JPS61151477A - Apparatus for diagnosis of electromotor - Google Patents

Abstract

PURPOSE:To enable accurate diagnosis, by displaying the phase non-equilibrium ratio and amplitude non-equilibrium ratio of the stator coil of a three-phase electromotor and the ratio of the power spectrum intensity of the primary current of the electromotor in the beat frequency and power source frequency of a rotor coil. CONSTITUTION:The primary radio waves of the first and third phases of a three-phase induction electromotor 1 are detected by current transformers 2, 3 and the number of rotations of said electromotor 1 are detected by a pulse generator 6. Signals of input terminals 4, 5, 7 are converted by A/D converters 8, 9, 10. A central processing unit 12 collects respective wave form data outputted from the A/D converters 8, 9, 10 to store the same in memory 13 to perform various operations and calculates data for performing the diagnosis (detection of layer short, disconnection and slackening) of a stator coil and the diagnosis (detection of layer short, disconnection and slackness) of a rotor coil and displays the same on display devices.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is capable of determining whether there is an interlayer short circuit (layer 7 short circuit), disconnection, or loosening of a stator coil of a three-phase induction motor. The present invention relates to a motor diagnostic device that can diagnose abnormalities such as disconnection of rotor bars.

Conventional technology 3-phase rust conduction! Layer shorts and loose stator coils caused by dielectric breakdown in the 1JtJSl stator coil are directly linked to the lifespan of the 3-phase induction motor, so it is necessary to regularly diagnose the presence or absence of such problems and strive for early detection. .

Diagnosis of layer 7 short circuits, looseness, etc. of the stator coil of a 3-phase induction motor can be made by observing the current waveform of each phase during rotation of the 3-phase induction motor using an onroscope, and recording it using a Visigraph, etc. Based on the results, the inspector determines the presence or absence of layer 7 short circuits and loosening (degree of interlayer dielectric breakdown). Specifically, the presence or absence of layer short-circuiting, loosening, etc. is determined by utilizing the fact that when a layer 7 short circuit, loosening, etc. occurs in the stator coil, the current waveforms of each phase become unbalanced.

On the other hand, if the rotor coil or loaf bar of a three-phase induction motor breaks, or a layer 7 short circuit occurs, smooth rotation will not be obtained and a serious failure will occur, so it is necessary to detect rotor abnormalities at an early stage.

For this reason, the current waveform of one phase of the rotating rotor coil is observed using an onroscope, and based on the observation results, an inspector determines whether the rotor is normal or abnormal. That is,
When an abnormality occurs in the rotor, the detected waveform differs from the normal one, which is used to determine whether the motor is normal or abnormal.

Problems to be Solved by the Invention In the stator coil diagnostic method described above, it is difficult to quantify the criteria for determining the presence or absence of layer shorts and loosening, and the determination must rely on the experience and intuition of the inspector. The problem was that there was considerable variation among individual patients, making it difficult to make accurate diagnoses.

In addition, in the case of rotor diagnosis, it is difficult to quantify the criteria for determining whether it is normal or abnormal, and the judgment is based on the experience and intuition of the inspector, which has the same problem as the stator coil diagnosis that it lacks accuracy.

This invention was made in view of the above-mentioned problems, such as layer short-circuiting of stator coils.

It is an object of the present invention to provide an electric tJ31 diagnostic device that can quantitatively determine disconnection, looseness, etc. and perform accurate diagnosis, and can quantitatively determine whether the rotor is normal or abnormal and perform accurate diagnosis. purpose.

Means for Solving the Problems As shown in FIG.
Current detector (current transformer) that detects the primary current of phase motor l
2.3, and rotation detection N for detecting the rotation of the three-phase electric motor.
(pulse generator) 6, and an A/D converter 8 that samples the output of the current detector 2.3 and converts it A/D.
．． 9, and a frequency variable sampling pulse generator Wit that provides a sampling pulse to the A/D converter 8.9.
and a frequency setting means 12A for selectively setting the sampling pulse frequency of the sampling pulse generator 11 to a waveform analysis frequency and a frequency analysis frequency lower than the waveform analysis frequency; A first data collecting means 12B collects the waveform data outputted from the A/D converter 8.9 by the number of cycles required for waveform analysis and stores it in the memory 13; a phase difference calculation means 12c for calculating the phase difference between the ttS flows of each phase from the waveform data stored in the memory 13; an amplitude calculation means 12D for calculating the amplitude of each phase current from the waveform data stored in the memory 13; A phase unbalance factor calculation means 12E calculates a phase imbalance rate from the difference between the maximum and minimum phase difference of each phase current calculated by the phase difference calculation means 12C, and the amplitude of each phase current calculated by the amplitude calculation means 12D. An amplitude unbalance rate calculation means 12F that calculates the amplitude unbalance rate from the difference between the maximum and minimum of , a rotation speed calculation means 12G that calculates the rotation speed of the three-phase motor l from the output of the rotation detector 6, and a second data collection means 12 that collects waveform data sampled at the analysis frequency and output from the A/D converter 8 for the number of cycles necessary for frequency analysis and stores it in the memory;
H, a frequency analysis means 121 that performs frequency analysis based on the waveform data stored in the memo 3 by the second data collection means 12H, and the three phases determined by the rotation speed calculation means 12G. A beat frequency calculation means 12J that calculates the beat frequency from the rotational speed of the electric motor 1, and a power spectrum ratio calculation means that calculates the ratio of the spectral intensity of the beat frequency to the spectral intensity of the power supply frequency based on the analysis result by the variable frequency type 9121. 12, and a display 14.15 for displaying the calculation results of the phase imbalance rate calculation means 12E, the amplitude imbalance rate calculation means 12F, and the power spectrum ratio calculation means 12, The stake coil is diagnosed as normal or abnormal based on the phase unbalance rate and amplitude unbalance rate displayed on the displays 14 and 15, and the rotor coil, etc. is diagnosed as normal or abnormal based on the ratio of the spectral intensities.

As described above, the motor diagnostic device of the present invention determines and displays the phase unbalance rate and amplitude unbalance rate that change depending on whether the stator coil of the three-phase motor is normal or abnormal, and also determines whether the rotor coil is normal or not.

By determining and displaying the ratio of the spectral intensity of the motor primary current at the beat frequency and power supply frequency that change due to abnormalities, it is possible to quantitatively compare the phase unbalance rate, amplitude unbalance rate, and spectral intensity ratio Diagnosis of stator coils, rotor coils, etc. can be performed at the same time with this device alone (accurately, depending on individual differences).

In addition, the A/D converter 8 is used for frequency analysis for rotor coil diagnosis rather than for waveform analysis for stator coil diagnosis.
In other words, because the sampling frequency is lower during low coil diagnosis, it is difficult to collect data even during frequency analysis, which requires collecting data for a fairly large number of cycles, approximately several tens of cycles. The total number of data to be processed does not increase significantly, and the memory capacity can be reduced.

Embodiment An embodiment of the present invention will be described with reference to FIGS. 2 to 9. As shown in Fig. 2, this electric motor diagnostic device has the following features:
1 of the 1st phase and 3rd phase of the 3-phase induction motor 1 to be diagnosed
The next current is detected by a current transformer (current detector) 2.3 and applied to the first input terminal 4 and the second input terminal 5, and the rotation speed of the three-phase induction motor 1 is detected by a pulse generator (rotation detector) 6. in addition to the third input terminal 7, each input terminal 4
The signal added to ゜5.7 is sent to A/D converter 8, 9゜10
This A/D is configured to perform A/D conversion respectively.
The A/D conversion process of the converter 8.9.10 is performed according to the sampling pulse from the frequency variable sampling pulse generator 11, and the output frequency of the sampling pulse generator 11 is the sampling pulse frequency from the central processing unit 12. .

It is determined by a setting signal, and during stator coil diagnosis (waveform analysis), the frequency is set to, for example, 256 times the power supply frequency, and during rotor coil diagnosis (frequency analysis), the frequency is set to, for example, 16 times the power supply frequency. It turns out.

The central processing unit 12 collects waveform data output from the A/D converters 8, 9, and 10, and stores them in the memory 13.
By performing various calculations based on the waveform data stored in the memory 13, diagnosis of the stator coil of a three-phase induction motor (layer short circuit) is performed.

Obtain data for diagnosing the rotor coil (detecting layer shorts and disconnections) and diagnosing the rotor coil.
This data is displayed on display devices 14 and 15.

Note that the memory 13 not only stores the collected waveform data but also stores programs for diagnosing the stator coils and rotor coils.

Hereinafter, the operation of this motor diagnostic device will be explained in detail with reference to FIGS. 3 to 9.

As shown in FIG. 3, the central processing unit 12 first performs a diagnostic operation for the stator coil (step LJ+), then performs a diagnostic operation for the rotor coil (step U2), and finally performs a diagnostic operation for the stator coil and rotor coil. Display (step U3).

In diagnosing the stator coil, the central processing unit 12:
As shown in FIG. 4, first, a sampling pulse frequency setting signal is given to the sampling pulse generator 11 to set the sampling frequency for stator coil diagnosis (for example, a frequency 256 times the power supply frequency) (step 1).
, As a result, the sampling pulse generator 11 generates a sampling pulse with a frequency 256 times the power supply frequency,
A/D change tease, 9 is based on this sampling pulse in Figure 5 (A1. (B), (C) not shown 3
Among the primary currents of the first phase, second phase, and third phase of the phase induction motor 1, the primary currents of the first phase and the third phase are converted into waveform data D1. The D3 column will be output.

Next, the central processing unit 12 receives the first phase and third phase waveform data D, .
Collect D3 and store it in memory 13, <Step 7 v2),
Waveform data D1. stored in the memory 13. Based on D3, the following equation is calculated for each waveform data DI and D3 at the same sample timing to obtain waveform data D2 corresponding to the primary current of the second phase of the three-phase induction motor l and store it in the memory 13. (Step ■3).

D2 = (D+ +D3)...f
l+The calculation of the above-mentioned formula il1 is established because the zero-sequence current is usually extremely small, and because there is a relationship of D, +02 + [)3 I=IQ. Note that the waveform data D2 of the second phase primary current is calculated by another one without performing the calculation of Equation 111.
It is also possible to provide a set of current transformers and an A/D converter.

Next, the central processing unit 12 stores the waveform data D1 . of each phase stored in the memory 13 . D2. 1st, 2nd, etc. from D3. Third
Zero-cross phases 11, 12 . when the current value of each phase changes from debt to positive value. II.

(Fig. 5) are obtained, and the waveform data Dl, D2 . Amplitude (peak value) All, AI from D3
2. Step 4) of selecting each AI3, and then calculating the phase difference PL2 of each phase from the zero cross phase 11°12.13 of each phase. P23. P31 is determined by the following formula (step v5).

Next, the first. Second. Phase difference of each third phase P12°P2
3. What is the largest P31? +^X and the smallest p
Select m I N, and further select one width AI1. AI2
Similarly, for ゜AI, select the maximum value A MAX and the minimum value AIMIN (step 6). Next, calculate the phase imbalance rate UBP by performing the calculation using the following formula.
and the amplitude unbalance rate UBA is determined (step v7).

ArMAX-AIM I N UBA=□...(4) AI, +AI2 +AI3 Next, in the diagnosis of the rotor coil, the central processing unit 1
2, as shown in FIG. 6, first supplies a sampling pulse frequency setting signal to the sampling pulse generator 11 to set the sampling frequency for rotor coil diagnosis (for example, 16 times the power supply frequency) (step W1
), the sampling pulse generator 11 generates a sampling pulse with a frequency 16 times the power supply frequency, and A
The /D converter 8.10 A/D converts the primary current of the first phase of the three-phase motor 1 based on this sampling pulse and outputs a sequence of waveform data D1'. The output will be A/D converted and data D4 will be output.

Then, the central processing unit 212 calculates +jΔ/' which is the number necessary for diagnosing the rotor coil (several tens of cycles of the power supply frequency).
Waveform data D1' and data D from D converter 8.10
4 is collected and stored in the memory 13 (step W2).

Next, the power spectrum of the primary current of the first phase is obtained by reading out the waveform data D1' from the memory 13 and performing frequency analysis (Fourier transform is performed with several tens of cycles of the power supply frequency as one cycle) (Step W3 ).

Next, data D4 is read from the memory 13, and the data D4 is read from the memory 13.
Count the number of sampling data within the period from the timing when D4 becomes "1" until the timing when data D4 becomes "1" next, and calculate the number of sampling data, the sampling frequency, and one revolution of the three-phase induction motor 1. 3 depending on the number of pulses output from the pulse generator 6
The rotation speed N (rpm) of the phase induction motor l is determined, and the slip S is calculated by calculating the following equation from this rotation speed N and the synchronous rotation speed NS (rpm) (step W,
).

5-N S@□ ...(5)s Next, the beat frequency fs is determined by calculating the following formula based on the slip S and the power supply frequency fo (Step W
too).

f 5=roX (12xS) H+ 16
Next, the power spectrum value P (fs) at the beat frequency rs and the power spectrum value P (fo) at the power supply frequency fo are selected from the Fourier transform results stored in the memory 13, and the power spectrum values P (fs), P
(fo) is calculated by the following formula (step W
6).

P((0) Next, in displaying the diagnosis results, the central processing unit 12 first digitally displays the data of the phase unbalance rate UBP and the amplitude unbalance rate UBA obtained in the stator coil diagnosis process on the display 14. At the same time, the data is plotted on the graph ink display 15 with the phase imbalance rate UBP on the horizontal axis and the amplitude imbalance rate UBA on the vertical axis.
Beating frequency f determined in the rotor coil diagnosis process
s and the ratio of the spectral intensity are digitally displayed on the display 14, and the power spectrum is graphically displayed on the display 15 with the power frequency component set as 100%.

The relationship between the above-mentioned phase unbalance rate UBP and amplitude unbalance rate UBA and layer short disconnection and loosening of the stator coil, and the power spectrum ([P(fs)) and power supply frequency P( fo
) and the relationship between the ratio with the power spectrum value P(ro) and the layer short and disconnection of the rotor coil will be explained.

First, the former will be explained. All of the test motors were three-phase induction motors with a rated output of 3 KW, and some had one pole of the stator coil short-circuited between the eyebrows or the windings were loose. For such a large number of three-phase induction motors, the phase unbalance rate UBP and amplitude unbalance υ
I asked for BA.

Figure 7 plots the detection results for each tested motor, with the horizontal axis representing the phase unbalance rate UBP and the vertical axis representing the amplitude unbalance rate UBA. The white squares indicate those with short circuits, and those with loose corners.

In addition, the Not motor is used as a representative of the normal motor group.
Further, the NO2 motor is selected as a representative of the motor group with interlayer short circuit, and the phase difference P12 for each motor is determined. P
23. P31. Amplitude AI, , AI2°Al1. Table 1 shows the phase unbalance rate UBP and the amplitude unbalance rate UBA.

(Leaving space below) Table 1 As is clear from Figure 7, the region where both the phase unbalance rate UBP and the amplitude unbalance rate tJBA are small, specifically, the area where UBP ≦ 20% and UBA ≦ 20%. , can be regarded as a normal region where no glabellar short circuit or loosening occurs in the three-phase induction motor, and the region where 20% < UBP < 40% or 20% < UBA < 40% occurs in the stator coil. An abnormal area where the glabella short circuit occurs in the stator coil or where a glabella short circuit occurs in a minute area, and an area where UBP ≥ 40% or UBA ≥ 40% or more can be regarded as an abnormal area where a glabella short circuit occurs in the stator coil. .

Therefore, if we detect the phase unbalance rate UBP and amplitude unbalance rate UBA for the three-phase induction motor actually used, and see where this three-phase induction motor is located in Fig. 7, we can find that the stator coil It is possible to quantitatively determine whether the eyebrows are short or loose. Further, as the plot position moves from left to right or from bottom to top in FIG. 7, that is, as the phase unbalance rate UBP or amplitude unbalance rate UBA increases, it can be determined that the abnormality of the stator coil is progressing. Monitoring of changes over time can also be performed.

As mentioned above, the phase unbalance rate UBP and the amplitude unbalance rate UBP can be quantified, so experiments were conducted.

The normal region shown in Fig. 7 obtained from actual results is determined in advance as a judgment standard, and the phase unbalance rate UBP and amplitude unbalance rate UBA of the three-phase induction motor to be judged are determined.
Plot the actual measurement results or 3 during normal operation.
By quantifying the phase unbalance rate UBP and the amplitude unbalance rate UBA of the phase induction motor and directly comparing them with the actually measured values, it is possible to accurately determine whether the three-phase induction motor is normal or abnormal.

Next, a description will be given of the relationship between the ratio of the power spectrum value P(Is) at the beat frequency fS and the power spectrum value P(fo) at the power supply frequency fo, and the layer short-circuit and disconnection of the rotor coil. The use of the test motor is as follows.

Rated output + 3KW Rated voltage: 4oov Rated current: 12A Maximum: 6 Rated rotation speed: 1144 rpm Synchronous rotation speed: 1200 rpm Power frequency: 60 Hz Figure 8 (A) shows the first phase when the rotation of the three-phase induction motor is normal. FIG. 1 is a primary current waveform diagram in which the vertical axis shows amplitude and the horizontal axis shows time.

FIG. 8(B) shows the power spectrum, where the vertical axis shows the percentage of the effective value and the horizontal axis shows the frequency.

FIG. 9(A) is a first phase primary current waveform diagram when the rotor winding is unbalanced, and FIG. 9(B) is its power spectrum.

Since the detected rotation speed during normal operation was 1144 rpm, the slip SI is 0.0467 as shown in equation (8).

Then, the beat frequency fs+ is 54.411z as shown in formula (91).

fs+ =6Qx (1-2X0.0467)=54.
4Hz...-+91 Figure 8 (A
), no beat waveform appears in the primary current waveform in this case, and from FIG. 8(B), 54.4
It can be seen that the Hz level is 0.

On the other hand, since the rotation speed detected at the time of abnormality was 1110 rpm, the slippage S2 becomes 0.075 as shown in the 0@th formula. Then, the beat frequency fs2 becomes 51 Hz as shown in equation (11).

r s2 =60X (12XO1075)-51Hz
...(11) As is clear from Fig. 9 (A), a beat waveform appears in the primary current waveform,
As is clear from FIG. 9(B), a power and spectrum of about 9% can be seen at 511Iz, and from this, D=9% can be known and an abnormality in rotation can be detected.

In this way, since the beat frequency can be accurately known, abnormalities in the rotation of the motor can be detected from the ratio with the power spectrum intensity at the power supply frequency.

Therefore, by establishing judgment reference values obtained through experiments and actual results (in some cases, by directly comparing the detection results with the judgment reference values, quantitative judgments of normality and abnormality can be made. As a result, individual differences It is possible to diagnose the electric motor without any problems, and to prevent serious failures of the electric motor.

Here, the reason why the waveform analysis frequency is set to 256 times the power supply frequency and the frequency analysis frequency is set to 16 times the power supply frequency will be explained.

First of all, the reason why the waveform analysis frequency is set to 256 times the power supply frequency is to increase the measurement precision of the phase unbalance rate UBP and amplitude unbalance rate UBA by keeping the waveform analysis accuracy below 2 degrees and to distinguish between normal and abnormal areas. This is to reduce misjudgments near the criticality, and if the 0 frequency is made higher, which is greater than 180 times, for example, 256 times, the accuracy will increase.

On the other hand, the reason why the frequency analysis frequency is set to 16 times the power supply frequency is as follows. In other words, data for at least several tens of cycles is required to perform frequency analysis, but if these tens of cycles' worth of data were sampled and collected at the waveform analysis frequency, the capacity of the memory 13 would be enormous. In order to reduce the capacity of this memory 13, the sampling frequency is lower than the waveform analysis frequency.
Sampling may be performed at a frequency higher than twice the frequency. However, in this case, the lower limit of the sampling frequency is about 8 times the electric frequency. If the frequency is lower than this, an aliasing error will appear, and the frequency analysis accuracy will decrease.

Effects of the Invention The motor diagnostic device of the present invention determines and displays the phase unbalance rate and amplitude unbalance rate that change depending on whether the stator coil of a three-phase motor is normal or abnormal, and also changes depending on whether the rotor coil is normal or abnormal. Since the ratio of the power spectrum intensity of the motor primary current at the beat frequency and the power supply frequency is determined and displayed, the ratio of the phase unbalance rate, amplitude unbalance rate, and power spectrum intensity can be quantitatively compared. diagnosis of rotor coils, rotor coils, etc. can be performed simultaneously and accurately with this device alone, regardless of individual differences.

In addition, the sampling frequency of the A/D converter is lower during frequency analysis for rotor coil diagnosis than during waveform analysis for stator coil diagnosis.In other words, the sampling frequency is lower for rotor coil diagnosis. Therefore, even during frequency analysis, which requires data collection for quite a large number of cycles (about several tens of cycles), the total number of data to be collected does not increase significantly, and the memory capacity can be small. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a block diagram of an embodiment of the invention, FIG. Figure 5 is a waveform diagram of the primary current of a three-phase induction motor, Figure 6 is a detailed flowchart of rotor coil diagnosis in Figure 3, Figure 7 is a phase unbalance rate. and an explanatory diagram of the relationship between amplitude unbalance rate and stator coil correctness and abnormality,
FIG. 8 and FIG. 9 are explanatory diagrams of the relationship between frequency analysis results and whether the rotor coil is normal or abnormal. 1...3-phase induction motor, 2.3...Current transformer (current detector), 6...Pulse generator (rotation detector),
8.9... A/D converter, 11... Sampling pulse generator, 12... Central processing unit, 12A... Frequency setting means, 12B... First data collection means, 1
2C: Phase difference calculation means, 12D: Amplitude calculation means, 12E: Phase unbalance rate calculation means, 12F: Amplitude imbalance rate calculation means, 12G: Rotation speed calculation means, 1
2H...Second data collection means, 121...Frequency analysis means, 12J...Beat frequency calculation means, 12K
...spectral ratio calculation means, 13...memory, 14
．． 15... Display Figure 2 Figure 3 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] A current detector for detecting the primary current of a three-phase motor;
a rotation detector that detects the rotation of a phase motor; an A/D converter that samples the output of the current detector and converts it into A/D; and a frequency variable sampling type that provides a sampling pulse to the A/D converter. a pulse generator; a frequency setting means for selectively setting the sampling pulse frequency of the sampling pulse generator to a waveform analysis frequency and a frequency analysis frequency lower than the waveform analysis frequency; a first data collection means for collecting waveform data outputted from the A/D converter for a number of cycles necessary for waveform analysis and storing it in a memory; phase difference calculation means for calculating the phase difference between each phase current from the waveform data stored in the memory, amplitude calculation means for calculating the amplitude of each phase current from the waveform data stored in the memory, and each phase calculated by the phase difference calculation means. a phase unbalance rate calculation means for calculating a phase unbalance rate from the difference between the maximum and minimum phase differences of the current; and an amplitude unbalance rate from the difference between the maximum and minimum amplitudes of each phase current calculated by the amplitude calculation means an amplitude unbalance factor calculation means for calculating the rotation speed of the three-phase motor from the output of the rotation detector; and a sampling pulse at the frequency analysis frequency and output from the A/D converter. a second data collecting means for collecting waveform data for a number of cycles required for frequency analysis and storing the collected waveform data in the memory;
a frequency analysis means for performing frequency analysis based on the waveform data stored in the memory by the data collection means; and a beat frequency calculation for calculating a beat frequency from the rotation speed of the three-phase motor obtained by the rotation speed calculation means. means, power spectrum ratio calculating means for calculating the ratio of the spectral intensity of the beat frequency to the spectral intensity of the power supply frequency based on the analysis result by the frequency analyzing means; the phase unbalance factor calculating means; and the amplitude unbalance factor calculating means. An electric motor diagnostic device comprising means and a display for displaying the calculation results of the power spectrum ratio calculation means.