CN104765003A - Asynchronous motor rotor bar break fault diagnosis method for engineering machine internet of things - Google Patents

Abstract

The invention discloses an asynchronous motor rotor bar break fault diagnosis method for the engineering machine internet of things. The method includes the following steps that the start rotary speed and the start current of an asynchronous motor in an engineering machine are acquired, an ARM processor compresses acquired data and transmits the acquired data to a remote monitoring center through a GPS module; the remote monitoring center reconstructs the received compressed data, fault diagnosis is conducted on the reconstructed data through a second-order discrete polynomial phase conversion method, and a diagnosis result is acquired; the remote monitoring center sends the diagnosis result to the GPRS module of the engineering machine through a wireless network, the ARM processor receives the data received by the GPRS module and controls an LCD to display the diagnosis result, and if a fault exists, an audible and visual alarm is simultaneously controlled to given an alarm; network terminal equipment has access to the remote monitoring center through the internet and looks over the rotor bar break fault state of the asynchronous motor in the engineering machine.

Description

For the asynchronous motor rotor strip-broken method for diagnosing faults of engineering machinery Internet of Things

Technical field

The invention belongs to engineering machinery Internet of Things remote monitoring and administration technical field, specifically a kind of asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things.

Background technology

Engineering machinery be integrate mechanical, electrical, liquid, control, the engineering construction equipment of interrogating, be widely used in building, mine, highway railway traffic constructed, harbour and municipal works etc.Along with socioeconomic development, China's power's development from construction machinery production big country to construction machinery production, a new generation's engineering machinery is all the high-tech, the "smart" products that highly merge, equipment is once break down, very large difficulty is brought to maintenance, must turn out expert teacher maintenance personal, and be distributed to all over the world, this must cause increasing substantially of maintenance cost.Therefore, in order to improve the market competitiveness of enterprise, engineering machinery Internet of Things remote control administrative system constantly rises.

Asynchronous motor is as a kind of driving arrangement, be widely applied in engineering machinery because it has the features such as structure is simple, cheap, sturdy and durable, operation and maintenance is convenient, particularly nowadays engineering machinery, just constantly from traditional hydraulic-driven, drives and driven by power future development toward hybrid power.But asynchronous motor belongs to again the multiple district of fault, particularly rotor bar breaking fault is wherein one of modal fault of asynchronous motor.Asynchronous motor directly affects engineering machinery construction operation once break down, and even causes fatal crass, bring huge economic loss and severe social influence time serious.Although current engineering machinery Internet of Things remote control administrative system has Distant supervision and control function to engineering machinery, but it is inadequate to the remote monitoring and administration dynamics of asynchronous motor in engineering machinery, particularly rotor bar breaking fault wherein, lacks asynchronous motor rotor strip-broken method for diagnosing faults effectively reliably.Therefore, be necessary on the basis of existing engineering machinery Internet of Things remote control administrative system, specially for the asynchronous motor rotor strip-broken accident design one in engineering machinery simply, remote fault diagnosis method fast and accurately.

Summary of the invention

Inadequate in order to solve the remote monitoring and administration dynamics of current engineering machinery Internet of Things remote control administrative system to the asynchronous motor in engineering machinery, particularly rotor bar breaking fault wherein, lack the problem of asynchronous motor rotor strip-broken method for diagnosing faults effectively reliably, the invention provides a kind of asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things, its can simply, remote diagnosis engineering machinery asynchronous motor rotor strip-broken fault quickly and accurately.

To achieve these goals, technical scheme of the present invention is as follows: a kind of asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things, comprises the following steps:

Step one: utilize the startup rotating speed of asynchronous motor and the starting current of the arbitrary phase of stator terminal in current sensor and speed measuring motor difference gathering project machinery, and respectively the data of collection are sent to arm processor, arm processor utilizes compressed sensing to compress the data gathered, and the data after compression are sent to remote monitoring center by GPRS module through wireless network;

Step 2: remote monitoring center receives the packed data that GPRS module sends, compressed sensing is utilized to be reconstructed the packed data received, fault diagnosis is carried out to the starting current data separate Second-Order Discrete polynomial-phase transform method of reconstruct, draws asynchronous motor rotor strip-broken fault diagnosis result;

Step 3: diagnostic result is sent to the GPRS module of engineering machinery by remote monitoring center by wireless network, the data of reception are sent to arm processor by GPRS module, arm processor controls LCD display display diagnostic result, if there is fault, then controls audible-visual annunciator simultaneously and reports to the police;

Step 4: network-termination device, by internet access remote monitoring center, checks asynchronous motor rotor strip-broken malfunction in engineering machinery.

Further, in step one, utilize compressed sensing to carry out compression to the data gathered and comprise the following steps: first utilize wavelet transform to carry out sparse transformation to the data gathered and obtain sparse data; Then gaussian random matrix is utilized to compress sparse data.

Further, in step one, remote monitoring center comprises the communication server, resolution server, database server and application server; The communication server is responsible for carrying out two-way communication with the GPRS module of engineering machinery by wireless network; The packed data that resolution server is responsible for the communication server receives is reconstructed, and to the data analysis process of reconstruct, draws analysis result; The intermediate data that the engineering machinery status data of reception is in charge of by database server, analyzing and processing obtains and diagnostic result: performance of work machinery Internet of Things remote control administrative system software is responsible for by application server.

Further, in step 2, compressed sensing is utilized to be orthogonal matching pursuit algorithm to the method that the packed data received is reconstructed.

Further, in step 2, utilize Second-Order Discrete polynomial-phase transform method to carry out fault diagnosis and comprise the following steps:

(1) utilize the starting current of rejection filter to reconstruct to carry out filtering, filtering power frequency component, obtain filtered signal x, avoid the impact of power frequency component;

(2) Hilbert transform is carried out to filtered signal x, obtain complex signal y, eliminate a symmetrical frequency in current of electric real signal, avoid the distracter in spectrogram;

(3) the Second-Order Discrete polynomial-phase conversion DPT of calculated complex signal y ₂[y, f, τ], obtains spectrogram, and wherein Second-Order Discrete polynomial-phase transformation for mula is:

${\mathrm{DPT}}_2[y,f,\mathrm{\τ}]=\underset{n=\mathrm{\τ}+1}{\overset{N}{\mathrm{\Σ}}}u\left[n\right]y^{*}[n-\mathrm{\τ}]e^{-j2\mathrm{\πnf\Δt}}$

In formula, DPT ₂[y, f, τ] represents that Second-Order Discrete polynomial-phase converts, y represents one-dimensional discrete complex signal, and f represents signal frequency, and unit is Hz, τ represents signal time delay, N represents sampling number, and n represents the n-th number in one-dimensional discrete complex signal, τ < n≤N, * conjugation is represented, e represents natural constant, and Δ t represents sampling interval, and unit is s;

(4) calculate frequency modulation rate k, its computing formula is:

$k=\frac{1}{\mathrm{\&tau;\&Delta;t}}\underset{f}{\arg \max }\left\{\right|{\mathrm{DPT}}_2[y,f,\mathrm{\&tau;}]\left|\right\}$

In formula, k represents frequency modulation rate, and unit is Hz/s, represent the frequency of composing peak in the spectrogram obtained through Second-Order Discrete polynomial-phase transformation calculations, unit is Hz;

(5) the rate of change t of relative revolutional slip start-up time is calculated _s, its estimation formulas is:

$t_s\&ap;\frac{\mathrm{\&Delta;}{t}_r}{\mathrm{\&Delta;s}}\&ap;\mathrm{\&Delta;}{t}_r$

In formula, t _srepresent the rate of change of relative revolutional slip start-up time, unit is s/slip, Δ t _rrepresent the time that electric motor starting experiences to stabilization of speed, unit is s, and Δ s represents the difference of electric motor starting revolutional slip s=1slip and stabilization of speed revolutional slip s ≈ 0slip, and unit is slip;

(6) the rate of change f of the relative revolutional slip of failure-frequency is calculated _bs, then with the theoretical value f of rotor bar breaking fault _bTcontrast, decision condition is relative error e _r≤ 5%, if relative error e _r≤ 5%, then there is rotor bar breaking fault, otherwise there is not rotor bar breaking fault, wherein the rate of change f of the relative revolutional slip of failure-frequency _bscomputing formula be:

f _bs＝|kt _s|

In formula, f _bsrepresent the rate of change of the relative revolutional slip of failure-frequency, unit is Hz/slip;

The theoretical value f of rotor bar breaking fault _bTcomputing formula be:

$f_{\mathrm{bT}}=\left|\frac{d\left((1\&PlusMinus;2s)f_1\right)}{\mathrm{ds}}\right|=2f_1$

In formula, f _bTrepresent the theoretical value of rotor bar breaking fault, unit is Hz/slip, f ₁represent Power supply frequency, unit is Hz;

Relative error e _rcomputing formula be:

$e_r=\left|\frac{f_{\mathrm{bs}}-f_{\mathrm{bT}}}{f_{\mathrm{bT}}}\right|=100\%$

In formula, e _rrepresent relative error, be expressed as a percentage.

Further, in step 4, network-termination device is by internet access remote monitoring center, and specifically network-termination device runs on the engineering machinery Internet of Things remote control administrative system on remote monitoring center application server by internet access.

The present invention adopts technique scheme, has following technique effect:

1, the present invention adopts compressed sensing, before status data is carried out remote transmission by engineering machinery, first compresses it, and then transmits, significantly reduce transmission cost and transmission time.

2, the Second-Order Discrete polynomial-phase transform method that the present invention adopts carries out detection from the rate of change of the relative revolutional slip of failure-frequency and analyzes, not by the impact of revolutional slip fluctuation, effectively prevent the harmful effect of motor load fluctuation to diagnostic result, can Accurate Diagnosis rotor bar breaking fault, the method computation complexity is low simultaneously.

Accompanying drawing explanation

The present invention has 7, accompanying drawing, wherein:

Fig. 1 is the schematic flow sheet of a kind of asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things of the present invention.

Fig. 2 is the structural representation of a kind of asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things of the present invention.

Fig. 3 is the schematic flow sheet of Second-Order Discrete polynomial-phase transform method.

Fig. 4 gathers the startup rotating speed and starting current oscillogram that in model machine 1, asynchronous motor obtains.

Tu5Shi Surveillance center reconstructs the startup rotating speed and starting current oscillogram that obtain.

Fig. 6 is the Second-Order Discrete polynomial-phase conversion spectrogram reconstructing the starting current obtained.

Fig. 7 is the asynchronous motor rotor strip-broken fault diagnosis result figure of model machine 1 in engineering machinery Internet of Things remote control administrative system.

Embodiment

The present invention to be described further by particular specific embodiment below in conjunction with accompanying drawing.As shown in Figure 1 and Figure 2, a kind of asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things, comprises the following steps:

Step one: utilize the startup rotating speed of asynchronous motor and the starting current of the arbitrary phase of stator terminal in current sensor and speed measuring motor difference gathering project machinery, and respectively the data of collection are sent to arm processor, arm processor utilizes compressed sensing to compress the data gathered, and the data after compression are sent to remote monitoring center by GPRS module through wireless network.

Specifically, in step one, utilize compressed sensing to carry out compression to the data gathered and comprise the following steps: first utilize wavelet transform to carry out sparse transformation to the data gathered and obtain sparse data; Then utilize gaussian random matrix to compress sparse data, wherein compressibility selects 0.6.

Specifically, in step one, remote monitoring center comprises the communication server, resolution server, database server and application server.The communication server is responsible for carrying out two-way communication with the GPRS module of engineering machinery by wireless network; The packed data that resolution server is responsible for the communication server receives is reconstructed, and to the data analysis process of reconstruct, draws analysis result; The intermediate data that the engineering machinery status data of reception is in charge of by database server, analyzing and processing obtains and diagnostic result; Performance of work machinery Internet of Things remote control administrative system software is responsible for by application server.

Step 2: remote monitoring center receives the packed data that GPRS module sends, compressed sensing is utilized to be reconstructed the packed data received, fault diagnosis is carried out to the starting current data separate Second-Order Discrete polynomial-phase transform method of reconstruct, draws asynchronous motor rotor strip-broken fault diagnosis result.

Specifically, in step 2, compressed sensing is utilized to be orthogonal matching pursuit algorithm to the method that the packed data received is reconstructed.

Specifically, in step 2, utilize Second-Order Discrete polynomial-phase transform method to carry out the flow process of fault diagnosis as shown in Figure 3, comprise the following steps:

(1) utilize the starting current of rejection filter to reconstruct to carry out filtering, filtering power frequency component, obtain filtered signal x, avoid the impact of power frequency component;

(2) Hilbert transform is carried out to filtered signal x, obtain complex signal y, eliminate a symmetrical frequency in current of electric real signal, avoid the distracter in spectrogram;

(3) the Second-Order Discrete polynomial-phase conversion DPT of calculated complex signal y ₂[y, f, τ], obtains spectrogram, and wherein Second-Order Discrete polynomial-phase transformation for mula is:

${\mathrm{DPT}}_2[y,f,\mathrm{\&tau;}]=\underset{n=\mathrm{\&tau;}+1}{\overset{N}{\mathrm{\&Sigma;}}}u\left[n\right]y^{*}[n-\mathrm{\&tau;}]e^{-j2\mathrm{\&pi;nf\&Delta;t}}$

In formula, DPT ₂[y, f, τ] represents that Second-Order Discrete polynomial-phase converts, y represents one-dimensional discrete complex signal, and f represents signal frequency, and unit is Hz, τ represents signal time delay (selecting τ=0.09N during calculating), N represents sampling number, and n represents the n-th number in one-dimensional discrete complex signal, τ < n≤N, * conjugation is represented, e represents natural constant, and Δ t represents sampling interval, and unit is s;

(4) calculate frequency modulation rate k, its computing formula is:

$k=\frac{1}{\mathrm{\&tau;\&Delta;t}}\underset{f}{\arg \max }\left\{\right|{\mathrm{DPT}}_2[y,f,\mathrm{\&tau;}]\left|\right\}$

In formula, k represents frequency modulation rate, and unit is Hz/s, represent the frequency of composing peak in the spectrogram obtained through Second-Order Discrete polynomial-phase transformation calculations, unit is Hz;

(5) the rate of change t of relative revolutional slip start-up time is calculated _s, its estimation formulas is:

$t_s\&ap;\frac{\mathrm{\&Delta;}{t}_r}{\mathrm{\&Delta;s}}\&ap;\mathrm{\&Delta;}{t}_r$

In formula, t _srepresent the rate of change of relative revolutional slip start-up time, unit is s/slip, Δ t _rrepresent the time that electric motor starting experiences to stabilization of speed, unit is s, and Δ s represents the difference of electric motor starting revolutional slip s=1slip and stabilization of speed revolutional slip s ≈ 0slip, and unit is slip;

(6) the rate of change f of the relative revolutional slip of failure-frequency is calculated _bs, then with the theoretical value f of rotor bar breaking fault _bTcontrast, decision condition is relative error e _r≤ 5%, if relative error e _r≤ 5%, then there is rotor bar breaking fault, otherwise there is not rotor bar breaking fault, wherein the rate of change f of the relative revolutional slip of failure-frequency _bscomputing formula be:

f _bs＝|kt _s|

In formula, f _bsrepresent the rate of change of the relative revolutional slip of failure-frequency, unit is Hz/slip;

The theoretical value f of rotor bar breaking fault _bTcomputing formula be:

$f_{\mathrm{bT}}=\left|\frac{d\left((1\&PlusMinus;2s)f_1\right)}{\mathrm{ds}}\right|=2f_1$

In formula, f _bTrepresent the theoretical value of rotor bar breaking fault, unit is Hz/slip, f ₁represent Power supply frequency, unit is Hz;

Relative error e _rcomputing formula be:

$e_r=\left|\frac{f_{\mathrm{bs}}-f_{\mathrm{bT}}}{f_{\mathrm{bT}}}\right|=100\%$

In formula, e _rrepresent relative error, be expressed as a percentage.

Step 3: diagnostic result is sent to the GPRS module of engineering machinery by remote monitoring center by wireless network, the data of reception are sent to arm processor by GPRS module, arm processor controls LCD display display diagnostic result, if there is fault, then controls audible-visual annunciator simultaneously and reports to the police.

Step 4: network-termination device, by internet access remote monitoring center, checks asynchronous motor rotor strip-broken malfunction in engineering machinery.

Specifically, in step 4, network-termination device is by internet access remote monitoring center, and specifically network-termination device runs on the engineering machinery Internet of Things remote control administrative system on remote monitoring center application server by internet access.

During concrete enforcement, as shown in Figure 2, the asynchronous motor number of the present invention's monitoring and diagnosis is depending on concrete engineering machinery number.

Specific embodiment: the present invention is for certain company domestic engineering machinery model machine (being labeled as model machine 1), and the asynchronous motor in model machine 1 exists rotor bar breaking fault.Basic parameter arranges as follows: asynchronous motor line frequency is f ₁=50Hz, sample frequency is 10kHz, and sample duration is 2s, then sampled point N=20000, sampling interval Δ t=0.0001s, signal time delay τ=0.09N=1800, the theoretical value f of rotor bar breaking fault _bT=2f ₁=100Hz/slip.

Gather startup rotating speed and the starting current of asynchronous motor in model machine 1, waveform as shown in Figure 4; Surveillance center is reconstructed the startup rotating speed of compression in the model machine 1 received and starting current, and obtain the startup rotating speed after reconstructing and starting current, waveform as shown in Figure 5; Utilize Second-Order Discrete polynomial-phase transform method to carry out fault diagnosis, obtain the Second-Order Discrete polynomial-phase conversion spectrogram of the starting current after reconstructing as shown in Figure 6.

Frequency modulation rate according to component negative in Fig. 6 and frequency modulation rate computing formula calculating chart 6: the rate of change of relative revolutional slip start-up time is calculated according to Fig. 5: calculate the rate of change of the relative revolutional slip of failure-frequency: f _bs=|-97.22 × 1.027|=99.84Hz/slip; Calculate relative error: obvious e _r=0.6%≤5%, illustrate that asynchronous motor exists rotor broken bar.This process may be used for the frequency modulation rate of positive component in Fig. 6 equally, and computation process is identical, obtains the relative error e that positive component is corresponding _r=2.70%, there is rotor broken bar in same explanation asynchronous motor.So the present invention can be used for the asynchronous motor rotor strip-broken fault of engineering machinery Internet of Things by Accurate Diagnosis.

Network-termination device runs on the engineering machinery Internet of Things remote control administrative system on remote monitoring center application server by internet access, check the asynchronous motor rotor strip-broken fault diagnosis result of model machine 1, and display result as shown in Figure 7.

Claims (6)

1., for an asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things, it is characterized in that: comprise the following steps:

Step one: utilize the startup rotating speed of asynchronous motor and the starting current of the arbitrary phase of stator terminal in current sensor and speed measuring motor difference gathering project machinery, and respectively the data of collection are sent to arm processor, arm processor utilizes compressed sensing to compress the data gathered, and the data after compression are sent to remote monitoring center by GPRS module through wireless network;

Step 2: remote monitoring center receives the packed data that GPRS module sends, compressed sensing is utilized to be reconstructed the packed data received, fault diagnosis is carried out to the starting current data separate Second-Order Discrete polynomial-phase transform method of reconstruct, draws asynchronous motor rotor strip-broken fault diagnosis result;

Step 3: diagnostic result is sent to the GPRS module of engineering machinery by remote monitoring center by wireless network, the data of reception are sent to arm processor by GPRS module, arm processor controls LCD display display diagnostic result, if there is fault, then controls audible-visual annunciator simultaneously and reports to the police;

Step 4: network-termination device, by internet access remote monitoring center, checks asynchronous motor rotor strip-broken malfunction in engineering machinery.

2. a kind of asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things according to claim 1, it is characterized in that: in described step one, the described compressed sensing that utilizes is carried out compression comprise the following steps the data gathered: first utilize wavelet transform to carry out sparse transformation to the data gathered and obtain sparse data; Then gaussian random matrix is utilized to compress sparse data.

3. a kind of asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things according to claim 1, it is characterized in that: in described step one, described remote monitoring center comprises the communication server, resolution server, database server and application server; The described communication server is responsible for carrying out two-way communication with the GPRS module of engineering machinery by wireless network; The packed data that described resolution server is responsible for the communication server receives is reconstructed, and to the data analysis process of reconstruct, draws analysis result; The intermediate data that the engineering machinery status data of reception is in charge of by described database server, analyzing and processing obtains and diagnostic result; Performance of work machinery Internet of Things remote control administrative system software is responsible for by described application server.

4. a kind of asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things according to claim 1, it is characterized in that: in described step 2, the described compressed sensing that utilizes is orthogonal matching pursuit algorithm to the method that the packed data received is reconstructed.

5. a kind of asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things according to claim 1, it is characterized in that: in described step 2, describedly utilize Second-Order Discrete polynomial-phase transform method to carry out fault diagnosis to comprise the following steps:

(1) utilize the starting current of rejection filter to reconstruct to carry out filtering, filtering power frequency component, obtain filtered signal x, avoid the impact of power frequency component;

(2) Hilbert transform is carried out to filtered signal x, obtain complex signal y, eliminate a symmetrical frequency in current of electric real signal, avoid the distracter in spectrogram;

(3) the Second-Order Discrete polynomial-phase conversion DPT of calculated complex signal y ₂[y, f, τ], obtains spectrogram, and wherein Second-Order Discrete polynomial-phase transformation for mula is:

${\mathrm{DPT}}_2[y,f,\mathrm{\&tau;}]=\underset{n=\mathrm{\&tau;}+1}{\overset{N}{\mathrm{\&Sigma;}}}y\left[n\right]y^{*}[n-\mathrm{\&tau;}]e^{j2\mathrm{\&pi;nf\&Delta;t}}$

In formula, DPT ₂[y, f, τ] represents that Second-Order Discrete polynomial-phase converts, y represents one-dimensional discrete complex signal, and f represents signal frequency, and unit is Hz, τ represents signal time delay, N represents sampling number, and n represents the n-th number in one-dimensional discrete complex signal, τ < n≤N, * conjugation is represented, e represents natural constant, and Δ t represents sampling interval, and unit is s;

(4) calculate frequency modulation rate k, its computing formula is:

$k=\frac{1}{\mathrm{\&tau;\&Delta;t}}\underset{f}{\arg \max }\left\{\right|{\mathrm{DPT}}_2[y,f,\mathrm{\&tau;}]\left|\right\}$

In formula, k represents frequency modulation rate, and unit is Hz/s, represent the frequency of composing peak in the spectrogram obtained through Second-Order Discrete polynomial-phase transformation calculations, unit is Hz;

(5) the rate of change t of relative revolutional slip start-up time is calculated _s, its estimation formulas is:

$t_s\&ap;\frac{{\mathrm{\&Delta;t}}_r}{\mathrm{\&Delta;s}}\&ap;{\mathrm{\&Delta;t}}_r$

In formula, t _srepresent the rate of change of relative revolutional slip start-up time, unit is s/slip, Δ t _rrepresent the time that electric motor starting experiences to stabilization of speed, unit is s, and Δ s represents the difference of electric motor starting revolutional slip s=1slip and stabilization of speed revolutional slip s ≈ 0slip, and unit is slip;

(6) the rate of change f of the relative revolutional slip of failure-frequency is calculated _bs, then with the theoretical value f of rotor bar breaking fault _bTcontrast, decision condition is relative error e _r≤ 5%, if relative error e _r≤ 5%, then there is rotor bar breaking fault, otherwise there is not rotor bar breaking fault, wherein the rate of change f of the relative revolutional slip of failure-frequency _bscomputing formula be:

f _bs＝|k _ts|

In formula, f _bsrepresent the rate of change of the relative revolutional slip of failure-frequency, unit is Hz/slip;

The theoretical value f of rotor bar breaking fault _bTcomputing formula be:

$f_{\mathrm{bT}}=\left|\frac{d\left((1\&PlusMinus;2s)f_1\right)}{\mathrm{ds}}\right|=2f_1$

In formula, f _bTrepresent the theoretical value of rotor bar breaking fault, unit is Hz/slip, f ₁represent Power supply frequency, unit is Hz;

Relative error e _rcomputing formula be:

$e_r=\left|\frac{f_{\mathrm{bs}}-f_{\mathrm{bT}}}{f_{\mathrm{bT}}}\right|\&times;100\%$

In formula, e _rrepresent relative error, be expressed as a percentage.

6. a kind of asynchronous motor rotor strip-broken method for diagnosing faults for engineering machinery Internet of Things according to claim 1, it is characterized in that: in described step 4, described network-termination device is by internet access remote monitoring center, and specifically network-termination device runs on the engineering machinery Internet of Things remote control administrative system on remote monitoring center application server by internet access.