CN114598224B - Respiratory mode vibration suppression method for surface magnetic pole type permanent magnet synchronous motor - Google Patents

Abstract

A respiratory mode vibration suppression method of a surface magnetic pole type permanent magnet synchronous motor relates to a motor vibration suppression method. Acquiring electromagnetic force frequency of exciting breathing mode vibration on the stator teeth; determining the number of rotor harmonic magnetomotive forces associated with respiratory mode vibrations; adjusting the amplitude of the harmonic magnetomotive force of the rotor related to the respiratory mode vibration; injecting harmonic current and calculating radial concentrated electromagnetic force on the injected stator teeth; acquiring amplitude and phase of harmonic electromagnetic force with the same frequency as respiratory mode vibration; the effect of harmonic current on loss and efficiency is calculated. The phase difference between electromagnetic forces exciting respiratory mode vibration on each stator tooth is changed by adjusting rotor harmonic magnetomotive force and injecting positive phase sequence and negative phase sequence harmonic current, so that the original respiratory mode vibration is converted into non-respiratory mode vibration, and the remarkable suppression of electromagnetic vibration noise is realized.

Description

A method for suppressing breathing mode vibration of surface-pole permanent magnet synchronous motor

Technical Field

The invention relates to a motor vibration suppression method, in particular to a breathing mode vibration suppression method for a surface magnetic pole type permanent magnet synchronous motor, belonging to the technical field of special motors.

Background Art

Electromagnetic vibration noise is generated when the internal electromagnetic force of the motor forces the stator to vibrate during operation, which causes noise pollution and damages the hearing of people around. The electromagnetic vibration noise of the surface pole permanent magnet synchronous motor mainly comes from the breathing mode vibration excited by the electromagnetic force.

The vibration and noise reduction methods currently used in surface pole permanent magnet synchronous motors usually first design the overall motor scheme according to technical indicators, and then use the finite element method to iteratively optimize the rotor magnetic steel pole arc shape and stator tooth slot size, such as cutting the magnetic steel sharp angle, adjusting the slot width, etc. In the optimization process, the goal is to reduce the amplitude of the electromagnetic force that excites the breathing mode vibration, but because the electromagnetic force cannot be reduced to zero, and the breathing mode vibration can be excited by a very small electromagnetic force, the breathing mode vibration is still not ideally suppressed.

In addition, there is still a certain error between the electromagnetic force calculated by the finite element method and the electromagnetic force in the manufactured motor. Therefore, it is difficult to reduce the electromagnetic force that excites the breathing mode vibration to the same level as the finite element calculation results through the magnetic pole arc shape and stator tooth slot size optimized by the finite element method in practice. As a result, the actual suppression effect of the breathing mode vibration fails to reach the level of the optimized design, and it is difficult to further improve the low vibration noise level of the motor.

Summary of the invention

In order to solve the problem that the existing vibration reduction and noise reduction methods of surface pole permanent magnet synchronous motors are difficult to significantly suppress breathing mode vibrations, the present invention provides a breathing mode vibration suppression method for a surface pole permanent magnet synchronous motor, which adjusts the rotor harmonic magnetomotive force and injects positive phase sequence and reverse phase sequence harmonic currents to change the phase difference between the electromagnetic forces that excite breathing mode vibrations on each stator tooth, thereby converting the original breathing mode vibrations into non-breathing mode vibrations, thereby achieving significant suppression of electromagnetic vibration noise.

To achieve the above object, the present invention adopts the following technical scheme: a method for suppressing breathing mode vibration of a surface pole type permanent magnet synchronous motor, comprising the following steps:

Step 1: Obtain the electromagnetic force frequency that excites the breathing mode vibration on the stator teeth

The radial concentrated electromagnetic force on each stator tooth is calculated by the finite element method, and the frequency, amplitude and phase of each harmonic electromagnetic force are obtained by Fourier transform. The phase difference of each harmonic electromagnetic force on adjacent stator teeth is calculated. When the phase difference between the harmonic electromagnetic forces is zero, the corresponding frequency is the frequency of the breathing mode vibration excited by the harmonic electromagnetic force on the stator.

Step 2: Determine the order of the rotor harmonic magnetomotive force associated with the breathing mode vibration

According to the Maxwell stress tensor method, the functional relationship between the rotor harmonic magnetomotive force, the fundamental current magnetomotive force and the electromagnetic force wave in the air gap is analyzed, and the amplitude, frequency and spatial order of each harmonic of the electromagnetic force wave are obtained. Considering the modulation effect of the stator tooth slot structure on the electromagnetic force wave, the electromagnetic force wave with a spatial order equal to 0 or an integer multiple of the number of stator tooth slots can excite the breathing mode vibration. In this way, the number of the rotor harmonic magnetomotive force that can make the spatial order of the electromagnetic force wave meet the conditions for exciting the breathing mode vibration is calculated;

Step 3: Adjust the amplitude of the rotor harmonic magnetomotive force associated with the breathing mode vibration

By changing the shape of the magnetic steel pole arc in the finite element model, the amplitude of the rotor harmonic magnetomotive force obtained in step 2 is reduced. The amplitude of the rotor harmonic needs to be gradually reduced during the iteration process, but cannot be completely reduced to zero until the suppression effect meets the requirements;

Step 4: Inject harmonic current and calculate the radial concentrated electromagnetic force on the stator teeth after injection

According to the Maxwell stress tensor method, the additional electromagnetic force wave after the harmonic current with the same frequency and opposite phase sequence is injected into the stator winding is analyzed. The formula is as follows:

Wherein, _Mδ represents the amplitude of the δth rotor magnetomotive force, _ω1 represents the rated electrical angular frequency, _Ma1 represents the amplitude of the 1st harmonic in the fundamental current magnetomotive force, Z represents the number of stator slots, p represents the number of pole pairs, _Λ0 represents the average air gap permeability, _Λv represents the vth harmonic air gap permeability, _μ0 represents the vacuum permeability, _Mk ⁺ represents the magnetomotive force amplitude of the kth positive phase sequence current, _Mk- ^represents the magnetomotive force amplitude of the kth negative phase sequence current, Indicates the phase of the positive sequence harmonic current, The phase of the reverse sequence harmonic current is represented. By making the newly added electromagnetic force wave equal to the breathing mode vibration in frequency, the frequency of the harmonic current to be injected is determined. The amplitude and phase of the harmonic current are obtained through iterative calculation. Finally, the radial concentrated electromagnetic force on the stator teeth after the harmonic current is injected is calculated.

Step 5: Obtain the amplitude and phase of the harmonic electromagnetic force with the same frequency as the breathing mode vibration

By performing Fourier transform on the radial concentrated electromagnetic force obtained in step 4, the amplitude and phase of the harmonic electromagnetic force with the same respiratory modal vibration frequency as determined in step 1 are obtained. If the amplitudes of the harmonic electromagnetic forces are equal and the phase difference is equal to 2p*360°/Z, the amplitude and phase of the harmonic current meet the requirements and the next step is performed. Otherwise, return to step 4.

Step 6: Calculate the impact of harmonic current on losses and efficiency

In the finite element model, the loss and efficiency of the motor after the harmonic current is injected are calculated, and compared to see whether the requirements are met. If so, the magnetic pole arc shape and harmonic current parameters are output as the final solution. If not, return to step three until the requirements are met.

Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention adjusts the rotor harmonic magnetomotive force and injects positive phase sequence and reverse phase sequence harmonic currents to change the phase difference between the electromagnetic forces that excite the breathing mode vibration on each stator tooth, and converts the original breathing mode vibration into non-breathing mode vibration, thereby reducing the vibration acceleration of the casing surface. Although the magnetic steel pole arc shape is adjusted and the harmonic current parameters are calculated based on the finite element method, the parameters of the injected harmonic current can be corrected by the controller during the prototype vibration test or debugging process, avoiding the situation in which the existing method causes the prototype vibration suppression effect to be unsatisfactory due to the error between the finite element results and the actual motor. Compared with the existing optimization or suppression methods, the present invention has a better suppression effect, can reduce the vibration acceleration of the original breathing mode by more than half, and achieve significant suppression of electromagnetic vibration noise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of the present invention.

DETAILED DESCRIPTION

The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

As shown in FIG1 , a method for suppressing breathing mode vibration of a surface pole permanent magnet synchronous motor comprises the following steps:

Step 1: Obtain the electromagnetic force frequency that excites the breathing mode vibration on the stator teeth

When the motor is running, the electromagnetic force wave in the air gap acts on the stator teeth in the form of distributed force. Through equivalent transformation, the distributed force can be equivalent to the concentrated electromagnetic force acting at the center of the stator tooth top. The formula is as follows:

Wherein, _Fr represents the radial concentrated electromagnetic force, _Ft represents the tangential concentrated electromagnetic force, _Le represents the core length, _Ris represents the stator inner diameter, _fr represents the radial electromagnetic force wave, _ft represents the tangential electromagnetic force wave, θ represents the circumferential angle at any position in the air gap, _θz represents the midline position of the zth stator tooth, and Δθ represents the stator tooth pitch.

Because the electromagnetic vibration of the motor is mainly excited by radial force, the radial concentrated electromagnetic force acting on each stator tooth is calculated by the finite element method, and the frequency, amplitude and phase (amplitude spectrum and phase spectrum) of each harmonic electromagnetic force are obtained by Fourier transform, and the phase difference of each harmonic electromagnetic force on adjacent stator teeth is calculated. When the phase of the harmonic electromagnetic force of a certain frequency on each stator tooth is equal, that is, the phase difference between the harmonic electromagnetic forces is zero, the breathing mode vibration can be excited at this frequency, that is, the harmonic electromagnetic force with a phase difference of zero can excite the breathing mode vibration, and its corresponding frequency is the electromagnetic force frequency that excites the breathing mode vibration on the stator tooth;

Step 2: Determine the order of the rotor harmonic magnetomotive force associated with the breathing mode vibration

The functional relationship between the rotor harmonic magnetomotive force, the fundamental current magnetomotive force and the electromagnetic force wave in the air gap is constructed, and the order of the rotor harmonic magnetomotive force corresponding to the breathing mode vibration is calculated.

Under the premise that there is no excessive saturation area inside the motor during operation, ignoring the fundamental current magnetomotive force harmonics except the 1st and Z/p±1st, the magnetomotive force formula of the air gap is as follows:

Where _Mδ represents the amplitude of the δth harmonic magnetomotive force of the rotor, _ω1 represents the rated electrical angular frequency, _Ma1 , M _(Z/p-1) , and M _(Z/p+1) represent the 1st, Z/p-1st, and Z/p+1st harmonic amplitudes of the fundamental current magnetomotive force, respectively, Z represents the number of stator slots, and p represents the number of pole pairs.

According to the relationship between the Maxwell stress tensor method and the magnetic circuit, the main electromagnetic force waves in the air gap are shown in Table 1:

Table 1 Main electromagnetic force waves in the air gap

Among them, _Λ0 represents the average air gap permeability, _Λv represents the vth harmonic air gap permeability, _μ0 represents the vacuum permeability, _Mδ1 and _Mδ2 represent the amplitudes of the rotor harmonic magnetomotive force of different orders, and _δ1 and _δ2 represent the orders corresponding to _Mδ1 and _Mδ2 respectively.

In addition, according to the modulation effect of the stator slot structure on the electromagnetic force wave, the electromagnetic force wave with a spatial order equal to 0 or an integer multiple of the number of stator slots can excite the breathing mode vibration, and the order of the rotor harmonic magnetomotive force related to the breathing mode is determined;

Step 3: Adjust the amplitude of the rotor harmonic magnetomotive force associated with the breathing mode vibration

By changing the magnetic steel pole arc shape in the finite element model, the amplitude of the rotor harmonic magnetomotive force obtained in step 2 is reduced. The magnetic steel pole arc shape can be adjusted using the existing magnetic steel pole arc shape optimization method. Different from the purpose of the existing magnetic steel pole arc shape optimization, it is necessary to gradually reduce the amplitude of the rotor harmonic magnetomotive force during the iteration process, but it cannot be completely reduced to zero until the suppression effect meets the requirements;

Step 4: Inject harmonic current and calculate the radial concentrated electromagnetic force on the stator teeth after injection

According to the Maxwell stress tensor method, after the harmonic currents of positive phase sequence and reverse phase sequence are injected into the stator winding, the main newly added electromagnetic force waves are shown in Table 2:

Table 2 Main new electromagnetic force waves

Wherein, M _k ⁺ represents the magnetomotive force amplitude of the kth positive phase sequence current, M _k ^- represents the magnetomotive force amplitude of the kth negative phase sequence current, Indicates the phase of the positive sequence harmonic current, Represents the phase of the reverse sequence harmonic current. By making the angular frequency in Table 2 equal to the frequency of the breathing mode vibration, the frequency of the injected harmonic current is determined. The amplitude and phase of the harmonic current need to be obtained through iterative calculation. First, the amplitude range of the harmonic current is determined according to the copper loss allowed to be increased by the motor. An arbitrary value is selected as the amplitude of the harmonic current within this range. Then, the phase of the harmonic current is selected within the range of 0 to 2π. Finally, the radial concentrated electromagnetic force on the stator teeth after the harmonic current is injected is calculated.

Step 5: Obtain the amplitude and phase of the harmonic electromagnetic force with the same frequency as the breathing mode vibration

By performing Fourier transform on the radial concentrated electromagnetic force obtained in step 4, the amplitude and phase of the harmonic electromagnetic force with the same respiratory modal vibration frequency as determined in step 1 are obtained. If the amplitudes of the harmonic electromagnetic forces are equal and the phase difference is equal to 2p*360°/Z, the amplitude and phase of the harmonic current meet the requirements and the next step is performed. Otherwise, return to step 4.

Step 6: Calculate the impact of harmonic current on losses and efficiency

In the finite element model, the loss and efficiency of the motor after the harmonic current is injected are calculated, and compared to see whether the requirements are met. If so, the magnetic pole arc shape and harmonic current parameters are output as the final solution. If not, return to step three until the requirements are met.

It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other forms of assembly without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and range of equivalents of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims (3)

1. A respiratory mode vibration suppression method of a surface magnetic pole type permanent magnet synchronous motor is characterized by comprising the following steps of: the method comprises the following steps:

Step one, acquiring electromagnetic force frequency of exciting respiratory mode vibration on stator teeth

Calculating radial concentrated electromagnetic force received by each stator tooth through a finite element method, carrying out Fourier transformation on the radial concentrated electromagnetic force to obtain frequency, amplitude and phase of each subharmonic electromagnetic force, and calculating phase difference of each subharmonic electromagnetic force on adjacent stator teeth, wherein the corresponding frequency is the frequency of respiratory mode vibration excited by the harmonic electromagnetic force when the phase difference between the harmonic electromagnetic forces is zero;

Step two, determining the times of rotor harmonic magnetomotive force related to respiratory mode vibration

Analyzing the functional relation of the rotor harmonic magnetomotive force, the fundamental wave current magnetomotive force and the electromagnetic wave in the air gap according to a Maxwell stress tensor method to obtain the amplitude, the frequency and the spatial order of each subharmonic of the electromagnetic wave, and considering the modulating effect of a stator tooth slot structure on the electromagnetic wave, wherein the spatial order is equal to 0 or the electromagnetic wave of which the number is integral multiple of the number of the stator tooth slots can excite respiratory mode vibration, so that the number of times of rotor harmonic magnetomotive force which can enable the spatial order of the electromagnetic wave to meet the condition of exciting respiratory mode vibration can be calculated;

step three, adjusting the amplitude of the harmonic magnetomotive force of the rotor related to the respiratory mode vibration

The amplitude of the rotor harmonic magnetomotive force obtained in the second step is reduced by changing the pole arc shape of the magnetic steel in the finite element model, and the amplitude of the rotor harmonic wave needs to be gradually reduced in the iterative process but cannot be completely reduced to zero until the inhibition effect meets the requirement;

Injecting harmonic current and calculating radial concentrated electromagnetic force on the injected stator teeth

And analyzing the newly added electromagnetic wave after the harmonic current with the same frequency and opposite phase sequence is injected into the stator winding according to a Maxwell stress tensor method, wherein the formula is as follows:

where M _δ represents the magnitude of the delta rotor magnetomotive force, ω ₁ represents the rated electrical angular frequency, M _a1 represents the 1 st harmonic magnitude of the fundamental current magnetomotive force, Z represents the stator tooth count, p represents the pole pair number, Λ ₀ represents the average air gap flux, Λ _v represents the v harmonic air gap flux, μ ₀ represents the vacuum permeability, M _k ⁺ represents the magnitude of the magnetomotive force of the k positive phase sequence currents, M _k ^- represents the magnitude of the magnetomotive force of the k negative phase sequence currents, Representing the phase of the positive phase sequence harmonic current,Representing the phase of the harmonic current of the reversed phase sequence, determining the frequency of the harmonic current to be injected by making the frequency of the newly added electromagnetic wave equal to the frequency of the respiratory mode vibration, obtaining the amplitude and the phase of the harmonic current through iterative calculation, and finally calculating the radial concentrated electromagnetic force on the stator teeth after the harmonic current is injected;

step five, obtaining amplitude and phase of harmonic electromagnetic force with the same frequency as respiratory mode vibration

The amplitude and the phase of the harmonic electromagnetic force which are the same as the respiratory mode vibration frequency determined in the step one are obtained through Fourier transformation of the radial concentrated electromagnetic force obtained in the step four, if the amplitude of the harmonic electromagnetic force is equal and the phase difference is equal to 2p x 360 degrees/Z, the amplitude and the phase of the harmonic current meet the requirements, the next step is carried out, and otherwise, the step four is returned;

Step six, calculating the influence of harmonic current on loss and efficiency

And (3) calculating the loss and efficiency of the motor after the harmonic current is injected into the finite element model, comparing whether the loss and the efficiency meet the requirements, if so, outputting the magnetic steel polar arc shape and the harmonic current parameters as a final scheme, and if not, returning to the step (III) until the requirements are met.

2. The method for suppressing respiratory mode vibration of a surface pole permanent magnet synchronous motor according to claim 1, wherein the method comprises the steps of: the radial concentration electromagnetic force formula in the first step is as follows:

Where F _r denotes a radially concentrated electromagnetic force, L _e denotes a core length, R _is denotes a stator inner diameter, F _r denotes a radial electromagnetic wave, θ denotes a circumferential angle at an arbitrary position in an air gap, θ _z denotes a center line position of a z-th stator tooth, and Δθ denotes a stator pitch.

3. The method for suppressing respiratory mode vibration of a surface pole permanent magnet synchronous motor according to claim 1, wherein the method comprises the steps of: in the iterative calculation process of the amplitude and the phase of the harmonic current in the fourth step, firstly, the amplitude range of the harmonic current is determined according to the copper loss allowed to be increased by the motor, any value is selected in the range to serve as the amplitude of the harmonic current, and then the phase of the harmonic current is selected in the range of 0-2 pi.