CN101034038A - Failure testing method of asynchronous motor bearing - Google Patents

Abstract

This invention relates to a malfunction dection means for asynchronous motor bearing, belongs to detection technique region, design to solve problem of asynchronous motor bearing on-line measurement. The technical proposal is; the invention through series refine Fourier transform to collective stator current momentary signal(is) to gain its principal wave namely reference signal(us); base on reference signal(us) and its frequency(f1) to do auto-adapted filtering to stator current momentary signal(is); then through series refine Fourier transform to output signal( eT) to ascertain amplitude value ratio of currently |f1+-mfv| side frequency component and fundamental component, and takes it as fault signature; at last, base on threshold of detection value to ascertain malfunction indices; according to malfunction indices to judge whether bearing malfunction existing.

Description

Failure testing method of asynchronous motor bearing

Technical field

The present invention relates to a kind of method and device that can the incipient failure of online detection asynchronous motor bearing, belong to the detection technique field.

Background technology

Rolling bearing is widely used among the asynchronous motor with overwhelming dominance.Rolling bearing is made up of interior raceway, outer raceway and the rolling body that rotates between them.Under the normal running conditions of balanced load, good centering, fatigue failure is from being positioned at the subsurface fine crack of raceway and rolling body, and expansion gradually, causes that then material fragment comes off, cause bearing fault, this type of fault probability of happening is about 40% of asynchronous motor fault.

At present, the vibration signal spectrum analysis is comparatively accurate, reliable failure testing method of asynchronous motor bearing.This method is gathered bearing time domain vibration signal and also is converted into frequency domain, so with frequency domain vibration signal and bearing intrinsic frequency domain vibration characteristics contrast, whether take place with the judgement bearing fault.The weak point of this method is to need to install vibration transducer, owing to vibration transducer cost height, damage easily, thereby has limited further applying of this method.

Someone has proposed the stator current signal frequency spectrum analysis method.The asynchronous motor bearing fault will occur in stator current after taking place | f _l± mf _v| the extra current component (f of frequency _lBe line frequency, f _vBe bear vibration feature (intrinsic) frequency, m=1,2,3 Λ).Bearing fault generally is divided into outer raceway fault, interior raceway fault, rolling body fault and retainer fault, and vibration performance (intrinsic) frequency is calculated according to formula (1), formula (2), formula (3), formula (4) respectively.

Outer raceway fault natural frequency: $f_{\mathrm{OD}}=\frac{n}{2}{f}_{\mathrm{rm}}(1-\frac{\mathrm{BD}}{\mathrm{PD}}\cos \mathrm{\Φ})...\left(1\right)$

Interior raceway fault natural frequency: $f_{\mathrm{ID}}=\frac{n}{2}{f}_{\mathrm{rm}}(1+\frac{\mathrm{BD}}{\mathrm{PD}}\cos \mathrm{\Φ})...\left(2\right)$

Rolling body fault natural frequency: $f_{\mathrm{BD}}=\frac{\mathrm{<figure-callout\; id="2"\; label="PD"\; filenames="A20071006163300151.png"\; state="\{\{state\}\}">PD</figure-callout>}}{2\mathrm{BD}}{f}_{\mathrm{rm}}(1-{\left(\frac{\mathrm{BD}}{\mathrm{PD}}\right)}^2{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20071006163300151.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2\mathrm{\&Phi;})...\left(3\right)$

Retainer fault natural frequency: $f_{\mathrm{CD}}=\frac{1}{2}{f}_{\mathrm{rm}}(1-\frac{\mathrm{BD}}{\mathrm{PD}}\cos \mathrm{\&Phi;})...\left(4\right)$

Wherein, f _RmBe the commentaries on classics frequency of motor, n is the rolling body number, and BD and PD are rolling body diameter and bearing pitch diameter, and Φ is the contact angle of rolling body.

According to above-mentioned natural frequency, can calculate the stator current characteristic frequency according to formula (5).

f _CF＝|f _l±mf _v| m＝1，2，3Λ (5)

Wherein, f _lBe line frequency, f _vFor by vibration natural frequency shown in the formula (1-4).

In view of stator current signal is easy to gather, vibration signal spectrum analysis relatively, this method has wide development, application prospect.But, because bearing fault feature---stator current | f _l± mf _v| the amplitude of frequency component is with respect to f _lComponent is very little, and this method can not guarantee to extract the sensitivity of fault signature.In addition and since motor itself intrinsic asymmetric, air gap eccentric centre, rotor misalignment and other factor, even asynchronous motor is in normal operating condition, also may comprise in its stator current | f _l± mf _v| frequency component, and for different asynchronous motors, the situation complexity.This easily obscures mutually with the bearing fault feature, causes erroneous judgement, influences the fault detect reliability.This method can not be taken into account above-mentioned factor, and reliability still remains to be improved.

Summary of the invention

The object of the present invention is to provide a kind of can high sensitivity, the failure testing method of asynchronous motor bearing and the device of the online detection asynchronous motor bearing incipient failure of high reliability ground.

The alleged problem of the present invention realizes with following technical proposals:

A kind of failure testing method of asynchronous motor bearing, it is by the stator current momentary signal i to gathering _sDo continuous refinement Fourier transform, obtaining its first-harmonic is reference signal u _S, again according to reference signal u _SAnd frequency f _lTo stator current momentary signal i _sDo auto adapted filtering, then to the filtering output signal e _TDo continuous refinement Fourier transform, determine current | f _l± mf _v| side frequency component and the ratio of fundametal compoment amplitude and it as fault signature, determine fault index according to detection threshold at last, judge bearing fault according to fault index.

Above-mentioned failure testing method of asynchronous motor bearing, fault index calculates according to the following steps:

A. gather a phase stator current momentary signal, be designated as i _s

B. to i _sDo continuous refinement Fourier transform, determine the frequency f of its fundametal compoment _l, amplitude I _mWith initial phase angle φ, form reference signal u _S:

For sample frequency is f _s, sampling number is the time series i (t of N _k),

u _S(K)＝I _msin(2πf _lkT _S+φ+π)

Wherein, k=0,1,2, Λ, N-1, I _m, f _l, φ determines by continuous refinement Fourier transform.

C. according to the frequency f of fundametal compoment _l, reference signal u _STo i _sDo auto adapted filtering, offset its f _lComponent, filtering output result is designated as e _T

D is to e _TDo continuous refinement Fourier transform, at e _TContinuous refinement spectrogram in inquire about f _CF(f _CF=| f _l± mf _v|, get m=1,2) component information, determine current f _CFComponent and f _lThe ratio ratio of component amplitude _FCF=ratio _Fl+fv+ ratio _{| fl-fv|}+ ratio _Fl+2fv+ ratio _{| fl-2fv|},

Wherein, ratio _Fl+fvBe f _l+ f _vComponent and f _lThe ratio of component amplitude, ratio _{| fl-fv|}Be f _l-f _vComponent and f _lThe ratio of component amplitude, ratio _Fl+2fvBe f _l+ 2f _vComponent and f _lThe ratio of component amplitude, ratio _{| fl-2fv|}Be f _l-2f _vComponent and f _lThe ratio of component amplitude;

E. determine fault index:

Under the situation of not setting up normal motor sample reference paper as yet, detection threshold (being generally 0.1%), ratio are set according to conventional experience _FCFBe fault index with its ratio;

F. whether exist according to the fault index failure judgement:

Fault index numerical value＜1, the expression motor is in health status, and its numerical value is littler, and health status is clearer and more definite; Fault index numerical value＞1, the expression motor is in malfunction, and its numerical value is bigger, and malfunction is more serious.

Above-mentioned failure testing method of asynchronous motor bearing is for can be in the filtering output signal e _TContinuous refinement spectrogram in accurate inquiry f _CFThe side frequency component information, should calculate revolutional slip s earlier:

$s=1-\frac{P}{Z_r}(\frac{f_{\mathrm{rsh}}}{f_1}\&PlusMinus;v),v=\mathrm{1,3,5},\mathrm{\&Lambda;}$

Wherein, f _RshFor rotor tooth slot harmonic component frequency, P are the motor number of pole-pairs, Z _rBe the rotor slot number,

Then according to the fundametal compoment frequency f _l, revolutional slip s, in the filtering output signal e _TContinuous refinement spectrogram in inquire about f _CFThe side frequency component information is determined current f _CFSide frequency component and f _lThe ratio ratio of component amplitude _FCF(motor changes f frequently in the natural frequency expression formula _Rm=(1-s) f _l).

Above-mentioned failure testing method of asynchronous motor bearing, for eliminate real electrical machinery itself the influence of intrinsic asymmetric, air gap eccentric centre, rotor misalignment and other factor, should be under the motor bearings normal condition, according to revolutional slip s and fault signature ratio _FCFConcrete numerical value set up sample database, and the detection threshold of adjusting in view of the above:

If the current numerical value of revolutional slip between sample data revolutional slip upper and lower limit, then adopts the linear interpolation mode that detection threshold is set; Otherwise, determine immediate with it sample data revolutional slip, as detection threshold, and make safety factor be not less than 1 the fault signature numerical value of correspondence.

The present invention utilizes current transformer CT to gather asynchronous motor stator winding current signal, and data acquisition card is sent to computing machine with this signal, by computing machine current signal is handled, and judges whether to exist bearing fault, and is simple in structure, easy to operate.The present invention adopts stator current f _CFThe side frequency component is as fault signature, continuous refinement Fourier transform, auto adapted filtering, the estimation of rotor tooth slot harmonic revolutional slip, detection threshold automatic-adjusting technique are organically combined, when improving sensitivity, eliminated real electrical machinery itself intrinsic asymmetric, air gap eccentric centre, rotor misalignment and other factor to extracting the influence of fault signature, effectively prevented erroneous judgement.The present invention can high sensitivity, the first property the sent out bearing fault of the various asynchronous motors of the high reliability online detection in ground.

Description of drawings

The invention will be further described below in conjunction with accompanying drawing.

Fig. 1 is an electric theory diagram of the present invention;

Fig. 2 is the theory diagram of adaptive filter method;

Fig. 3 is the schematic diagram of signal acquisition circuit;

Fig. 4 is that the fully loaded and bearing of Y100L-2 type experiment motor exists the stator a phase current under the outer raceway failure condition;

Fig. 5 is the f of Y100L1-2 type experiment motor stator a phase current frequency spectrum _l+ f _vFrequency range;

Fig. 6 is the f of Y100L1-2 type experiment motor stator a phase current frequency spectrum _l-f _vFrequency range;

Fig. 7 is the f of Y100L1-2 type experiment motor stator a phase current frequency spectrum _l+ 2f _vFrequency range;

Fig. 8 is the f of Y100L1-2 type experiment motor stator a phase current frequency spectrum _l-2f _vFrequency range.

Each label is among the figure: CT, current transformer, PT, voltage transformer (VT), M, motor; R1, R2, resistance.

The meaning of used each symbol in the literary composition; S, revolutional slip; f _Rm, motor commentaries on classics frequently; N, rolling body number; BD, rolling body diameter; PD, bearing pitch diameter; The contact angle of Φ, rolling body; f _v, vibration natural frequency; f _l, stator current fundamental frequency (line frequency); f _OD, outer raceway fault natural frequency; f _ID, interior raceway fault natural frequency; f _BD, rolling body fault natural frequency; f _CD, retainer fault natural frequency; f _CF, the stator current characteristic frequency; Ratio _FCF, f _CFComponent and f _lThe ratio of component amplitude; Ratio _Fl+fv, f _l+ f _vComponent and f _lThe ratio of component amplitude; Ratio _{| fl-fv|}, f _l-f _vComponent and f _lThe ratio of component amplitude; Ratio _Fl+2fv, f _l+ 2f _vComponent and f _lThe ratio of component amplitude; Ratio _{| fl-2fv|}, f _l-2f _vComponent and f _lThe ratio of component amplitude; i _s, stator current signal; S _T, auto adapted filtering signal to be extracted; n _T, noise signal; u _S, (auto adapted filtering) reference signal; e _T, the filtering output signal; y _T, filter response; I _m, the reference signal amplitude; φ, reference signal initial phase angle; f _s, sample frequency; N, sampling number; I (t _k), the current sample instantaneous value; t _k, sampling instant; f _Rsh, rotor tooth slot harmonic component frequency, P, motor number of pole-pairs; Z _r, the rotor slot number; T _s, sampling time interval; A (n), b (n), a (0) represent fourier coefficient; Δ f, frequency discrimination unit.

Embodiment

The present invention adopts circuit shown in Figure 1 to detect, this circuit is made up of current transformer CT, data acquisition card and computing machine, described current transformer is connected on the phase line of asynchronous motor stator winding, its signal output part connects the simulating signal input channel 5 (input terminal 5 and 17) of data acquisition card, and the output port of described data acquisition card connects the USB mouth of computing machine.Data acquisition card adopts auspicious rich magnificent RBH8321 type data acquisition card, and the model of computing machine is DELL M1210, data acquisition card is integrated circuit such as low-pass filter, signals collecting maintenance, mould/number conversion.The stator current momentary signal is delivered to data acquisition card, and data acquisition card is connected in portable computer by USB interface.Portable computing machine control signal capture card is with appropriate frequency sampling stator current momentary signal, and is stored in hard disk, by computing machine current signal handled again, judges whether to exist bearing fault.This matched with devices software is based on WindowsXP operating system and adopt the establishment of Visual C++ application development platform.

The basic ideas of adaptive filter method are: adopt adaptive filter method to offset motor stator electric current f _lComponent, outstanding f in spectrogram _CFSide frequency component---bearing fault feature, thus the sensitivity that bearing fault detects significantly improved.Reference signal u _SUsing continuous refinement Fourier transform determines.

The principle of auto adapted filtering is as follows:

Figure below is the theory diagram of adaptive filter method.Among the figure, i _sRepresent actual stator current signal, it comprises signal S to be extracted _TWith noise n _T, and u _SIt is reference signal.Here, S _TBe in the stator current | f _l± mf _v| frequency component, n _TBe the f in the stator current _lFrequency component, and e _TThen represent i _sMake auto adapted filtering and handle resulting signal afterwards.If the response of sef-adapting filter is y _T, obviously, e _T=i _s-y _TAccording to e _TSize, adjust the parameter of wave filter, appropriate change y by adaptive algorithm _T, can make y _TUnder the meaning of least mean-square error, offset n _T, and e _TTo under the meaning of least mean-square error, approach signal S to be extracted _T

Fig. 2 is the theory diagram of adaptive filter method, among Fig. 2, and i _sRepresent actual stator current signal, it comprises signal S to be extracted _TWith noise n _T, and u _SIt is reference signal.Here, S _TBe in the stator current | f _l± mf _v| frequency component, n _TBe the f in the stator current _lFrequency component, and e _TThen represent i _sMake auto adapted filtering and handle resulting signal afterwards.If the response of sef-adapting filter is y _T, obviously, e _T=i _s-y _TAccording to e _TSize, adjust the parameter of wave filter, appropriate change y by adaptive algorithm _T, can make y _TUnder the meaning of least mean-square error, offset n _T, and e _TTo under the meaning of least mean-square error, approach signal S to be extracted _T

Fig. 3 is the current signal Acquisition Circuit.Obviously, resistance R ₁On voltage signal be i among Fig. 2 _s

Use continuous refinement Fourier transform and auto-adaptive filtering technique and can guarantee to extract in high sensitivity motor stator electric current f _CFThe side frequency component is used continuous refinement fourier transform method, can obtain the accurate and analytical expression of a certain main frequency component in the signal to be analyzed, i.e. frequency, amplitude and initial phase angle.

For sample frequency is f _s, sampling number is the time series i (t of N _k), discrete Fourier progression is:

$\left\{\begin{array}{c}a\left(n\right)=\frac{2}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}i\left(t_k\right)\cos (2\mathrm{\&pi;kn}/N)\\ b\left(n\right)=\frac{2}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}i\left(t_k\right)\sin (2\mathrm{\&pi;kn}/N)\\ a\left(0\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}i\left(t_k\right)\\ n=\mathrm{0,1},2,\mathrm{\&Lambda;},N-1\end{array}\right....\left(6\right)$

Wherein, t _k=kT _s, T _s=1/f _s, k=0,1,2, Λ, N-1, a (n), b (n), a (0) represent fourier coefficient.

Fast Fourier Transform (FFT) is the special circumstances of above-mentioned discrete transform, i.e. N=2 ^m(m is a positive integer), at this moment, Fourier transform can adopt the recursion fast algorithm.This conversion, frequency discrimination unit are Δ f=f _s/ N, N is inversely proportional to sampling number.Obviously,, must increase sampling number exponentially if wish to improve the frequency discrimination ability, sampling number one timing, the frequency discrimination ability can't further improve.

Time series i (t _k) comprise signal 0 to f _sInformation in/2 these frequency domains if spectrum curve is regarded as continuously, thinks that promptly the n in the formula (6) is a continuous real number that belongs to interval [0, N/2], and formula (6) can be rewritten an accepted way of doing sth (7).At this moment, the frequency discrimination ability no longer is subjected to the restriction of sampling number, and the value of frequency f is continuous.

$\left\{\begin{array}{c}a\left(f\right)=\frac{2}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}i\left(t_k\right)\cos (2\mathrm{\&pi;kf}/f_s)\\ b\left(f\right)=\frac{2}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}i\left(t_k\right)\sin (2\mathrm{\&pi;kf}/f_s)\\ 0<f\&le;f_s/2\end{array}\right....\left(7\right)$

When using continuous refinement Fourier transform, refinement scope, refinement density can be carried out step by step, to improve computing velocity.

Reference signal u _SDetermine according to formula (8).

u _S(K)＝I _msin(2πf _lkT _S+φ+π) (8)

Wherein, k=0,1,2, Λ, N-1, I _m, f _l, φ determines by continuous refinement Fourier transform.

Bearing fault after taking place in real electrical machinery, and its stator current frequency spectrum often comprises a plurality of spectrums peak, and f _CFFrequency component spectrum peak-to-peak value may not be maximum.This be attributable to real electrical machinery itself intrinsic asymmetric, air gap eccentric centre, rotor misalignment and other factor.

Above-mentioned side frequency component very easily with bearing fault feature---f _CFFrequency component is obscured mutually, causes erroneous judgement, influences the reliability that bearing fault detects.Therefore, when carrying out the bearing fault detection, should predict f _lWith the concrete numerical value of s, thereby in the stator current frequency spectrum, on purpose inquire about f _CFFrequency component, and it is done quantitative test, to guarantee the bearing fault detecting reliability.

In motor operation course, because rotor mmf teeth groove harmonic wave and first-harmonic air-gap flux reciprocation will comprise rotor tooth slot harmonic component in the stator current.According to its frequency f _Rsh, motor number of pole-pairs P and rotor slot count Z _rCan determine motor slip ratio by formula (9):

$s=1-\frac{P}{Z_r}(\frac{f_{\mathrm{rsh}}}{f_1}\&PlusMinus;\mathrm{v\&nu;}),\mathrm{v\&nu;}=\mathrm{1,3,5},\mathrm{\&Lambda;}---\left(9\right)$

In engineering reality, often select f _CFFrequency component and f _lLikening to of component amplitude is fault signature, by judging whether its numerical value surpasses a certain threshold value and realize that bearing fault detects.

Owing to technology, manufacturing and reason is installed, intrinsic asymmetric, air gap eccentric centre, the rotor misalignment to a certain degree of any real electrical machinery certainty itself, other factors even motor is in normal operating condition, also may comprise f in its stator current in addition _CFAnd other frequency component.And for different asynchronous motors, the situation complexity.

How suitably this be provided with detection threshold to take into account this problem of sensitivity and reliability simultaneously with regard to having proposed.If it is too high that detection threshold is provided with, then be unfavorable for improving sensitivity.On the other hand, low if detection threshold was provided with, so that be lower than motor stator current f when normal operation _CFComponent and f _lThe ratio of component amplitude must cause the fault erroneous judgement, and reliability is not just known where to begin yet.

The analysis showed that more than the bearing fault that carries out high sensitivity, high reliability detects, must at first clear and definite normal motor f _CFFrequency component and f _lThe ratio of component amplitude is provided with suitable detection threshold in view of the above, to avoid fault omission and erroneous judgement.

For take into account real electrical machinery itself intrinsic asymmetric, air gap eccentric centre, rotor misalignment and other factor, should adopt detection threshold based on sample learning from the strategy of adjusting to improve sensitivity and reliability.

Suppose that initial motor bearings is normal, according to revolutional slip s and fault signature ratio _FCFConcrete numerical value set up sample database, this is because fault signature ratio _FCFBasically only depend on revolutional slip s.Set up sample database, should pay attention to its simple and direct property, and, contain the revolutional slip normal fluctuation as far as possible in conjunction with the motor actual operating.

As soon as the normal motor sample database is set up, can carry out from adjusting detection threshold according to the current numerical value of revolutional slip, specific as follows: if the current numerical value of revolutional slip between sample data revolutional slip upper and lower limit, then adopts the linear interpolation mode that detection threshold is set; Otherwise, determine immediate with it sample data revolutional slip, as detection threshold, and make safety factor be not less than 1 the fault signature numerical value of correspondence.

Behind the asynchronous motor generation bearing fault, stator current f _CF(f _CF=| f _l± mf _v|, get m=1,2) frequency component is that coupling occurs.For bearing fault detection sensitivity and reliability consideration, should inquire about f simultaneously _CFFrequency component information.The asynchronous motor just property sent out bearing fault detection method promptly adopts stator current f simultaneously _CF(comprise f _l+ f _v, | f _l-f _v|, f _l+ 2f _v, | f _l-2f _v|) frequency component is as fault signature.

Use the present invention Y100L-2 type experiment motor is carried out the bearing fault test experience, the motor bearings model is 6206-2RS, external diameter 62mm, internal diameter 30mm, inside and outside raceway thickness is identical, bearing pitch diameter PD=46mm then, this bearing ball number n=9, the about 10mm of ball diameter (BD), contact angle β=0 °.There is outer raceway fault (there is the aperture of diameter 1.5mm, a degree of depth 10mm in outer raceway face) in this bearing.

Fig. 4～Fig. 8 represents the experimental result under the motor full load conditions, and concrete data are shown in table 1.

There is the experimental result under the outer raceway failure condition in the fully loaded and bearing of table 1 motor

f l(Hz)

49.99

s(％)	3.1
		f v(Hz)	170.6
f l+f v(Hz)	220.6
		|f l-f v|(Hz)	120.6
f l+2f v(Hz)	391.2
		|f l-2f v|(Hz)	291.2
f lComponent amplitude (A)	5.9603
		f l+f vComponent amplitude (mA)	0.62
|f l-f v| component amplitude (mA)	0.32
		f l+2f vComponent amplitude (mA)	0.2
|f l-2f v| component amplitude (mA)	1.41
		Fault signature amount ratio fl+fv+ratio |fl-fv|+ratio fl+2fv+ratio |fl-2fv|(％)	0.043
Do not set up the detection threshold (%) under the normal motor sample reference paper situation as yet	0.1
		Set up the detection threshold (%) under the normal motor sample reference paper situation	0.0324

The bearing fault experimental result

Above-mentioned bearing is experimentized, and the motor load situation is set to zero load, semi-load and fully loaded respectively.Gather three-phase current signal and write down motor speed.By formula (1), formula (2) difference calculation bearing Features of Vibration Trouble frequency f _v, utilize continuous refinement Fourier transform to determine line frequency f _l, calculate bearing fault characteristic frequency f in the stator current by formula (5) again _CF, its result of calculation sees Table 2.

Table 2 bearing fault characteristic frequency

		f l(Hz)	f rm(Hz)	f v(Hz)	f CF(Hz)(m＝1)
							The outer ring fault	Fully loaded	50.02	48.45	170.6	120.6	220.6
Semi-load	50.03	49.3	173.6	123.6	223.6
						Unloaded		50	49.85	175.6	125.6	225.6

The inner ring fault	Fully loaded	50.01	48.47	265.5	215.6	315.5
							Semi-load	49.98	49.3	270.0	220.0	320.0
	Unloaded	49.99	49.87	273.2	223.2	323.2

Claims (3)

1, a kind of failure testing method of asynchronous motor bearing is characterized in that, it is by the stator current momentary signal i to gathering _sDo continuous refinement Fourier transform, obtaining its first-harmonic is reference signal u _S, again according to reference signal u _SAnd frequency f ₁To stator current momentary signal i _sDo auto adapted filtering, then to the filtering output signal e _TDo continuous refinement Fourier transform, determine current | f ₁± mf _v| side frequency component and the ratio of fundametal compoment amplitude and it as fault signature, determine fault index according to detection threshold at last, judge bearing fault according to fault index.

2, according to the described failure testing method of asynchronous motor bearing of claim 1, it is characterized in that fault index calculates according to the following steps:

A. gather a phase stator current momentary signal, be designated as i _s

B. to i _sDo continuous refinement Fourier transform, determine the frequency f of its fundametal compoment ₁, amplitude I _mWith initial phase angle φ, form reference signal u _S:

For sample frequency is f _s, sampling number is the time series i (t of N _k),

u _S(K)＝I _msin(2πf ₁kT _S+φ+π)

Wherein, k=0,1,2, Λ, N-1, I _m, f ₁, φ determines by continuous refinement Fourier transform.

C. according to the frequency f of fundametal compoment ₁, reference signal u _STo i _sDo auto adapted filtering, offset its f ₁Component, filtering output result is designated as e _T

D. to e _TDo continuous refinement Fourier transform, at e _TContinuous refinement spectrogram in inquire about f _CFComponent information, f _CF=| f ₁± mf _v|, get m=1,2, determine current f _CFComponent and f ₁The ratio of component amplitude

${\mathrm{ratio}}_{f_{\mathrm{CF}}}={\mathrm{ratio}}_{f_1+f_v}+{\mathrm{ratio}}_{|f_1-f_v|}+{\mathrm{ratio}}_{f_1+2f_v}+{\mathrm{ratio}}_{|f_1-2f_v|},$

Wherein, ratio _F1+fvBe f ₁+ f _vComponent and f ₁The ratio of component amplitude, ratio _{| f1-fv|}Be f ₁-f _vComponent and f ₁The ratio of component amplitude, ratio _F1+2fvBe f ₁+ 2f _vComponent and f ₁The ratio of component amplitude, ratio _{| f1-2fv|}Be f ₁-2f _vComponent and f ₁The ratio of component amplitude:

E. determine fault index:

Under the situation of not setting up normal motor sample reference paper as yet, according to conventional experience detection threshold is set, be generally 0.1%, ratio _FCFBe fault index with its ratio;

F. whether exist according to the fault index failure judgement:

Fault index numerical value＜1, the expression motor is in health status, and its numerical value is littler, and health status is clearer and more definite; Fault index numerical value＞1, the expression motor is in malfunction, and its numerical value is bigger, and malfunction is more serious.

Above-mentioned failure testing method of asynchronous motor bearing is for can be in the filtering output signal e _TContinuous refinement spectrogram in accurate inquiry f _CFThe side frequency component information, should calculate revolutional slip s earlier:

$s=1-\frac{P}{Z_r}(\frac{f_{\mathrm{rsh}}}{f_1}\&PlusMinus;v),v=\mathrm{1,3,5},\mathrm{\&Lambda;}$

Wherein, f _RshFor rotor tooth slot harmonic component frequency, P are the motor number of pole-pairs, Z _rBe the rotor slot number,

Then according to the fundametal compoment frequency f ₁, revolutional slip s, in the filtering output signal e _TContinuous refinement spectrogram in inquire about f _CFThe side frequency component information is determined current f _CFSide frequency component and f ₁The ratio ratio of component amplitude _FCFMotor changes f frequently in the natural frequency expression formula _Rm=(1-s) f ₁

3, according to claim 1 or 2 described failure testing method of asynchronous motor bearing, it is characterized in that, under the motor bearings normal condition, according to revolutional slip s and fault signature ratio _FCFConcrete numerical value set up sample database, and the detection threshold of adjusting in view of the above:

If the current numerical value of revolutional slip between sample data revolutional slip upper and lower limit, then adopts the linear interpolation mode that detection threshold is set; Otherwise, determine immediate with it sample data revolutional slip, as detection threshold, and make safety factor be not less than 1 the fault signature numerical value of correspondence.

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