KR101046328B1 - Three phase ac motor stator core state diagnosis apparatus, method, and a medium having recorded thereon a computer readable program for executing the method - Google Patents

Abstract

Disclosed are a three-phase AC motor stator core diagnostic apparatus, a method, and a medium having recorded thereon a computer readable program for executing the method. The three-phase AC motor stator core state diagnosis device includes a magnetic flux generator, an input power measurement unit, and a core state diagnosis unit. The magnetic flux generator generates a plurality of magnetic fluxes passing through the rotary shaft on a plane perpendicular to the rotor rotation axis of the motor when the three-phase AC motor stops, and the input power measuring unit includes a plurality of magnetic fluxes corresponding to the plurality of directions in which the magnetic flux is generated. The input power is measured, and the core state diagnosis unit diagnoses the motor stator core state by using a corresponding relationship between the magnetic flux generation direction and the measured input power. With such a configuration, it is possible to easily diagnose the core state of the motor stator without disassembling the motor or operating under a special environment.

Motor, stator, core, diagnostic

Description

Apparatus and method for diagnosing stator state of three phase AC motors, and a medium having computer readable program for executing the method }

The present invention relates to an electrical equipment diagnostic apparatus and method, and more particularly, to an apparatus and method for diagnosing a stator core state of a three-phase AC motor.

Electric motors, which convert electrical energy into mechanical energy, are essential equipments that are used in various fields from home appliances to industrial and power generation. As technology advances, users of motors are demanding higher levels of performance, efficiency, reliability, and stability.

In order to accommodate this demand, stable operation of the electrical equipment system as shown in FIG. 1 and prevention of accidental problems are essential, and for this, development of the electrical equipment diagnosis field is required. 1 is a schematic block diagram of an energy conversion system.

If there is a problem in the condition of the electrical installation, the economic loss due to the failure of the electricity supply, as well as a decrease in the reliability of the quality and stability of the electricity. In order to prevent such a problem in advance, it is required to diagnose the electrical equipment, especially the development of reliable condition diagnosis of the electric motor.

The stator core of the motor enables the flow of magnetic flux in the motor and is a laminated structure for minimizing losses as a part that mechanically supports the motor. When the core is exposed to excessive heat and mechanical stress, the properties of the material change, increasing hysteresis losses, generating heat and reducing the efficiency of the motor.

In addition, as shown in FIG. 2, if the core surface is damaged for various reasons and short-circuited, eddy currents flow to increase losses and generate heat. FIG. 2 is a schematic diagram illustrating a short circuit of lamination, formation of a fault eddy current, and a method of performing a core loss test.

As such, if the core is abnormal, the core may be damaged due to heat, which may cause a failure of the motor. As such, the failure of the motor core degrades the reliability, safety, and efficiency of the motor. Therefore, it is very important to regularly diagnose the state of the core to prevent an accident.

Currently, the following methods are used to diagnose the motor stator core.

1) Core ring test (Loop test): After separating the rotor from the motor, apply rated flux to the stator core. IR thermography is then used to look at the temperature distribution of the inner surface of the stator core to see if there is a temperature increase due to a fault.

This method has the disadvantage of wasting time and labor in that the rotor must be separated and requiring a special detector.

2) Low energy core test (EL CID): Separate the rotor from the motor and apply 3-4% flux to the core. Then use a leakage flux sensor to check all slots for short circuit faults.

Like this method, this method also has the disadvantage that the rotor must be separated and special equipment is required. Method 1) -2) is mainly used for high voltage motors or generators.

3) Core loss test: After removing the rotor from the motor, a flux close to the rating of 1.32 [T] is applied (see Fig. 2). As shown in FIG. 2, a voltage is applied to generate 1.32 [T], and the current value is measured to obtain a power value. If there is a fault in the stator core, power loss increases, and the condition is diagnosed by comparing with the power value when the motor is normal.

This method, like other methods, has a large loss of time and manpower in that the rotor must be separated, which makes frequent state diagnosis impossible.

4) Core loss separation from the no load test (IEEE STD 112): This method operates the motor at no load without disconnecting the motor, and then diagnoses the condition by measuring the power value at that time by switching to various voltage levels. (See FIG. 3).

 As shown in FIG. 3, in the no load state, only stator resistance loss, friction loss, wind loss, and core loss exist. 3 is a graph of the correlation between load and loss of induction equipment.

By measuring the power value at several voltage levels, the friction loss and wind loss are separated, and the stator resistance value is compensated for to compensate for the stator resistance loss, and only the core loss value is left to diagnose the condition.

This method requires a specific environment to change the voltage value under no load condition, which is cumbersome to use in actual field and frequent diagnosis is difficult.

Disclosure of Invention The present invention has been made to solve the above-described problems, and an object thereof is to provide an apparatus and method for easily diagnosing the core state of a motor stator without disassembling the motor or operating under a special environment. .

In order to achieve the above object, the three-phase AC motor stator core state diagnosis apparatus according to the present invention includes a magnetic flux generating unit, an input power measuring unit, and a core state diagnosis unit.

The magnetic flux generator generates a plurality of magnetic fluxes passing through the rotary shaft on a plane perpendicular to the rotor rotation axis of the motor when the three-phase AC motor is stopped, and the input power measuring unit includes a plurality of inputs corresponding to the plurality of directions in which the magnetic flux is generated. The power state is measured, and the core state diagnosis unit performs diagnosis of the motor stator core state by using a corresponding relationship between a magnetic flux generation direction and the measured input power.

With such a configuration, it is possible to easily diagnose the core state of the motor stator without disassembling the motor or operating under a special environment.

The magnetic flux generator may generate alternating magnetic flux. By generating the alternating magnetic flux, it is possible to perform precise diagnosis by preventing the rotation of the rotor despite the occurrence of the magnetic flux to the rotor.

The core state diagnosis unit may diagnose that there is an abnormality in the stator core portion located in a direction 90 degrees apart from the magnetic flux generation direction corresponding to the maximum value of the measured input power and the electrical angle. Such a configuration makes it possible to grasp not only the abnormality of the stator core but also the occurrence position of the abnormality.

According to the present invention, it is possible to easily diagnose the state of the core of the three-phase AC motor stator easily without disassembling the motor or operating in a special environment.

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

4 is a schematic block diagram of an embodiment of a three-phase AC motor stator core state diagnosis apparatus according to the present invention.

The three-phase AC motor stator core state diagnosis apparatus 100 includes a magnetic flux generating unit 110, an input power measuring unit 120, and a core state diagnosis unit 130.

When the three-phase AC motor stops, the magnetic flux generating unit 110 generates magnetic flux in a plurality of directions passing through the rotating shaft on a plane perpendicular to the rotating shaft of the motor. At this time, the magnetic flux generating unit 110 may generate alternating magnetic flux. In this case, the magnetic flux generating unit 110 generates alternating magnetic flux, thereby preventing the rotation of the rotor in spite of the occurrence of the magnetic flux to the rotor, thereby performing precise diagnosis.

The input power measuring unit 120 measures a plurality of input powers corresponding to a plurality of directions in which magnetic flux is generated.

The core state diagnosis unit 130 performs diagnosis of the motor stator core state by using a corresponding relationship between a magnetic flux generation direction and the measured input power. In this case, the core state diagnosis unit 130 may diagnose that there is an abnormality in the stator core portion positioned in a direction 90 degrees apart from the magnetic flux generation direction corresponding to the measured maximum value of the input power and the electrical angle. In this case, the core state diagnosis unit 130 may grasp not only the abnormality of the stator core but also the occurrence position of the abnormality in the stator core.

With such a configuration, it is possible to easily diagnose the core state of the motor stator without disassembling the motor or operating under a special environment.

5 is a diagram illustrating an example in which the stator core state diagnosis apparatus of FIG. 1 is applied to an inverter driving induction motor.

The key idea of the new proposed method is to use an inverter to diagnose the condition of the stator core when the motor is not running. It is a method to control the inverter so that the flux of high frequency AC is generated at a fixed position by using DSP and to check and diagnose the power loss at each position.

5 well represents a method for diagnosing the condition of a new stator core. As shown in FIG. 5, an AC magnetic field is applied using an inverter to excite the core without induction of torque. The switch of the inverter is operated so that the voltage vector, i.e. the magnetic flux vector, intersects θ and θ + π to form an alternating magnetic field. When the magnetic flux vector is applied in a fixed direction, the input power at each position is measured using voltage and current.

The flux vector induces a voltage in the rotor rods that causes current in the rotor, but the motor does not rotate because torque is not induced. When the flux vector is applied in this way, the input power (= power loss) is made up of the resistance loss (Ps & Pr) and core loss (Pcs & Pcr) of the stator and rotor.

Pin = Ps + Pr + Pc.s + Pc.r = vas ias + vbs ibs + vcs ics

As can be seen from the above equation, the input power is equal to the sum of each power loss above, so it is possible to observe the increase in core loss caused by the core problem by measuring the input power. Finally, in the newly proposed method, Pin is calculated as a function of, and correlation with Pin is observed to find core problems that lead to an increase in hysteresis loss and eddy current loss.

In order to analyze the phenomenon that may occur when there is a problem in the stator core in the correlation with the pin, the cross section of the induction motor should be examined (see FIG. 6). FIG. 6 is a diagram showing a magnetic flux vector position and a core fault position in the cross section of the stator core. FIG.

 When generating a magnetic flux vector that crosses the electric angle by 180 degrees, the maximum of the magnetic field in the air gap of the motor and the maximum of the magnetic field in the back of the core show a difference of 90 degrees in the electric angle.

In other words, the maximum of the magnetic field of the void is located in the void in the same direction as the generated flux vector, while the maximum at the back of the core is located 90 degrees away from the magnetic flux vector. And the magnetic flux on the backside of these cores induces eddy currents that cause increased power loss.

If the direction of the generated flux vector is toward the fault position, the pin has the minimum value because the magnetic flux behind the core that induces the fault current is minimal. Also, if the flux vector is oriented 90 degrees away from the fault, the pin will have a maximum because the magnetic flux behind the core that induces the fault current is maximum.

In the case of a normal motor, the pin is a symmetrical circular structure, so it is independent of the position of the flux vector and always constant. If a problem occurs in the lamination of the core, the pin will increase, and the amount of change of the pin is determined by the position of the relative magnetic flux vector θ relative to the fault (θf). If the fault (θf) of the core is located near 210 degrees as shown in FIG. 7, the maximum value of the pin will appear at a 120 degree position 90 degrees away from the fault (θf) (see FIG. 7).

7 is a graph of input power, Pin, expressed as a function of the electrical angle of the flux vector for a motor with a normal stator core and a faulty stator core.

This diagnostic method can not only find local problems in the stator core but also locate faults by observing the distribution of losses. Since the spatial distribution of losses can be easily observed with the eye, it is possible to examine local problems of the core state with high sensitivity. As a result, the state of the stator core can be diagnosed by comparing the distribution values of the pins having a constant distribution of the normal motors with the distribution values of the pins of the problematic motors.

8 is a schematic flowchart of an embodiment of a three-phase motor stator core diagnostic method according to the present invention.

First, when the three-phase AC motor is stopped, the magnetic flux in a plurality of directions passing through the rotating shaft is generated on a plane perpendicular to the rotor rotating shaft of the motor (S110).

At this time, the generation of the magnetic flux may be an alternating magnetic flux. As described above, when the alternating magnetic flux is generated, it is possible to perform precise diagnosis by preventing the rotation of the rotor despite the occurrence of the magnetic flux to the rotor.

Next, a plurality of input powers corresponding to a plurality of directions in which magnetic flux is generated are measured (S120).

Finally, the diagnosis of the motor stator core state is performed using the corresponding relationship between the magnetic flux generation direction and the measured input power (S130). At this time, it may be diagnosed that there is an abnormality in the stator core portion located in a direction spaced 90 degrees from the magnetic flux generating direction corresponding to the maximum value of the measured input power. In this case, it is possible to grasp not only the abnormality of the stator core but also the occurrence position of the abnormality in the stator core.

With such a configuration, it is possible to easily diagnose the core state of the motor stator without disassembling the motor or operating under a special environment.

The stator core of the induction motor is laminated to minimize hysteresis loss and eddy current loss for efficient operation. As a result, lamination of the stator core serves to minimize core loss. Stator core loss at rated load accounts for approximately 20% of the total power loss (see Figure 3).

This core loss will increase for a number of reasons, eventually destroying the lamination. Overheating of the stator core, damage during manufacturing and repair, and friction caused by vibration and mechanical contact between the rotor and the stator can cause short circuits between the laminations, resulting in large eddy currents.

In particular, when driving the motor through a PWM inverter, stator cores and laminations are exposed to high thermal and electrical stresses. High frequency voltage and current harmonics due to PWM switching create larger eddy currents in the stator core and increase core loss.

This increase in eddy current will result in greater core loss and will greatly reduce the efficiency of the motor and may even destroy the insulation of the stator windings. After all, the characteristic of the motor that can detect it before it is destroyed or damaged is whether the core loss is increased.

The increase in core loss is a symptom until the motor breaks down and is destroyed. Therefore, it is very important to monitor the increase of core loss for the reliability and efficiency of the motor. Has been required.

As mentioned above, in the conventional method, 1) -2) is economical only in a high voltage motor or a generator, so it is not used for an inverter driven motor, 3) has the disadvantage of disassembling the motor, and 4) the load of the motor. There is a disadvantage that a separate voltage source is required. 3) -4) All methods are impossible of remote diagnosis in the motor, and it is a method of diagnosing the overall average state, not local abnormality.

In the present invention, a simple method for diagnosing the state of a stator core based on power measurement for an inverter driven induction motor is proposed. The main concept is to use an inverter to generate a high frequency alternating flux vector to the motor when the motor is stopped. Power loss according to the position of the magnetic flux vector helps to find out the problem of the stator core that causes the core loss to increase in advance, which can be very helpful in preventing the motor failure and increasing the reliability.

In addition, since the diagnosis method proposed in the present invention can diagnose the state of the stator core whenever the motor stops, the diagnosis of the state of the stator core is much more frequent than the conventional off-line diagnosis method performed every 3-6 years. It is possible. The advantage of such frequent diagnostics is that it can be detected before the motor damage, such as breakdown of the stator winding due to faults, and before breakdown, which greatly improves the reliability and efficiency of the motor.

In addition, this diagnosis method can frequently diagnose the state of the stator core without disassembly and operation of the motor, and it can be said that the convenience and efficiency of diagnosis and repair have been greatly improved compared to the existing technology. It also makes it possible to plan the diagnosis and repair of the motor in a more efficient way and to reduce the cost of maintenance as no special equipment is required. In addition, remote diagnosis can be done automatically whenever the motor is stopped, and the inverter does not require any hardware. By looking at the power distribution, the local can also observe the core abnormally.

The existing methods described in the background have several disadvantages, such as the need for special equipment, the disassembly of the motor, and the operation of the motor under certain conditions. These drawbacks reduce the frequency of diagnosis and the convenience of diagnostic methods, and further doubt the efficiency and reliability of the motor. The diagnostic method of the present invention includes the advantage of improving the disadvantages of the existing technologies and further obtaining other information such as the location of the fault, thus playing a big role in increasing the reliability of the motor and reducing the large accidents caused by the failure. Expect to be able.

What's new in this method is a method of automatically diagnosing remotely using an inverter whenever the motor stops operating. By applying a high frequency alternating magnetic field to multiple locations and observing the distribution of power losses, it is possible to sensitively observe local core abnormalities.

Although the present invention has been described in terms of some preferred embodiments, the scope of the present invention should not be limited thereby, but should be construed as modifications or improvements of the embodiments supported by the claims.

1 is a schematic block diagram of an energy conversion system.

FIG. 2 is a schematic diagram illustrating a short circuit of lamination and formation of a faulty current, and a method of performing a core loss test. FIG.

3 is a correlation graph of the loss of load and induction equipment.

4 is a schematic block diagram of an embodiment of a three-phase AC motor stator core state diagnosis apparatus according to the present invention;

FIG. 5 is a diagram illustrating an example in which the stator core state diagnosis apparatus of FIG. 1 is applied to an inverter driven induction motor; FIG.

Fig. 6 shows the magnetic flux vector position and the core fault position in the cross section of the stator core;

7 is a graph of the input power as a function of the electrical angle of the flux vector for a motor with a normal stator core and a faulty stator core.

8 is a schematic flowchart of an embodiment of a three-phase motor stator core diagnostic method according to the present invention;

Claims (7)

A magnetic flux generator for generating magnetic flux in a plurality of directions passing through the rotary shaft on a plane perpendicular to the rotor rotary shaft of the motor when the three-phase AC motor is stopped; An input power measuring unit measuring a plurality of input powers corresponding to a plurality of directions in which the magnetic flux is generated; And And a core state diagnosis unit for diagnosing an abnormality in the motor stator core when the measured input power changes according to the magnetic flux generation direction. The method of claim 1, The magnetic flux generating unit generates alternating magnetic flux. 3. The method of claim 2, The core state diagnosis unit diagnoses that there is an error in a part of the stator core located in a direction 90 degrees apart from the magnetic flux generating direction corresponding to the maximum value of the measured input power and an electrical angle. Health diagnostic device. A magnetic flux generating step of generating magnetic flux in a plurality of directions passing through the rotating shaft on a plane perpendicular to the rotor rotating shaft of the motor when the three-phase AC motor is stopped; An input power measuring step of measuring a plurality of input powers corresponding to a plurality of directions in which the magnetic flux is generated; And And a core state diagnosis step of diagnosing an abnormality in the motor stator core when the measured input power changes according to the magnetic flux generation direction. 3. The method of claim 4, wherein The magnetic flux generating step is a three-phase AC motor stator core state diagnostic method, characterized in that for generating alternating magnetic flux. The method of claim 5, The core state diagnosis unit diagnoses that there is an error in a part of the stator core located in a direction separated from the magnetic flux generating direction corresponding to the maximum value of the input power by 90 degrees with an electric angle. How to diagnose the condition. A medium having a computer readable program recorded thereon for executing the method of claim 4.

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