CN102121968A - Generalized protection measurement and control device of asynchronous motor - Google Patents

Abstract

The invention introduces a generalized protection measurement and control device aiming at a 380V-10kV asynchronous motor, providing an integral solution integrating electromotor state monitoring, electromotor fault protection and electromotor measurement and control from the intelligent angle of the equipment. The invention provides a method for identifying the operation state of the electromotor by a conjugate character signal filter. On the basis of the infinite impulse response (IIR) filter of a sequence, the current signal of the electromotor is measured in real time, thus the variation situation of the conjugate character signal is monitored in the electromotor starting process. According to the comparison of the output conjugate character signals, faults such as broken electromotor rotor bars, rotor eccentricity and the like, can be identified, and the electromotor state is monitored in an online mode, thereby providing a preventative protection function for the electromotor. The criterion is simple to calculate and is easy to realize and has the advantage of high precision. The digital protection measurement and control function of the electromotor which is widely used at present serves as the basis, the state monitoring function can be integrated without additional external signals, and comprehensive protection is further provided for the electromotor.

Description

A kind of broad sense protection measure and control device of asynchronous motor

Technical field

The present invention is the broad sense protection measure and control device of asynchronous motor.Asynchronous motor is widely used in industrial enterprise, therefore the invention belongs to industrial circle.

Background technology

Asynchronous motor is important electric load of industrial enterprise and power-equipment, and status in process of production is very important.The typical most common failure of asynchronous motor can be divided three classes, and is as shown in table 1:

Table 1 asynchronous motor most common failure

At present; China overwhelming majority industrial enterprise all has been equipped with intelligentized protection measure and control device to asynchronous motor; functions such as stall, overcurrent, overheated, superpotential, low-voltage, imbalance are provided, have played perfect defencive function for electric fault and external fault.For mechanical fault, vast researcher also provides multiple solution, such as vibration monitoring, torque monitoring, the monitoring of axle leakage flux, fluctuation of speed monitoring, stator current monitoring etc.

The stator current monitoring method is used wider, and its theoretical foundation is as follows: when bar appears breaking in motor, can occur characteristic frequency in its stator current and be (1 ± 2s) f _eComponent; When motor occurs when eccentric, can occur in its stator current characteristic frequency for) component.F wherein _eFor system's rated frequency, s are that motor slip ratio, p are the motor number of pole-pairs.Motor is in starting process, and the variation tendency of revolutional slip s is 110, and the character pair frequency component can be done change along with the variation of revolutional slip.Based on this theory, researcher has been studied multiple algorithm, as auto adapted filtering method, Parker transform vector method, Hilbert transform method and instantaneous power method.The calculated amount of these algorithms is bigger, is subject to the intrinsic noise influence, and resolution is lower.

The asynchronous motor range of application is vast, and One's name is legion is discerned its mechanical fault with a kind of cost-effective method and had important practical significance and using value.

Summary of the invention

The present invention proposes a kind of broad sense protection measure and control device of motor; it is based on existing protection measure and control device; do not need to increase new external signal, the mechanical fault of the algorithm identified motor by the advanced person, thus provide comprehensive protection and state on_line monitoring for motor.

The present invention is by gathering in real time stator current in motor starting procedure, at wherein arbitrary be the extraction that the conjugate character signal is carried out on the basis with the iir filter group, discern concrete mechanical fault according to the situation of change of conjugate character signal.

Concrete steps and criterion that the present invention extracts the conjugate character signal are as follows:

1. design iir filter, the transport function that each iir filter adopts is as follows:

Low pass IIR: $H\left(s\right)=\frac{1}{1+s/{\mathrm{\ω}}_L+{(s/{\mathrm{\ω}}_L)}^2}$

High pass IIR: $H\left(s\right)=\frac{{(s/{\mathrm{\ω}}_H)}^2}{1+s/{\mathrm{\ω}}_H+{(s/{\mathrm{\ω}}_H)}^2}$

The logical IIR of band: $H\left(s\right)=\frac{s/{\mathrm{\ω}}_P}{1+6\mathrm{\πs}/{\mathrm{\ω}}_P+{(s/{\mathrm{\ω}}_P)}^2}$

Band resistance IIR: $H\left(s\right)=\frac{1+{(s/{\mathrm{\ω}}_B)}^2}{1+4\mathrm{\πs}/{\mathrm{\ω}}_B+{(s/{\mathrm{\ω}}_B)}^2}$

2. the frequency values of conjugate character signal will meet the following conditions:

The ■ frequency values is in 0～50Hz scope;

The ■ frequency values is in the scope of motor eccentric nature frequency;

3. gather stator current signal in real time, (hinder IIR and f by 5Hz high pass IIR, 52Hz low pass IIR, 50Hz band by the 1st group of iir filter group ₁Band is logical

Formation) obtains f ₁Band signal; (hinder IIR and f by the 2nd group of iir filter group by 5Hz high pass IIR, 52Hz low pass IIR, 50Hz band ₂The bandpass filter formation) obtains f ₂Band signal; Wherein.Obtain the 50Hz band signal by the 3rd group of iir filter group (constituting) by 5Hz high pass IIR, 52Hz low pass IIR and 50Hz bandpass filter.

4. if there is rotor broken bar in motor, in starting process, revolutional slip is from 1 when 0.5 changes, and the characteristic signal frequency can change to 0Hz from 50Hz; Revolutional slip is from 0.5 when 0 changes, and the characteristic signal frequency can change to 0Hz from 50Hz.Ought enter f like this ₁During frequency band, f ₁The band signal output valve is bigger, and f ₂Output valve is very little; When entering f ₂During frequency band, f ₁The band signal output valve is less, and f ₂Output valve is very big.We can judge whether to take place rotor broken bar according to this situation of change and in conjunction with the amplitude of characteristic signal.Described in concrete criterion such as the claim 1,2.

5. if there is rotor eccentricity in motor, in starting process, along with reducing of revolutional slip, the characteristic signal frequency can change (the supposition number of pole-pairs is 2) to 25Hz from 50Hz.Ought enter f like this ₂During frequency band, f ₂The band signal output valve is bigger, and f ₁Output valve is very little; When entering f ₁During frequency band, f ₂The band signal output valve is less, and f ₁Output valve is very big.We can judge whether to take place rotor broken bar according to this situation of change and in conjunction with the amplitude of characteristic signal.Described in concrete criterion such as the claim 3,4.

Description of drawings

Fig. 1 is the conjugate character input synoptic diagram based on IIR;

Fig. 2 constitutes for device hardware;

Embodiment

Invention has been introduced based on the conjugated signal extracting method of IIR and rotor broken bar and eccentric criterion.In existing motor protection measure and control device, increase the related software function, can finish commercialization, release the motor broad sense protection measure and control device of high performance-price ratio.

Claims (5)

1. the broad sense motor protection measure and control device of an integration electric machine status monitoring, emergency protection, measurement and control function.(IIR) extracts characteristic signal from electric parameters based on IIR filter, and mechanical fault is discerned.

2. one kind is passed through on-line monitoring motor current signal, utilizes the method for conjugate character signal identification motor rotor strip-broken defective.This method comprises following content:

1) selects arbitrary phase current to export, the characteristic signal bank of filters is set as feature

Levy signal.(centre frequency is made as f respectively to adopt cascade connection type iir filter group (being made of 5Hz high pass IIR and 52Hz low pass IIR), some resistance IIR (centre frequency is 50Hz) and the logical IIR of band ₁And f ₂), extracting the signal record that obtains is g _F1(x) and g _F2(x).Setting is based on same cascade connection type iir filter group and the logical IIR of 50Hz band, and extracting the signal record that obtains is g _F50(x);

2) utilize motor start-stop switching signal and stator current identification motor to begin starting;

3) in motor starting procedure, continuous monitoring g _F1(x), g _F2(x) and g ₅₀(x) output of signal, according to the time series of the time interval recording of output signals amplitude of IT (as 100ms), as follows:

A _f1(k ₁)，A _f1(k ₂)，A _f1(k ₃)，……，A _f1(k _n)

A _f2(k ₁)，A _f2(k ₂)，A _f2(k ₃)，……，A _f2(k _n)

A ₅₀(k ₁)，A ₅₀(k ₂)，A ₅₀(k ₃)，……，A ₅₀(k _n)

Do following condition judgment for the time series of signal amplitude:

■ condition 1:Max (A _F1(k _i), A _F2(k _i))＞λ A ₅₀(k _i) (λ II0.01)

■ condition 2:A _F2(k _i)＞i＜a

＞ i＞b b＞a

＞ i＞c c＞b

Promptly in motor starting procedure, variation has relatively taken place in the output size of two conjugate character signals.At first high-frequency characteristic output is greater than low frequency, and characteristics of low-frequency output subsequently is greater than high frequency, and high-frequency characteristic output is again greater than low frequency then.

If satisfy above-mentioned two conditions, judge that then there is rotor broken bar in motor, its disconnected strip defect degree with

Be directly proportional.

3. as in the claim 2, in motor starting procedure, according to 3 time series A of time interval acquisition of IT (as 100ms) _F1(k _i), A _F2(k _i) and A ₅₀(k _i), do following calculating:

$\mathrm{\λ}\left(k_i\right)=\frac{\left|\mathrm{difA}\left(k_i\right)\right|}{A_{50}\left(k_i\right)}$

As λ (k _i) greater than setting value (as 0.01) and difA (k _i) occur from negative value to rotor broken bar occurring on the occasion of then judging to the variation tendency of negative value again.

4. described in claim 2, when in motor starting procedure, at first the high frequency of two conjugate character signals is exported greater than characteristics of low-frequency, and low frequency is exported greater than high-frequency characteristic subsequently, judges that then rotor eccentricity appears in motor.

5. described in claim 3, as λ (k _i) greater than setting value (as 0.01) and difA (k _i) occur from negative value on the occasion of variation then judge and rotor eccentricity occurs.

Images