Device and method for detecting out-of-roundness of rotor magnetic pole of synchronous generator

Abstract

The invention discloses a synchronous generator rotor magnetic pole out-of-roundness detection device and method, and belongs to the technical field of synchronous generator fault diagnosis. The device comprises a U-shaped iron core, an enameled coil, a lead and a data acquisition device. The method comprises the steps that a U-shaped iron core is tightly attached to the outer surface of a stator shell of the synchronous generator, and the U-shaped iron core is opposite to a stator iron core; recording an induced voltage signal output by the coil in real time by using a data acquisition device; performing harmonic analysis on the induced voltage signal to obtain a voltage spectrogram; the voltage spectrogram of the induced voltage signal correspondingly outputs fault characteristic harmonic waves; and diagnosing the out-of-roundness fault of the rotor magnetic pole of the synchronous generator to obtain a diagnosis result. The method has the capability of diagnosing the out-of-roundness fault of the rotor magnetic pole of the synchronous generator under the no-load and load working conditions, does not interfere with the normal operation of a unit, has high sensitivity, effectively avoids the safety risk caused by the installation of a sensor in the unit, and has higher reliability compared with a detection mode of measuring the external leakage magnetic flux of the unit. And the anti-interference performance is better.

Description

Technical Field

[0001] The invention relates to the technical field of synchronous generator fault diagnosis, and in particular to a synchronous generator rotor magnetic pole out-of-roundness detection device and method. Background Art

[0002] At present, in large salient pole synchronous generator sets, the original roundness of the rotor will change due to the errors generated during the assembly process and the stress it bears during operation. The rotor out-of-roundness beyond the design allowable range may cause serious consequences, including severe vibration of the stator core and operation failures such as the occurrence of bore scraping between the rotor and the stator, which seriously threatens the stable operation of the unit.

[0003] In recent years, domestic and foreign scholars have conducted a lot of research on rotor pole out-of-roundness faults and proposed relevant online detection methods. The vibration monitoring method uses the characteristics of low-frequency vibration of the stator core caused by rotor out-of-roundness faults to identify faults based on the even and fractional harmonics of the vibration signal, and the vibration mode of the stator core can reflect the out-of-round shape of the rotor pole. The air gap monitoring method uses flat capacitor sensors, optical fiber sensors, eddy current sensors, etc. to directly measure the air gap length, thereby reflecting the shape of the rotor outer edge.

[0004] The essence of the rotor pole out-of-roundness fault is that the uneven distribution of the air gap leads to the asymmetry of the magnetic field inside the generator. In terms of the external manifestation of the fault, it is highly similar to the rotor dynamic eccentricity and rotor inter-turn short-circuit fault, so the detection methods of the three can learn from each other. The flux monitoring method is a common method for monitoring the three types of faults. For example, an air gap flux sensor is installed on the surface of the stator teeth or the inner wall of the stator. By monitoring the changes in the flux waveform and the rate of change of magnetic flux density, the rotor dynamic eccentricity and the pole out-of-roundness fault can be judged. In addition, the U-shaped coil installed on the stator yoke and the through-screw inside the stator core are used as equivalent flux sensors. By analyzing the characteristics of the induced voltage waveform, the fault can be identified and located. The above methods are all classified as intrusive detection technologies.

[0005] It also has the ability to detect rotor out-of-roundness faults for the leakage magnetic field outside the motor. The detection coils and weak magnetic sensors arranged outside the casing capture the leakage magnetic flux, and use the k / p fractional harmonics in its spectrum as the fault judgment criterion. The installation of such sensors does not require direct intrusion into the motor, and is a non-intrusive detection technology.

[0006] At present, the mainstream fault diagnosis method relies on intrusive sensors to obtain magnetic flux information. Although such sensors have high detection accuracy, their installation difficulty and installation cost are also relatively high. However, since the peripheral leakage magnetic signal is relatively weak, direct measurement using non-contact non-invasive sensors is easily affected by external noise. Therefore, under the premise of ensuring the safe operation of the unit, it is particularly urgent and important to develop a non-invasive detection technology with strong anti-interference to achieve high-sensitivity monitoring of rotor out-of-roundness faults.

[0007] In the prior art, the invention patent "201910771543.6-A method for measuring the non-roundness of a turbine rotor" proposes a rotor non-roundness measurement method based on an air gap sensor. The invention uses the collected air gap length information, combined with the least squares circle method and statistical concepts, to obtain single and comprehensive non-roundness indicators. When the comprehensive non-roundness index is greater than the rotor roundness tolerance standard, the rotor roundness is judged to be unqualified. Pasting multiple air gap sensors on the inner wall of the stator core is an invasive detection method. Directly obtaining the air gap length, reflecting the rotor profile, and then obtaining the comprehensive non-roundness index is a non-electrical quantity criterion.

[0008] The invention patent "202310998923.X-A diagnostic method and system for asymmetric magnetic field faults of synchronous generators" proposes an online diagnostic method for rotor dynamic eccentricity, excessive magnetic pole out-of-roundness, short circuit between turns of magnetic pole coils, and two-point grounding faults of rotor windings. The invention installs a flux measurement coil on the back of the stator core of the synchronous generator, collects the induced voltage signal in real time during the operation of the motor, and uses Fourier transform to extract the fault characteristics. The leakage magnetic field signal is acquired by utilizing the natural shunt effect of the casing. Since the leakage magnetic signal itself is relatively weak, its acquisition and analysis process is easily affected by noise. Summary of the invention

[0009] The purpose of the present invention is to provide a synchronous generator rotor pole out-of-roundness detection device and method, which can solve the disadvantages of the prior art of high installation difficulty and high installation cost, and effectively improve the sensitivity and anti-interference of fault detection.

[0010] To achieve the above-mentioned purpose, the present invention provides a detection device for the out-of-roundness of the magnetic poles of the synchronous generator rotor, including a U-shaped iron core, which is arranged on the outer surface of the stator casing of the synchronous generator, and an enameled coil with a preset number of turns is wound around the U-shaped iron core to form a drainage magnetic field measurement device. When the synchronous generator set is running, the cross-section of the U-shaped iron core is made to fit the stator casing of the synchronous generator, and the induced voltage signal output by the coil is transmitted to a data acquisition device through a lead wire.

[0011] Preferably, the stator housing of the synchronous generator is made of a high magnetic permeability material;

[0012] The U-shaped core is made of high magnetic permeability material and is used to drain and amplify the leakage magnetic field of the casing.

[0013] A method for detecting the out-of-roundness of a synchronous generator rotor magnetic pole comprises the following steps:

[0014] S1, using a data acquisition device to record the induced voltage signal output by the coil in real time;

[0015] S2, performing harmonic analysis on the induced voltage signal to obtain a voltage spectrum diagram;

[0016] S3. When the synchronous generator has a rotor pole out-of-roundness fault, the voltage spectrum of the induced voltage signal corresponds to the output fault characteristic harmonic;

[0017] S4. According to the amplitude variation state of the fault characteristic harmonic, the synchronous generator rotor magnetic pole out-of-roundness fault is diagnosed to obtain a diagnosis result.

[0018] Preferably, in step S3, a stationary stator coordinate system is established, and at the initial moment, the stator axis coincides with the rotor axis. For a certain magnetic pole, the arc length spanned by the edge of its yoke relative to the initial position of the stator coordinate system is l, and the air gap permeance of the corresponding generator is expressed by the following formula:

[0019]

[0020] Among them, λ d , q are the air gap permeabilities of the motor d and q respectively, and ω is the electrical angular velocity;

[0021] When any magnetic pole of the rotor is convex or concave, the air gap permeance is expressed as:

[0022]

[0023] Among them, ω is the electrical angular velocity, τ is the pole pitch expressed in arc length, and p is the number of motor pole pairs;

[0024] When the rotor poles are irregularly concave and convex, the air gap flux density is expressed as:

[0025]

[0026] Where ω is the electrical angular velocity, τ is the pole pitch expressed in arc length, p is the number of motor pole pairs, F(t, l) is the air gap magnetomotive force, Δλ kis the amplitude of the fault permeability with a pole pair number of k. In a p-pole generator, when the rotor poles are irregularly concave and convex, i+k / p harmonics appear in the air gap magnetic field, where i is an odd number and k is a positive integer; when one side of the rotor is convex and the other side is concave, i+1 / p harmonics appear in the air gap magnetic field, where i is an odd number; when the rotor poles are j-times concave and convex at intervals, i±j / p harmonics appear in the air gap magnetic field, where p is an integer multiple of j and i is an odd number.

[0027] Preferably, in step S4, the magnetic flux flowing through the U-shaped core periodically alternates as the rotor rotates. When the motor has a rotor out-of-roundness fault, k / p harmonics are generated in the air gap magnetic field. The alternating frequency of the harmonic magnetic field in the U-shaped core is expressed as:

[0028]

[0029] Among them, f1 is the fundamental frequency, p is the number of motor pole pairs, and n is the motor speed.

[0030] Preferably, in step S4, the characteristic harmonic amplitude of the coil induced voltage is measured to be proportional to the degree of the rotor pole out-of-roundness fault.

[0031] Therefore, the present invention adopts a synchronous generator rotor magnetic pole out-of-roundness detection device and method of the above structure, which has the following beneficial effects:

[0032] (1) The present invention extracts the induced voltage characteristics of the drainage magnetic field measurement coil, and can realize online diagnosis of the synchronous generator rotor magnetic pole out-of-roundness fault through real-time harmonic analysis.

[0033] (2) The present invention has the ability to diagnose the synchronous generator rotor pole out-of-roundness fault under both no-load and load conditions, does not interfere with the normal operation of the unit, and has high sensitivity.

[0034] (3) The present invention utilizes the external structure and material properties of the synchronous generator and adopts a non-invasive diagnostic method, thereby reducing the influence of irrelevant information outside the machine and making the fault characteristics of the rotor pole out-of-roundness more prominent.

[0035] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of the position relationship between the rotor magnetic poles and the stator of a salient pole synchronous generator of a synchronous generator rotor magnetic pole out-of-roundness detection device and method of the present invention;

[0037] Figure 2 A schematic flow chart of a synchronous generator rotor magnetic pole out-of-roundness detection method of a synchronous generator rotor magnetic pole out-of-roundness detection device and method of the present invention;

[0038] Figure 3 A schematic diagram of air gap permeability characteristics of a rotor outer edge with one side convex and the other side concave in a synchronous generator rotor magnetic pole out-of-roundness detection device and method of the present invention;

[0039] Figure 4 A schematic diagram of air gap permeability characteristics of concave and convex intervals on the outer edge of a rotor of a synchronous generator rotor magnetic pole out-of-roundness detection device and method of the present invention;

[0040] Figure 5 A schematic diagram of the air gap permeability characteristics of the irregular concave and convex outer edge of the rotor of a synchronous generator rotor magnetic pole out-of-roundness detection device and method of the present invention;

[0041] Figure 6 It is a schematic diagram of the flow law of the drainage magnetic field of a 10-pole synchronous generator at t=0 in a synchronous generator rotor magnetic pole out-of-roundness detection device and method of the present invention;

[0042] Figure 7 It is a schematic diagram of the flow law of the drainage magnetic field of a 10-pole synchronous generator when t=T / 20 in a synchronous generator rotor magnetic pole out-of-roundness detection device and method of the present invention;

[0043] Figure 8 It is a schematic diagram of the flow law of the drainage magnetic field of a 10-pole synchronous generator when t=2T / 20 in a synchronous generator rotor magnetic pole out-of-roundness detection device and method of the present invention;

[0044] Fig. 9 It is a schematic diagram of the flow law of the drainage magnetic field of a 10-pole synchronous generator when t=3T / 20 in a synchronous generator rotor magnetic pole out-of-roundness detection device and method of the present invention;

[0045] Fig.10 A schematic diagram of the induced voltage waveform of the magnetic field measuring coil of a synchronous generator when the generator is unloaded, according to a device and method for detecting the non-circularity of the rotor magnetic poles of the present invention;

[0046] Fig.11 A schematic diagram of the induced voltage spectrum of the magnetic field measurement coil of a synchronous generator rotor pole out-of-roundness detection device and method of the present invention when the generator is unloaded;

[0047] Fig.12 A schematic diagram of characteristic harmonic amplitude of induced voltage of a magnetic field measuring coil when the generator is unloaded, of a synchronous generator rotor magnetic pole non-circularity detection device and method of the present invention;

[0048] Fig.13 A schematic diagram of the induced voltage waveform of the magnetic field measuring coil when the generator is fully loaded, according to a device and method for detecting the non-circularity of the magnetic poles of a synchronous generator rotor of the present invention;

[0049] Fig.14 A schematic diagram of the induced voltage spectrum of the magnetic field measurement coil when the generator is fully loaded, according to a device and method for detecting the non-circularity of the magnetic poles of a synchronous generator rotor of the present invention;

[0050] Fig.15 A schematic diagram of characteristic harmonic amplitude of induced voltage of a magnetic field measuring coil when the generator is fully loaded, of a synchronous generator rotor magnetic pole non-circularity detection device and method of the present invention;

[0051] Reference numerals

[0052] 1. Synchronous generator stator housing, 2. U-shaped iron core, 3. Insulation shell, 4. Enameled coil, 5. Lead wire, 6. Data acquisition device. DETAILED DESCRIPTION

[0053] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0054] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0055] Example

[0056] like Figure 1 As shown, the present invention provides a detection device for the non-circularity of the magnetic poles of the synchronous generator rotor. A U-shaped iron core 2 is customized according to the size of the synchronous generator stator housing 1, embedded in an insulating shell 3, and an enameled coil 4 with an appropriate number of turns is wound thereon to form a drainage magnetic field measurement device. When the unit is running, the U-shaped iron core section is closely fitted with the synchronous generator stator housing 1, and the induced voltage signal is transmitted to the data acquisition device 6 through the lead wire 5.

[0057] The U-shaped core 2 is made of a high magnetic permeability material, which plays a role in draining and amplifying the leakage magnetic field of the synchronous generator stator housing 1. In the process of obtaining the induced voltage of the enameled coil 4, the winding number of the enameled coil 4 is determined according to the equipment conditions to obtain an induced voltage signal suitable for collection and analysis.

[0058] The synchronous generator rotor pole non-roundness detection device according to the embodiment of the present invention has high diagnostic sensitivity, effectively avoids the safety risks brought by installing sensors inside the unit, and has better anti-interference performance compared to the detection method of measuring the leakage magnetic flux outside the unit.

[0059] In order to implement the above embodiment, Figure 2 As shown, this embodiment also provides a method for detecting the out-of-roundness of the magnetic poles of the synchronous generator rotor, including:

[0060] S1, using a data acquisition device to record the induced voltage signal output by the coil in real time;

[0061] S2, performing harmonic analysis on the induced voltage signal to obtain a voltage spectrum diagram;

[0062] S3. When the synchronous generator has a rotor pole out-of-roundness fault, the voltage spectrum of the induced voltage signal corresponds to the output fault characteristic harmonic;

[0063] S4. According to the amplitude variation state of the fault characteristic harmonic, the synchronous generator rotor magnetic pole out-of-roundness fault is diagnosed to obtain a diagnosis result.

[0064] Specifically, when the unit is running, the U-shaped core section is closely fitted with the stator casing, which plays a drainage and amplification role in the casing leakage magnetic field, and the induced voltage signal output by the coil is recorded in real time by a data acquisition device; harmonic analysis is performed on the induced voltage to obtain a voltage spectrum diagram; when a synchronous generator has a rotor magnetic pole out-of-roundness fault, the induced voltage of the magnetic field measurement coil will have fault characteristic harmonics; based on the changes in the characteristic harmonic amplitude of the induced voltage of the magnetic field measurement coil, an accurate judgment is made on the synchronous generator rotor magnetic pole out-of-roundness fault.

[0065] A stationary stator coordinate system is established. At the initial moment, the stator axis coincides with the rotor q axis. For a certain magnetic pole, the arc length spanned by the edge of the yoke relative to the initial position of the stator coordinate system is l. Figure 1 It reflects the position of the magnetic pole in the stator coordinates. At this time, the air gap permeability of the generator can be expressed by the following formula:

[0066]

[0067] Among them, λ d , q are the air gap permeabilities of the motor d and q respectively, and ω is the electrical angular velocity.

[0068] Taking the air gap permeability under normal conditions as a reference, when a rotor out-of-roundness fault occurs, the minimum distance between the outer edge of the rotor pole and the inner circle of the stator will change, causing a fault permeability to be generated when the rotor rotates. At this time, the air gap permeability is equivalent to the superposition of the normal permeability and the fault permeability. When different types of rotor out-of-roundness faults occur, the outer edge shape and air gap permeability characteristics are as follows: Figure 3-5 As shown, from top to bottom, one side of the rotor outer edge is convex and the other side is concave, the rotor outer edge has interval convex and concave, and the rotor outer edge has irregular convex and concave.

[0069] Taking the general case as an example, when any magnetic pole of the rotor is convex or concave, the air gap permeance can be expressed as:

[0070]

[0071] Among them, ω is the electrical angular velocity, τ is the pole pitch expressed in arc length, and p is the number of motor pole pairs.

[0072] Therefore, when the rotor poles are irregularly concave and convex, the air gap flux density can be expressed as:

[0073]

[0074] Where ω is the electrical angular velocity, τ is the pole pitch expressed in arc length, p is the number of motor pole pairs, F(t, l) is the air gap magnetomotive force, Δλ k is the magnitude of the fault permeability with pole pair number k.

[0075] Therefore, for a p-pole generator, when the rotor poles are irregularly concave and convex, (i+k / p) harmonics will appear in the air-gap magnetic field, where i is an odd number and k is a positive integer; when one side of the rotor is convex and the other side is concave, (i+1 / p) harmonics will appear in the air-gap magnetic field, where i is an odd number; when the rotor poles are j-times concave and convex at intervals, (i±j / p) harmonics will appear in the air-gap magnetic field, where p is an integer multiple of j and i is an odd number. The specific principle will not be described in detail here.

[0076] Therefore, when a salient pole synchronous generator has a rotor pole out-of-roundness fault, k / p harmonics (k=1, 2, 3...) will appear in the air gap magnetic field. The frequency characteristics of these harmonics are directly related to the number of pole pairs of the generator and the deformation mode of the rotor outer edge.

[0077] In the process of obtaining the coil induced voltage, since the casing is made of magnetic conductive material, the air gap magnetic field leaks into the casing, forming a casing leakage magnetic field. When a rotor out-of-roundness fault occurs, the casing leakage magnetic flux contains the same fault characteristic magnetic field information as the air gap magnetic field.

[0078] To make the leakage magnetic field signal easier to collect and analyze, the U-shaped core section is tightly fitted to the casing when the unit is running. The leakage magnetic flux will form a forced drainage loop along the stator core-casing-U-shaped core-casing-stator core. Taking a 10-pole synchronous generator as an example, the distribution law of the drainage magnetic field along this loop is as follows: Figure 6-9 As shown, they are t=0, t=T / 20, t=2T / 20, and t=3T / 20.

[0079] The magnetic flux flowing through the U-shaped core periodically alternates as the rotor rotates. When the motor has a rotor out-of-roundness fault, k / p harmonics are generated in the air gap magnetic field. The alternating frequency of the harmonic magnetic field in the U-shaped core can be expressed as:

[0080]

[0081] Among them, f1 is the fundamental frequency, p is the number of motor pole pairs, and n is the motor speed.

[0082] The magnetic field measurement coil is tightly wound on the insulating shell outside the U-shaped core. When the alternating magnetic field passes through the measurement coil, a corresponding voltage will be induced in the coil. The induced voltage is analyzed in the frequency domain, and the k / p harmonics are used as the key diagnostic indicators to achieve real-time monitoring and diagnosis of synchronous generator rotor magnetic pole out-of-roundness faults.

[0083] This embodiment is experimentally verified on a three-phase four-pole salient synchronous generator, and the unit parameters are shown in Table 1. By grinding a certain magnetic pole of the rotor twice, the out-of-roundness conditions with fault degrees of δ = 0.3 and δ = 0.6 are simulated respectively. The effectiveness of the new fault detection method is tested under two working conditions of the generator: no-load and load.

[0084] Table 1

[0085] Basic parameters Numeric Rated power / kW 2 Rated voltage / V 220 Rated excitation current / A 3.54 Rated speed / (r / min) 1500 Pole pairs 2 Radial air gap length / mm 0.5 Stator inner diameter / mm 75 Rotor pole outer diameter / mm 74.5

[0086] After a certain magnetic pole of the rotor is sunken to different degrees, the induced voltage waveform of the measuring coil under no-load condition is as follows: Fig.10 The harmonic analysis of the induced voltage is shown as follows: Fig.11 As shown in Figure 1, its spectrum contains fractional harmonic components such as 1 / 2, 3 / 2, and 5 / 2 (25Hz, 75Hz, and 125Hz). Compare the characteristic harmonic amplitudes under different fault conditions, such as Fig.12 As shown in the figure, it can be found that the amplitudes of the 1 / 2 and 3 / 2 harmonics show an obvious increasing trend with the increase of the fault severity.

[0087] Under load conditions, the induced voltage waveform of the measuring coil is as follows: Fig.13 The induced voltage spectrum is shown in Fig.14As shown in Figure 1, there are fractional harmonics such as 1 / 2, 3 / 2, 5 / 2, and 9 / 2 (25Hz, 75Hz, 125Hz, and 225Hz). The characteristic harmonic amplitudes under different fault conditions are further extracted, as shown in Figure 1. Fig.15 As shown, it can be seen that under load conditions, the 1 / 2, 3 / 2, and 9 / 2 harmonic amplitudes are positively correlated with the fault severity.

[0088] The above experimental results are consistent with the theoretical analysis, proving that under no-load and load conditions, there is a good correspondence between the amplitude of the fractional harmonics and the degree of rotor pole depression. Therefore, the detection device and method proposed in the present invention can effectively detect the rotor out-of-roundness fault, further evaluate the severity of the fault, and provide accurate diagnostic results.

[0089] The synchronous generator rotor pole non-roundness detection method according to the embodiment of the present invention has high diagnostic sensitivity, effectively avoids the safety risks brought by installing sensors inside the unit, and has better anti-interference performance compared to the detection method of measuring the leakage magnetic flux outside the unit.

[0090] In the present invention, a U-shaped core with an insulating shell is tightly fitted to the stator housing of a synchronous generator, and a magnetic field measurement coil is wound thereon. When the synchronous generator is running, the induced voltage signal of the measuring coil is collected, and the frequency domain characteristic information of the induced voltage is obtained by using a data analysis device to detect the rotor magnetic pole out-of-roundness fault in real time. The present invention has a high diagnostic sensitivity, effectively avoids the safety risks brought by installing sensors inside the unit, and has better anti-interference performance than the detection method of measuring the leakage magnetic flux outside the unit.

[0091] In summary, in view of the prior art, the present invention attaches a U-shaped iron core outside the machine and winds a magnetic field measuring coil thereon, which is a non-invasive detection method. The present invention utilizes a U-shaped iron core to drain the leakage magnetic field of the casing, and reflects the change of the motor magnetic field through the coil induced voltage, which belongs to the electrical quantity judgment criterion and is relatively simple in signal acquisition and processing. The present invention utilizes the forced drainage effect to strengthen and measure the leakage magnetic field, and has a stronger anti-interference performance. The present invention winds the magnetic field measuring coil on a special iron core to form an independent drainage magnetic field measuring device, which has good portability. The present invention utilizes the forced drainage effect to strengthen and measure the leakage magnetic field, and has a stronger anti-interference performance. The magnetic field measurement coil is wrapped around the positioning rib or ring plate, and its operation depends on the original structure of the unit.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A synchronous generator rotor magnetic pole out-of-roundness detection device, characterized in that: It includes a U-shaped iron core, which is arranged on the outer surface of the stator casing of the synchronous generator, and an enameled coil with a preset number of turns is wound around the U-shaped iron core to form a drainage magnetic field measuring device. When the synchronous generator set is running, the cross-section of the U-shaped iron core is fitted with the stator casing of the synchronous generator, and the induced voltage signal output by the coil is transmitted to the data acquisition device through the lead wire.

2. The device for detecting the out-of-roundness of the rotor magnetic poles of a synchronous generator according to claim 1, characterized in that: The U-shaped iron core is made of high magnetic permeability material and is used for draining the leakage magnetic field of the casing.

3. A method for detecting the non-circularity of a synchronous generator rotor magnetic pole, applied to a device for detecting the non-circularity of a synchronous generator rotor magnetic pole according to claims 1-2, characterized in that: The following steps are involved: S1, using a data acquisition device to record the induced voltage signal output by the coil in real time; S2, performing harmonic analysis on the induced voltage signal to obtain a voltage spectrum diagram; S3. When the synchronous generator has a rotor pole out-of-roundness fault, the voltage spectrum of the induced voltage signal corresponds to the output fault characteristic harmonic; S4. According to the amplitude variation state of the fault characteristic harmonic, the synchronous generator rotor magnetic pole out-of-roundness fault is diagnosed to obtain a diagnosis result.

4. The method for detecting the out-of-roundness of the magnetic poles of a synchronous generator rotor according to claim 3, characterized in that: In step S3, a stationary stator coordinate system is established. At the initial moment, the stator axis coincides with the rotor axis. For a certain magnetic pole, the arc length spanned by the edge of its yoke relative to the initial position of the stator coordinate system is l, and the air gap permeance of the corresponding generator is expressed by the following formula: Among them, λ d , q are the air gap permeabilities of the motor d and q respectively, and ω is the electrical angular velocity; When any magnetic pole of the rotor is convex or concave, the air gap permeance is expressed as: Among them, ω is the electrical angular velocity, τ is the pole pitch expressed in arc length, and p is the number of motor pole pairs; When the rotor poles are irregularly concave and convex, the air gap flux density is expressed as: Where ω is the electrical angular velocity, τ is the pole pitch expressed in arc length, p is the number of motor pole pairs, F(t, l) is the air gap magnetomotive force, Δλ k is the amplitude of the fault permeability with a pole pair number of k. In a p-pole generator, when the rotor poles are irregularly concave and convex, i+k / p harmonics appear in the air gap magnetic field, where i is an odd number and k is a positive integer; when one side of the rotor is convex and the other side is concave, i+1 / p harmonics appear in the air gap magnetic field, where i is an odd number; when the rotor poles are j-times concave and convex at intervals, i±j / p harmonics appear in the air gap magnetic field, where p is an integer multiple of j and i is an odd number.

5. The method for detecting the out-of-roundness of the rotor magnetic poles of a synchronous generator according to claim 3, characterized in that: In step S4, the magnetic flux flowing through the U-shaped core periodically alternates as the rotor rotates. When the motor has a rotor out-of-roundness fault, k / p harmonics are generated in the air gap magnetic field. The alternating frequency of the harmonic magnetic field in the U-shaped core is expressed as: Among them, f1 is the fundamental frequency, p is the number of motor pole pairs, and n is the motor speed.

6. The method for detecting the out-of-roundness of the magnetic poles of a synchronous generator rotor according to claim 3, characterized in that: In step S4, the characteristic harmonic amplitude of the coil induced voltage is measured to be proportional to the degree of the rotor pole out-of-roundness fault.

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