WO2013108971A1

WO2013108971A1 - Apparatus and method for diagnosing flaws in rotor of indcution motor, and medium on which is recorded computer-readable program for executing method

Info

Publication number: WO2013108971A1
Application number: PCT/KR2012/006081
Authority: WO
Inventors: 이상빈; 현두수
Original assignee: 고려대학교 산학협력단
Priority date: 2012-01-18
Filing date: 2012-07-31
Publication date: 2013-07-25
Also published as: KR20130084775A; KR101326586B1; CN103217644B; CN103217644A

Abstract

The invention relates to an apparatus and method for diagnosing flaws in the rotor of an induction motor, and to a medium on which is recorded a computer-readable program for executing the method. The apparatus for diagnosing flaws in the rotor of an induction motor comprises a voltage supply unit, a current measuring unit, a reactance computing unit, and an eccentricity diagnosing unit. The voltage supply unit supplies a single-phase voltage to the induction motor. The current measuring unit measures the current supplied to the induction motor due to the supplied voltage. The reactance computing unit computes the reactance of the induction motor by using the voltage supplied to the motor and the measured current during the rotation of the rotor of the induction motor. The eccentricity diagnosing unit diagnoses that the induction motor air gap is eccentric if the reactance value computed during one revolution of the rotor of the induction motor is always greater than a predetermined reactance value. By virtue of this arrangement, the apparatus for diagnosing flaws in the rotor of an induction motor according to the present invention may be applied to any type of an induction motor, thereby facilitating the diagnosis of induction-motor eccentricity even without additional expensive equipment.

Description

Apparatus and method for diagnosing a rotor defect of an induction motor and a medium having a computer readable program for executing the method

TECHNICAL FIELD The present invention relates to power equipment, and more particularly, to an apparatus and method for performing a diagnosis of an electric motor condition.

1 is a view schematically showing the structure of an induction motor. As can be seen in FIG. 1, in an induction motor, the magnetic flux Ф _s generated in the stator core 1 by applying voltage and current to the windings 3 of the stator is the conductor bar 4 of the squirrel rotor 2. Current is generated in the magnetic field, thereby generating magnetic flux Ф _r .

At this time, if an input power source having a 120 ° phase difference is applied to the three-phase winding of the stator, the stator flux Ф _s rotates at a constant speed according to the input power source, which is called a rotating magnetic field.

The squirrel cage induction motor operates with a torque τ derived according to the correlation of magnetic flux generated in the stator and the rotor. At this time, the torque τ which makes the induction motor rotate is proportional to the vector cross product of the magnetic flux Ф _s and the magnetic flux Ф _r .

There is a gap 5 between the stator and the rotor of the induction motor. The state where this space | gap 5 is not constant is called eccentricity. Air gap eccentric failures where the air gap between the stator and the rotor are not constant are classified into static, dynamic, and mixed eccentricity, depending on the relative position of the center axis of the stator and the center axis of the rotor / rotation. .

2 is a view schematically showing the state of the motor gap. 2 shows a normal motor, a middle motor in a static eccentric state, and a right motor in a dynamic eccentric state.

Static eccentricity is when the rotor's central axis does not coincide with the stator's central axis, so that the rotor rotates about the central axis of the rotor. The minimum part of the air gap is always constant when the motor is operating.

Dynamic eccentricity is a case where the central axis of the stator and the central axis of the rotor do not coincide and rotate about the central axis of the stator. The portion where the gap is minimum varies as the rotor rotates.

Static eccentricity is caused by manufacturing defects due to manufacturing defects such as ellipsoid of stator and misalignment of stator and rotor position. Dynamic eccentricity can occur due to the bending of the rotor shaft, deterioration of bearings, misalignment of motor and load, or mechanical resonance. Compound eccentricity refers to the case where a static eccentricity and a compound eccentricity exist simultaneously.

If the eccentric eccentric failure occurs due to this cause, the uneven air gap leads to a strong unbalanced magnetic pull in one direction only between the rotor and the stator.

This plays a direct role in bending the rotor or damaging the bearings. In addition, if the torque pulsation and vibration of the motor is increased to bring the performance of the motor and continue, the stator and the rotor come into contact with each other, causing the core and winding of the stator and the rotor to fail, thereby reaching an unrepairable level. Therefore, it is very important to diagnose the gap eccentricity of the motor early.

There are two methods of diagnosing the eccentricity of induction motor voids: the off-line test, which is performed without the motor being operated, and the on-line monitoring, which is carried out during operation.

1) Off-line test

a. Total Indicated Reading Test

It is used for diagnosing defects when the manufacturer makes the motor for the first time.Dynamic Eccentricity is determined by disassembling the motor and manually rotating the rotor through the dial test indicator. It is a test to diagnose. However, there is a difficulty in making a special device for the rotor separation and the TIR in the motor.

b. RIC (Rotor Influence Check) test

Like the TIR test, the rotor is manually rotated without disassembling the motor, and a low voltage and high frequency signal is injected into the stator's three-phase winding to compare the inductance values of each phase's winding.

If the induction motor has an eccentricity, the inductance value of each phase is different to diagnose the eccentricity. However, this test uses low voltage and high frequency signals, so the result of the test is not clear due to the influence of the residual magnetic flux of the stator core.

c. Method using surge tester

Surge tester is a device for diagnosing insulated motor insulation by applying a much higher voltage than rated voltage for insulation test of stator winding. The method of diagnosing the eccentricity with the surge tester is, like other diagonal tests, by manually rotating the rotor and measuring the eccentricity by measuring the time to the zero-crossing point of the output waveform of the surge tester. To test. In eccentric motors, the results of this test are shorter in time to the zero point.

This diagnostic test requires an expensive surge tester and may have an adverse effect on the reliability of the motor because a very high voltage is applied to the stator windings. In addition, because the time is recorded and the results are displayed, another apparatus for processing them is required.

2) On-line monitioring

a. Method using Capacitive airgap sensors

A method of diagnosing eccentricity during operation of an electric motor is a method of determining a degree of air gap by attaching a capacitor air gap sensor to a part where the air gap of a stator is in contact with each other. However, this method is so large that the capacity and size of the induction motor can be applied only to a wide motor of air gap.

b. Frequency Phase Analysis

This test is to diagnose vibration, noise, magnetic flux, and current flowing through stator windings during the operation of the motor, and to diagnose the frequency component generated when there is an air gap eccentricity through spectrum analysis.

Frequency-phase analysis of vibration, noise, and magnetic flux is an economical problem that incurs additional cost of the sensor to measure it. The current is transmitted through a current sensor (CT) attached to the motor control center (MCC) of the motor. The motor current signature analysis (MCSA) method of measuring spectra and analyzing the spectrum is representative.

If there is an eccentricity, this changes the air gap according to the rotor position of the motor and distorts the spatial and temporal distribution of the magnetic field in the motor. In this case, the frequency generated by spectrum analysis of the measured current includes a component measured in the low frequency region and a component measured in the high frequency region.

Where f _s is the fundamental frequency of the power supply, k is an arbitrary integer, s is the slip of the induction motor, p is the number of pole pairs of the induction motor, R is the slot number of the rotor, and n _d is the eccentric order , v is the order of the stator time harmonic.

However, low frequency components can only be diagnosed in the presence of complex eccentricity, while high frequency components can be applied to static, dynamic, and complex eccentricity faults more generally than low frequencies, but the number of rotor slots (R) must be known and -No defect is detected in the rotor slot number (pR relation).

And this frequency analysis requires a lot of data to be stored, and it is difficult to detect the exact fault frequency if the load changes during operation and the speed and slip change. In addition, there is a disadvantage in that it is difficult to determine even when overlapping with the pore eccentric frequency due to the influence of a specific load (load torque oscillation).

The present invention has been made to solve the above-mentioned conventional problems, can be applied to any type of induction motor, diagnosis of the rotor defects of the induction motor that can easily diagnose the eccentric state of various forms without expensive separate equipment It is an object to provide an apparatus and a method.

In order to achieve the above object, the apparatus for diagnosing a rotor defect of an induction motor according to the present invention includes a current measuring unit, a reactance calculating unit, and an eccentric diagnosis unit.

The current measuring unit measures the current supplied to the induction motor, the reactance calculating unit calculates the reactance of the induction motor by using the voltage and the measured current supplied to the induction motor, and the eccentric diagnosis unit calculates while the rotor of the induction motor rotates once. If the reactance value is larger than the preset reactance value in at least some sections, the induction motor gap is diagnosed as eccentric.

By such a configuration, the apparatus for diagnosing the rotor defect of the induction motor according to the present invention can be applied to any type of induction motor, and it is possible to easily diagnose the eccentric state of the induction motor without expensive separate equipment.

At this time, the eccentric diagnosis unit may diagnose that the void of the induction motor is static or dynamic eccentricity when the calculated reactance value is larger than the normal state and constant while the rotor is rotated, and the eccentric diagnosis unit may rotate one revolution of the rotor. If the calculated reactance value is larger than the normal state and changes in one cycle, the gap of the induction motor may be diagnosed as a compound eccentricity. With such a configuration, the apparatus for diagnosing rotor defects of the induction motor according to the present invention can easily diagnose various types of eccentric states.

In addition, the rotor fault diagnosis apparatus of the induction motor according to the present invention is a conductor bar defect for diagnosing that the rotor conductor bar is defective when the reactance value calculated during the rotation of the rotor of the induction motor changes by a period of the number of rotor poles. The diagnosis unit may further include. This configuration makes it possible to diagnose not only the void eccentricity of the induction motor but also the defect of the rotor conductor bar by using the rotor defect diagnosis device of the induction motor according to the present invention.

The apparatus may further include a voltage measuring unit measuring the AC voltage. This configuration makes the calculated reactance value more reliable by making more accurate voltage values available.

In addition, the rotor may further include a rotating part for rotating the rotor. This configuration makes it possible to fully automate the rotor fault diagnosis process of induction motors.

In addition, an invention in which the apparatus is implemented in the form of a method and a medium on which a computer readable program for executing the method is recorded.

The apparatus for diagnosing a rotor defect of an induction motor according to the present invention can be applied to any type of induction motor, and can easily diagnose an eccentric state of an induction motor without expensive separate equipment.

In addition, the rotor defect diagnosis apparatus of the induction motor according to the present invention can easily diagnose various types of eccentric state.

In addition, it is possible to diagnose not only the gap eccentricity of the induction motor, but also the defect of the rotor conductor bar.

1 schematically shows the structure of an induction motor;

2 is a view schematically showing a state of an electric motor gap;

3 is a schematic block diagram of one embodiment of a rotor defect diagnosis device of an induction motor according to the present invention;

4 is a diagram schematically illustrating a state for performing an SPRT.

Fig. 5 shows an equivalent circuit at the time of applying single-phase alternating current in a stationary induction motor.

Figure 6 is a view for explaining the zigzag leakage inductance of the leakage inductance of the induction motor.

7 is a graph showing leakage inductance of a motor with 50% eccentricity.

8 is a graph showing changes in leakage inductance with increasing eccentricity.

9 is a graph showing the change in reactance (X) value calculated by SPRT according to the case of a normal motor, a static / dynamic eccentricity, a complex eccentricity, and a rotor conductor bar defect.

FIG. 10 is a graph showing the change in reactance (X) value calculated by the SPRT calculated in the combined eccentric state and the steady state of an induction motor having two rotor conductor bars defective;

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

3 is a schematic block diagram of an embodiment of a rotor defect diagnosis apparatus of an induction motor according to the present invention.

In FIG. 3, the apparatus 100 for diagnosing the rotor defect of the induction motor includes a voltage supply unit 110, a current measurement unit 120, a voltage measurement unit 122, a reactance calculation unit 130, an eccentric diagnosis unit 140, and a conductor. The bar defect diagnosis unit 150 and the rotating unit 160 are included.

In this case, each component of the rotor defect diagnosis apparatus 100 of the induction motor may be implemented entirely in hardware, or may be implemented as a general-purpose computer device combined with software.

The voltage supply unit 110 supplies a single phase voltage to the induction motor, and the current measurement unit 120 measures the current supplied to the induction motor by the supply voltage.

In this embodiment, the single phase voltage is supplied to the induction motor through the voltage supply unit 110, but the rotor defect diagnosis apparatus 100 may be implemented to receive a voltage from the outside without having the voltage supply unit 110 separately. The voltage supplied is not limited to the single phase voltage as long as it is an AC voltage.

The voltage measuring unit 122 measures an AC voltage supplied to the induction motor. The AC voltage value may be calculated using the voltage value supplied to the induction motor, but in this way, a more accurate voltage value can be obtained when the measured voltage value is directly measured.

The reactance calculator 130 calculates the reactance of the induction motor using the voltage supplied to the induction motor and the measured current.

The rotating unit 160 rotates the rotor. At this time, the rotation of the rotor may be performed manually by the attraction, but may be rotated by a separate configuration for the rotation of the rotor. This configuration allows for the automation of the rotor fault diagnosis process of the induction motor according to the present invention by automating the rotation of the rotor for the reactance calculation process.

The eccentric diagnostic unit 140 diagnoses that the induction motor gap is eccentric when the reactance value calculated while the rotor of the induction motor is one revolution is larger than the preset reactance value in at least some section.

Here, the preset reactance value is a value set in advance by the motor manager or the like, and it will generally be a reactance value when the motor is in a normal state instead of an eccentric state.

At this time, the eccentric diagnostic unit 140 may diagnose that the void of the induction motor is a static or dynamic eccentricity when the reactance value calculated while the rotor rotates one rotation is larger than the normal state. In addition, the eccentric diagnostic unit 140 may diagnose that the air gap of the induction motor is a complex eccentricity when the reactance value calculated during the rotation of the rotor is larger than the normal state and changes in one cycle.

In general, the reactance value calculated for an eccentric induction motor is always larger than the steady state, but may not be large in some intervals. This is because if the air gap of the induction motor is a complex eccentricity, the lowest point of the calculated reactance value may coincide with the steady state reactance value, and there may be a slight variation depending on the measurement.

By such a configuration, the apparatus for diagnosing rotor defects of the induction motor according to the present invention can easily diagnose various types of eccentric states such as static / dynamic or complex eccentricity.

In addition, the conductor bar defect diagnosis unit 150 diagnoses that the rotor conductor bar is defective when the reactance value calculated during the rotation of the rotor of the induction motor changes at a cycle of the number of poles of the rotor.

This configuration makes it possible to diagnose not only the void eccentricity of the induction motor but also the defect of the rotor conductor bar by using the rotor defect diagnosis device of the induction motor according to the present invention.

Hereinafter, the present invention will be described in detail with more specific examples.

In the present invention, a single phase rotation test (SPRT) is used to diagnose a rotor failure of an induction motor in order to diagnose an air gap eccentricity of an induction motor.

4 is a diagram schematically illustrating a state for performing an SPRT. SPRT is a technique mainly used for diagnosing a defect in the rotor bars of a squirrel rotor of an induction motor. The SPRT is an off-line test that is performed while the motor is stopped.

A single phase is applied to the stator winding, for example, by applying an alternating single phase voltage between one and two phases to measure the current that changes when there is a failure in the rotor conductor bar. Apply a voltage of ~ 1/4. As with the eccentric diagonal test, the rotor is rotated to diagnose the condition during this test.

The present invention diagnoses the eccentricity of an induction motor by using the SPRT test, by applying 1/8 to 1/4 of the rated voltage of the motor to the stator winding by applying a single-phase AC voltage to the stator winding. Determine the failure by observing the change in the calculated impedance.

However, in the general SPRT for diagnosing the defect of the rotor conductor bar of the induction motor, the reactant component is calculated by applying the applied voltage and the measured current. To determine the degree of eccentricity.

FIG. 5 is a diagram showing an equivalent circuit at the time of applying single-phase alternating current to a stationary induction motor.

As can be see in Figure 5, when the electric motor is still a single-phase AC voltage due to the SPRT is equivalent to the equivalent circuit of the induction motor resistance R _s and R _r it is only affected to the temperature regardless of the eccentricity.

The magnetization reactance X _m is a negligible component because there is little component penetrating into the rotor from the stator core because the motor is stationary. In contrast, the leakage reactance components, X _ls and X _lr , change with eccentricity.

The leakage inductance of a squirrel cage induction motor has slot, end-winding, and zigzag components. Among them, the zigzag leakage inductance component increases as the pore length becomes shorter.

6 is a view for explaining a zigzag leakage inductance of the leakage inductance of the induction motor.

Therefore, by analyzing the impedance component calculated from the applied voltage and the measured current in the SPRT test, it is possible to determine the degree of eccentricity according to the change of the gap as the leakage inductance component.

7 is a graph illustrating leakage inductance of a motor having a 50% eccentricity, and FIG. 8 is a graph illustrating a change of leakage inductance with an increase in eccentricity.

In Fig. 7, when 50% of eccentricity is present in the induction motor, the leakage zigzag inductance, L _zz , changes in the form of a cosine function as the position of the rotor changes by one turn. It can be seen that the value rises. In addition, in FIG. 8, when the eccentricity increases by 10%, the average value of the leakage inductance increases in the form of an exponential function.

Therefore, if there is static or dynamic eccentricity in the motor alone, the reactance value calculated by applying the applied voltage and measured current using SPRT does not change the amount of eccentricity even if the rotor position changes. Irrespective of this, it has a form that increases with the reactance value of a normal motor.

However, in the case of mixed eccentricity in which both static and dynamic eccentricity exist, the amount of reactance calculated by SPRT changes mechanically by 360 ° because the total eccentricity changes as the rotor changes. When rotating, it has a component that repeats once, that is, a sinusoidal component.

In addition, the SPRT for diagnosing the defect of the rotor conductor bar of the induction motor generally rotates the rotor to measure the magnitude of the measured current, and the method calculates the reactance component based on the applied voltage and the measured current. To determine the degree of eccentricity.

This reactance value can also be used for defects in the rotor conductor bar, whose components change by the number of poles of the motor when the rotor's position changes one revolution (mechanically 360 °). Therefore, the eccentricity of the induction motor can be diagnosed by this method, and the defect of the rotor conductor bar, which is the main purpose of the SPRT, can be diagnosed and distinguished simultaneously.

9 is a graph showing the change in the reactance (X) value calculated by the SPRT according to the case of a normal motor, a static / dynamic eccentricity, a complex eccentricity, and a rotor conductor bar defect.

In FIG. 9, when the induction motor having four poles is a complex eccentricity, the reactance value is changed by one period while the induction motor is rotated one time, but in the case of a defect in the conductor bar, it can be seen that the period is changed by the number of poles.

The period of these reactance values appears for both complex eccentric and conductor bar defects when both complex eccentric and conductor bar defects are present.

FIG. 10 is a graph showing the change in reactance (X) value calculated by the SPRT calculated in the combined eccentric state and the steady state of an induction motor having two rotor conductor bars defective.

In the case of the conductor bar defect in FIG. 10, the period of the rotor poles is equal to the number of rotor poles, but when the composite eccentricity is present, it can be seen that the entire waveform has a large period other than the small period.

According to the present invention, the SPRT test, which is a conventional technique for diagnosing a rotor conductor bar defect of an induction motor, may also be used for diagnosing gap eccentricity. In addition, the SPRT test is very simple, inexpensive, and highly reliable.

Unlike conventional diagnostic techniques, it is possible to diagnose / differentiate static, dynamic and complex eccentricity, and because it is an off-line test, it is not affected by load. In addition, regardless of the specific number of pole-rotor slots, no information such as the number of rotor slots and speed or slip is required.

The implementation of the algorithm is very simple because the reactance component, which is the eccentric failure factor used in the present invention, is easily calculated from the applied voltage and measured current of the SPRT test.

Although the present invention has been described in terms of some preferred embodiments, the scope of the present invention should not be limited by this, but modifications or improvements of the above embodiments, which are supported by the claims, will also extend.

Claims

A current measuring unit measuring an alternating current supplied to the induction motor;

A reactance calculator configured to calculate a reactance of the induction motor by using the AC voltage supplied to the induction motor and the measured AC current; And

Rotor defect of the induction motor, characterized in that it comprises an eccentric diagnostic unit for diagnosing that the induction motor gap is eccentric when the reactance value calculated during the rotation of the induction motor is one rotation than at least a predetermined reactance value Diagnostic device.
The method of claim 1,

And the eccentric diagnosis unit diagnoses that the void of the induction motor is a static or dynamic eccentricity when the calculated reactance value is constant while the rotor rotates for one revolution.
The method of claim 1,

And the eccentric diagnosis unit diagnoses that the void of the induction motor is a complex eccentricity when the calculated reactance value changes by one cycle while the rotor rotates for one revolution.
The method of claim 1,

The rotor of the induction motor further comprises a conductor bar defect diagnosis unit for diagnosing that the rotor conductor bar is defective when the calculated reactance value changes at a cycle of the number of poles of the rotor during one rotation of the rotor. Fault diagnosis device.
The method of claim 1,

The apparatus for diagnosing rotor defects further comprises a voltage measuring unit measuring the AC voltage.
The method of claim 1,

Rotor defect diagnosis apparatus further comprises a rotating unit for rotating the rotor.
Measuring an alternating current supplied to the induction motor;

Calculating a reactance of the induction motor by using the AC voltage supplied to the induction motor and the measured AC current; And

And an eccentric diagnosis step of diagnosing that the induction motor gap is eccentric when the reactance value calculated while the rotor of the induction motor is rotated for one rotation is greater than a preset reactance value in at least some sections. Fault diagnosis method.
The method of claim 7, wherein

And diagnosing that the void of the induction motor is a static or dynamic eccentricity when the calculated reactance value is constant during one rotation of the rotor.
The method of claim 7, wherein

And diagnosing that the void of the induction motor is a complex eccentricity when the calculated reactance value changes by one cycle while the rotor is rotated once.
The method of claim 6,

And the rotor conductor bar is diagnosed as defective if the calculated reactance value changes in a cycle of the number of poles of the rotor during one revolution of the rotor.
And measuring the AC voltage.
A medium having a computer readable program recorded thereon for executing the method of claim 7.