Degaussing circuit and degaussing device for rotor of steam turbine generator

Abstract

The utility model relates to a steam turbine generator rotor degaussing circuit and degaussing device.The degaussing circuit comprises a degaussing winding, a direct current degaussing sub-circuit and an alternating current degaussing sub-circuit, the degaussing winding is used for providing a degaussing direct current magnetic field or alternating current magnetic field, and the degaussing winding is wound on the surface of a steam turbine generator rotor; the output end of the direct current degaussing sub-circuit is connected with the degaussing winding, and the direct current degaussing sub-circuit is used for providing direct current and degaussing the first part of the steam turbine generator rotor; the output end of the alternating current degaussing sub-circuit is connected with the degaussing winding, the alternating current degaussing sub-circuit is used for providing alternating current and degaussing a second part of the steam turbine generator rotor, and the cross sectional area of the second part is smaller than that of the first part. According to the rotor demagnetizing circuit of the steam turbine generator, the problem that different magnetized parts of the rotor are difficult to demagnetize by using the same equipment can be solved, so that the rotor demagnetizing work of the steam turbine generator becomes simple, convenient and efficient.

Description

Technical Field

[0001] This application relates to the field of generator technology, and in particular to a demagnetizing circuit and demagnetizing device for a steam turbine generator rotor. Background Technology

[0002] Steam turbine generator rotors are prone to magnetization due to factors such as inter-turn short circuits in the windings, two-point grounding faults, or magnetic circuit imbalance caused by asymmetry in the air gap between the stator and rotor. Rotor magnetization results in axial or radial remanence, meaning the rotor retains magnetic induction even when the magnetic field strength is zero. Axial remanence generates a unipolar potential during rotor operation, ultimately forming a shaft voltage. If the rotor remanence is too high and the rotor bearing insulation is poor, a large shaft current will be generated in the circuit between the rotor shaft, bearings, and ground. If the rotor remanence is too low, it leads to rotor electro-corrosion, potentially burning out the bearings, and also causes abnormally increased rotor vibration, severely affecting the safe operation of the generator. To prevent rotor malfunctions caused by excessive remanence, it is necessary to demagnetize the areas of the rotor where remanence exists.

[0003] In related technologies, commonly used methods for eliminating residual magnetism in steam turbine generator rotors include heating demagnetization, direct current demagnetization, and alternating current demagnetization. However, since different demagnetization methods are applicable to different objects and scenarios, and the axial cross-section of steam turbine generator rotors also varies, if a simple DC or AC welding machine is used to demagnetize the generator rotor, the demagnetization efficiency is low and the demagnetization effect is poor due to the limited output DC or AC current. Utility Model Content

[0004] Therefore, it is necessary to provide a turbine generator rotor demagnetization circuit and demagnetization device to address the problems of low demagnetization efficiency and poor demagnetization effect of the demagnetization methods mentioned above.

[0005] In a first aspect, this application provides a demagnetizing circuit for a steam turbine generator rotor, comprising:

[0006] The demagnetizing winding is used to provide a demagnetizing DC or AC magnetic field. The demagnetizing winding is wound around the surface of the turbine generator rotor.

[0007] The DC demagnetizing sub-circuit is connected to the demagnetizing winding at its output. It provides DC power to demagnetize the first part of the turbine generator rotor.

[0008] The AC demagnetizing sub-circuit has its output terminal connected to the demagnetizing winding. The AC demagnetizing sub-circuit is used to provide AC power to demagnetize the second part of the turbine generator rotor, wherein the cross-sectional area of ​​the second part is smaller than that of the first part.

[0009] In one embodiment, the DC demagnetizing sub-circuit includes the following sequentially connected components:

[0010] The first power switch is used to turn on and off the input of the mains power supply;

[0011] The first rectifier module is used to convert AC power from the grid into high-voltage pulsating DC power.

[0012] Inverter module, used to convert high-voltage pulsating DC power into high-voltage high-frequency AC voltage square wave with adjustable pulse width;

[0013] The first transformer is used to convert a high-voltage, high-frequency AC voltage square wave into a low-voltage, high-frequency AC voltage square wave.

[0014] The second rectifier module is used to convert low-voltage, high-frequency AC square wave into low-voltage, high-current DC.

[0015] A DC output switch is used to turn on and off the output of low-voltage DC with high current.

[0016] In one embodiment, the first rectifier module includes an even number of first rectifier diodes, each of which is divided into an upper part and a lower part. The anode of the first rectifier diode located in the upper part and the cathode of the first rectifier diode located in the lower part are connected to form one of the input terminals of the first rectifier module.

[0017] The cathodes of the first rectifier diodes located at the top are connected together, serving as the positive voltage output terminal of the first rectifier module; the anodes of the first rectifier diodes located at the bottom are connected together, serving as the negative voltage output terminal of the first rectifier module.

[0018] When the first rectifier module is working, each of its input terminals has a first rectifier diode located at the top and a first rectifier diode located at the bottom that are turned on.

[0019] In one embodiment, the first rectifier module further includes a first filter capacitor, one end of which is connected to the positive voltage output terminal, and the other end of which is connected to the negative voltage output terminal.

[0020] In one embodiment, the inverter module includes a first bridge arm, a second bridge arm, a third bridge arm, and a fourth bridge arm. Each bridge arm includes an N-type AC enhancement-mode MOSFET, a parallel capacitor, and a diode. The drain of the MOSFET is connected to the cathode of the diode, and the source of the MOSFET is connected to the anode of the diode. The diode is used to prevent reverse breakdown of the MOSFET. The parallel capacitor is used to enable fast switching of the MOSFET and reduce power consumption. The inverter module controls the first bridge arm and the fourth bridge arm, or the second bridge arm and the third bridge arm, to alternately turn on and off by inputting two sets of drive signals from the gate of the MOSFET, so as to control the voltage and frequency of the output AC power.

[0021] In one embodiment, the drain of the first bridge arm is connected to the drain of the third bridge arm, serving as the first input terminal of the inverter module; the source of the second bridge arm is connected to the source of the fourth bridge arm, serving as the second input terminal of the inverter module; the source of the first bridge arm is connected to the drain of the second bridge arm, serving as one output terminal of the inverter module; the source of the third bridge arm is connected to the drain of the fourth bridge arm, serving as the other output terminal of the inverter module; the first input terminal of the inverter module is connected to the positive voltage output terminal of the first rectifier module, and the second input terminal of the inverter module is connected to the negative voltage output terminal of the first rectifier module; the output terminal of the inverter module is connected to the input terminal of the first transformer.

[0022] In one embodiment, the inverter module further includes a resonant inductor and a DC blocking capacitor. The resonant inductor is connected in series at one of the output terminals of the inverter module to enhance the resonant energy of the lagging bridge arm; the DC blocking capacitor is connected in series at the other output terminal of the inverter module to prevent DC bias of the first transformer.

[0023] In one embodiment, the second rectifier module includes two second rectifier diodes, an absorption capacitor, a current-limiting resistor, a freewheeling diode, a filter inductor, a second filter capacitor, a Hall current sensor, and a DC ammeter. The anodes of the two second rectifier diodes serve as the input terminals of the second rectifier module and are respectively connected to the two output terminals of the first transformer. The cathodes of the two second rectifier diodes are connected together and then connected to one end of the filter inductor. The absorption capacitor and the current-limiting resistor are connected in series and then in parallel with the output terminal of the first transformer. The absorption capacitor and the current-limiting resistor are used to absorb the surge voltage and high-frequency oscillation voltage generated during the reverse recovery of the second rectifier diodes. The cathode of the freewheeling diode... The cathode of the first rectifier diode is connected to the cathode of the second rectifier diode, and the anode of the freewheeling diode is connected to the center tap of the first transformer. The freewheeling diode provides a freewheeling path for the DC current to reduce the freewheeling current at the input of the first transformer. One end of the filter inductor is connected to the cathode of the second rectifier diode, and the other end of the filter inductor is connected to one end of the second filter capacitor, which then serves as the output terminal of the second rectifier module and is connected to the input terminal of the DC output switch. The other end of the second filter capacitor is connected to the center tap of the first transformer, which then serves as the other output terminal of the second rectifier module and is connected to the other input terminal of the DC output switch. The filter inductor and the second filter capacitor are used to reduce the ripple of the DC voltage.

[0024] In one embodiment, the AC demagnetizing sub-circuit includes the following sequentially connected components:

[0025] Second power switch;

[0026] Voltage regulator;

[0027] Second transformer;

[0028] Current measuring instrument;

[0029] An AC output switch is provided; wherein, the input terminal of the voltage regulator is connected to the phase line and neutral line of the power grid, the second power switch is connected in series between the phase line of the power grid and the input terminal of the voltage regulator, the output terminal of the voltage regulator is connected to the input terminal of the second transformer, the output terminal of the second transformer is connected to the input terminal of the AC output switch, and the output terminal of the AC output switch is connected to the demagnetizing winding.

[0030] Secondly, this application provides a demagnetizing device, including any of the turbine generator rotor demagnetizing circuits provided in the first aspect.

[0031] The aforementioned demagnetizing circuit for the turbine generator rotor includes a demagnetizing winding, a DC demagnetizing sub-circuit, and an AC demagnetizing sub-circuit. The demagnetizing winding is used to provide a DC or AC magnetic field for demagnetization and is wound around the surface of the turbine generator rotor. The output terminal of the DC demagnetizing sub-circuit is connected to the demagnetizing winding and is used to provide DC power to demagnetize the first part of the turbine generator rotor. The output terminal of the AC demagnetizing sub-circuit is connected to the demagnetizing winding and is used to provide AC power to demagnetize the second part of the turbine generator rotor, wherein the cross-sectional area of ​​the second part is smaller than that of the first part. The turbine generator rotor demagnetizing circuit in this application, through the combined operation of a demagnetizing winding, a DC demagnetizing sub-circuit, and an AC demagnetizing sub-circuit, possesses both DC and AC demagnetizing functions. Users can select an appropriate demagnetizing method based on the specific magnetized part of the rotor (e.g., one or more parts of the first or second part), the residual magnetism, and the available power capacity. This solves the problem of using the same equipment to demagnetize different magnetized parts of the rotor, making turbine generator rotor demagnetizing simple and efficient. Furthermore, the turbine generator rotor demagnetizing circuit of this application can output stable and adjustable high-current DC and AC currents. By adjusting the output current magnitude and time, the residual magnetism can be eliminated. The AC and DC demagnetizing sub-circuits are interlocked, isolated from each other, and do not interfere with each other. The DC demagnetizing sub-circuit has a current reversing function, allowing it to output reverse voltage without changing the wiring, achieving reverse DC demagnetization, making operation simple and convenient. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the demagnetization circuit of the turbine generator rotor in some embodiments of this application;

[0034] Figure 2 This is a schematic diagram of the DC demagnetizing sub-circuit in some embodiments of this application;

[0035] Figure 3 This is a circuit connection diagram of the demagnetization circuit of the turbine generator rotor in some embodiments of this application;

[0036] Figure 4 This is a schematic diagram of the AC demagnetizing sub-circuit in some embodiments of this application.

[0037] Explanation of icon numbers:

[0038] 100. Demagnetizing winding; 200. DC demagnetizing sub-circuit; 210. First power switch; 220. First rectifier module; 230. Inverter module; 240. First transformer; 250. Second rectifier module; 260. DC output switch; 300. AC demagnetizing sub-circuit; 310. Second power switch; 320. Voltage regulator; 330. Second transformer; 340. Current meter; 350. AC output switch; D1. First rectifier diode; C1. First filter circuit. Capacitors; B1, First bridge arm; B2, Second bridge arm; B3, Third bridge arm; B4, Fourth bridge arm; C2, Parallel capacitor; D2, Diode; Q, MOSFET; L1, Resonant inductor; C3, DC blocking capacitor; D3, Second rectifier diode; C4, Absorption capacitor; R, Current limiting resistor; D4, Freewheeling diode; L2, Filter inductor; C5, Second filter capacitor; CS, Hall effect current sensor; A1, DC ammeter; A2, AC ammeter; CT, Current transformer. Detailed Implementation

[0039] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0040] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0042] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0043] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0044] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0045] Steam turbine generator rotors are prone to magnetization due to factors such as inter-turn short circuits in the windings, two-point grounding faults, or magnetic circuit imbalance caused by asymmetry in the air gap between the stator and rotor. Rotor magnetization results in axial or radial remanence, meaning the rotor retains magnetic induction even when the magnetic field strength is zero. Axial remanence generates a unipolar potential during rotor operation, ultimately forming a shaft voltage. If the rotor remanence is too high and the rotor bearing insulation is poor, a large shaft current will be generated in the circuit between the rotor shaft, bearings, and ground. If the rotor remanence is too low, it leads to rotor electro-corrosion, potentially burning out the bearings, and also causes abnormally increased rotor vibration, severely affecting the safe operation of the generator. To prevent rotor malfunctions caused by excessive remanence, it is necessary to demagnetize the areas of the rotor where remanence exists.

[0046] In related technologies, commonly used methods for eliminating residual magnetism in turbine generator rotors include heating demagnetization, direct current demagnetization, and alternating current demagnetization. Heating demagnetization utilizes a heat source to raise the rotor's temperature, accelerating the movement of metal atoms and causing the ordered magnetic domains to realign randomly, thus achieving demagnetization. However, heating demagnetization is difficult to implement in the field, and the rotor heating process may damage the rotor coils.

[0047] DC demagnetization works by continuously changing the magnitude and direction of a direct current to reduce the hysteresis loop, thus achieving demagnetization. Because direct current has no reactance, the voltage required for the applied current in DC demagnetization is very low, and the power supply capacity is also small. However, DC demagnetization requires repeatedly changing the direction of the current, resulting in low demagnetization efficiency. Therefore, DC demagnetization is mainly used for rotor components with large cross-sectional areas, such as rotor journals, slip rings, and fan discs.

[0048] Alternating current (AC) demagnetization utilizes the alternating magnetic field generated by alternating current to continuously change the alignment of magnetic domains within a magnetic object, thereby achieving demagnetization. AC demagnetization is simple to operate and has higher demagnetization efficiency; however, it suffers from the skin effect, making it less effective for large components. Furthermore, AC demagnetization requires a high-capacity power supply. Therefore, AC demagnetization is primarily used for rotor components with small cross-sectional areas, such as rotor retaining rings and center rings.

[0049] In summary, since different demagnetization methods are applicable to different objects and scenarios, and the axial cross-section of the turbine generator rotor is also of different sizes, if a simple DC or AC welding machine is used to demagnetize the generator rotor, the demagnetization efficiency is low and the demagnetization effect is poor due to the limited output DC or AC current.

[0050] To address the issues of low demagnetization efficiency and poor demagnetization effect in the aforementioned related technologies, firstly, referring to... Figure 1 One embodiment of this application provides a demagnetizing circuit for a steam turbine generator rotor, including a demagnetizing winding 100, a DC demagnetizing sub-circuit 200, and an AC demagnetizing sub-circuit 300. The demagnetizing winding 100 is used to provide a demagnetizing DC magnetic field or AC magnetic field, and the demagnetizing winding 100 is wound around the surface of the steam turbine generator rotor. The output terminal of the DC demagnetizing sub-circuit 200 is connected to the demagnetizing winding 100, and the DC demagnetizing sub-circuit 200 is used to provide DC power to demagnetize a first part of the steam turbine generator rotor. The output terminal of the AC demagnetizing sub-circuit 300 is connected to the demagnetizing winding 100, and the AC demagnetizing sub-circuit 300 is used to provide AC power to demagnetize a second part of the steam turbine generator rotor, wherein the cross-sectional area of ​​the second part is smaller than the cross-sectional area of ​​the first part.

[0051] The first part includes rotor components with larger cross-sectional areas, such as the rotor journal, slip rings, and fan disc. The second part includes rotor components with smaller cross-sectional areas, such as the bearing shells, rotor retaining rings, and center ring.

[0052] Specifically, DC demagnetization involves applying a DC current in the opposite direction to the rotor's magnetic field to gradually reduce the rotor's magnetic field strength, ultimately achieving demagnetization. Due to the characteristics of DC current, it can be evenly distributed over a large cross-sectional area, thus effectively eliminating the magnetic field across the entire large cross-sectional area. Therefore, for rotor sections with large cross-sectional areas, the DC demagnetization sub-circuit 200 is used for demagnetization.

[0053] Alternating current (AC) demagnetization works by applying an alternating current, causing the magnetic field to fluctuate back and forth in the positive and negative directions. This gradually weakens the magnetic field to zero by narrowing the hysteresis loop. The frequency and amplitude of the AC current can be adjusted as needed, making it suitable for handling small-area magnetic field problems. Therefore, AC demagnetization sub-circuit 300 is used for demagnetization.

[0054] The turbine generator rotor demagnetizing circuit in this embodiment, through the combined operation of the demagnetizing winding 100, the DC demagnetizing sub-circuit 200, and the AC demagnetizing sub-circuit 300, possesses both DC and AC demagnetizing functions. Users can select an appropriate demagnetizing method based on the specific magnetized part of the rotor (e.g., any one or more parts of the first or second part), the residual magnetism, and the available power capacity. This solves the problem of using the same equipment to demagnetize different magnetized parts of the rotor, making turbine generator rotor demagnetizing simple and efficient. Furthermore, the turbine generator rotor demagnetizing circuit in this embodiment can output stable and adjustable high-current DC and AC currents. By adjusting the output current magnitude and time, the residual magnetism can be eliminated. The AC demagnetizing sub-circuit 300 and the DC demagnetizing sub-circuit 200 have an interlocking function, ensuring mutual isolation and no interference. The DC demagnetizing sub-circuit 200 has a current reversing function, allowing it to output reverse voltage without changing the wiring, achieving reverse DC demagnetization, making operation simple and convenient.

[0055] Reference Figure 2 In some embodiments, the DC demagnetizing sub-circuit 200 includes a first power switch 210, a first rectifier module 220, an inverter module 230, a first transformer 240, a second rectifier module 250, and a DC output switch 260 connected in sequence. The first power switch 210 is used to turn on and off the input of the grid power supply; the first rectifier module 220 is used to convert the AC power from the grid power supply into high-voltage pulsating DC power; the inverter module 230 is used to convert the high-voltage pulsating DC power into a high-voltage high-frequency AC voltage square wave with adjustable pulse width; the first transformer 240 is used to convert the high-voltage high-frequency AC voltage square wave into a low-voltage high-frequency AC voltage square wave; the second rectifier module 250 is used to convert the low-voltage high-frequency AC voltage square wave into a low-voltage DC high current; and the DC output switch 260 is used to turn on and off the output of the low-voltage DC high current.

[0056] The first power supply is a three-stage switch used to turn the grid power input on and off. The three input terminals of the first power switch 210 are connected to phases A, B, and C of the grid power supply, respectively, and its three output terminals are connected to the input terminals of the first rectifier module 220. The first transformer 240 is a high-frequency step-down transformer with a center tap at its output terminal. The center tap divides the output winding into two symmetrical windings, upper and lower. The upper and lower windings output AC voltages of equal magnitude but opposite polarity. The input terminal of the first transformer 240 is connected to the output terminal of the inverter module 230, and the output terminal of the first transformer 240 is connected to the input terminal of the second rectifier module 250.

[0057] In this embodiment, the first power switch 210, the first rectifier module 220, the inverter module 230, the first transformer 240, the second rectifier module 250 and the DC output switch 260 work together to achieve the output of DC current, so as to effectively demagnetize rotor parts with large cross-sectional areas such as rotor journals, slip rings, and fan discs.

[0058] Reference Figure 3 In some embodiments, the first rectifier module 220 includes an even number of first rectifier diodes D1, each of which is divided into an upper part and a lower part. The anode of the upper first rectifier diode D1 and the cathode of the lower first rectifier diode D1 are connected to form one of the input terminals of the first rectifier module 220. The cathodes of the upper first rectifier diodes D1 are connected together to serve as the positive voltage output terminal of the first rectifier module 220, and the anodes of the lower first rectifier diodes D1 are connected together to serve as the negative voltage output terminal of the first rectifier module 220. When the first rectifier module 220 is working, the upper and lower first rectifier diodes D1 corresponding to one of the input terminals are turned on.

[0059] In this embodiment, six first rectifier diodes D1 are used to form a bridge rectifier structure. Three first rectifier diodes D1 are located at the top, and the remaining three are located at the bottom. The anodes of the three upper first rectifier diodes D1 are connected to the cathodes of the three lower first rectifier diodes D1, forming the three input terminals of the first rectifier module 220. The cathodes of the three upper first rectifier diodes D1 are connected together as the positive voltage output terminal of the first rectifier module 220, and the anodes of the three lower first rectifier diodes D1 are connected together as the negative voltage output terminal of the first rectifier module 220. When the first rectifier module 220 is working, two specific first rectifier diodes D1 are conducting at any given time, ensuring that the current always flows in the same direction, thereby converting alternating current into direct current.

[0060] Reference Figure 3 In some embodiments, the first rectifier module 220 further includes a first filter capacitor C1, one end of which is connected to the positive voltage output terminal, and the other end of which is connected to the negative voltage output terminal.

[0061] Specifically, the first filter capacitor C1 is used to filter out the AC components caused by the rectification process, reduce the ripple of the output voltage, and make the output DC voltage more stable.

[0062] Reference Figure 3In some embodiments, the inverter module 230 includes a first bridge arm B1, a second bridge arm B2, a third bridge arm B3, and a fourth bridge arm B4. Each bridge arm includes an N-type AC enhancement-mode MOSFET Q, a parallel capacitor C2, and a diode D2. The drain of the MOSFET Q is connected to the cathode of the diode D2, and the source of the MOSFET Q is connected to the anode of the diode D2. The diode D2 is used to prevent reverse breakdown of the MOSFET Q. The parallel capacitor C2 is used to enable fast switching of the MOSFET Q and reduce power consumption. The inverter module 230 controls the first bridge arm B1 and the fourth bridge arm B4, or the second bridge arm B2 and the third bridge arm B3, to alternately turn on and off by inputting two sets of drive signals from the gate of the MOSFET Q, thereby controlling the voltage and frequency of the output AC power. The output terminal of the inverter module 230 is connected to the input terminal of the first transformer 240.

[0063] The first rectifier module 210 converts AC power into DC power and outputs positive and negative voltages. The first bridge arm B1, the second bridge arm B2, the third bridge arm B3, and the fourth bridge arm B4 can form an H-bridge inverter.

[0064] Specifically, the first input terminal of the inverter module 230 is connected to the positive voltage output terminal of the first rectifier module 220, and the second input terminal is connected to the negative voltage output terminal of the first rectifier module 220, forming a DC voltage source. Two sets of drive signals are input from the gate of the MOSFET Q to control the first bridge arm B1 and the fourth bridge arm B4, or the second bridge arm B2 and the third bridge arm B3, to alternately turn on and off. When the first bridge arm B1 and the fourth bridge arm B4 are on, current flows from the positive terminal through the first bridge arm B1 to the load, and then returns to the negative terminal through the fourth bridge arm B4, outputting a positive voltage. When the second bridge arm B2 and the third bridge arm B3 are on, current flows from the positive terminal through the second bridge arm B2 to the load, and then returns to the negative terminal through the third bridge arm B3, outputting a negative voltage.

[0065] Reference Figure 3 In some embodiments, the drain of the first bridge arm B1 is connected to the drain of the third bridge arm B3, serving as the first input terminal of the inverter module 230; the source of the second bridge arm B2 is connected to the source of the fourth bridge arm B4, serving as the second input terminal of the inverter module 230; the source of the first bridge arm B1 is connected to the drain of the second bridge arm B2, serving as one output terminal of the inverter module 230; the source of the third bridge arm B3 is connected to the drain of the fourth bridge arm B4, serving as the other output terminal of the inverter module 230; the first input terminal of the inverter module 230 is connected to the positive voltage output terminal of the first rectifier module 220, and the second input terminal of the inverter module 230 is connected to the negative voltage output terminal of the first rectifier module 220.

[0066] Specifically, the H-bridge inverter converts DC voltage to AC voltage by controlling the switching devices in its four arms. When the first arm B1 and the fourth arm B4 are on, current flows from the first arm B1 to the fourth arm B4, resulting in a positive output voltage. When the second arm B2 and the third arm B3 are on, current flows from the second arm B2 to the third arm B3, resulting in a negative output voltage. By alternately controlling the switching states of the four arms, an AC voltage waveform can be generated. The output AC voltage of the inverter module 230 is applied to the primary winding of the first transformer 240. The first transformer 240 transforms the voltage and current to ultimately output the desired AC voltage. By adjusting the pulse width of the drive signal, the on-time of the MOSFET Q can be controlled, thereby adjusting the frequency and amplitude of the output AC voltage.

[0067] Reference Figure 3 In some embodiments, the inverter module 230 further includes a resonant inductor L1 and a DC blocking capacitor C3. The resonant inductor L1 is connected in series with one of the output terminals of the inverter module 230 to enhance the resonant energy of the lagging bridge arm; the DC blocking capacitor C3 is connected in series with the other output terminal of the inverter module 230 to prevent the first transformer 240 from being DC biased.

[0068] Reference Figure 3 In some embodiments, the second rectifier module 250 includes two second rectifier diodes D3, an absorption capacitor C4, a current-limiting resistor R, a freewheeling diode D4, a filter inductor L2, a second filter capacitor C5, a Hall current sensor CS, and a DC ammeter A1. The anodes of the two second rectifier diodes D3 serve as the input terminals of the second rectifier module 250, respectively connected to the two output terminals of the first transformer 240. The cathodes of the two second rectifier diodes D3 are connected together and then connected to one end of the filter inductor L2. The absorption capacitor C4 and the current-limiting resistor R are connected in series and then in parallel with the output terminal of the first transformer 240. The absorption capacitor C4 and the current-limiting resistor R are used to absorb the impulse voltage and high-frequency oscillation voltage generated when the second rectifier diodes D3 reverse recover. The cathodes of the freewheeling diodes D4... The cathode of the second rectifier diode D3 is connected to the cathode of the freewheeling diode D4, and the anode of the freewheeling diode D4 is connected to the center tap of the first transformer 240. The freewheeling diode D4 provides a freewheeling circuit for the DC current to reduce the freewheeling current at the input terminal of the first transformer 240. One end of the filter inductor L2 is connected to the cathode of the second rectifier diode D3, and the other end of the filter inductor L2 is connected to one end of the second filter capacitor C5, which serves as the output terminal of the second rectifier module 250 and is connected to the input terminal of the DC output switch 260. The other end of the second filter capacitor C5 is connected to the center tap of the first transformer 240, which serves as the other output terminal of the second rectifier module 250 and is connected to the other input terminal of the DC output switch 260. The filter inductor L2 and the second filter capacitor C5 are used to reduce the ripple of the DC voltage.

[0069] Specifically, the first transformer 240 outputs AC voltage, which is converted to DC voltage through full-wave rectification by two second rectifier diodes D3. An absorption capacitor C4 and a current-limiting resistor R are connected in series and parallel to the output terminal of the first transformer 240 to absorb the surge voltage and high-frequency oscillation voltage generated by the second rectifier diodes D3 during reverse recovery, protecting the circuit from overvoltage and high-frequency interference. A freewheeling diode D4 provides a freewheeling loop for DC current. When the second rectifier diodes D3 are not conducting, the freewheeling diode D4 conducts, allowing current to flow through the center tap of the first transformer 240, thereby reducing the freewheeling current at the input terminal of the first transformer 240 and lowering duty cycle and conduction losses. A filter inductor L2 and a second filter capacitor C5 form an LC filter circuit to reduce the ripple of the rectified pulsating DC voltage and improve the smoothness of the output voltage. A Hall current sensor CS and a DC ammeter A1 monitor the current value output by the DC demagnetizing sub-circuit 200 to ensure the safe and stable operation of the system.

[0070] Reference Figure 3 and Figure 4 In some embodiments, the AC demagnetizing sub-circuit 300 includes a second power switch 310, a voltage regulator 320, a second transformer 330, a current meter 340, and an AC output switch 350 connected in sequence. The input terminal of the voltage regulator 320 is connected to the phase and neutral lines of the power grid. The second power switch 310 is connected in series between the phase line of the power grid and the input terminal of the voltage regulator 320. The output terminal of the voltage regulator 320 is connected to the input terminal of the second transformer 330. The output terminal of the second transformer 330 is connected to the input terminal of the AC output switch 350. The output terminal of the AC output switch 350 is connected to the demagnetizing winding 100.

[0071] The second transformer 330 is a step-down transformer used to output a large low-voltage AC current. One output terminal of the second transformer 330 is equipped with a current measuring device 340, which consists of a through-core current transformer (CT) and an AC ammeter A2, used to monitor the current value output by the AC demagnetizing sub-circuit 300. The AC output switch 350 is a double-pole switch that can simultaneously turn on or off the AC current output. The AC output switch 350 and the DC output switch 260 have an interlocking function, which is accomplished by two relays. When the AC output switch 350 is on, the DC output switch 260 is off, and the DC demagnetizing sub-circuit 200 and the AC demagnetizing sub-circuit 300 are isolated from each other and do not interfere with each other.

[0072] Specifically, the AC demagnetizing sub-circuit 300, through the joint operation of the second power switch 310, voltage regulator 320, second transformer 330, current measuring device 340 and AC output switch 350, realizes the output of AC power to demagnetize rotor parts with small cross-sectional areas such as bearings, rotor retaining rings, and center rings.

[0073] Reference Figure 3 In some embodiments, the DC output switch 260 is a double-pole double-throw switch used to turn on and off the DC output. The double-pole double-throw switch has three states: forward conduction, intermediate off, and reverse conduction. By switching the switch to the opposite conduction position, the output direction of the DC power can be changed, achieving reverse DC demagnetization. The DC output switch 260 and the AC output switch 350 have an interlocking function, which is accomplished by two relays. When the DC output switch 260 is on, the AC output switch 350 is off, and the DC demagnetization sub-circuit 200 and the AC demagnetization sub-circuit 300 are isolated from each other and do not interfere with each other. The input terminal of the DC output switch 260 is connected to the output terminal of the second rectifier module 250, and the output terminal of the DC output switch 260 is connected to the demagnetization winding 100.

[0074] The turbine generator rotor demagnetizing circuit of this application has both DC and AC demagnetizing functions. Users can select the appropriate demagnetizing method based on the specific magnetized parts of the rotor, the residual magnetism, and the available power supply capacity. This solves the problem of using the same equipment to demagnetize different magnetized parts of the rotor, making turbine generator rotor demagnetizing work simple and efficient. Furthermore, this demagnetizing circuit can output stable and adjustable high-current DC and AC currents. By adjusting the output current magnitude and time, the residual magnetism can be eliminated. AC and DC demagnetizing have an interlocking function, ensuring that the two circuits are isolated and do not interfere with each other. The DC demagnetizing subcircuit 200 has a current reversing function, allowing it to output reverse voltage without changing the wiring, achieving reverse DC demagnetizing, making operation simple and convenient.

[0075] Secondly, one embodiment of this application provides a demagnetizing device, including any of the turbine generator rotor demagnetizing circuits provided in the first aspect above.

[0076] Specifically, after the demagnetizing device has any of the demagnetizing circuits for the turbine generator rotor provided in the first aspect above, it also has the functions of DC demagnetization and AC demagnetization. Users can select the appropriate demagnetizing method to effectively demagnetize the rotor according to the specific magnetized part, the residual magnetism, and the available power supply capacity. This solves the problem that it is difficult to use the same equipment to demagnetize different magnetized parts of the rotor, making the demagnetizing work of the turbine generator rotor simple and efficient.

[0077] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0078] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A demagnetizing circuit for a steam turbine generator rotor, characterized in that, The turbine generator rotor demagnetization circuit includes: A demagnetizing winding, used to provide a demagnetizing DC magnetic field or AC magnetic field, is wound around the surface of the turbine generator rotor; A DC demagnetizing sub-circuit, the output of which is connected to the demagnetizing winding, is used to provide DC power to demagnetize the first part of the turbine generator rotor. An AC demagnetizing sub-circuit is provided, the output of which is connected to the demagnetizing winding. The AC demagnetizing sub-circuit is used to provide AC power to demagnetize a second part of the turbine generator rotor, wherein the cross-sectional area of ​​the second part is smaller than that of the first part.

2. The turbine generator rotor demagnetization circuit according to claim 1, characterized in that, The DC demagnetizing sub-circuit includes the following components connected in sequence: The first power switch is used to turn on and off the input of the mains power supply; The first rectifier module is used to convert the AC power from the grid into high-voltage pulsating DC power. The inverter module is used to convert the high-voltage pulsating DC power into a high-voltage high-frequency AC voltage square wave with adjustable pulse width. The first transformer is used to convert the high-voltage high-frequency AC voltage square wave into a low-voltage high-frequency AC voltage square wave. The second rectifier module is used to convert the low-voltage high-frequency AC voltage square wave into a low-voltage DC high current. A DC output switch is used to turn on and off the output of the low-voltage DC high current.

3. The demagnetizing circuit for the turbine generator rotor according to claim 2, characterized in that, The first rectifier module includes an even number of first rectifier diodes, each of which is divided into an upper part and a lower part. The anode of the first rectifier diode located in the upper part and the cathode of the first rectifier diode located in the lower part are connected to form one of the input terminals of the first rectifier module. The cathodes of the first rectifier diodes located at the top are connected together, serving as the positive voltage output terminal of the first rectifier module; the anodes of the first rectifier diodes located at the bottom are connected together, serving as the negative voltage output terminal of the first rectifier module. When the first rectifier module is working, one of the first rectifier diodes located at the upper part and the other at the lower part corresponding to the input terminal is turned on.

4. The demagnetizing circuit for a steam turbine generator rotor according to claim 3, characterized in that, The first rectifier module further includes a first filter capacitor, one end of which is connected to the positive voltage output terminal, and the other end of which is connected to the negative voltage output terminal.

5. The demagnetizing circuit for a steam turbine generator rotor according to claim 3, characterized in that, The inverter module includes a first bridge arm, a second bridge arm, a third bridge arm, and a fourth bridge arm. Each bridge arm includes an N-type AC enhancement-mode MOSFET, a parallel capacitor, and a diode. The drain of the MOSFET is connected to the cathode of the diode, and the source of the MOSFET is connected to the anode of the diode. The diode is used to prevent the MOSFET from reverse breakdown. The parallel capacitor is used to enable fast switching of the MOSFET and reduce power consumption. The inverter module controls the first bridge arm and the fourth bridge arm, or the second bridge arm and the third bridge arm, to alternately turn on and off by inputting two sets of drive signals from the gate of the MOSFET, thereby controlling the voltage and frequency of the output AC power.

6. The demagnetizing circuit for a steam turbine generator rotor according to claim 5, characterized in that, The drain of the first bridge arm is connected to the drain of the third bridge arm, serving as the first input terminal of the inverter module; the source of the second bridge arm is connected to the source of the fourth bridge arm, serving as the second input terminal of the inverter module; the source of the first bridge arm is connected to the drain of the second bridge arm, serving as one output terminal of the inverter module; the source of the third bridge arm is connected to the drain of the fourth bridge arm, serving as the other output terminal of the inverter module; the first input terminal of the inverter module is connected to the positive voltage output terminal of the first rectifier module, and the second input terminal of the inverter module is connected to the negative voltage output terminal of the first rectifier module; the output terminal of the inverter module is connected to the input terminal of the first transformer.

7. The demagnetizing circuit for a steam turbine generator rotor according to claim 5, characterized in that, The inverter module also includes a resonant inductor and a DC blocking capacitor. The resonant inductor is connected in series at one of the output terminals of the inverter module to enhance the resonant energy of the lagging bridge arm. The DC blocking capacitor is connected in series at the other output terminal of the inverter module to prevent the first transformer from being DC biased.

8. The demagnetizing circuit for a steam turbine generator rotor according to claim 2, characterized in that, The second rectifier module includes two second rectifier diodes, an absorption capacitor, a current-limiting resistor, a freewheeling diode, a filter inductor, a second filter capacitor, a Hall current sensor, and a DC ammeter. The anodes of the two second rectifier diodes serve as the input terminals of the second rectifier module and are respectively connected to the two output terminals of the first transformer. The cathodes of the two second rectifier diodes are connected together and then connected to one end of the filter inductor. The absorption capacitor and the current-limiting resistor are connected in series and then in parallel with the output terminal of the first transformer. The absorption capacitor and the current-limiting resistor are used to absorb the impulse voltage and high-frequency oscillation voltage generated during the reverse recovery of the second rectifier diodes. The cathode of the freewheeling diode is connected to the cathode of the second rectifier diode, and the anode of the freewheeling diode is connected to the center tap of the first transformer. The freewheeling diode provides a freewheeling circuit for the DC current to reduce the freewheeling current at the input terminal of the first transformer. One end of the filter inductor is connected to the cathode of the second rectifier diode, and the other end of the filter inductor is connected to one end of the second filter capacitor and then serves as the output terminal of the second rectifier module, which is connected to the input terminal of the DC output switch. The other end of the second filter capacitor is connected to the center tap of the first transformer and then serves as another output terminal of the second rectifier module, which is connected to the other input terminal of the DC output switch; the filter inductor and the second filter capacitor are used to reduce the ripple of the DC voltage.

9. The demagnetizing circuit for a steam turbine generator rotor according to claim 1, characterized in that, The AC demagnetizing sub-circuit comprises the following sequentially connected components: Second power switch; Voltage regulator; Second transformer; Current measuring instrument; An AC output switch is provided; wherein the input terminal of the voltage regulator is connected to the phase line and neutral line of the power grid, the second power switch is connected in series between the phase line of the power grid and the input terminal of the voltage regulator, the output terminal of the voltage regulator is connected to the input terminal of the second transformer, the output terminal of the second transformer is connected to the input terminal of the AC output switch, and the output terminal of the AC output switch is connected to the demagnetizing winding.

10. A demagnetizing device, characterized in that, The demagnetizing circuit for the turbine generator rotor is included in any one of claims 1-9.

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