• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    method to identify a fault in an electrical machine, monitoring system to identify a fault in an electrical machine and induction motor. to identify a fault in an electrical machine, vibration is measured in a plurality of radial directions of the stator (30). Based on the vibration measurements, a vibration frequency and a vibration mode format at that frequency are determined. vibration characteristics in terms of both vibration frequency and mode shape are used to identify an electrical machine failure condition.
    公开号:BR112013033553B1
    申请号:R112013033553-0
    申请日:2012-06-28
    公开日:2020-10-06
    发明作者:Pedro Rodriguez
    申请人:Abb Schweiz Ag；
    IPC主号:
    专利说明:

    TECHNICAL FIELD
    [0001] The present invention relates to a method and a monitoring system to identify a fault in an electrical machine, as well as an induction motor equipped with such a system. BACKGROUND OF THE TECHNIQUE
    [0002] Like any device in the art, electric machines can suffer from different types of failures, both electrical and mechanical. Since electric machines have a rotor-like moving element, many of the most common failure conditions cause machine vibrations. Different failure conditions are known to cause different types of vibrations. In turn, it is concluded that, knowing what type of vibration a certain fault condition causes, it is possible to detect the failure by monitoring the machine's vibration characteristics.
    [0003] Vibration monitoring has been conventionally used to detect mechanical failures in electrical machines. This monitoring method has been successful, for example, to detect bearing defects. However, it was not possible to detect electrical failures in a satisfactory manner by means of vibration monitoring, even if attempts were made to do so. For example, the reference act "An analytical approach to solving motor vibration problems" by Finley, W. R. et al. 1999 (D1) reveals a table (Table I) with indicators to identify both mechanical and electrical failures in an induction motor. The main failure indicators are the vibration frequencies and their side bands. It requires a lot of empirical interpretation to determine the root source of the vibration with the help of D1 and it is not possible to distinguish between different failure conditions in a satisfactory way. SUMMARY OF THE INVENTION
    [0004] An objective of the invention is to provide a method that allows an improved identification of a fault in an electrical machine.
    [0005] An additional objective of the invention is to provide a monitoring system that allows an improved identification of a fault in an electrical machine.
    [0006] The invention is based on the perception that a mode shape of a vibration at a particular frequency is an important indicator for many failure conditions. In the prior art, a certain vibration mode shape was not considered to be a failure indicator. For example, with the measurement definition revealed in D1, Figure 15 it is not even possible to determine the mode formats of the different vibration frequencies.
    [0007] According to a first aspect of the invention, a method is provided to identify a failure in an electrical machine that has a rotor and a stator. The method comprises the steps of: performing a first vibration measurement in a first radial direction of the stator; perform a second vibration measurement in a second radial direction of the stator; determining, based on at least one of the first vibration measurement and the second vibration measurement, a first vibration frequency; determine, based on the first vibration measurement and the second vibration measurement, a vibration mode format on the first vibration frequency; and use a combination of the first vibration frequency and the mode shape to identify an electrical machine failure condition.
    [0008] Using a combination of the first vibration frequency and the shape as a fault indicator, a more reliable identification of a fault condition is achieved.
    [0009] According to an embodiment of the invention, the method comprises the steps of: performing a plurality of vibration measurements in at least three different radial directions of the stator, such as at least four, at least six or at least eight different directions stator radials; determining, based on at least one of the plurality of vibration measurements, a first vibration frequency; and determining, based on the plurality of vibration measurements, a vibration mode format at the first vibration frequency. The more measurements there are in different radial directions of the stator, the greater the number of modes that can be detected and the better the reliability of this detection.
    [00010] According to an embodiment of the invention, the fault condition is identified when a vibration amplitude at the first vibration frequency exceeds a predetermined threshold value. It is reasonable to determine a threshold value for the vibration amplitude since a very small vibration amplitude is not harmful to the machine and a false diagnosis of a fault condition can thus be avoided.
    [00011] According to an embodiment of the invention, the method comprises the steps of: performing vibration measurements with a first load and a second load of the machine; determining a difference in vibration amplitudes with a first charge and a second charge at the first vibration frequency; and use a combination of the first vibration frequency, the shape format and the difference in vibration amplitudes to identify a fault condition of the electrical machine. Using the difference in vibration amplitudes as an additional fault indicator, differences between additional fault conditions are allowed and more reliable identification of a fault condition is achieved.
    [00012] According to an embodiment of the invention, the fault condition is one of the following: a broken rotor bar, dynamic eccentricity, static eccentricity, short circuit between loop, short circuit between coil. The present method is particularly suitable for identifying the fault conditions listed as clear correlations between the vibration characteristics and the fault conditions that can be encountered.
    [00013] According to an embodiment of the invention, the method comprises the step of: determining, on the basis that the first frequency of vibration f and the shape of m meet one of the following conditions: f = n ■ frou f = n - fr ± 2-s -fse m = n, where n = (1,3,5, ...), fr = frequency of rotation of the motor, s = slip of the rotor and 4 = frequency of feeding, in that a rotor bar is broken. It was found that the mentioned conditions are a reliable failure indicator for a broken rotor bar.
    [00014] According to an embodiment of the invention, the method comprises the step of: determining, on the basis that the first frequency of vibration f and the mode of m form fulfill one of the following conditions: f = 2-fre m = 2 ; f = 2-fs-fre m = 2-p - r, f = 2 ■ fs + fre m = 2-p + 1, where fr = frequency of motor rotation, 4 = supply frequency and p = number of pairs of stator pole, that the rotor is dynamically eccentric. It was found that the mentioned conditions are a reliable failure indicator for a dynamic rotor eccentricity.
    [00015] According to an embodiment of the invention, the method comprises the step of: determining, on the basis that the first frequency of vibration f and the shape of the shape meets the following conditions: f = 2 ■ f3e m = 2 ■ p + 1 or m = 2 • p- 1, where 4 = frequency of supply and p = number of stator pole pairs, where the rotor is statically eccentric. It was found that the mentioned conditions are a reliable failure indicator for a static rotor eccentricity.
    [00016] According to an embodiment of the invention, the method comprises the step of: determining, on the basis that the first frequency of vibration f and the shape format meet one of the following conditions: f = 2 -k -fse m = (2,4,6, ...), where k = (1,2,3, ...) and fs = supply frequency, in which the stator coils have both a short circuit between turn and one short-circuit between coils. It was found that the mentioned conditions are a reliable failure indicator for both a short circuit between turns and a short circuit between coils.
    [00017] According to an embodiment of the invention, the method comprises the steps of: performing vibration measurements with a first load and a second load of the machine, where the first load is less than the second load; determining a difference in vibration amplitudes with a first charge and a second charge at the first vibration frequency; and determining, on the basis that the amplitude of vibration increases with an increasing load and that the increase in the amplitude of vibration exceeds a predetermined threshold value, that the stator coils have a short circuit between turns. An increasing amplitude of vibration with an increasing load has been found to be a reliable failure indicator for distinguishing between a short circuit between coil and a short circuit between coil.
    [00018] According to an embodiment of the invention, the electric machine is an induction motor. The present method is particularly suitable for identifying fault conditions in induction motors where clean correlations between vibration characteristics and fault conditions can be found.
    [00019] According to a second aspect of the invention, a monitoring system is provided to identify a failure in an electrical machine that has a rotor and a stator. The monitoring system comprises a first sensor arranged to measure vibration in a first radial direction of the stator and a second sensor arranged to measure vibration in a second radial direction of the stator. A processor receives measurement signals from the first sensor and the second sensor. The processor comprises a first algorithm for detecting from the measurement signals a first vibration frequency and a vibration mode format at the first vibration frequency. The processor further comprises a second algorithm to identify an electrical machine failure condition from the combination of the first vibration frequency and the mode shape. With a monitoring system capable of using a combination of the first vibration frequency and the shape of the mode as a fault indicator, more reliable identification of a fault condition is achieved.
    [00020] According to an embodiment of the invention, the monitoring system comprises a plurality of sensors arranged to measure vibration in at least three radial directions of the stator, such as at least four, at least six or at least eight different radial directions of the stator and the processor receives measurement signals from the plurality of sensors. The high number of measurements in different radial directions of the stator allows high numbers of modes to be detected with good reliability.
    [00021] According to an embodiment of the invention, the sensors are accelerometers. Accelerometers are preferred vibration sensors because of their small size and low price.
    [00022] In accordance with an embodiment of the invention, an induction motor is provided which comprises a monitoring system, as described above in this document. BRIEF DESCRIPTION OF THE DRAWINGS
    [00023] The invention will be explained in more detail with reference to the accompanying drawings, in which Figure 1 shows a physical installation, according to an embodiment of the invention, Figure 2 shows the first four formats of vibration mode, and Figure 3 shows a table that lists correlations between certain vibration characteristics and certain failure conditions. DESCRIPTION OF THE PREFERRED EMBODIMENTS
    [00024] With reference to Figure 1, a measuring installation 10 for measuring vibrations in an electrical machine is shown. There are eight accelerometers 20 evenly distributed around the circumference of a stator 30. A large number of accelerometers 20 allows the detection of high number modes, so the more accelerometers 20 the better the fault identification ability the measuring installation 10 has. However, since interests are focused on a low number of modes (from 1 to 4), eight accelerometers 20 or even less may be enough. The accelerometers 20 are connected by measuring cables 40 to an amplifier 50 and also to an A / D converter 60. The accelerometers 20 give the vibration information in time, that is, the acceleration as a function of time. In addition, the angular position of each accelerometer 20 is known. The measurement results are finally stored digitally in a computer memory 70 for additional processing.
    [00025] A processor 80 receives and processes the measurement results from computer memory 70. The processor 80 comprises a first algorithm 90 to detect from the measurement signals a first vibration frequency and a vibration mode format at the first frequency of vibration. The first algorithm 90 comprises a two-dimensional Fourier transformation explained in more detail below. Processor 80 further comprises a second algorithm 100 for identifying an electrical machine failure condition of the combination of the first vibration frequency and the mode format.
    [00026] The Fourier transformation of two dimensions, in relation to the position (defined by the location sensor) and in relation to time, is applied to the measurement results with the purpose of revealing the formats and the frequencies of the vibrations. The equation for the Fourier transformation can be written as:
    where a = measured acceleration, θ = angular position along the perimeter of the stator, t = time, A = calculated acceleration coefficients and ω = feed frequency, and where m determines the shape format and n determines the frequency of vibration . It should be understood that detecting high indefinite number modes is not possible since theoretically an indefinite number of accelerometers 20 may be required. In practice, however, only the least numbered modes are of interest and the number of accelerometers 20 required is respectively low. It is assumed that a knowledgeable person has the ability to determine the number of accelerometers 20 required to detect a certain shape format. Eight accelerometers 20 are considered sufficient to detect the mode formats up to the mode number four. The first four formats of mode 1 to 4 are illustrated in Figure 2.
    [00027] Summarizing the detailed description so far, the measurement installation 10 revealed along with the well-known mathematical theory allows not only the detection of vibration frequencies, but also the detection of vibration formats, the so-called mode formats. These mode formats are also used to identify fault conditions in the electrical machine.
    [00028] Figure 3 shows a table in which characteristics of certain vibrations in terms of vibration frequencies and mode formats are listed for certain failure conditions. For example, detecting a vibration at the frequency f = 2-fsp may not allow a distinction between the "static eccentricity" and "short circuit between coil" / "short circuit between coil" fault conditions since all three fault conditions exhibit vibration at that frequency. After determining the shape of the vibration mode, however, such a distinction may be possible since the shape of the vibration caused by "static eccentricity" is different from that caused by "short circuit between loop" or "short circuit between coil" .
    [00029] The distinction between "short circuit between coil" and "short circuit between coils" can also be made by monitoring the behavior of the machine's vibration amplitude under load. That is, it was found that the amplitude of vibration increases proportionally with an increasing load in the case of "short circuit between turns". Consequently, by measuring the vibration amplitude with two different loads, the distinction between the two failure conditions can be made. If the amplitude of vibration increases by a certain predetermined threshold value, the fault condition will be identified as "short circuit between turns". Otherwise, the fault condition will be identified as "short circuit between coil".
    [00030] Descriptions of the failure conditions listed in the table in Figure 3 are given below:
    [00031] Broken bar - A conductive bar that runs on a rotor periphery in an axial direction is broken.
    [00032] Dynamic eccentricity - The rotor periphery is eccentric in relation to the geometric axis of rotation. The eccentricity varies when the rotor is turning.
    [00033] Static eccentricity - The rotor periphery is eccentric in relation to the geometric axis of rotation. The eccentricity remains constant even when the rotor is turning.
    [00034] Short circuit between turns - A stator coil short-circuits between two turns within one and the same stator coil.
    [00035] Short-circuit between coil - Two stator coils are short-circuited between each other.
    [00036] The correlations between vibration characteristics and failure conditions listed in the table in Figure 3 should be considered as examples of such correlations hitherto revealed by the inventor. It must be respected that other correlations between the vibrations and failure conditions listed may exist and that vibrations and failure conditions in addition to those listed certainly exist with many correlations between them. The revealed method can therefore be used to identify the failure conditions listed using an alternative combination of frequency and vibration mode format and additional failure conditions can be identified using the frequency and format combinations. so listed or alternative.
    权利要求:
    Claims (15)
    [0001]
    1. Method to identify a failure in an electrical machine that has a rotor and a stator (30), characterized by the fact that it comprises the steps of: performing a first vibration measurement in vibrations of the stator in a first radial direction of the stator ( 30); perform a second vibration measurement in vibrations of the stator in a second radial direction of the stator (30); determining, based on at least one of the first vibration measurement and the second vibration measurement, a first vibration frequency; determine, based on the first vibration measurement and the second vibration measurement, a vibration mode format on the first vibration frequency; and use a combination of the first vibration frequency and the mode format to identify an electrical machine failure condition.
    [0002]
    2. Method, according to claim 1, characterized by the fact that it comprises the steps of: performing a plurality of vibration measurements in at least three different radial directions of the stator (30), such as at least four, at least six or at least eight different radial directions of the stator (30); determining, based on at least one of the plurality of vibration measurements, a first vibration frequency; and determining, based on the plurality of vibration measurements, a vibration mode format at the first vibration frequency.
    [0003]
    3. Method according to claim 1 or 2, characterized by the fact that the fault condition is identified when a vibration amplitude at the first vibration frequency exceeds a predetermined threshold value.
    [0004]
    Method according to any one of claims 1 to 3, characterized by the fact that it comprises the steps of: performing vibration measurements with a first load and a second load of the machine; determining a difference in vibration amplitudes with a first charge and a second charge at the first vibration frequency; and use a combination of the first vibration frequency, the shape format and the difference in vibration amplitudes to identify a fault condition of the electrical machine.
    [0005]
    5. Method according to any one of claims 1 to 4, characterized by the fact that the failure condition is one of the following: a broken rotor bar, dynamic eccentricity, static eccentricity, short circuit between turn, short circuit circuit between coil.
    [0006]
    6. Method according to any one of claims 1 to 5, characterized by the fact that the method comprises the step of: determining, on the basis that the first vibration frequency of the form shape meets one of the following conditions: f = n- frou f = n ■ fr ± 2 ■ s ■ fse m = n, where n = (1,3,5, ...), fr = frequency of motor rotation, s = rotor slip and 4 = supply frequency, where a rotor bar is broken.
    [0007]
    Method according to any one of claims 1 to 6, characterized by the fact that it comprises the step of: determining, on the basis that the first frequency of vibration f and the shape meet one of the following conditions: f = 2-fre m = 2; f = 2-fs-fre m = 2-p-i; f = 2 -fs + fre m = 2-p + 1, where fr = motor rotation frequency, 4 = supply frequency and p = number of stator pole pairs, that the rotor is dynamically eccentric.
    [0008]
    Method according to any one of claims 1 to 7, characterized by the fact that it comprises the step of: determining, on the basis that the first vibration frequency f and the shape format meet the following conditions: f = 2- fse m = 2 ■ p + 1 or m = 2 ■ p - 1, where fs = supply frequency and p = number of stator pole pairs, that the rotor is statically eccentric.
    [0009]
    9. Method according to any one of claims 1 to 8, characterized by the fact that the method comprises the step of: determining, on the basis that the first frequency of vibration f the shape meets one of the following conditions: f = 2 ■ k ■ fse m = (2,4,6, ...), where k = (1,2,3, ...) and fs = supply frequency, where the stator coils have both a short circuit between coil and a short circuit between coil.
    [0010]
    10. Method, according to claim 9, characterized by the fact that the method comprises the steps of: performing vibration measurements with a first load and a second load of the machine, where the first load is less than the second load ; determining a difference in vibration amplitudes with a first charge and a second charge at the first vibration frequency; and determining, on the basis that the amplitude of vibration increases with an increasing load and that the increase in the amplitude of vibration exceeds a predetermined threshold value, in which the stator coils have a short circuit between turns.
    [0011]
    11. Method according to any one of claims 1 to 10, characterized by the fact that the electric machine is an induction motor.
    [0012]
    12. Monitoring system to identify a failure in an electrical machine that has a rotor and a stator (30) characterized by the fact that it comprises: a first sensor arranged to measure vibrations of the stator in a first radial direction of the stator (30), a second sensor arranged to measure vibrations of the stator in a second radial direction of the stator (30), a processor (80) that receives measurement signals from the first sensor and the second sensor, the processor (80) comprising a first algorithm (90) to detect from the measurement signals a first vibration frequency and a vibration mode format on the first vibration frequency and the processor (80) further comprises a second algorithm (100) to identify a machine failure condition electrical from the combination of the first vibration frequency and the mode shape.
    [0013]
    13. Monitoring system according to claim 12, characterized by the fact that the monitoring system comprises a plurality of sensors arranged to measure vibration in at least three radial directions of the stator (30), such as in at least four , in at least six or at least eight different radial directions of the stator (30) and the processor (80) receives measurement signals from the plurality of sensors.
    [0014]
    14. Monitoring system, according to claim 12 or 13, characterized by the fact that the sensors are accelerometers (20).
    [0015]
    15. Induction motor characterized by the fact that it comprises a monitoring system, as defined in any one of claims 12 to 14. v
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    法律状态:
    2018-12-11| B06F| Objections, documents and/or translations needed after an examination request according art. 34 industrial property law|
    2019-12-03| B06U| Preliminary requirement: requests with searches performed by other patent offices: suspension of the patent application procedure|
    2020-05-12| B09A| Decision: intention to grant|
    2020-06-23| B25A| Requested transfer of rights approved|Owner name: ABB SCHWEIZ AG (CH) |
    2020-06-30| B25G| Requested change of headquarter approved|Owner name: ABB SCHWEIZ AG (CH) |
    2020-10-06| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 28/06/2012, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    EP11171814.4|2011-06-29|
    EP11171814.4A|EP2541217B1|2011-06-29|2011-06-29|A method for identifying a fault in an electrical machine|
    PCT/EP2012/062526|WO2013000984A1|2011-06-29|2012-06-28|A method for identifying a fault in an electrical machine|
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