Generator stator end welding head defect detection system

Abstract

The utility model relates to a generator stator end welding head defect detection system which comprises a high-frequency power supply circuit, the first end of the high-frequency power supply circuit is connected with the output end of an alternating current power supply, and the second end of the high-frequency power supply circuit is connected with a stator winding of a to-be-detected generator. The high-frequency power supply circuit is used for converting output current of an alternating-current power supply into high-frequency pulse current and introducing the high-frequency pulse current into the stator winding; and the temperature measurement module is used for measuring the temperature of the end welding heads at the two sides of the steam turbine and the exciter of the generator to be measured to obtain measured temperature data, and the measured temperature data is used for determining the defect condition of the terminal corresponding to the stator winding. Therefore, 20kHz high-frequency square-wave pulse current is stably output by utilizing the high-frequency power supply circuit, and the current output capability is strong, so that the heating effect of welding heads on two sides of a steam turbine and an exciter of the generator to be detected is obvious, and the defect detection precision is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of generators, in particular to a generator stator end welding head defect detection system. BACKGROUND

[0002] The generator stator winding end has many welding heads, including the joints between the upper and lower layer wire rods, the joints between the wire rods and the ring-shaped connecting wires, and the joints between the lead-out wires. These welding heads require firmness and reliability, and good electrical conductivity. Since the end welding heads are subjected to alternating electromagnetic force during normal operation of the generator, and are also subjected to short-time impact electromagnetic force during outlet short circuit of the generator, in addition to the virtual welding or lack of welding caused by poor welding process. After long-term operation of the generator, the quality of individual welding heads will deteriorate, and the strands of the welding heads will be subject to fatigue fracture and other defects. Once the welding head has defects, the joint resistance will increase, and local overheating will occur during operation. Light will burn the insulation, and heavy will melt the solder, open the joint, and cause arc to cause inter-phase short circuit and other serious faults. In order to prevent such accidents from occurring, it is necessary to effectively supervise and inspect the quality of the welding heads.

[0003] For the inspection of the quality of the end welding heads, there are generally direct current resistance measurement method and current detection method. Since the generator stator winding is connected by many wire rods and welding heads, and the wire rods generally do not have the defect of wire strand breakage, the quality problems such as strand breakage, welding and virtual welding of the welding heads can be reflected in the size and change of the direct current resistance of the stator winding. By measuring the direct current resistance of the stator winding and comparing, the defects of the welding heads can be checked to a certain extent. However, since large generators, such as hydroelectric generators, have a large number of wire rods, and the welding heads are up to thousands, the change of the direct current resistance of the whole phase winding caused by the deterioration of the quality of individual welding heads is very small, and it is difficult to reflect it through the direct current resistance.

[0004] The current detection method is to arrange temperature sensors on the end welding heads, then use a direct current welding machine to pass a certain direct current to the stator winding to heat the winding, and then compare and analyze the temperature of the welding heads to find out the defective welding heads.

[0005] However, the direct current output by the direct current welding machine is limited, usually below 1000A, and the current in each branch winding is smaller. When the current is small, the stator winding does not heat up significantly, which is not conducive to finding defective welding heads, and the defect detection precision is low. Moreover, the power supply capacity required by the direct current welding machine is large, the energy consumption is high, and the energy waste is serious. CONTENT OF THE NEW TYPE

[0006] Therefore, it is necessary to provide a generator stator end welding head defect detection system with high detection precision in view of the problems in the prior art.

[0007] The application provides a generator stator end welding joint defect detection system, which adopts the following technical scheme:

[0008] A generator stator end welding joint defect detection system comprises:

[0009] A high-frequency power supply circuit, a first end of the high-frequency power supply circuit is connected with an output end of an alternating current power supply, and a second end of the high-frequency power supply circuit is connected with a stator winding of a generator to be detected, the high-frequency power supply circuit is used for converting an output current of the alternating current power supply into a high-frequency pulse current and passing the high-frequency pulse current into the stator winding.

[0010] A temperature measurement module is used for measuring the temperature of the end welding joints on both sides of a turbine and an exciter of the generator to be detected, obtaining measurement temperature data, and determining the defect condition of the corresponding end of the stator winding.

[0011] In one of the embodiments, the high-frequency power supply circuit comprises:

[0012] An input rectifier, an input end of the input rectifier is connected with an output end of the alternating current power supply, and the input rectifier is used for converting a first alternating current output by the alternating current power supply into a first direct current;

[0013] An inverter, an input end of the inverter is connected with an output end of the input rectifier, and the inverter is used for converting the first direct current into a second alternating current;

[0014] An alternating current transformer, an input end of the alternating current transformer is connected with an output end of the inverter, and the alternating current transformer is used for boosting the second alternating current into a third alternating current;

[0015] An output rectifier, an input end of the output rectifier is connected with an output end of the alternating current transformer, an output end of the output rectifier is connected with the stator winding, and the output rectifier is used for converting the third alternating current into a high-frequency pulse current and passing the high-frequency pulse current into the stator winding.

[0016] In one of the embodiments, the input rectifier is composed of semiconductor diodes.

[0017] In one of the embodiments, the inverter is composed of metal oxide semiconductor field effect transistors.

[0018] In one of the embodiments, the output rectifier is composed of semiconductor diodes.

[0019] In one of the embodiments, a first output end of the output rectifier is connected with a neutral point terminal in the stator winding, and a second output end of the output rectifier is connected with a lead wire terminal in the stator winding.

[0020] In one of the embodiments, the first output end of the output rectifier is connected with the neutral point terminal in the stator winding through a connecting cable, and the second output end of the output rectifier is connected with the lead-out line terminal in the stator winding through a connecting cable, and the connecting cable is composed of a plurality of copper core unarmored cables.

[0021] In one of the embodiments, the generator stator end joint defect detection system further comprises a centralized controller connected with the input rectifier, the inverter and the output rectifier through control cables respectively.

[0022] In one of the embodiments, the generator stator end joint defect detection system further comprises a current transformer, the first end of the current transformer is connected with the output end of the output rectifier, and the second end of the current transformer is connected with the centralized controller.

[0023] In one of the embodiments, the temperature measurement module is an infrared thermal imager.

[0024] The above generator stator end joint defect detection system comprises a high-frequency power supply circuit, the first end of the high-frequency power supply circuit is connected with the output end of the alternating current power supply, the second end of the high-frequency power supply circuit is connected with the stator winding of the to-be-tested generator, and the high-frequency power supply circuit is used for converting the output current of the alternating current power supply into a high-frequency pulse current and passing the high-frequency pulse current into the stator winding; a temperature measurement module is used for measuring the temperature of the end joint on the two sides of the turbine and the exciter of the to-be-tested generator, obtaining measurement temperature data, and the measurement temperature data are used for determining the defect condition of the corresponding terminal of the stator winding. In this way, the high-frequency square wave pulse current with a stable output of 20 kHz is output by the high-frequency power supply circuit, the current output capacity is strong, the heating effect of the joint on the two sides of the turbine and the exciter of the to-be-tested generator is obvious, and thus the precision of defect detection is improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the generator stator end joint defect detection system in one embodiment.

[0026] Figure 2 It is a circuit structural schematic diagram of the generator stator end joint defect detection system in one embodiment.

[0027] BRIEF DESCRIPTION OF DRAWINGS

[0028] 1, high-frequency power supply circuit; 11, input rectifier; 12, inverter; 13, alternating current transformer; 14, output rectifier; 15, centralized controller; 16, current transformer; 2, alternating current power supply; 3, to-be-tested generator; 31, end joint; 32, lead-out line terminal; 33, neutral point terminal; 4, temperature measurement module; 5, connecting cable. DETAILED DESCRIPTION

[0029] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in a number of different ways beyond the specific embodiments described herein and by one of ordinary skill in the art without departing from the spirit and scope of the present application, and it is therefore intended that all such variations be considered as falling within the scope of the present application. Accordingly, the present application should not be limited by the following description and examples.

[0030] In the description of the present application, it should be understood that, if these terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0031] In addition, if these terms "first", "second" appear, these terms are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implying the number of technical features indicated. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, if the term "a plurality of" appears, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified.

[0032] In the present application, unless otherwise explicitly specified and limited, if the terms "mounting", "connecting", "connecting", "fixing" and the like appear, these terms should be interpreted broadly. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] In the present application, unless specifically defined and limited otherwise, if there is a description of a first feature on a second feature, or similar descriptions, it can mean that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature can be above, above and above the second feature, or it can only mean that the first feature is higher than the second feature in horizontal height. The first feature can be below, below and below the second feature, or it can only mean that the first feature is lower than the second feature in horizontal height.

[0034] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or there can be an intermediate element. If an element is considered to be "connected" to another element, it can be directly connected to the other element or there can be an intermediate element. If present, the terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used in the present application are for illustrative purposes only and do not represent the only implementation.

[0035] The following will be described in detail below in combination with the accompanying drawings Figures 1-2 The embodiments of the present application will be further described in detail.

[0036] Figure 1 The structure of the generator stator end weld joint 31 defect detection system in an embodiment of the present application is shown, Figure 2 The circuit structure of the generator stator end weld joint 31 defect detection system in an embodiment of the present application is shown. Referring to Figure 1 and Figure 2 The generator stator end weld joint 31 defect detection system provided by an embodiment of the present application includes a high-frequency power supply circuit 1, the first end of the high-frequency power supply circuit 1 is connected to the output end of an alternating current power supply 2, the second end of the high-frequency power supply circuit 1 is connected to the stator winding of a to-be-tested generator 3, the high-frequency power supply circuit 1 is used to convert the output current of the alternating current power supply 2 into a high-frequency pulse current, and the high-frequency pulse current is passed into the stator winding; a temperature measurement module 4 is used to measure the temperature of the end weld joint 31 on both sides of the turbine and the exciter of the to-be-tested generator 3, to obtain measurement temperature data, and the measurement temperature data is used to determine the defect condition of the corresponding terminal of the stator winding.

[0037] Among them, the alternating current power supply 2 is a three-phase 380V alternating current power supply 2 on site.

[0038] In a possible implementation, the temperature measurement module 4 is an infrared thermal imager.

[0039] The infrared thermal imager has a temperature measurement range of -20-200 DEG C, a temperature resolution of not more than 0.15 DEG C, and an emissivity of 0.01-1 adjustable. The infrared image resolution is up to 640*480 pixels, and the infrared thermal imager has an automatic cold / hot spot tracking function and can display the maximum, minimum and average values of temperature.

[0040] In the embodiment, the high-frequency power supply circuit 1 stably outputs a high-frequency square wave pulse current of 20 kHz, has strong current output capacity, and makes the welding joints on both sides of the steam turbine and the exciter of the generator 3 generate heat obviously, thereby improving the precision of defect detection.

[0041] In a possible implementation, the high-frequency power supply circuit 1 in the generator stator end welding joint 31 defect detection system comprises: an input rectifier 11, an input end of the input rectifier 11 being connected with an output end of the alternating current power supply 2, for converting first alternating current output by the alternating current power supply 2 into first direct current; an inverter 12, an input end of the inverter 12 being connected with an output end of the input rectifier 11, for converting the first direct current into second alternating current; an alternating current transformer 13, an input end of the alternating current transformer 13 being connected with an output end of the inverter 12, for boosting the second alternating current into third alternating current; and an output rectifier 14, an input end of the output rectifier 14 being connected with an output end of the alternating current transformer 13, and an output end of the output rectifier 14 being connected with the stator winding, for converting the third alternating current into high-frequency pulse current and passing the high-frequency pulse current into the stator winding.

[0042] The input rectifier 11 and the output rectifier 14 are electronic devices for converting alternating current into direct current. Optionally, the input rectifier 11 and the output rectifier 14 can be diode-based rectifiers, composed of one PN junction, conducting under the action of forward voltage and cutting off under the action of reverse voltage; or can be silicon controlled rectifiers (SCR), composed of three PN junctions or four PN junctions, with an anode, a cathode and a gate, and conducting by triggering the gate; or can be power rectification modules integrated by multiple diodes or thyristors.

[0043] In a possible implementation, the input rectifier 11 is composed of semiconductor diodes. In a possible implementation, the output rectifier 14 is composed of semiconductor diodes.

[0044] For example, the input rectifier 11 composed of semiconductor diodes can be composed of six semiconductor diodes, one forward diode and one reverse diode being connected to each phase of the alternating current power supply 2, the diodes conducting under forward bias and cutting off under reverse bias, so as to output three-phase alternating current output by the alternating current power supply 2 as first direct current after rectification.

[0045] Optionally, in order to reduce the fluctuation of the first direct current, a filter circuit can be connected to the output end of the semiconductor diode: by connecting a large-capacity capacitor in parallel or connecting an inductor in series, the current output by the semiconductor diode is smoothed.

[0046] For the description of the output rectifier 14, refer to the description of the input rectifier 11 above.

[0047] In this embodiment, the input rectifier 11 and the output rectifier 14 are composed of semiconductor diodes, which utilize the low conduction voltage drop of diodes, do not have complex control circuits, and only rely on the natural characteristics of semiconductor devices to work, thereby reducing energy loss and maintenance complexity, improving reliability and applicability.

[0048] The inverter 12 is a device that converts direct current into alternating current. The inverter 12 can include a direct current input end, a power switching device, a control circuit, an output filter circuit, and a protection circuit, wherein the direct current input end is used to receive the first direct current output by the input rectifier 11, the first direct current is filtered by a direct current capacitor to stabilize the voltage; the power switching device can be an IGBT (Insulate-Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor); the control circuit includes a PWM (Pulse Width Modulation) generation circuit, which is used to control the switching state of the power device and adjust the output alternating current; the output filter circuit can include an inductor and a capacitor, which are used to smooth the output alternating voltage and reduce high-frequency noise; the protection circuit can provide overvoltage, overcurrent, and overtemperature protection functions to ensure the safe operation of the inverter 12.

[0049] In one possible embodiment, the inverter 12 is composed of a metal oxide semiconductor field effect transistor. The first direct current output by the input rectifier 11 is high-voltage, low-current direct current, which is inverted by the inverter 12 to obtain low-voltage, high-current second alternating current, and the second alternating current is input to the input end of the alternating current transformer 13; the alternating current transformer 13 raises the voltage of the second alternating current to obtain third alternating current, and inputs the third alternating current to the output rectifier 14; the output rectifier 14 rectifies the third alternating current to obtain high-frequency pulse current.

[0050] Optionally, the adjustable range of the high-frequency pulse current is 0-4000A, the voltage is less than 12V, and the frequency is as high as 20kHz.

[0051] In a possible implementation, the generator stator end weld joint 31 defect detection system provided also includes a centralized controller 15 connected with the input rectifier 11, the inverter 12 and the output rectifier 14 through control cables respectively.

[0052] The centralized controller 15 mainly includes a power management module, a micro control unit (MCU) or a digital signal processor (DSP), a signal acquisition circuit, a driving circuit, a control algorithm module, a communication module and a protection circuit. The power management module provides a stable low-voltage direct-current power supply for the centralized controller 15, ensuring stable operation of the whole system; the signal acquisition circuit collects electrical signals such as input voltage, current and output load through sensors and transmits these electrical signals to the micro control unit or the digital signal processor. The micro control unit or the digital signal processor serves as the brain of the centralized controller 15, is responsible for real-time processing of the collected electrical signals, running of the control algorithm, generation of driving signals according to the collected electrical signals and the control algorithm to control the input rectifier 11, the inverter 12 and the output rectifier 14.

[0053] In a possible implementation, the generator stator end weld joint 31 defect detection system provided also includes a current transformer 16, a first end of the current transformer 16 being connected with an output end of the output rectifier 14, and a second end of the current transformer 16 being connected with the centralized controller 15.

[0054] The current transformer 16 is arranged at a current output end of the output rectifier 14, is used for measuring an output current of the output rectifier 14, and transmits the measured output current signal to the centralized controller 15.

[0055] For example, the centralized controller 15 obtains the output current of the output rectifier 14 according to the output current signal sent by the current transformer 16, compares the output current of the output rectifier 14 with the amplitude and frequency of the target output current, obtains an error value, performs control processing on the error value, for example, based on proportional-integral control or predictive control, generates an adjustment control instruction, and adjusts the working state of the input rectifier, the inverter 12 and the output rectifier 14 according to the adjustment control instruction, so as to realize real-time adjustment of the output current. Specifically, the centralized controller 15 can change the size of the output voltage of the output rectifier 14 by adjusting the triggering angle of the thyristor in the input rectifier 11. If the triggering angle increases, the conduction time of the thyristor shortens, and the output voltage of the input rectifier 11 decreases; on the contrary, the triggering angle decreases, which increases the output voltage, thereby effectively controlling the direct current voltage entering the inverter 12. In the inverter 12 part, the centralized controller 15 generates the voltage amplitude and frequency of the target alternating current waveform by adjusting the switching frequency and duty cycle of the power switching device, such as IGBT or MOSFET. For the output rectifier, the centralized controller 15 can optimize the ripple characteristics or direction control of the output current by adjusting the conduction state of the internal power device. For example, by adjusting the conduction angle of the diode or thyristor of the output rectifier, the smooth output of the current or the energy feedback can be realized.

[0056] In the embodiment, the centralized controller 15 changes the angle of the semiconductor diode and the semiconductor field effect transistor inside the input rectifier 11, the inverter 12 and the output rectifier 14 to adjust the amplitude and frequency of the output current, so as to obtain the high-frequency pulse current meeting the requirement of the defect detection of the generator stator end weld joint 31.

[0057] In the process of detection by the generator stator end weld joint 31 defect detection system, the generator 3 to be detected includes the end weld joint 31, the lead-out wire and the neutral point. The lead-out wire terminal 32 is U, V, W in Figure 2 ; the neutral point terminal 33 is X, Y, Z in Figure 2 The stator winding of the generator 3 to be detected includes U-X phase winding, V-Y phase winding and W-Z phase winding.

[0058] In a possible embodiment, the first output end of the output rectifier 14 is connected with the neutral point terminal 33 in the stator winding, and the second output end of the output rectifier 14 is connected with the lead-out wire terminal 32 in the stator winding.

[0059] In a possible embodiment, the first output end of the output rectifier 14 is connected with the neutral point terminal 33 in the stator winding through the connecting cable 5, and the second output end of the output rectifier 14 is connected with the lead-out wire terminal 32 in the stator winding through the connecting cable 5. The connecting cable 5 is composed of a plurality of copper core unarmored cables.

[0060] The connecting cable 5 is composed of multiple 70mm 2 Each cable can continuously and stably pass through 300A of current. In specific implementation, the number of connecting cables 5 is selected according to the size of high-frequency pulse current.

[0061] Before defect detection is performed on the stator winding of the to-be-tested generator 3, the connecting soft wires between the outgoing line terminals U, V, and W and the closed bus, and the connecting soft wires between the neutral point terminals X, Y, and Z need to be removed; the rotor of the generator is extracted, the operation of the stator cooling water system is stopped, and then the U-X phase winding, the V-Y phase winding, and the W-Z phase winding are sequentially subjected to defect detection.

[0062] Taking defect detection on one of the stator windings, for example, the U-X phase winding, the first output end of the output rectifier 14 is connected to the wiring copper plate of the neutral point terminal X in the stator winding through the connecting cable 5; the second output end of the output rectifier 14 is connected to the wiring copper plate of the outgoing line terminal U in the stator winding through the connecting cable 5, and the connecting cable 5 is bolted to each terminal.

[0063] The AC power supply 2 is turned on, the centralized controller 15 is operated to slowly increase the current, 300A of test current is passed to the U-X phase winding, and the infrared thermal imager is used to monitor whether there is abnormal heating phenomenon at each connecting terminal of the connecting cable 5. If there is, it indicates that the connecting terminal of the connecting cable 5 is not in good contact, and the connecting terminal needs to be re-tightened before the current is continued to be increased. If there is no abnormality, the output current is continued to be increased until the set test current value. The test current value is 5% to 25% of the rated current of the generator. The current passing time lasts for more than 1 hour, the temperature of the end welding joint 31 on the two sides of the steam turbine and the exciter is measured every 15 minutes using the infrared thermal imager, and the highest temperature, the lowest temperature, and the maximum temperature difference are recorded.

[0064] Before the current passing time ends, the end welding joint 31 with the largest temperature difference is marked. For the welding joints without insulation, when the temperature difference reaches 5K or above, the one with higher temperature is determined as the defective welding joint. For the welding joints with insulation, when the temperature difference reaches 3K or above, the one with higher temperature is determined as the defective welding joint.

[0065] The current is reduced to zero by operating the centralized controller 15, the AC power supply 2 is turned off, and the connecting bolts of the connecting cable 5 and the outgoing line terminal 32 and the neutral point terminal 33 are removed.

[0066] In the description of the present specification, the description referring to the terms "some embodiments", "other embodiments", and the like means that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example.

[0067] Any combination of the technical features in the above embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, any combination of the technical features should be considered as within the scope of the present disclosure, as long as the combination is not contradictory.

[0068] The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be pointed out that for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A generator stator end weld joint defect detection system, characterized by, The generator stator end joint defect detection system comprises: a high-frequency power supply circuit, a first end of the high-frequency power supply circuit being connected with an output end of an alternating current power supply, a second end of the high-frequency power supply circuit being connected with a stator winding of a to-be-tested generator, the high-frequency power supply circuit being used for converting an output current of the alternating current power supply into a high-frequency pulse current and passing the high-frequency pulse current into the stator winding; a temperature measurement module, used for measuring temperatures of end joints on two sides of a steam turbine and an exciter of the to-be-tested generator to obtain measurement temperature data, the measurement temperature data being used for determining a defect condition of a corresponding terminal of the stator winding.

2. The generator stator end weld joint defect detection system of claim 1, wherein, The high-frequency power supply circuit comprises: an input rectifier, an input end of the input rectifier being connected with an output end of the alternating current power supply, the input rectifier being used for converting a first alternating current output by the alternating current power supply into a first direct current; an inverter, an input end of the inverter being connected with an output end of the input rectifier, the inverter being used for converting the first direct current into a second alternating current; an alternating current transformer, an input end of the alternating current transformer being connected with an output end of the inverter, the alternating current transformer being used for boosting the second alternating current into a third alternating current; an output rectifier, an input end of the output rectifier being connected with an output end of the alternating current transformer, an output end of the output rectifier being connected with the stator winding, the output rectifier being used for converting the third alternating current into the high-frequency pulse current and passing the high-frequency pulse current into the stator winding.

3. The generator stator end weld joint defect detection system of claim 2, wherein, The input rectifier is composed of semiconductor diodes.

4. The generator stator end weld joint defect detection system of claim 2, wherein, The inverter is composed of metal oxide semiconductor field effect transistors.

5. The generator stator end weld joint defect detection system of claim 2, wherein, The output rectifier is composed of semiconductor diodes.

6. The generator stator end weld joint defect detection system of claim 2, wherein, A first output end of the output rectifier is connected with a neutral point terminal in the stator winding, and a second output end of the output rectifier is connected with a lead wire terminal in the stator winding.

7. The generator stator end turn weld joint defect detection system of claim 6, wherein, A first output end of the output rectifier is connected with a neutral point terminal in the stator winding through a connecting cable, and a second output end of the output rectifier is connected with a lead wire terminal in the stator winding through the connecting cable, the connecting cable being composed of a plurality of copper core unarmored cables.

8. The generator stator end weld joint defect detection system of claim 2, wherein, The generator stator end joint defect detection system further comprises a centralized controller, the centralized controller being connected with the input rectifier, the inverter and the output rectifier through control cables respectively.

9. The generator stator end weld joint defect detection system of claim 8, wherein, The generator stator end joint defect detection system further comprises a current transformer, a first end of the current transformer being connected with an output end of the output rectifier, and a second end of the current transformer being connected with the centralized controller.

10. The generator stator end turn weld joint defect detection system of claim 1, wherein, The temperature measurement module is an infrared thermal imager.

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