CN117452077A - Nondestructive testing method for dielectric loss factor of stator coil of high-voltage motor - Google Patents
Nondestructive testing method for dielectric loss factor of stator coil of high-voltage motor Download PDFInfo
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- CN117452077A CN117452077A CN202311417509.1A CN202311417509A CN117452077A CN 117452077 A CN117452077 A CN 117452077A CN 202311417509 A CN202311417509 A CN 202311417509A CN 117452077 A CN117452077 A CN 117452077A
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- 238000000034 method Methods 0.000 title claims abstract description 27
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- 238000012360 testing method Methods 0.000 claims abstract description 73
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- 238000009413 insulation Methods 0.000 claims abstract description 21
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- 230000001680 brushing effect Effects 0.000 claims abstract description 7
- 238000005259 measurement Methods 0.000 claims description 13
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- 238000007731 hot pressing Methods 0.000 claims description 3
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- 239000011889 copper foil Substances 0.000 description 3
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- 238000007796 conventional method Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2688—Measuring quality factor or dielectric loss, e.g. loss angle, or power factor
- G01R27/2694—Measuring dielectric loss, e.g. loss angle, loss factor or power factor
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/64—Electric machine technologies in electromobility
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Abstract
The invention discloses a nondestructive testing method for dielectric loss factors of a stator coil of a high-voltage motor, which comprises the steps of firstly, continuously and semi-overlapping a low-resistance anti-corona layer on the surface of a main insulating linear part of the stator coil; then, respectively brushing two sections of low-resistance anti-corona paint on the surface of the low-resistance anti-corona layer along the length direction of the coil by taking two ends of the low-resistance anti-corona layer as starting points; then the stator coil is placed on a dielectric loss test tool, the large surface of a wire rod of the linear part of the stator coil is placed on a lower measuring electrode plate of the tool, an upper measuring electrode plate of the tool is covered on the large surface of the wire rod, the upper measuring electrode plate and the lower measuring electrode plate are connected through a wire to form a measuring electrode, then the two ends of the linear part of the stator coil are respectively provided with a grounded protective electrode, and finally the measuring electrode is connected into a dielectric loss detection device. The detection method of the invention does not damage the low-resistance anti-corona layer of the stator coil, and improves the stable reliability of stator insulation in motor installation and operation.
Description
Technical Field
The invention relates to the technical field of generator insulation detection, in particular to a nondestructive detection method for dielectric loss factors of a stator coil of a high-voltage motor.
Background
The insulation performance of the stator coil is a key core factor for the long-term safe and reliable operation of the motor, and a plurality of electrical performance detection tests such as dielectric loss factors, partial discharge, corona prevention, power frequency alternating current withstand voltage and the like are required to be carried out after the stator coil is manufactured and molded in an insulation mode. With the improvement of the rated capacity and rated voltage of the high-voltage motor, the requirements on the index value of the dielectric loss factor of the stator coil are higher and higher, for example, the dielectric loss value under the voltage of 0.2Un (Un, rated voltage of the motor) is required to be not more than 0.90%, and the dielectric loss increment of 0.6Un-0.2Un is not more than 0.30%.
The conventional method for testing the dielectric loss factor of the stator coil of the high-voltage motor adopts a three-section three-electrode testing system, and is divided into a high-voltage electrode, a measuring electrode and a protecting electrode. The high-voltage electrode is connected with a copper conductor of the stator coil, and a measurement voltage is applied; the measuring electrode is formed by wrapping aluminum foil or copper foil with good conductivity on the surface of a low-resistance anti-corona layer of a linear part of the stator coil, and is connected with a measuring instrument or a measuring unit, and the length of the measuring electrode is longer than that of the stator core; the protection electrode is used for shielding or eliminating loss generated by insulating mediums except the measuring electrode in parallel, and is usually arranged on a low-resistance anti-corona layer at the tail end of a linear part of the stator coil in order to meet index value requirements specified by medium loss factors, the low-resistance anti-corona layer is wrapped in three sections, a measuring gap is reserved at each of two ends of the low-resistance anti-corona layer, or the low-resistance anti-corona layer is cut off after being solidified, the rest part of the low-resistance anti-corona layer at the linear part and the end part of the coil are used as the protection electrode, the insulating medium loss factors under the low-resistance anti-corona layer at the linear part are measured, and the reserved gap width of the low-resistance anti-corona layer is 5 mm-10 mm.
After the stator coil dielectric loss factor test is completed, the stator coil is lifted and transported from the test room to the stator coil anti-corona treatment room, a layer of low-resistance anti-corona paint is coated on the surface of the straight line part of the stator coil, and the main insulation surface leaked from the reserved part of the low-resistance anti-corona layer is covered with the low-resistance anti-corona paint, so that the low-resistance anti-corona layer of the stator coil forms a continuous conductive channel again, and the partial discharge phenomenon at the reserved part of the low-resistance anti-corona layer is avoided.
The traditional stator coil dielectric loss factor three-electrode measuring system has high data accuracy, can truly reflect the insulation performance of the stator coil, but breaks the continuity of the stator coil corona-preventing layer, and brings certain hidden trouble to the stator coil corona-preventing test and the safe operation of the unit. For example, when the stator coil protection electrode is positioned at the lap joint of the tail end of the low-resistance anti-corona layer and the head end of the high-resistance anti-corona layer, the newly-painted low-resistance anti-corona paint cannot be completely and effectively lap-jointed with the original low-resistance anti-corona layer, and corona discharge and ultraviolet photons can occur when an anti-corona test is performed; the thickness of the low-resistance anti-corona coating of the stator coil is 0.3mm, the thickness of the low-resistance anti-corona paint coated at the cut-off part of the protective electrode is 0.1mm, the current carrying capacity of the low-resistance anti-corona coating which is too thin at the protective gap is poor, and the electric corrosion phenomenon can occur on the surface of the low-resistance anti-corona layer at the reserved part of the coil after the machine set is operated for a long time.
Disclosure of Invention
In order to solve the problems and the defects in the prior art, the invention provides a nondestructive testing method for dielectric loss factors of a stator coil of a high-voltage motor, and the method is convenient, practical and efficient, does not damage the continuity of a low-resistance anti-corona layer of the stator coil, can also increase the current carrying capacity and the partial discharge resistance of the low-resistance anti-corona layer of a notch of the stator coil, and improves the stability and the reliability of stator insulation in motor installation and operation.
In order to achieve the above object, the technical scheme of the present invention is as follows:
a nondestructive testing method for dielectric loss factors of stator coils of high-voltage motors comprises the following steps:
s1, after the main insulation wrapping of a stator coil is completed, continuously and semi-overlapping a low-resistance anti-corona layer on the surface of a main insulation straight line part of the stator coil;
s2, after insulating, hot-pressing, baking and solidifying the stator coil, respectively brushing two sections of low-resistance anti-corona paint with the length of L on the surface of the low-resistance anti-corona layer along the length direction of the coil by taking two ends of the low-resistance anti-corona layer of the linear part of the stator coil as starting points;
s4, placing the stator coil on a dielectric loss test tool, placing the large surface of a linear part of the stator coil on a lower measuring electrode plate of the tool, covering an upper measuring electrode plate of the tool on the large surface of the wire rod, conducting and connecting the measuring electrode plates through a wire to form measuring electrodes, respectively setting grounded protective electrodes at two ends of the linear part of the stator coil, and finally connecting the measuring electrodes into a dielectric loss detection device.
Preferably, when the low-resistance anti-corona paint is painted, the anti-corona paint is uniformly painted along the length direction of the coil by taking the head end and the tail end of the low-resistance anti-corona layer as starting points respectively, two sections of low-resistance anti-corona paint structures with the length L are formed on the surface of the low-resistance anti-corona layer, and the painting length L of the low-resistance anti-corona paint is calculated by the formula (1)
Wherein U is N Is the rated voltage of the motor.
Preferably, when the low-resistance anti-corona paint is painted, a circle of adhesive tape is respectively stuck at the starting point and the end point of the painting along the circumferential direction of the coil.
Preferably, the low-resistance anti-corona paint has a paint thickness of 80 μm.ltoreq.d.ltoreq.150 μm and a curing time at room temperature of not less than 8 hours.
Preferably, the protection electrode of the stator coil is a single protection electrode structure or a double protection electrode structure; when a single protection electrode structure is used, the gap between the protection electrode and the measurement electrode is 15 mm-30 mm; when the double-protection electrode structure is used, the gap between the first protection electrode and the measuring electrode is 3-8 mm, and the gap between the second protection electrode and the first protection electrode is 2-6 mm.
Preferably, the test fixture comprises an upper measuring electrode and a lower measuring electrode covered on the upper measuring electrode, the lower measuring electrode plate comprises a supporting vertical plate and a lower measuring electrode plate, a groove for installing the lower measuring electrode plate is formed in the supporting vertical plate, the lower measuring electrode plate and the groove enclose to form a containing groove for placing a large surface of a coil rod, the lower measuring electrode comprises a cover plate and an upper measuring electrode plate arranged on the cover plate, and the upper measuring electrode plate corresponds to the lower measuring electrode plate below.
Preferably, the test tools are arranged at intervals along the straight line part of the stator coil, and the distance between each test tool is 50 mm-300 mm.
Preferably, the low-resistance anti-corona layer of the stator coil is formed by continuously and semi-overlapping the surface of the main insulation straight line part, and the thickness of the low-resistance anti-corona layer is 0.06 mm-0.09 mm.
Preferably, the low-resistance anti-corona paint has a surface resistance value ranging from 5kΩ to 12kΩ.
The invention has the beneficial effects that:
1. the nondestructive testing method provided by the invention has the advantages of high accuracy, quick test, no damage to the low-resistance anti-corona layer of the stator coil, no need of secondary repair of the low-resistance anti-corona layer, increased current carrying capacity and partial discharge resistance of the low-resistance anti-corona layer of the notch of the stator coil, and improved stability and reliability of stator insulation in motor installation and operation.
2. The sectional type measuring electrode plate used by the nondestructive testing method can be reused, so that the use amount of aluminum foil, copper strips and the like which are used as measuring electrodes to wrap the surface of a coil is obviously reduced, and the effects of reducing cost and enhancing efficiency are achieved; and the dismantling of the measuring electrode after measurement is simpler and quicker, so that the measuring efficiency can be effectively improved.
3. The nondestructive testing method provided by the invention is matched with the intelligent and digital testing method, and stator coils with different sizes and lengths have universality.
Drawings
The foregoing and the following detailed description of the invention will become more apparent when read in conjunction with the following drawings in which:
FIG. 1 is a schematic diagram of a continuous three-electrode test (low resistance anti-blooming layer is not broken) according to the present invention;
FIG. 2 is a schematic diagram of a conventional three-stage three-electrode test (low resistance anti-blooming layer with break gap);
FIG. 3 is a schematic diagram of a stator coil test setup of the present invention;
FIG. 4 is a schematic view of an experimental tooling of the present invention;
FIG. 5 is a schematic diagram of the dielectric loss detection of the coil of the present invention;
fig. 6 is a schematic diagram of a detection principle of the dielectric loss detection device of the present invention.
In the figure:
1. a stator coil; 2. protecting the electrode; 3. a low resistance anti-corona layer; 4. the low-resistance anti-corona layer breaks the gap; 5. a measuring electrode; 6. dielectric loss test fixture; 7. an upper measuring electrode; 8. a lower measuring electrode; 9. a cover plate; 10. a measuring electrode plate is arranged on the upper surface; 11. a supporting vertical plate; 12. a lower measuring electrode plate;
Detailed Description
In order for those skilled in the art to better understand the technical solution of the present invention, the technical solution for achieving the object of the present invention will be further described through several specific embodiments, and it should be noted that the technical solution claimed in the present invention includes, but is not limited to, the following embodiments. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, based on the embodiments of the present invention shall fall within the scope of protection of the present invention.
The conventional method for testing the dielectric loss factor of the stator coil of the high-voltage motor adopts a three-section three-electrode testing system, and is divided into a high-voltage electrode, a measuring electrode and a protecting electrode. The high-voltage electrode is connected with a copper conductor of the stator coil, and a measurement voltage is applied; the measuring electrode is formed by wrapping aluminum foil or copper foil with good conductivity on the surface of a low-resistance anti-corona layer of a linear part of the stator coil, and is connected with a measuring instrument or a measuring unit, and the length of the measuring electrode is longer than that of the stator core; the protection electrode is used for shielding or eliminating loss generated by insulating mediums except the measuring electrode in parallel, and is usually arranged on a low-resistance anti-corona layer at the tail end of a linear part of the stator coil in order to meet index value requirements specified by medium loss factors, the low-resistance anti-corona layer is wrapped in three sections, a measuring gap is reserved at each of two ends of the low-resistance anti-corona layer, or the low-resistance anti-corona layer is cut off after being solidified, the rest part of the low-resistance anti-corona layer at the linear part and the end part of the coil are used as the protection electrode, the insulating medium loss factors under the low-resistance anti-corona layer at the linear part are measured, and the reserved gap width of the low-resistance anti-corona layer is 5 mm-10 mm.
The traditional stator coil dielectric loss factor three-electrode measuring system has high data accuracy, can truly reflect the insulation performance of the stator coil, but breaks the continuity of the stator coil corona-preventing layer, and brings certain hidden trouble to the stator coil corona-preventing test and the safe operation of the unit. For example, when the stator coil protection electrode is positioned at the lap joint of the tail end of the low-resistance anti-corona layer and the head end of the high-resistance anti-corona layer, the newly-painted low-resistance anti-corona paint cannot be completely and effectively lap-jointed with the original low-resistance anti-corona layer, and corona discharge and ultraviolet photons can occur when an anti-corona test is performed; the thickness of the low-resistance anti-corona coating of the stator coil is 0.3mm, the thickness of the low-resistance anti-corona paint coated at the cut-off part of the protective electrode is 0.1mm, the current carrying capacity of the low-resistance anti-corona coating which is too thin at the protective gap is poor, and the electric corrosion phenomenon can occur on the surface of the low-resistance anti-corona layer at the reserved part of the coil after the machine set is operated for a long time.
Based on the above, the embodiment of the invention particularly provides a nondestructive testing method for dielectric loss factors of a stator coil of a high-voltage motor, and the method is convenient, practical and efficient, does not damage the continuity of a low-resistance anti-corona layer of the stator coil, can also increase the current carrying capacity and the partial discharge resistance of a notch low-resistance anti-corona layer of the stator coil, and improves the stable reliability of stator insulation in motor installation and operation.
In the present invention, it is first noted that dielectric loss is an energy loss caused in an insulating material by the hysteresis effect of dielectric conduction and dielectric polarization under the action of an electric field. The larger the dielectric loss factor, the lower the energy conversion rate of the dielectric in the electric field, which results in more heat dissipation.
Example 1
The embodiment discloses a nondestructive testing method for dielectric loss factors of a stator coil of a high-voltage motor, which mainly comprises the following steps:
s1, after the main insulation wrapping of the stator coil 1 is finished, continuously and semi-overlapping the low-resistance anti-corona layer 3 with the thickness of 0.06-0.09 mm on the surface of a linear part of the main insulation of the stator coil, wherein a measuring gap is not reserved in the low-resistance anti-corona layer 3.
In the present invention, the anti-corona structure of the stator coil 1 is generally divided into a straight partial region low-resistance anti-corona structure and a curved (end) partial region high-resistance anti-corona structure; the low-resistance anti-corona structure and the high-resistance anti-corona structure are made of different materials, that is, the straight portions of the stator coil 1 are usually wrapped with the low-resistance anti-corona layer, the curved portions are usually wrapped with the high-resistance anti-corona layer, and the curved portions (coil ends) do not affect the dielectric loss test.
In the invention, the low-resistance anti-corona layer 3 is continuously and semi-overlapped on the straight line part, and the anti-corona layer is not cut off after being overlapped, so that the effect of not damaging the continuity of the low-resistance anti-corona layer can be realized, and the anti-corona layer has no measuring gap.
Step S2, wrapping the low-resistance anti-corona layer 3, hot-pressing, baking, solidifying and forming the low-resistance anti-corona layer together with main insulation of the stator coil 1, airing at room temperature for at least 30min, and then respectively brushing two sections of low-resistance anti-corona paint with the length L on the surface of the low-resistance anti-corona layer 3 along the length direction of the coil by taking two ends of the low-resistance anti-corona layer 3 of the linear part of the stator coil as starting points.
Specifically, the surface of the low-resistance anti-corona layer 3 is coated with anti-corona paint in the following manner:
after the low-resistance anti-corona layer 3 is wrapped, two ends, a head end and a tail end are arranged, so that when the low-resistance anti-corona paint is painted, the head end and the tail end of the low-resistance anti-corona layer 3 are respectively used as starting points for painting, the anti-corona paint is evenly painted on the surface of the anti-corona layer along the length direction of the coil towards the midpoint of the straight line part, two sections of low-resistance anti-corona paint structures with the length L are finally formed on the surface of the low-resistance anti-corona layer 3, and the painting length L of the low-resistance anti-corona paint at the two ends of the coil is calculated by the following formula:
wherein U is N The rated voltage of the motor is usually the rated voltage of the motor with the range of
6≤U N ≤30。
Further, in order to better control the brushing length and thickness of the low-resistance anti-corona paint, a circle of adhesive tape is respectively stuck at the starting point of brushing and the end point position determined according to the brushing length along the circumferential direction of the coil before the low-resistance anti-corona paint is painted, then the low-resistance anti-corona paint is uniformly coated by a foam rubber roller along the length direction of the coil, the thickness of the anti-corona paint is 80 mu m less than or equal to d less than or equal to 150 mu m after the low-resistance anti-corona paint is painted, and the curing time is not less than 8 hours under the room temperature condition.
Step S4, placing the stator coil 1 on a dielectric loss test tool 6, placing the large surface of a linear part of the stator coil 1 on a lower measuring electrode plate 12 of the tool, covering an upper measuring electrode plate 10 of the tool on the large surface of the linear part, connecting the measuring electrode plates through wires to form measuring electrodes 5, connecting the measuring electrodes 5 into a dielectric loss detection device, and finally respectively arranging grounded protective electrodes 2 at two ends of the linear part of the stator coil 1.
In the present invention, a soft-fitting conductive material is generally used as the guard electrode 2, for example, a copper tape, a copper wire, an aluminum foil, or the like. The guard electrode 2 is disposed on the low-resistance anti-corona layer 3 at the straight portion of the coil and is 20mm to 40mm from the end of the low-resistance anti-corona layer 3.
In the invention, the section of the bar is a rectangle, the long sides are called big faces, and the short sides are called small faces.
As can be seen from comparing the accompanying drawings 1 and 2 of the specification, the whole low-resistance anti-corona layer 3 of the stator coil 1 obtained by the method is of a continuous structure, no gap exists in the anti-corona layer, two end parts of the low-resistance anti-corona layer 3 of the stator coil 1 corresponding to the existing three-section three-electrode test mode are provided with obvious breaking gaps, and the whole anti-corona layer is not of a continuous structure. The measuring electrode 5 of the present invention is a segmented measuring electrode composed of a plurality of upper and lower electrode plates arranged at intervals along the length direction of a straight line part, while the measuring electrode 5 of the prior art is a measuring electrode 5 composed of a continuously wrapped aluminum foil or copper foil with good conductivity.
Further, in the present invention, in order to prevent the leakage current at the coil end from flowing into the measuring electrode due to the excessively low surface resistance value of the low-resistance anti-corona paint, which affects the accuracy of the coil dielectric loss power factor measurement data, the low-resistance anti-corona paint applied to the stator coil 1 has a surface resistance value ranging from 5kΩ to 12kΩ.
Further, in the present invention, the guard electrode 2 of the stator coil 1 may be provided in a single guard electrode structure or a double guard electrode structure; when the single-protection electrode structure is used, the gap between the protection electrode 2 and the measurement electrode 5 is 15 mm-30 mm; when the double-protection electrode structure is used, the gap between the first protection electrode and the measuring electrode 5 is 3-8 mm, and the gap between the second protection electrode and the first protection electrode is 2-6 mm. Through the double-protection electrode structure, leakage current at the end part can be effectively reduced to flow into the measuring electrode, and the precision of a coil dielectric loss power factor test result is improved.
Based on the same inventive concept, the embodiment of the invention also provides nondestructive testing equipment for dielectric loss factors of a stator coil of a high-voltage motor, the nondestructive testing equipment comprises dielectric loss test tools 6 and dielectric loss detection devices, the test tools comprise an upper measuring electrode 7 and a lower measuring electrode 8, the lower measuring electrode 8 is fixed on a test flat car, the lower measuring electrode 8 covers the upper measuring electrode 7, when the dielectric loss factors of the stator coil 1 are measured, the number of the test tools is increased and decreased according to the length of a straight line part of the stator coil 1, the test tools are arranged at intervals along the straight line part, the interval between each test tool is generally 50-300 mm, each test tool is connected in a conducting way through conductive materials such as conductive copper wires, the test tools after the conducting connection finally form a measuring electrode 5 on the surface of the stator coil 1, and the measuring electrode 5 is connected into the dielectric loss detection devices through wires.
Specifically, referring to fig. 3 to fig. 4 of the specification, the lower measuring electrode 8 includes two supporting risers 11, the two supporting risers 11 are provided with U-shaped grooves for mounting the lower measuring electrode plates 12, the lower measuring electrode plates 12 are fixedly mounted in the U-shaped grooves and then combined with the two supporting risers 11 into a whole, and the upper surfaces of the lower measuring electrode plates 12 and the inner walls of the U-shaped grooves of the supporting risers 11 jointly enclose a U-shaped accommodating groove for accommodating the straight line part of the stator coil; the upper measuring electrode 7 comprises a cover plate 9 and an upper measuring electrode plate 10 arranged on the cover plate 9; the lower measuring electrode plate 12 and the upper measuring electrode plate 10 are connected in a conducting way through a wire, and the upper measuring electrode plate 10 and the lower measuring electrode plate 12 after the connection form the measuring electrode 5 in the original testing procedure.
Further, in order to improve the testing efficiency of the testing tool, in the present invention, the supporting vertical plate 11 is provided with a plurality of U-shaped grooves side by side at intervals, each U-shaped groove is provided with a lower measuring electrode plate 12, that is, the number of the lower measuring electrode plates 12 is matched with the number of the U-shaped grooves, and the number of the upper measuring electrode plates 10 and the number of the lower measuring electrode plates 12 arranged on the cover plate 9 are matched and the positions are in one-to-one correspondence. Based on this, the dielectric loss factor of a plurality of stator coils 1 can be tested in one measurement process.
Further, in order to facilitate the taking of the upper measuring electrode 7, a handle is further provided on the cover plate 9 of the upper measuring electrode 7.
Referring to fig. 5-6 of the specification, the dielectric loss detection device comprises a high-voltage power supply module for providing test voltage for a detected sub-coil, a power supply module for supplying power for the detection device, and a dielectric loss signal processing unit, a PLC control unit, a standard signal acquisition branch and a test signal acquisition branch which are connected with the power supply module, wherein the dielectric loss signal processing unit is also connected with the PLC control unit, the input ends of the standard signal acquisition branch and the test signal acquisition branch are connected with the output end of the power supply module together, and the output ends of the standard signal acquisition branch and the test signal acquisition branch are connected with a standard signal acquisition interface and a test signal acquisition interface on the dielectric loss signal processing unit respectively; the standard test circuit comprises a standard capacitor Cp and a standard signal sensor R which are sequentially connected in the circuit, wherein a current signal acquired by the output of the standard signal sensor R is input into the dielectric loss signal processing unit through a standard signal acquisition interface, the test signal acquisition circuit comprises a sample Csn (the sample consists of a measured sub-coil and a measuring electrode 5 arranged on the surface of the coil) and a measuring signal sensor M which are sequentially connected in the circuit, and the current signal acquired by the output of the measuring signal sensor M is input into the dielectric loss signal processing unit through the test signal acquisition interface; the PLC control unit is also connected with a high-voltage power supply module, the conductor part of the tested stator coil is connected with the high-voltage power supply module to serve as a high-voltage electrode, and the high-voltage power supply module automatically applies corresponding test voltage to the stator coil 1 according to set measurement parameters.
It should be noted that, when testing a plurality of stator coils 1, the measuring electrode 5 corresponding to each stator coil 1 is respectively connected to the corresponding test signal acquisition branch of the dielectric loss detection device, and the conductor portion of the coil is respectively connected to the high-voltage power supply module.
In this embodiment, the standard signal sensor R, the measurement signal sensor M, and the dielectric loss signal processing unit may constitute one dielectric loss tester.
When measuring the dielectric loss factor of the stator coil, firstly, the stator coil 1 manufactured in the steps S1-S4 is lifted to a test flat car, the linear part of the stator coil 1 is installed on a test tool of the test flat car, wherein the lower surface of the large surface of a wire rod is in good contact with a lower measuring electrode plate 12 fixed on the test flat car, then an upper measuring electrode 7 is covered on the large surface of the wire rod, wherein the upper measuring electrode plate 10 is in good contact with the upper surface of the large surface of the wire rod, and the upper measuring electrode plate 10 and the lower measuring electrode plate 12 are in one-to-one correspondence. The corresponding formed measuring electrode 5 of each stator coil 1 is connected to a test signal acquisition branch of the dielectric loss detection device, and the conductor part of the stator coil 1 is connected to a high-voltage power supply module. Before testing, all closing switches in the detection device are in an opened state, a dielectric loss factor test is started, a control system automatically closes a switch in a corresponding test circuit and a switch of a high-voltage power supply module, a PLC control unit automatically boosts and reduces voltage under each test voltage, and dielectric loss factor measurement results under each test voltage are collected, recorded and analyzed in real time.
In this embodiment, the power module may be connected to a mains supply for supplying power to the entire dielectric loss detection device; the high-voltage power supply module can also be connected with the mains supply, and the mains supply is converted into high voltage required in the test process through an internal transformation processing unit; the standard signal sensor and the measuring signal sensor transmit the collected current signals of the corresponding branches to the dielectric loss signal processing unit, and the dielectric loss signal processing unit processes and converts the received current signals into dielectric loss factor values and transmits the dielectric loss factor values to the PLC control unit; the PLC control unit is a module for controlling, recording, summarizing and analyzing the high-voltage power supply, the switch, the dielectric loss test software and the test data, and is also connected with the industrial personal computer and used for receiving signals such as test instructions and the like issued by the industrial personal computer. In this embodiment, the switches involved in the test circuit are programmable switches.
Example 2
In the embodiment, a unit with the rated voltage of 24kV is taken as an example, the length of a measuring electrode of a stator coil is 3m, five stator coils continuously produced in the same batch are taken as the example, the insulation structure of the stator coil is subjected to insulation treatment (a low-resistance anti-corona layer is continuously wrapped without reserving a measuring gap), the stator coil adopts a continuous multi-section measuring electrode formed by a single-protection electrode structure and a test tool to carry out dielectric loss factor test, the gap between the protection electrode and the measuring electrode is 20mm, and the dielectric loss factor test is carried out on the stator coil after the insulation and anti-corona solidification of the stator coil are finished. Further, after the multi-section type measuring electrode structure is tested, the test tool is removed, meanwhile, the low-resistance anti-corona layer of the stator coil is cut off, a 5mm gap is reserved, and the dielectric loss factor of the coil is tested again by adopting a traditional three-section type three-electrode measuring method. The test results are shown in table 1 below.
Table 1 stator coil dielectric loss tangent test
The test results show that the measurement result obtained by the nondestructive testing method for the dielectric loss factor of the stator coil of the high-voltage motor is basically the same as the measurement result obtained by the traditional three-section three-electrode testing method, and the method is practical and reliable.
The foregoing description is only a preferred embodiment of the present invention and is not intended to limit the invention in any way, but any simple modification, equivalent variation, etc. of the above embodiment according to the technical substance of the present invention falls within the scope of the present invention.
Claims (9)
1. A nondestructive testing method for dielectric loss factors of stator coils of high-voltage motors is characterized by comprising the following steps:
s1, after the main insulation wrapping of a stator coil is completed, continuously and semi-overlapping a low-resistance anti-corona layer on the surface of a main insulation straight line part of the stator coil;
s2, after insulating, hot-pressing, baking and solidifying the stator coil, respectively brushing two sections of low-resistance anti-corona paint with the length of L on the surface of the low-resistance anti-corona layer along the length direction of the coil by taking two ends of the low-resistance anti-corona layer of the linear part of the stator coil as starting points;
s4, placing the stator coil on a dielectric loss test tool, placing the large surface of a linear part of the stator coil on a lower measuring electrode plate of the tool, covering an upper measuring electrode plate of the tool on the large surface of the wire rod, conducting and connecting the measuring electrode plates through a wire to form measuring electrodes, respectively setting grounded protective electrodes at two ends of the linear part of the stator coil, and finally connecting the measuring electrodes into a dielectric loss detection device.
2. The nondestructive testing method for dielectric loss factor of stator coil of high voltage motor as set forth in claim 1, wherein when the low resistance anti-corona paint is applied, the anti-corona paint is uniformly applied along the length direction of the coil with the head end and the tail end of the low resistance anti-corona layer as starting points, two sections of low resistance anti-corona paint structures with length L are formed on the surface of the low resistance anti-corona layer, and the applied length L of the low resistance anti-corona paint is calculated by formula (1)
Wherein U is N Is the rated voltage of the motor.
3. The method for non-destructive testing of dielectric loss factors of stator coils of high-voltage motor according to claim 1, wherein a ring of adhesive tape is respectively adhered to the starting point and the end point of the application along the circumferential direction of the coil when the low-resistance anti-corona paint is applied.
4. The nondestructive testing method for dielectric loss factors of stator coils of high-voltage motors according to claim 1, wherein the low-resistance anti-corona paint is coated with a thickness of 80 μm or less and d or less and 150 μm or less, and the curing time is not less than 8h at room temperature.
5. The nondestructive testing method for dielectric loss factors of stator coils of high-voltage motor according to claim 1, wherein the protection electrodes of the stator coils are of a single protection electrode structure or a double protection electrode structure; when a single protection electrode structure is used, the gap between the protection electrode and the measurement electrode is 15 mm-30 mm; when the double-protection electrode structure is used, the gap between the first protection electrode and the measuring electrode is 3-8 mm, and the gap between the second protection electrode and the first protection electrode is 2-6 mm.
6. The nondestructive testing method for dielectric loss factors of stator coils of high-voltage motors according to claim 1, wherein the test fixture comprises an upper measuring electrode and a lower measuring electrode covered on the upper measuring electrode, the lower measuring electrode plate comprises a supporting vertical plate and a lower measuring electrode plate, a groove for installing the lower measuring electrode plate is formed in the supporting vertical plate, the lower measuring electrode plate and the groove are enclosed to form a containing groove for placing a large surface of a coil rod, the lower measuring electrode comprises a cover plate and an upper measuring electrode plate arranged on the cover plate, and the upper measuring electrode plate corresponds to the lower measuring electrode plate below.
7. The nondestructive testing method for dielectric loss factors of stator coils of high-voltage motors according to claim 1, wherein the test tools are arranged at intervals along the straight line part of the stator coils, and the distance between each test tool is 50 mm-300 mm.
8. The nondestructive testing method for dielectric loss factors of stator coils of high-voltage motors according to claim 1, wherein the low-resistance anti-corona layer of which the surface of the main insulating linear part of the stator coil is continuously and semi-overlapped is 0.06-0.09 mm thick.
9. The method for non-destructive testing of dielectric loss factors of stator coils of high-voltage motors according to claim 1, wherein the low-resistance anti-corona paint has a surface resistance value ranging from 5kΩ to 12kΩ.
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