator winding, so as to realize the lag of the initial phase angle of the current of the second stator winding.

[0046] Finally, it should be noted that in this document, relational terms such as first and second and the like can only be used to distinguish one entity or action from another entity or action, without necessarily requiring or implying that there is any such actual relationship or order between these entities or actions. The terms "comprises", "comprising", or any other variations thereof are intended to cover non-exclusive inclusions, so that a process, method, article, or apparatus that includes a list of elements does not only include those elements, but also includes other elements not explicitly listed, or other elements inherent to such process, method, article, or apparatus. Without more limitations, an element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0047] The various embodiments described in this specification are intended to be illustrative only and in no way limit the scope of the application. Changes and modifications can be made by those skilled in the art, which employ the principles of the application, without departing from the scope of the application. Accordingly, the application is not limited to the embodiments described herein, but instead has scope to encompass any choice whatsoever that is dependent on, or can be substituted in, the principal, new and inventive features that are disclosed and claimed herein.

[0048] The above description discloses only an example of the disclosed embodiments. The modifications of these embodiments for other embodiments will be apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Accordingly, the application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dual stator axial flux motor, characterized by, The axial flux motor comprises two stators, each of which has a stator winding, and each of the stator windings generates a magnetic field harmonic, the magnetic field harmonic comprises a target harmonic and a fundamental wave, and each of the stator windings, the magnetic field harmonic, the target harmonic and the fundamental wave is two; In the two stators, the second stator is ahead of the first stator by α degrees in the rotation direction of the axial flux motor, and the current initial phase angle of the second stator lags behind the current initial phase angle of the first stator by θ degrees, so that the two target harmonics cancel each other out, and the amplitudes of the two fundamental waves remain unchanged; When the rotation direction of the target harmonic is the same as the rotation direction of the axial flux motor, the α = α1 = 180 / (n-p), and θ = θ1 = pα, wherein n is the spatial order of the target harmonic, and p is the spatial order of the fundamental wave; When the rotation direction of the target harmonic is opposite to the rotation direction of the axial flux motor, the α = α2 = 180 / (n-p), and θ = θ2 = pα, wherein n is the spatial order of the target harmonic, and p is the spatial order of the fundamental wave.

2. The dual stator axial flux motor of claim 1, wherein, The n is obtained by simulation software calculation, and the p is equal to the pole pair number of the axial flux motor.

3. The dual stator axial flux motor of claim 1, wherein, The axial flux motor is a six-phase axial flux motor.

4. The dual stator axial flux motor of claim 3, wherein, The axial flux motor is an 18-slot 16-pole motor, in which the second stator is ahead of the first stator by 10 degrees in the rotation direction of the axial flux motor, and the current initial phase angle of the second stator lags behind the current initial phase angle of the first stator by 80 degrees.

5. The dual stator axial flux motor of claim 1, wherein, The axial flux motor further comprises a power supply system, which comprises a power supply bus line, a first power supply branch line and a second power supply branch line, the second stator winding is connected to the power supply bus line through the second power supply branch line, and the first stator winding is connected to the power supply bus line through the first power supply branch line. The first power supply branch line is connected in series with a first control switch, and the second power supply branch line is connected in series with a second control switch.

6. The dual stator axial flux motor of claim 5, wherein, The second power supply branch line is further connected in series with a time delay device, and the time delay device acts on the second control switch.

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