Passive portable generator rotor large shaft demagnetization device and method

Abstract

The invention discloses a passive portable generator rotor large shaft demagnetizer and a demagnetization method thereof, and belongs to the technical field of generator maintenance. The demagnetizer comprises a closed-loop coil composed of a superconducting flexible cable, a hand-operated rotary permanent magnet excitation device, a refrigerant and a detection device. The zero resistance characteristic and the flux pump effect of the superconducting material are utilized, and a demagnetizing magnetic field is generated for charging and discharging of the coil through the hand-cranking permanent magnet. The refrigerant system maintains a superconducting state, and the detection device monitors residual magnetism. During demagnetization, the coil is cooled firstly, after residual magnetism is detected, a proper coil is selected for installation, current charging and discharging are controlled, and attenuation is conducted according to stages till the residual magnetism reaches the standard. The demagnetizer gets rid of dependence on a heavy power supply and a connecting line thereof, is convenient to move to a plurality of units for overhaul and overhaul during power failure, is small in volume and mass, and facilitates demagnetization operation in a narrow space of an on-site generator.

Description

Technical Field

[0001] This invention relates to the field of generator maintenance technology, specifically to a passive portable generator rotor shaft demagnetizing device and method. Background Technology

[0002] The generator is the core equipment for energy conversion in the power plant. The main shaft of the generator rotor will be axially or radially magnetized under some operating conditions: (1) The short circuit between the turns of the rotor winding causes an unbalanced magnetic flux on the shaft, which in turn forms a slight magnetization phenomenon; if it develops into a short circuit between two points of the rotor winding and burns the insulation between the winding and the rotor to form a rotor grounding fault, the main shaft of the rotor will generate a huge grounding current and form a serious main shaft magnetization; (2) During some routine electrical tests on the generator rotor, the main shaft may be magnetized due to electromagnetic interference; (3) The rotor fan and the stationary blades or the guide ring rub against each other to generate high temperature static electricity, which forms a discharge circuit through the stator frame or the shaft coupling, and magnetizes the shaft and the guide ring. Once the main shaft is magnetized, the rotor will form irregular axial or radial residual magnetism, which will cause the rotor vibration to increase abnormally, as well as the main shaft to overheat, and accidents such as bearing burnout or journal electric burnout.

[0003] Existing rotor shaft demagnetization technologies mainly include DC polarity conversion demagnetization and AC demagnetization, which are similar in principle: a demagnetizing coil is wound around the shaft to remagnetize it, the direction of the current in the demagnetizing coil is periodically changed, and the current amplitude is gradually reduced in each cycle until the current in the demagnetizing coil is zero. This process alternately changes the direction of the residual magnetic flux density of the shaft and gradually corrects the residual magnetic flux density of the shaft to the origin of the magnetization curve. Among them, the DC polarity conversion demagnetization method applies a DC magnetic field with alternating directions, and maintains a constant DC magnetic field for a period of time, while the AC demagnetization method applies a periodic alternating magnetic field with a higher frequency of magnetic field direction changes.

[0004] In implementing the above demagnetization method, traditional implementation devices often suffer from being active and lacking portability, which limits their field application. (1) Active demagnetizing coils require heavy components such as power supply, high-power and large-volume power conditioning devices, and power connection cables, which restricts their flexible application in the field. First, in extreme power outages due to plant power failures, the power supply is difficult to guarantee. Second, demagnetizing coils often need to be connected to power conditioning devices (usually referred to as "power supplies") to continuously adjust the magnitude and direction of the current to achieve demagnetization. However, due to the large demagnetizing area required by the generator shaft and the large amount of magnetic energy and ohmic heat required to supply the demagnetizing coil, these power conditioning devices are usually large in power, weight, and volume. Not only is the adjustable power supply (usually a DC welding machine) required by the DC polarity conversion demagnetizing method relatively large and heavy, but the AC demagnetizing method also requires an adjustable power supply to overcome the larger AC impedance of the demagnetizing coil. Therefore, the output voltage and volume of the transformer of the power conditioning device are larger, making it rarely used in situations with a large demagnetizing area. For details, see "Wang Zhongming, Discussion on Demagnetizing Methods of 390 H-type Generator Rotor, Huadian Technology, 2017". This problem is particularly serious in large generator sets (where the shaft is also larger). Third, the demagnetizing device requires a long cable for power supply, and the cable greatly reduces the flexibility and mobility of the demagnetizing device. In particular, when it is necessary to move the demagnetizing device to operate multiple units in the plant, the long cable connection will cause additional chaos in the complex maintenance environment.

[0005] (2) If the demagnetizer uses conventional conductors (such as copper, aluminum, etc.), the volume and weight of the wires wound around the shaft of a large generator will be enormous (because the safe current density that can pass through conventional conductors is very low), which is not conducive to operation in the narrow maintenance space of the generator, nor is it conducive to the hoisting of the demagnetizing cable under the influence of gravity of the vertical hydro generator. However, the current density that can pass through the safe range in superconducting wires is dozens of times higher, and even if it is made into a superconducting cable including refrigerant, the volume and weight of the wires will be greatly reduced. It is expected that the demagnetizer based on superconducting wires can realize the demagnetization operation in a narrow space, and can avoid the generator disassembly and overhaul and the huge waste of manpower and material resources and the time delay in the power generation schedule.

[0006] Therefore, providing passive and portable (portability includes reduction in size and weight) large-shaft demagnetizers is of great significance to the production site. Summary of the Invention

[0007] The present invention aims to provide a passive portable generator rotor shaft demagnetizing device and method to solve the problems of existing demagnetizing devices relying on external power supply, poor portability, inconvenience in operation in the confined space inside the generator, and inconvenience in hoisting heavy demagnetizing cables in vertical generators, thereby achieving efficient and convenient generator rotor shaft demagnetization.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A passive portable generator rotor shaft demagnetizing device includes a high-temperature superconducting closed-loop coil, a hand-cranked rotating permanent magnet device, a refrigerant system, and a detection device. The high-temperature superconducting closed-loop coil is made of high-temperature superconducting material and is used to generate the magnetic field required for demagnetization. The hand-cranked rotating permanent magnet device is used to charge and discharge the high-temperature superconducting closed-loop coil based on the superconducting flux pump effect. The refrigerant system is used to provide a low-temperature environment for the high-temperature superconducting closed-loop coil to maintain its superconducting state. The detection device is used to detect the residual magnetism of the generator rotor shaft.

[0009] Furthermore, the high-temperature superconducting closed-loop coil is a flexible cable structure, including a support tube, a superconducting conductor layer wound on the support tube, a refrigerant layer wrapped around the superconducting conductor layer, a heat insulation layer wrapped around the refrigerant layer, and a protective layer wrapped around the heat insulation layer.

[0010] Furthermore, the hand-cranked rotating permanent magnet device includes a permanent magnet and a gear transmission mechanism, the gear transmission mechanism being used to accelerate the rotational speed of the permanent magnet.

[0011] Furthermore, the refrigerant system includes a small top-mounted fiberglass Dewar flask for storing liquid nitrogen, which is used to replenish the refrigerant for the high-temperature superconducting closed-loop coil and to release gas.

[0012] Furthermore, the detection device includes a Hall current sensor and a handheld gaussmeter. The Hall current sensor is used to measure the current of the high-temperature superconducting closed-loop coil without contact, and the handheld gaussmeter is used to detect the residual magnetism position, direction, and density of the generator rotor shaft in real time.

[0013] A technical solution is also provided: a method for demagnetizing the rotor shaft of a passive portable generator, utilizing the demagnetizing device described above, including the following steps: The high-temperature superconducting closed-loop coil was cooled using liquid nitrogen to bring it into a superconducting state. Use a handheld gaussmeter to test the residual magnetism of the generator rotor shaft; Based on the detected direction of residual magnetism, select a high-temperature superconducting cable, wind it into a suitable shape, and install it on the generator rotor shaft; The hand-cranked rotating permanent magnet device controls the charging and discharging of a high-temperature superconducting closed-loop coil, thereby controlling the direction and magnitude of the current. According to the preset current decay stage, the current amplitude in the high-temperature superconducting closed-loop coil is gradually reduced until the residual magnetism of the generator rotor shaft reaches the preset standard.

[0014] Furthermore, the selection of a suitable high-temperature superconducting closed-loop coil includes: when the generator rotor shaft is axially magnetized, selecting a solenoid or spiral high-temperature superconducting closed-loop coil; when the generator rotor shaft is radially magnetized, selecting a saddle-shaped high-temperature superconducting closed-loop coil.

[0015] Furthermore, the solenoid-shaped high-temperature superconducting closed-loop coil is wound from bottom to top along the main axis, and the spiral-shaped high-temperature superconducting closed-loop coil is wound from inside to outside along the main axis.

[0016] Furthermore, in the step of controlling the direction and magnitude of the current, the required current direction and target current value are calculated based on the detected remanent magnet direction and intensity, and the target current value is achieved by operating a hand-cranked rotating permanent magnet device.

[0017] Furthermore, in the step of gradually reducing the current amplitude in the high-temperature superconducting closed-loop coil according to the preset current decay stages, after each current decay stage, the residual magnetism of the generator rotor shaft is re-detected using a handheld gaussmeter, and the parameters of the next current decay stage are adjusted based on the detection results.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. It does not require bulky components such as power supply, power conditioning device and connecting cable. Demagnetization can be achieved by hand-cranking. It is lightweight and portable, suitable for demagnetization operation of multiple units, and also suitable for special scenarios such as emergency repair and power outage. 2. The conductor is made of high-temperature superconducting material with high current carrying density. For the main shaft of a large generator, it can significantly reduce the volume and weight of the demagnetizer conductor, making it easier to operate in the confined space of the generator on site. It is expected to avoid disassembly and overhaul and the resulting manpower consumption and delay in the power generation period. Combined with the flexible cable structure and simple refrigerant system, the demagnetizer is flexible to move, easy to carry and operate. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a demagnetizer based on high-temperature superconducting cables, used to eliminate the axial magnetization of a large shaft. Figure 2 This is a schematic diagram of a demagnetizer based on high-temperature superconducting cables, used to eliminate radial magnetization of a large shaft; Figure 3 This is a schematic diagram of the internal structure of a superconducting cable; Figure 4 This is an equivalent circuit diagram of a passive portable demagnetizer; Figure 5 A schematic diagram of the working current of a demagnetizing coil controlled by a hand-cranked rotating permanent magnet. Figure 6This is a schematic diagram illustrating the change in residual magnetic flux density of the generator shaft under the magnetic field generated by the demagnetizing coil. Figure 7 This is a schematic diagram of the operation steps of a passive portable demagnetizer.

[0020] In the picture: 1. Generator shaft; 2. High-temperature superconducting cable; 201. Support tube; 202. Superconducting conductor layer; 203. Refrigerant layer; 204. Insulation layer; 205. Sheath; 3. Solenoid coil based on superconducting cable; 4. Hand-cranked rotating permanent magnet device; 401. Rotor core; 402. Permanent magnet; 403. Gear drive; 404. Rotating handle; 5. Current sensor; 6. Handheld gaussmeter; 601. Gaussmeter body; 602. Hall effect probe; 7. Refrigerant inlet / outlet and discharge valve; 701. Refrigerant inlet / outlet; 702. Discharge valve; 8. Pressure gauge and vent; 801. Pressure gauge; 802. Vent; 9. Small refrigerant storage tank; 10. Saddle-shaped coil based on superconducting cable. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Figure 1 A schematic diagram of a demagnetizing coil for eliminating axial magnetization of the main shaft 1, based on a high-temperature superconducting cable 2, is provided. This includes a solenoid coil 3 based on the superconducting cable, wound from bottom to top along the main shaft axis; a hand-cranked rotating permanent magnet rotor 4; a current sensor 5; and a handheld gaussmeter 6. Alternatively, the demagnetizing coil for eliminating axial magnetization of the main shaft 1 can also be a helical coil based on the superconducting cable, wound radially from the inside to the outside along the main shaft axis.

[0023] Figure 2 A schematic diagram of a demagnetizing coil for eliminating radial magnetization of the large shaft 1 based on a high-temperature superconducting cable 2 is given, including a saddle-shaped coil 10 based on the superconducting cable, a hand-cranked rotating permanent magnet rotor 4, a current sensor 5, and a handheld gaussmeter 6.

[0024] Figure 3A schematic diagram of the high-temperature superconducting cable 2 is provided. From the inside out radially, it consists of: a support tube 201, a superconducting conductor layer 202, a liquid nitrogen layer 203, an insulation layer 204, and a protective layer 205. The superconducting conductor layer 202 is cooled by the liquid nitrogen layer 203. A single cable comprises multiple layers of superconducting conductors, each layer containing multiple parallel superconducting conductors arranged spirally on the support tube. All superconducting conductors are in strip form.

[0025] The closed-loop circuit of the superconducting demagnetizing coil can be constructed by directly manufacturing a continuous and closed-loop cable, or by making a connector and connecting the cable ends. For the cable connector, the resistance should be as low as possible to minimize the decay of the closed-loop coil current over time, thus enhancing the current holding capacity during DC operation and the current control capability during charging and discharging. The cable connector should be manufactured during the coil manufacturing process. The cable connector manufacturing process involves first stripping the end cable, and the connection from the inside out is as follows: ① Connecting the support tube by welding; ② Connecting the two ends of the superconducting wire with a superconducting short wire. The connection can be made by welding low-resistance materials such as In66.3Bi33.7, In52Sn48, In97Ag3, and Sn63Pb37, or by directly connecting with superconducting materials to form a connector with even lower resistance, i.e., connecting by creating a growth region of superconducting ceramic material on the substrate of two adjacent high-temperature superconducting strips; ③ Sequentially wrapping the outside with an insulation layer, an insulating layer, and a protective layer.

[0026] The demagnetizing coil has a small refrigerant storage tank 9 on top for timely replenishment of lost refrigerant. This tank is a lightweight, insulated fiberglass Dewar flask with refrigerant inlet / outlet 701 and valve 702 for adding or removing refrigerant. It also has a pressure gauge 801 and an exhaust port 802 for timely gas discharge. Inside the small refrigerant storage tank is a cable with its sheath 205 and insulation layer 204 stripped, allowing the refrigerant in the storage tank 9 to exchange with the refrigerant in the liquid nitrogen layer 203 of the cable. To minimize damage to the cable, the cable connector is positioned to coincide with the location of the small refrigerant storage tank.

[0027] The features described below are applicable to Figure 1 and Figure 2 Examples of all demagnetizer devices.

[0028] The high-temperature superconducting wire should be selected as a strip wire, referred to as a high-temperature superconducting tape. This is because the tape has a relatively flat and wide shape, which makes it easier to accept more of the traveling wave magnetic field brought by the rotating permanent magnet, thereby generating a larger DC electromotive force through the flux pump principle.

[0029] The high-temperature superconducting wire is typically structured as a high-temperature superconducting material filled in a metal protective material. The filling method should be to select a form in which the superconducting material is integrally filled in the metal, rather than a form in which the non-superconducting material is filled in metal pores in the form of multi-core filaments. The latter is not conducive to the permanent magnet forming a large magnetic flux area and magnetization current loop on the superconducting material, and thus it is difficult to generate a large electromotive force through the magnetic flux pump principle.

[0030] The high-temperature superconducting wire can be insulated with polyacetylimide tape, or even without insulation, to further reduce the coil volume and weight. In the high-temperature superconducting wire, because the resistivity of the superconducting material layer is extremely low, the metal protective layer encapsulating the superconducting material has a relatively high resistivity and can serve as insulation.

[0031] The hand-cranked rotating permanent magnet rotor 4 has a structure including a rotor core 401 made of stacked silicon steel sheets, a permanent magnet 402 embedded in the core, a gear transmission 403, and a rotating handle 404.

[0032] The hand-cranked rotating permanent magnet rotor 4 should be placed close enough to the end of the high-temperature superconducting closed-loop coil to ensure the flux pump effect is fully utilized and sufficient electromotive force is generated. At the same time, it should be placed far away from the generator rotor shaft 1 to avoid magnetizing the shaft.

[0033] The permanent magnet 402 on the hand-cranked rotating permanent magnet rotor should have a size that satisfies the requirement that the width of the permanent magnet is less than 50% of the width of the high-temperature superconducting tape, so that it can cause a sufficiently minute magnetic flux change process in the high-temperature superconducting tape and complete the magnetic flux pump physical process of generating DC electromotive force.

[0034] The permanent magnets 402 on the hand-cranked rotating permanent magnet device should be spaced apart by a distance greater than the width of the high-temperature superconducting tape, so as to avoid the situation where two permanent magnets simultaneously pass over the high-temperature superconducting tape, weakening the generation of DC electromotive force.

[0035] The hand-cranked rotating permanent magnet device includes a gear transmission device 403. The large gear is connected to the hand crank handle, and the small gear is connected to the rotating permanent magnet rotor, so that the rotation speed of the permanent magnet is several times that of the hand crank, thereby accelerating the charging and discharging speed of the high-temperature superconducting closed-loop coil.

[0036] The current sensor 5 used for measuring the current of the demagnetizing coil should be a current sensor that can perform DC current measurement without contact, such as a Hall current sensor that uses electromagnetic induction effect to measure the magnitude of DC current, to avoid introducing additional resistance in the high-temperature superconducting closed-loop coil of the series ammeter, which would cause current attenuation and instability.

[0037] The handheld gaussmeter 6 includes a gaussmeter body 601 and a Hall probe 602, and is used to check the position, direction and intensity of residual magnetism on the main shaft 1.

[0038] The demagnetizer is fixed on the main shaft in the following ways: when the main shaft is in a vertical position, the demagnetizer can be placed on various parts of the main shaft using insulating straps, elastic retaining rings, or suspension devices for demagnetization; when the main shaft is in a horizontal position, the demagnetizer can be directly placed on various parts of the main shaft for demagnetization.

[0039] The demagnetizer should be equipped with a liquid nitrogen storage tank. After being replenished with liquid nitrogen from the storage tank, the demagnetizer should be transported separately to the maintenance or emergency repair site.

[0040] The high-temperature superconducting coil has a current-carrying capacity that is dozens of times that of copper wire per unit volume. Therefore, with proper design, even taking into account the volume and weight of the refrigerant, the high-temperature superconducting coil can usually generate a larger coercivity with a smaller volume and mass.

[0041] Figure 4 This is an equivalent circuit diagram of a passive portable demagnetizer, used to explain the principle of the demagnetizer or to simulate the demagnetizer.

[0042] The demagnetizing coil is exposed to the traveling wave magnetic field generated by the rotating permanent magnet at its end, and an electromotive force Vout is generated through the flux pump principle unique to superconductors.

[0043] The electromotive force generated at the end of the demagnetizing coil excites the entire demagnetizing coil, generating a continuous current circulating along the closed loop in the demagnetizing coil.

[0044] When the permanent magnet stops rotating, Vout will become zero. At this time, since the resistances Req1 and Req2 in the superconducting closed-loop coil are extremely small, the decay time constant of the DC current (Leq1+Leq2) / (Req1+Req2) is close to infinity. Therefore, the closed-loop coil can transport approximately steady-state continuous DC current.

[0045] Among them, the generator shaft is equivalent to the inductance Lmag that is magnetically coupled to the demagnetizing coil, the leakage inductance Lσ that is not magnetically coupled to the demagnetizing coil, the equivalent resistance Rmag for hysteresis loss and eddy current loss, and the resistance Rσ of other parts of the shaft.

[0046] The main body of the demagnetizing coil is tightly electromagnetically coupled to the generator shaft. By properly operating the rotating permanent magnet device, the current generated by the demagnetizing coil follows the requirements of the DC polarity-changing method, presenting a DC current with changing polarity, thus bringing a demagnetizing effect to the generator shaft.

[0047] Figure 5This diagram illustrates the operating current of the demagnetizing coil under the control of a hand-cranked rotating permanent magnet device during charging and discharging. As can be seen from the diagram, when the handle is cranked, the central magnetic field of the demagnetizing coil increases; when the handle is stopped, the central magnetic field remains constant; when the handle is cranked in the opposite direction, the central magnetic field decreases and begins reverse excitation after crossing zero.

[0048] like Figure 5 and Figure 6 As shown, the DC current in the demagnetizing coil alternates direction and decreases periodically until it approaches zero. This causes the remanent magnetization of the main shaft to alternate direction and decrease in amplitude until it approaches zero. This is due to the gradual collapse of the magnetization curve loop of the main shaft, which is a ferromagnetic material.

[0049] according to Figure 7 The present invention provides a method for demagnetizing the main shaft of a passive portable generator, the specific operation steps of which are as follows: 1. At the liquid nitrogen storage tank site, a cryogenic conduit is used to connect the liquid nitrogen storage tank and the liquid nitrogen inlet / outlet 701 of the demagnetizing coil for liquid nitrogen filling. At the same time, the air squeezed out by the liquid nitrogen is discharged using the exhaust valve 8. After the superconducting demagnetizing coil is filled with liquid nitrogen, the demagnetizer is transported separately to the maintenance site.

[0050] 2. Use a gaussmeter 6 to detect the residual magnetism position and density of the generator rotor shaft 1. B rem and the direction of remanence.

[0051] 3. For axial magnetization, a solenoid or spiral demagnetizing coil 3 is selected and nested around the outer circumference of the magnetization region; for radial magnetization, a saddle-shaped coil 10 based on a superconducting cable is selected and placed tightly against the outer wall of the magnetization region. Then, a current sensor 5 is nested at a certain position at the end of the demagnetizing coil to monitor the current magnitude in the demagnetizing coil in real time. A hand-cranked rotating permanent magnet device 4 is placed in a position sufficiently close to the coil end wire. The demagnetizing coil is securely fixed to the main shaft using a fixing device.

[0052] 4. Determine the direction of the charging current for the demagnetizing coil based on the direction of remanence. (Charging current direction) e I The direction of its generated magnetic flux e B satisfy: The direction of the magnetic flux density generated by the demagnetizing coil afterwards e B It needs to be in the opposite direction to the residual magnetism of the main shaft.

[0053] 5. Determine the direction of cranking the handle of the hand-cranked permanent magnet rotor based on the direction of the charging current. Based on the principle of superconducting flux pumps, determine the direction of movement of the permanent magnet. ev relative to the direction of charging current e I The direction of magnetic flux density generated by permanent magnets e p satisfy: .

[0054] 6. Based on remanence density B rem Determine the required charging current for the demagnetizing coil. The magnitude of the DC magnetic field applied in the DC polarity conversion demagnetizing method should be equal to the residual magnetism of the demagnetized part. B rem N times, that is, producing N* B rem The magnetic flux density, where the multiple N is determined by the coercivity required by the main shaft material, is typically 4 to 5. According to the Biot-Schaffer law... From this, we can derive estimation formulas for the required current magnitude of the three types of demagnetizing coils described in this disclosure: For a helical coil (with the wire wound radially from the inside out), integrating the Biot-Saffar expression along the circumference yields the relationship between the central magnetic flux density and current of a single-turn helical coil: Where R is the coil radius. Assuming the spiral coil has a total of Turns, the relationship between the required current and the residual magnetism of the main shaft is approximately: The actual demagnetizing current applied should be significantly greater than this value.

[0055] For a solenoid coil (with the conductor wound axially from bottom to top), assuming the turns are evenly distributed along the coil's axis, the relationship between the magnetic flux density and current at the coil's center can be derived using the Biot-Savart expression: Where R is the radius of the solenoid coil and L is the length of the solenoid coil. Therefore, the relationship between the magnetic flux density of the helical coil and the remanence at the center of the main shaft is approximately: The actual demagnetizing current applied should be significantly greater than this value.

[0056] For a saddle-shaped coil, neglecting its end effects and treating the two straight sides as infinitely long wires, we can obtain the relationship between the current in a single infinitely long wire and the magnetic flux density at the center of production: , where d is the vertical distance from the straight side to the center of the coil. Considering the saddle-shaped coil, there are a total of Turn Since each turn has two straight sides, the relationship between the required current of the coil and the remanence of the shaft is approximately: However, this formula only considers the contribution of the straight side of the coil to the magnetic field and does not consider the curved side, so the estimated demagnetizing current is too large. This is permissible in a demagnetizer, and a larger demagnetizing current will not cause demagnetization failure.

[0057] 7. Operate handle 403 in the direction determined in step 5 to energize the demagnetizing coil with hand-cranked permanent magnet 402, while observing the reading on current sensor 5 until the current reaches the target applied current calculated in step 6. I appl .

[0058] 8. Stop cranking handle 403. At this time, the coil current is at the target applied current magnitude. I appl The upper part maintains a constant and stable DC magnetic field output, and maintains this state for tens of seconds, so that the remanence of the large shaft is fully coerced.

[0059] 9. Shake handle 403 in the opposite direction to the direction of handle shaking in step 8, reducing the demagnetizing coil current to zero. Continue shaking the handle until the coil current, after crossing zero, increases in the opposite direction to -90%. I appl .

[0060] 10. Stop cranking handle 403. At this point, the coil current is at -90%. I appl The current remains constant for tens of seconds, allowing the stable DC magnetic field output to fully coerce the remanent magnetization of the large shaft.

[0061] 11. Reverse the direction of the handle rotation again, that is, rotate the handle 403 in the same direction as in step 8, so that the current of the demagnetizing coil changes to zero.

[0062] 12. Remeasure the residual magnetic flux density of the main shaft using a handheld gaussmeter. B rem and direction. If B rem Less than the required value of remanence B req If so, the demagnetization operation is complete; if B rem Greater than B req Then repeat steps 4 to 11 until the remanence density of the major axis is reached. B rem Reduced to below the required value.

[0063] All of the above-mentioned undisclosed matters can be implemented using existing technologies, so they will not be elaborated further.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A passive portable generator rotor shaft demagnetizing device, characterized in that, The system includes a high-temperature superconducting closed-loop coil, a hand-cranked rotating permanent magnet device, a refrigerant system, and a detection device. The high-temperature superconducting closed-loop coil is made of high-temperature superconducting material and is used to generate the magnetic field required for demagnetization. The hand-cranked rotating permanent magnet device is used to charge and discharge the high-temperature superconducting closed-loop coil based on the superconducting flux pump effect. The refrigerant system is used to provide a low-temperature environment for the high-temperature superconducting closed-loop coil to maintain its superconducting state. The detection device is used to detect the residual magnetism of the generator rotor shaft.

2. The passive portable generator rotor shaft demagnetizing device according to claim 1, characterized in that: The high-temperature superconducting closed-loop coil is a flexible cable structure, including a support tube, a superconducting conductor layer wound on the support tube, a refrigerant layer wrapped around the superconducting conductor layer, a heat insulation layer wrapped around the refrigerant layer, and a protective layer wrapped around the heat insulation layer.

3. The passive portable generator rotor shaft demagnetizing device according to claim 1, characterized in that: The hand-cranked rotating permanent magnet device includes a permanent magnet and a gear transmission mechanism, the gear transmission mechanism being used to accelerate the rotational speed of the permanent magnet.

4. The passive portable generator rotor shaft demagnetizing device according to claim 1, characterized in that: The refrigerant system includes a small top-mounted fiberglass Dewar flask, which stores liquid nitrogen to replenish the refrigerant for the high-temperature superconducting closed-loop coil and to release gas.

5. The passive portable generator rotor shaft demagnetizing device according to claim 1, characterized in that: The detection device includes a Hall current sensor and a handheld gaussmeter. The Hall current sensor is used to measure the current of the high-temperature superconducting closed-loop coil without contact, and the handheld gaussmeter is used to detect the residual magnetism position, direction and density of the generator rotor shaft in real time.

6. A method for demagnetizing the rotor shaft of a passive portable generator, characterized in that, The demagnetizing device according to any one of claims 1 to 5 includes the following steps: The high-temperature superconducting closed-loop coil was cooled using liquid nitrogen to bring it into a superconducting state. Use a handheld gaussmeter to test the residual magnetism of the generator rotor shaft; Based on the detected direction of residual magnetism, select a high-temperature superconducting cable, wind it into a suitable shape, and install it on the generator rotor shaft; The hand-cranked rotating permanent magnet device controls the charging and discharging of a high-temperature superconducting closed-loop coil, thereby controlling the direction and magnitude of the current. According to the preset current decay stage, the current amplitude in the high-temperature superconducting closed-loop coil is gradually reduced until the residual magnetism of the generator rotor shaft reaches the preset standard.

7. The method for demagnetizing the rotor shaft of a passive portable generator according to claim 6, characterized in that: The selection of a suitable high-temperature superconducting closed-loop coil includes: when the generator rotor shaft is axially magnetized, selecting a solenoid or spiral high-temperature superconducting closed-loop coil; when the generator rotor shaft is radially magnetized, selecting a saddle-shaped high-temperature superconducting closed-loop coil.

8. The method for demagnetizing the rotor shaft of a passive portable generator according to claim 6, characterized in that: The solenoid-shaped high-temperature superconducting closed-loop coil is wound from bottom to top along the main axis, and the spiral-shaped high-temperature superconducting closed-loop coil is wound from inside to outside along the main axis.

9. The method for demagnetizing the rotor shaft of a passive portable generator according to claim 6, characterized in that: In the step of controlling the direction and magnitude of the current, the required current direction and target current value are calculated based on the detected direction and intensity of the residual magnetism, and the target current value is achieved by operating a hand-cranked rotating permanent magnet device.

10. The method for demagnetizing the rotor shaft of a passive portable generator according to claim 6, characterized in that: In the step of gradually reducing the current amplitude in the high-temperature superconducting closed-loop coil according to the preset current decay stages, after each current decay stage, the residual magnetism of the generator rotor shaft is re-detected using a handheld gaussmeter, and the parameters of the next current decay stage are adjusted according to the detection results.

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