CN104767344B - Method for eliminating vibration of PWM powered brushless direct current motor through frequency calculation - Google Patents
Method for eliminating vibration of PWM powered brushless direct current motor through frequency calculation Download PDFInfo
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Abstract
The invention provides a method for eliminating vibration of a PWM powered brushless direct current motor through frequency calculation. For the motor preliminarily designed in a electromagnetic scheme, spatial harmonic distribution of air gap flux density is firstly calculated, then the time harmonic wave change of the air gap flux density is calculated within a commutation period and is compared with the inherent vibration frequency of a motor iron core, and if the frequencies are similar, resonance is produced, the electromagnetic design scheme of the motor is needed to be optimized, and the frequencies are re-calculated till the vibrations produced by spatial harmonic flux density and harmonic wave flux density are not resonant with the iron core. The space and time changes of flux density causing motor vibration under the operating working condition of the motor are fully considered in the method, the accuracy of motor vibration calculation in a motor product development phase is improved, accordingly the success rate of motor design is improved, a development and trial-manufacturing period of the motor is shortened, and non-renewable resources including copper, iron, aluminum and the like are effectively saved.
Description
Technical field
The present invention relates to one kind is for the brushless direct current motor under PWM (pulse width modulation) power supplies, by meter
Method of the electric machine stator iron vibration frequency that calculation air gap flux density harmonic wave causes so as to suppress motor oscillating, belongs to dc motor
Technical field.
Background technology
The vibration source of brushless direct current motor vibration can be divided into three kinds of electromagnetic force, air force and frame for movement, these three
Vibration source difference in vibration frequency is larger, and the noise produced by vibration is easily discriminated.As vibration source air force and
The vibration that frame for movement is produced is mechanical oscillation, can be optimized by motor construction, such as improves motor ventilation knot
Structure, physical dimension of change Electric machine structure part etc., and the vibration that the electromagnetic force in vibration source is produced is electric and magnetic oscillation, needs to pass through
The electromagnetism of motor calculates to analyze and optimize, and it is all most complicated to calculate and suppress.
In the patent of motor oscillating, CN103219940A " a kind of suppression method of electromotor vibration ", CN103762806A
" a kind of suppressing method of shaded-pole single-phase ac asynchronous motor Vibration Torque " and CN104158464A " suppress intrinsic vibration
Control device of electric motor " etc. proposes the suppressing method of motor oscillating, but it is humorous still not solve the PWM close spaces of lower magnetic that power
Ripple binding time harmonic wave causes the computational methods of motor oscillating.
The power supply mode of brshless DC motor typically adopts PWM power supplys, in Speed Process of DC Motor, by changing PWM's
The dutycycle of pulse carrys out equivalent different supply voltage value, it is seen that power with General Electric Network or the direct power supply of dc source it is electronic
Machine is compared, and the air-gap field of brushless, permanently excited direct current motor is not only close comprising space harmonics magnetic, and will be subject to time harmonic
The impact of voltage and current, this vibration for resulting in motor becomes apparent from, so can not reflect the time by traditional method
The electric and magnetic oscillation change of motor, objectively reduces the accuracy of design under harmonic wave.
Generally the magnetic potential of stator and rotor was calculated first using the computational methods of equivalent magnetic circuit, then calculated gas in the past
Gap magnetic conductance, according to magnetic potential and permeance calculation air-gap field, finally according to the Reeb that stator and rotor field harmonic field are produced, will
Reeb number of times merges, and according to the close amplitude of its magnetic radial load is calculated, and calculates Reeb frequency.
Conventional method calculates the vibration frequency of the brushless direct current motor that PWM powers, and there is following defect：
1. it is equivalence value to use the parameters such as the computational methods of equivalent magnetic circuit, magnetic conductance, does not account for slot form to magnetic
The impact led；
2. by magnetic potential and permeance calculation, air gap flux density result of calculation is equivalence value to the close value of magnetic, the close each harmonic of magnetic
Crest meter is not calculated accurately really；
3. take into consideration only the space harmonics of air gap flux density produced by rotor, when not powering in view of PWM air gap flux density with
The situation of change of time.
Drawbacks described above causes the motor oscillating frequency meter in the case where PWM powers not calculate accurately really.
The content of the invention
The technical problem to be solved in the present invention is to provide a kind of brushless direct current motor under powering for PWM, by standard
Method of the electric machine stator iron vibration frequency that really calculating air gap flux density harmonic wave causes so as to suppress motor oscillating.
In order to solve above-mentioned technical problem, the technical scheme is that a kind of PWM of offer brshless DC motors of powering lead to
Overfrequency calculates the method for suppressing vibration, and the motor is the good motor of electromagnetic structure Preliminary design, it is characterised in that：The method
It is made up of following 8 steps：
Step 1：The calculating rotating speed of motor is set according to operating mode；
Step 2：Calculate the commutation angle of the minimum period of the close changes in distribution of motor magnetic；
Step 3：According to the switching frequency and dutycycle of PWM, the voltage minimum step of setup algorithm；
Step 4：The air gap flux density value of motor is calculated, air gap flux density Fourier decomposition is carried out into, according to the close amplitude size of magnetic
The amplitude and phase place of harmonic wave are obtained, the rotating speed of harmonic wave is calculated in the phase difference of different step-lengths according to same first harmonic, obtain humorous
The frequency of ripple；
Step 5：The each harmonic value of each step-length is extracted, the change curve of each harmonic amplitude is obtained；By each harmonic
The numerical value of amplitude is arranged by axle of the time, carries out Fourier decomposition, obtains the air gap flux density amplitude time dependent each time
The frequency of harmonic wave；
Step 6：Calculate the eigentone of stator core；
Step 7：The frequency relation of comparison step 4, step 5 and step 6：
1) when the close space harmonics frequency of magnetic, time harmonic frequency and intrinsic frequency three's numerical value unshakable in one's determination are in resonance region, electricity
Machine produces resonance；
2) when the close space harmonics frequency of magnetic and inherent frequency numerical value unshakable in one's determination are in resonance region, motor can also produce resonance；
3) when the close time harmonic frequency of magnetic and inherent frequency numerical value unshakable in one's determination are in resonance region, motor can also produce resonance；
Step 8：If occurring resonance, redesign electromagnetism or frame for movement in step 7, repeat step 1 to step 7, directly
To resonance is not produced.
Preferably, in the step 3, the voltage minimum step frequency of calculating necessarily be greater than switching frequency.
Preferably, it is to simplify calculating in the step 5, it will be assumed that the Changing Pattern of each harmonic is essentially identical, with relatively
The close amplitude situation of change of magnetic of the close value maximum point of magnetic of stationary rotor replaces the amplitude situation of change of each harmonic, the magnetic that this is put
The numerical value of close amplitude with the time as axle arrange, carry out Fourier decomposition, obtain air gap flux density amplitude it is time dependent each time when
The frequency of m-Acetyl chlorophosphonazo.
Preferably, in the step 7, if frequency-splitting is in the range of ± the 2% of intrinsic frequency unshakable in one's determination, then it is assumed that in resonance
In area.
Preferably, in the step 7, redesigning the scheme of electromagnetic structure includes：Optimization stator and rotor cores trench structure,
Groove is backed down in stator tooth, gas length, stator core welding reinforcement is adjusted.
The present invention has taken into full account the room and time change for causing the magnetic of motor oscillating close under motor operation operating mode, carries
The high accuracy that motor oscillating is calculated in motor product development, this will improve the success rate of design of electrical motor, objectively contract
In the short Development and Trial cycle of motor, effectively save the non-renewable resources such as copper, iron, aluminium.
Description of the drawings
Fig. 1 is the electric machine structure figure of Preliminary design in embodiment；
Fig. 2 for PWM power brshless DC motor by frequency calculate suppress vibration method flow diagram；
Fig. 3 is the close curve of initial time motor gas-gap magnetic and its Fourier decomposition curve；
Fig. 4 is the frequency curve of the time dependent each time harmonic of air gap flux density amplitude.
Specific embodiment
The PWM that the present invention is provided brshless DC motors of powering are calculated by frequency and suppress the thinking of method vibrated to be：It is right
In the good motor of an electromagnetic scheme Preliminary design, the space harmonics distribution of air gap flux density is calculated first, then a commutation week
The time harmonic change of air gap flux density is calculated in phase, and compared with the eigentone of electric machine iron core, such as frequency is close to, i.e.,
In resonance region, then resonance can be produced, the Electromagnetic Design scheme of motor need to be optimized, each frequency be recalculated, until space harmonics
Close and the close generation of time harmonic magnetic the vibration of magnetic not with resonance unshakable in one's determination.
The factors such as the frequency range of resonance region and the equivalent stiffness of stator core, quality are relevant, in electric machine frequency is calculated
Typically empirically defining resonance region is：The frequency-splitting of each object is in the range of ± the 2% of electric machine iron core eigentone.
To become apparent the present invention, hereby with a preferred embodiment, and accompanying drawing is coordinated to be described in detail below.
By taking the pole of stator 6, the inner-rotor brushless dc motor of the pole of rotor 8 as an example, stator winding is concentratred winding, fixed
Rotor is straight trough, and without support, as shown in figure 1, A is stator yoke in Fig. 1, B is stator winding to electric machine structure, and C is stator tooth, D
For rotor core, E is rotor magnetic steel, and F is axle, and G is air gap.Motor is PWM power supply modes, and switching frequency is 10kHz, using H_
The modulation system of PWM-L_PWM.
With reference to Fig. 2, the PWM that the present invention is provided brshless DC motors of powering calculate the meter of the method for suppressing to vibrate by frequency
Calculate step as follows：
Step one, calculating analysis is carried out according to the parameter of electric machine of above-mentioned Preliminary design, and according to operating mode, set this brushless straight
The rotating speed of stream motor is 3000r/min, and now dutycycle is 0.5.
Step 2, due to motor stator be 6 poles, rotor be 8 poles, when motor rotate 15 degree when complete a rotor teeth groove
Corresponding relation commutation, so calculating rotor rotates 15 degree of dynamic process.The motor gas-gap magnetic close change energy generation in this cycle
The close situation of change of whole magnetic of motor under table this operating mode.
Step 3, switching frequency are 1 × 10 for the pulse period of 10kHz-4S, high level and low level duration are 5
×10-5Commutation cycle when s, 3000 turns of motor is 5 × 10-3 s, it is 5 × 10 to select material calculation-6s。
Step 4, computer aided calculation can be carried out using FEM electromagnetic computing softwares；Or by electric machine rotor structural member
It is divided into some zonules with air gap, the whole domain of motor is divided into vortex and non-vortex area, in vortex magnetic need to be calculated
Field and electric field, use respectively vector magnetic potentialAnd electric scalar potentialTo state, calculating magnetic field is only needed in non-vortex area, use vector magnetic potentialTo state.According to maxwell equation group, using above-mentioned Method obtains the boundary value problem of Three dimensional transient vortex field such as
Under：
Eddy region V of model in end1In：
In end model non-vortex area V2In：
In formula：JsFor ource electric current density；μ is magnetic conductivity；σ is electrical conductivity；T is the time；Y is magnetic reluctance.
There is unique solution to make the above differential equation, following definite condition need to be given：
Ferromagnetic material external boundary
Nonferromagnetic material external boundary
In formula,For vector magnetic potential；For scalar magnetic potential；N is normal vector；Y is magnetic reluctance；WithCan be by motor
The two-dimensional vortex Flow Field Calculation of stack of lamination is obtained.
It is as shown in Figure 3 by being calculated the close distribution of initial time motor gas-gap magnetic and its Fourier decomposition curve.Figure
Middle abscissa is the mechanical angle of motor circumference, and ordinate is magnetic flux density tesla, and H is the distribution curve of air gap flux density, its
Its curve in Sine distribution is the Fourier decomposition curve of airgap density distribution curve.The curve map at other moment is similar to, here
Do not list one by one.According to Maxwell's law, the instantaneous value p of unit area radial electromagnetic force in motor gas-gaprFor：
In formula, brIt is close for air gap radial direction magnetic；μ0For air permeability；θ is circumferential angle；T is the time.
As can be seen from the above equation, the amplitude of radial direction Reeb is close to radial direction magnetic square is directly proportional, i.e. motor radial air gap magnetic
Close bigger, radial direction Reeb is also bigger.Each harmonic is arranged from big to small by amplitude, the amplitude and phase place of each harmonic is obtained,
The frequency of each harmonic is obtained by the phase place change of the air gap flux density of each time step, due to the slot effect of motor and full
With the impact of degree, calculated frequency is change, and can averaging, it is equivalent to carry out.By the big minispread of amplitude, each harmonic
Harmonic amplitude, phase and frequency it is as shown in table 1.
Amplitude, the phase and frequency of each space harmonics of motor of table 1
| Overtone order | Harmonic amplitude/T | Phase angle/deg | Frequency/Hz |
| 4 | 0.7013 | 269.9857 | 207 |
| 10 | 0.1760 | 90.0498 | 12929 |
| 2 | 0.1746 | 89.9962 | 121 |
| 28 | 0.1135 | 269.8754 | - |
| 12 | 0.0934 | 89.9630 | 5632 |
| 8 | 0.0640 | 89.9574 | 1744 |
| 36 | 0.0525 | 89.7463 | - |
| 14 | 0.0492 | -89.8154 | 9889 |
| 52 | 0.0486 | 269.8624 | - |
| 34 | 0.0469 | 90.2877 | 10389 |
Step 5, the numerical value to the close amplitude of magnetic of the close maximum point of rotor geo-stationary magnetic are arranged by axle of the time, carry out Fu
In leaf decompose, the frequency for obtaining the time dependent each time harmonic of air gap flux density amplitude is as shown in Figure 4.Abscissa in Fig. 4
For the step number for calculating, 168 altogether, ordinate is magnetic flux density tesla, and I is curve of the air gap flux density along Annual distribution, its
Its curve in Sine distribution is the Fourier decomposition curve of the close curve of time magnetic.The amplitude and phase place such as table of gained each harmonic
Shown in 2.
The amplitude and frequency of each time harmonic of motor of table 2
| Overtone order | Harmonic amplitude/T | Frequency/Hz |
| 1 | 0.0290 | 1200 |
| 2 | 0.0228 | 2400 |
| 3 | 0.0184 | 3600 |
| 4 | 0.0149 | 4800 |
| 5 | 0.0148 | 6000 |
| 8 | 0.0184 | 9600 |
Step 6, the eigentone for calculating stator core, as a result as shown in table 3.
The exponent number and frequency of the motor intrinsic vibration of table 3
| Exponent number | Frequency/Hz |
| 2 | 2415 |
| 3-1 | 6102 |
| 3-2 | 6839 |
| 4 | 11503 |
| 5 | 16235 |
| 6 | 13698 |
The vibration frequency of step 7, contrast table 1, table 2 and table 3 can be seen that：
1st, the close space harmonics of magnetic, time harmonic and intrinsic frequency unshakable in one's determination substantially resonate not in resonance region without producing；
2nd, the close space harmonics of magnetic and intrinsic frequency unshakable in one's determination substantially resonate not in resonance region without producing；
3rd, the close time harmonic of magnetic and intrinsic frequency 2400Hz unshakable in one's determination and 6000Hz can produce resonance in resonance region.
Step 8, optimization design of electrical motor scheme, it is contemplated that the electromagnetic performance of design of electrical motor scheme has met the requirements, and
The space harmonics and time harmonic of motor does not resonate, thus using only change stator core eigentone scheme, i.e.,
In the ring stiffener of stator core 2 circumferencial directions of cylindrical welding.Now the space harmonics of motor and time harmonic calculate knot
Fruit keeps constant, it is only necessary to re-start calculating to the intrinsic vibration frequency of electric machine stator iron, as a result as shown in table 4：
The exponent number and frequency of the motor intrinsic vibration of table 4
| Exponent number | Frequency/Hz |
| 2 | 2474 |
| 3-1 | 6248 |
| 3-2 | 6984 |
| 4 | 11737 |
| 5 | 16489 |
| 6 | 13707 |
The vibration frequency of contrast table 1, table 2 and table 4 can be seen that the close space harmonics of magnetic, time harmonic and stator core
Intrinsic frequency does not resonate not in resonance region, and motor will not produce significantly vibration.
Claims (5)
1. a kind of PWM power brshless DC motor by frequency calculate suppress vibration method, the motor be electromagnetic structure at the beginning of
The motor that step is designed, it is characterised in that：The method is made up of following 8 steps：
Step 1：The calculating rotating speed of motor is set according to operating mode；
Step 2：Calculate the commutation angle of the minimum period of the close changes in distribution of motor magnetic；
Step 3：According to the switching frequency and dutycycle of PWM, the voltage minimum step of setup algorithm；
Step 4：The air gap flux density value of motor is calculated, air gap flux density is carried out into Fourier decomposition, obtained according to the close amplitude size of magnetic
The amplitude and phase place of harmonic wave, the rotating speed of harmonic wave is calculated according to same first harmonic in the phase difference of different step-lengths, obtains the close sky of magnetic
M-Acetyl chlorophosphonazo frequency；
Step 5：The each harmonic value of each step-length is extracted, the change curve of each harmonic amplitude is obtained；By each harmonic amplitude
Numerical value with the time as axle arrange, carry out Fourier decomposition, obtain the time dependent time harmonic frequency of air gap flux density amplitude；
Step 6：Calculate the intrinsic frequency unshakable in one's determination of stator core；
Step 7：The frequency relation of comparison step 4, step 5 and step 6：
1) when the close space harmonics frequency of magnetic, time harmonic frequency and intrinsic frequency three's numerical value unshakable in one's determination are in resonance region, motor is produced
Raw resonance；
2) when the close space harmonics frequency of magnetic and inherent frequency numerical value unshakable in one's determination are in resonance region, motor can also produce resonance；
3) when the close time harmonic frequency of magnetic and inherent frequency numerical value unshakable in one's determination are in resonance region, motor can also produce resonance；
Step 8：If occurring resonance in step 7, redesign electromagnetism or frame for movement, repeat step 1 to step 7, until not
Till producing resonance.
2. a kind of PWM as claimed in claim 1 brshless DC motors of powering calculate the method for suppressing vibration by frequency, its spy
Levy and be：In the step 3, the voltage minimum step frequency of calculating is higher than switching frequency.
3. a kind of PWM as claimed in claim 1 brshless DC motors of powering calculate the method for suppressing vibration by frequency, its spy
Levy and be：It is to simplify calculating in the step 5, it is assumed that the Changing Pattern of each harmonic is identical, it is close with the static magnetic of relative rotor
The close amplitude situation of change of magnetic of value maximum point replaces the amplitude situation of change of each harmonic, by the numerical value of this close amplitude of magnetic put with
Time is axle arrangement, carries out Fourier decomposition, obtains the frequency of the time dependent each time harmonic of air gap flux density amplitude.
4. a kind of PWM as claimed in claim 1 brshless DC motors of powering calculate the method for suppressing vibration by frequency, its spy
Levy and be：In the step 7, if frequency-splitting is in the range of ± the 2% of intrinsic frequency unshakable in one's determination, then it is assumed that in resonance region.
5. a kind of PWM as claimed in claim 1 brshless DC motors of powering calculate the method for suppressing vibration by frequency, its spy
Levy and be：In the step 7, redesigning the scheme of electromagnetic structure includes：Optimization stator and rotor cores trench structure, in stator tooth
Groove is backed down, gas length, stator core welding reinforcement is adjusted.
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| CN114019907B (en) * | 2021-10-25 | 2023-07-18 | 安徽理工大学 | Realization method for eliminating self-excited vibration of linear feed servo system |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4435751A (en) * | 1980-07-03 | 1984-03-06 | Hitachi, Ltd. | Vibration/noise reduction device for electrical apparatus |
| JPH09289787A (en) * | 1996-04-23 | 1997-11-04 | Toyo Electric Mfg Co Ltd | Pwm controller for making effective value of harmonic current minimum |
| CN103633917A (en) * | 2013-12-11 | 2014-03-12 | 陈卫兵 | Method and device for reducing vibration noise of motor |
| CN104270047A (en) * | 2014-09-30 | 2015-01-07 | 山东艾磁驱动科技有限公司 | Method and system for achieving voltage reduction control in low-speed running process of motor |
-
2015
- 2015-04-14 CN CN201510174204.1A patent/CN104767344B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4435751A (en) * | 1980-07-03 | 1984-03-06 | Hitachi, Ltd. | Vibration/noise reduction device for electrical apparatus |
| JPH09289787A (en) * | 1996-04-23 | 1997-11-04 | Toyo Electric Mfg Co Ltd | Pwm controller for making effective value of harmonic current minimum |
| CN103633917A (en) * | 2013-12-11 | 2014-03-12 | 陈卫兵 | Method and device for reducing vibration noise of motor |
| CN104270047A (en) * | 2014-09-30 | 2015-01-07 | 山东艾磁驱动科技有限公司 | Method and system for achieving voltage reduction control in low-speed running process of motor |
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