JPS6256876A - Diagnosing device for motor - Google Patents

Abstract

PURPOSE:To detect the extent of the loosening of a stator coil precisely even if a primary current contains many opposite-phase current components due to the unbalance of a primary voltage by providing an opposite-phase current value difference calculating means which calculates the amplitude of the mutual difference between the opposite-phase current values. CONSTITUTION:Primary currents of phases U and W among primary currents of phases U, V, and W of a three-phase induction motor 1 are detected by current transformers 12 and 13 and A/D-converted by A/D converters 14 and 15, their waveform data are stored in memories 16 and 17, and the stored data are processed by a CPU 18. Namely, the CPU 18 connects a rated load and no load (or light load) as the load 21 of the motor 11 and carries out waveform data collection processing, Fourier analytic processing, opposite-phase current value calculation processing, etc., to find the opposite-phase current value. Then, the amplitude of the difference between the opposite-phase currents in both primary currents and displays the amplitude on a display device 19 as the standard for the loosening of the stator coil.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is capable of removing loose stator coils of three-phase induction motors without applying high voltage to the stator coils or disconnecting the 1118 wiring to the three-phase induction motors. The present invention relates to a motor diagnostic device that can easily detect a motor.

BACKGROUND ART Looseness of the stator coil of a three-phase induction motor is directly linked to the life of the three-phase induction motor, so it is necessary to regularly diagnose its presence or absence and try to discover it early.

Diagnosis of loosening of the stator coil of a three-phase induction motor has been performed by utilizing the fact that when the stator coil becomes loose, the current waveforms of each phase become unbalanced.

Diagnosis method for this three-phase induction motor (Patent application No. 58-2157)
No. 62) is a method for detecting the primary current waveform of each phase during rotation of a three-phase induction motor and diagnosing the degree of loosening of the stator coil of the three-phase induction motor based on the detection result, From the primary current detection waveform of each phase, find the phase unbalance rate associated with the difference between the maximum and minimum phase difference between each phase, and also calculate the maximum amplitude of the primary 'gl flow waveform of each phase. This is a method for determining the degree of loosening of the stator coil of a three-phase induction motor by determining the amplitude unbalance factor associated with the difference between the maximum and the minimum values.

Problem to be Solved by the Invention When the primary voltage of a three-phase induction motor is unbalanced and includes an out-of-phase component, the unbalanced primary current is divided into a component caused by loosening of the stator coil and a component caused by loosening of the stator coil. Since it is the sum of the components generated by the negative phase bone of the primary voltage, when simply determining the unbalance rate of the primary current as described above and using it as a guide to the degree of loosening of the stator coil, the negative phase of the primary voltage If the mating ribs are large, this will cause an error and there is a problem that the degree of loosening of the stator coil cannot be accurately detected.

An object of the present invention is to provide a motor diagnostic device that can accurately detect the degree of loosening of a stator coil even if the primary current contains many negative sequence current components due to unbalanced primary voltage. It is to be.

Means for Solving the Problems As shown in FIG.
A data acquisition means 1 that acquires waveform data of the primary current of at least two phases of a three-phase induction motor, and a primary current value of each phase is determined from the waveform data acquired by the data acquisition means 1 at a rated load. a first primary current value calculation means 2;
A first negative-sequence current value calculation means 3 that calculates a negative-sequence current value from the primary current value of each phase obtained by the first primary current value calculation means 2, and A second primary current value calculation means 4 calculates the primary current value of each phase from the waveform data taken in by the acquisition means l, and The second negative sequence current value calculation means 5 which calculates the negative sequence current value from the primary current value, and the mutual relationship between the negative sequence current values calculated by the first and second negative sequence current value calculation means 3.5. negative-sequence current value difference calculation means 6 for calculating the amplitude of the difference, and display means 7 for displaying the calculation results of this negative-sequence current value difference calculation means 6
It is equipped with

According to the configuration of the present invention, the amplitude of the difference between the negative sequence current in the primary current at the rated load and the negative sequence current in the primary current at no load or light load is determined, and this amplitude is calculated by the stator. In order to display this as a measure of coil loosening, the negative sequence current in the primary current includes the negative sequence current component caused by the imbalance of the primary leakage reactance of the three-phase induction motor due to the loosening of the stator coil. Even if there is a large amount of negative sequence current component due to voltage unbalance, this negative sequence current component due to primary voltage imbalance hardly changes depending on the load size, and the negative sequence current at rated load is By taking the difference between the negative sequence current and the negative sequence current at no load or light load, the negative sequence current component caused by the unbalance of the primary voltage is eliminated, and the unbalance of the primary leakage reactance that changes depending on the load size is eliminated. Only the negative sequence current component caused by is left.

Therefore, even if the negative sequence current in the primary current contains many negative phase components due to unbalanced primary voltage, the degree of loosening of the stator coil can be accurately determined without being affected by this. Can be detected.

Embodiment A practical embodiment of the present invention will be described with reference to FIGS. 2 to 7. As shown in Fig. 2, this electric motor diagnostic device has the following features:
U phase and ■ phase of the three-phase induction motor 11.

Out of the W-phase primary current, the U-phase and W-phase primary currents are transferred to current transformer 1.
2.13, each waveform data is A/D converted by A/D converter 14.15, and then each waveform data is stored in memory 16.13.
By processing the waveform data stored in the memories 16 and 17 with the CPU 18, the degree of loosening of the stator coil is displayed on the diagnostic result display 19.

20 is a measurement start key, and 21 is a load driven by the induction motor 11.

The processing operation of the CPUI 8 will be explained below based on the flowcharts of FIGS. 3 and 4.

First, as shown in FIG. 3, the load 21 of the three-phase induction motor 11 is set to the rated load by manual operation, and the measurement start key 20 is pressed.

When the measurement start key 20 is pressed, the CPU 18 detects this and performs waveform data collection processing at rated load, Fourier analysis processing, negative sequence current value calculation processing, etc., and calculates the negative sequence current value INI (1N+ is a complex number). Find and memorize this.

Then, by manual operation again, the three-phase induction motor 1
Set the load 21 of No. 1 to no load or light load, and press the measurement start key 20.

When the measurement start key 20 is pressed, the CPU 18 detects this and performs waveform data collection processing, Fourier analysis processing, negative sequence current value calculation processing, etc. during no load or light load, and calculates the negative sequence current value Ixz. (Isi is a complex number) and store it.

Next, the difference in negative sequence current value! . 1113=INI Iwt・
...Calculated based on the calculation formula (1), and also the difference in negative sequence current value with respect to the rated current value ■. The amplitude ratio Rate of is determined based on . Through this processing, the CPU 18 constitutes the negative phase current value difference calculation means 6.

Then, the ratio Rate is displayed on the diagnostic result display 19. Through this process, cpuis displays the diagnostic result display 19.
Together with this, the display means 7 is constructed.

Next, each process such as waveform data collection, Fourier analysis, negative phase current value calculation, etc. will be explained in detail with reference to FIG.

In this process, the waveform of the primary current of the U phase among the primary currents of the IJ phase, the The U-phase waveform data stored in the memory 16 is subjected to Fourier analysis, and the first order of the U-phase is calculated by calculating the amplitude and phase of the fundamental wave component of the flow (U-phase Find the primary current value +u).

In the same manner as above, the waveform of the W-phase primary current is transferred to the current transformer 13.
The W-phase waveform data is detected by the A/D converter 15 and A/D converted by the A/D converter 15, and the obtained W-phase waveform data is stored in the memory 17.Fourier analysis is performed on the W-phase waveform data stored in the memory 7. , find the amplitude and phase of the fundamental wave component of the W-phase primary current (W-phase primary current value + w).

Next, from the condition that there is no zero-sequence current, the amplitude and phase of the fundamental wave component of the V-phase primary current (the primary current value Iv of the ■phase is expressed as Iv − (Iu + Iw ) −−(
Obtained based on 31.

Next, the negative sequence current IN (1N + 1 at rated negative section or 1H at no load or light load) is 1N ''' - (Iu +a '' Iv +a Iw
)......(4). However, −1+ child j a; □ ......(5).

This process is performed in the same way during rated load, no load, or light load, and the CPU 18 performs the same process when the current transformer 12. 13
．． A/D converter 14.15. Together with the memory 16.17, the data acquisition means l, the first and second primary current value calculation means 2.4. The first and second reversed phases constitute a flow value calculation means 3.5.

In this way, find the difference between the negative sequence current value at rated load and the negative sequence current value at no load or light load, and then calculate the amplitude of this negative sequence current value difference 1 and 12 by the amplitude of the rated current value. The ratio R te is obtained by dividing the ratio R te and this ratio R te is displayed as a guideline for the loosening of the stator coil.
In addition to the negative phase tl component caused by the imbalance in the primary leakage reactance of the phase induction motor 11, even if there is a large amount of negative sequence current component caused by the imbalance in the primary voltage, this primary voltage imbalance The negative sequence current component caused by balance hardly changes depending on the size of the load 21, and by taking the difference between the negative sequence current value at rated load and the negative sequence current value at no load or light load, the primary The negative-sequence current component caused by the unbalanced voltage is erased, and only the negative-sequence current component caused by the unbalanced primary leakage reactance, which changes depending on the magnitude of the load, remains.

Therefore, even if the negative sequence IT current value contains many negative sequence current components due to unbalanced primary voltage, it is possible to accurately detect the degree of loosening of the stator coil without being affected by this. can.

Here, the reason why the degree of loosening of the stator coil of the three-phase induction motor 11 corresponds to the amplitude of the negative sequence current value difference will be explained.

The primary leakage reactance of the three-phase induction motor 81111 can be expressed as the sum of three elements: slot leakage reactance, gap leakage reactance, and coil FeaB leakage reactance.

FIG. 5(A) shows a schematic diagram of the slot portion when the insulating layer between the conductors in the stator coil is normal during operation;
FIG. 5(B) shows a schematic diagram of the slot portion when the insulating layer between the conductors in the stator coil is abnormal during operation.
22 is a slot, 23 stator coils, 23a
is a conductor, and 23I) is an insulating layer. If the insulating layer between the conductors in the stator coil is insufficient and the stator coil 23 becomes loose, the stator may become loose due to the Lorentz force caused by the mutual currents during operation of the three-phase induction motor 1, as shown in Figure 5 (B). As the conductors 23a of the coil 23 concentrate and the entire stator coil 23 contracts in the height direction of the slot 22, the slot leakage reactance increases in each phase, and the primary leakage reactance of each phase becomes unbalanced. Become.

The unbalance of the primary leakage reactance caused by the loosening of the stator coil of the three-phase induction motor 11 is detected as follows.

FIG. 6 shows an equivalent circuit for one phase of the three-phase induction motor 11. In the figure, x is the primary leakage reactance, r
, is t resistance, x2 is reactance, go is conductance, bo is susceptance, ryo/S is resistance to positive sequence voltage, rz/2S is resistance to negative sequence voltage, Z is positive sequence impedance, Z8 is negative sequence It is impedance.

In the equivalent circuit of Fig. 6, the positive sequence impedance ZP,
Assuming that the value of the negative phase impedance ZN is the same for all three phases, the equivalent circuit for the three phases will be as shown in FIG. In the same figure, ■o is the primary voltage of the U phase, vv is the primary voltage of the ■phase, ■1 is the primary voltage of the W phase, Iu is the primary current of the U phase, and Iv
is the primary current of the ■ phase, I0 is the primary current of the W phase, ■ is the midpoint voltage, the primary leakage reactance of the oXIL beam phase, and
IV is the primary leakage reactance of the ■ phase, XY is the primary leakage reactance of the W phase, Z is the impedance, and the positive phase component is Z.
, and the reverse phase component is Z. and the primary leakage reactance xlL
l+ xIV+ xI, only I will be different for each phase.

Next, a procedure for calculating the imbalance of the primary current, specifically, calculating the positive sequence current (2) and the negative sequence current nIs, will be explained based on the above equivalent circuit. This calculation is based on the primary voltage
. ,V,,V, unbalance and primary leakage reactance xIL
l+ XIV, primary current 1u based on X engineering unbalance
+ This is to calculate the imbalance of Iv and In.

In the equivalent circuit of FIG. 7, the primary voltages V, , VV.

Vw and primary leakage reactance xllJ+ Xll
When 1+X engineering is decomposed into symmetrical parts, it becomes as follows.

However, it is assumed that there is no zero-phase component in the primary voltage.

V, = V, 10 V, ...
...(6) V, = a ” V, + a V,
・・・・・・(71V, m a V
, + a ”V, ・・・・・・(
81j X+u-j XIP+ j XIN+ j X
+z −−fQ)j X+v−ja ” x,
,,+jax,,+ J X+z -+++++11J
X+w-JaX+P”ja”X+n+jX1z −
-QD However, ■, is the positive sequence voltage, ■8 is the negative sequence voltage, XI
F is positive sequence reactance, XIN is negative sequence reactance,
I2 is the actance corresponding to the unbalanced component.

Moreover, when the primary electric currents Uiu, IV, and 1w are decomposed into symmetrical components, the following equation is obtained. However, it is assumed that there is no zero-phase component.

L-IP +l,l...
・(2) Iv “a” It +a IN
“””α-yu[,-a +, +a”! ,
-α In addition, in each of the above formulas, a=expt+j(2/3)aJ.

The circuit equations of the equivalent circuit of FIG. 7 from Equations 6 to 00 above are as follows.

■. -V, +V.

-J X1uIu ”ZF IF +ZN IN
10V= fJ XIP”J XIN” (jX+z+Z
r )) IP+ (jX+p+jX++i+ (
jx+z+ZH)3Is+V
...QIVv=a ” VP +a V
N = (ja”x+p+jax+N +(jx+z
+ ZP ) )a”l p+ (ja”x+
r+jaxrN+(jx+z+Zw) l al
＊＋V・・・・・・a
ηV, =aV, +a''V).

= fjax+r +ja"x+n"(jx+z+
Zp ) ) air+ (jaX+r +j
azX++++ (jXiz + ZN)
) aJ, +V
...... From the above OQ formula to α-th formula, positive phase type/ILI P and negative sequence current I1. I is expressed as follows.

・・・・・・Ol ・・・・・・Q@ The negative sequence voltage ■8 is about 1% of the positive sequence voltage ■, and the reactance xlIP+XIN is Zr +J
Considering that x+z+Z N '' J

1, #----・■, ・・・・・・(21) Z
r”jXiz Z 工＋j
......(22) The first term of the negative sequence current r8 expressed by the above equation (22) is a component due to the imbalance of the primary leakage reactance, and the second term is a component due to the imbalance of the primary leakage reactance.
The term is a component due to unbalance of the primary voltage. This negative sequence current 1. Of these, the component due to the unbalance of the primary voltage is the (22nd
) As is clear from 2, the load 2 of the three-phase induction motor 11
It can be seen that there is almost no change depending on the size of 1. This is because the negative phase impedance ZN hardly changes depending on the magnitude of the load. On the other hand, the component of the negative sequence current I8 due to the unbalance of the primary leakage reactance is the (22nd
) As is clear from the equation, the load 2 of the three-phase induction motor 11
It can be seen that the larger 1 is, the thicker it becomes. This is because the positive sequence impedance Z changes greatly depending on the magnitude of the load.

Therefore, if there is unbalance in the primary leakage reactance, the primary voltage The component due to the unbalance of the stator coil is eliminated, and only the component due to the unbalance of the primary leakage reactance remains, so that the unbalance of the primary leakage reactance, that is, the degree of loosening of the stator coil can be detected.

In addition, the equation (4) for finding the negative sequence current summer is the first equation and the first equation a! It can be obtained by adding the product obtained by multiplying .

Effects of the Invention According to the motor diagnostic device of the present invention, it is possible to detect negative phase in the primary current at rated load. In order to calculate the amplitude of the difference between the negative sequence current in the primary current and the negative sequence current in the primary current at no load or light load, and to display this amplitude as a guide to the loosening of the stator coil, the negative sequence current value is added to the negative sequence current value of the stator coil. In addition to the negative sequence current component caused by the unbalance of the primary leakage reactance of the three-phase induction motor due to loosening, even if there is a large negative sequence current component due to the unbalanced primary voltage, there is no effect on this. The degree of loosening of the stator coil can be detected with high accuracy without being affected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of this invention, FIG. 2 is a block diagram showing the configuration of an embodiment of this invention, FIGS. 3 and 4 are flowcharts showing the operation of the embodiment, and FIG. A schematic diagram of the slot part of a three-phase induction motor, Figure 6 is 3
An equivalent circuit for one phase of a phase induction motor, and FIG. 7 is an equivalent circuit for three phases. DESCRIPTION OF SYMBOLS 1... Data acquisition means, 2... First primary current value calculation means, 3... First negative phase current value calculation means, 4...
Second primary current value calculation means, 5... Second negative sequence current value calculation means, 6... Negative sequence current value difference calculation means, 7... Display means

Claims (1)

[Claims] data acquisition means for acquiring the waveform data of the primary current of at least two phases of the three-phase induction motor;
a first primary current value calculation means for calculating a secondary current value; and a first negative sequence current for calculating a negative sequence current value from the primary current value of each phase calculated by the first primary current value calculation means. a value calculation means, a second primary current value calculation means for calculating a primary current value of each phase from the waveform data acquired by the data acquisition means at no load or light load; a second negative sequence current value calculation means for calculating a negative sequence current value from the primary current value of each phase calculated by the current value calculation means, and a negative sequence current value calculated by the first and second negative sequence current value calculation means, respectively. A motor diagnostic device comprising a negative sequence current value difference calculation means for calculating the amplitude of the mutual difference between negative sequence current values, and a display means for displaying the calculation result of the negative sequence current value difference calculation means.