Non-contact superconducting motor rotor winding temperature detection method based on optical fiber interference principle

Abstract

The invention relates to a non-contact superconducting motor rotor winding temperature detection method based on an optical fiber interference principle. The core idea of the method is that the temperature change of the superconducting motor rotor winding is reflected by using the change of the number of bright and dark fringes in an interference image, a measurement system comprises a plurality of equal-length measurement optical fibers and reference optical fibers, and the measurement optical fibers are tightly arranged on the surface of the superconducting excitation winding of each pole in a snakelike manner; the reference optical fiber surrounds the superconducting excitation winding of each pole, and the head ends of the measuring optical fiber and the reference optical fiber corresponding to the same winding are connected with the optical splitter. When the rotor rotates, light enters the two optical fibers through the light-transmitting window on the low-temperature Dewar and enters the two optical fibers through the optical splitter, interference is generated through the focusing lens at the tail end, and the temperature of each pole winding can be obtained by calculating the optical path difference by detecting the number change of bright and dark fringes in an interference image. According to the invention, the problem of non-contact temperature detection of the current superconducting motor rotor winding is solved, the detection precision is high, the anti-electromagnetic interference capability is strong, and the operation stability of the superconducting motor is improved.

Description

Technical Field

[0001] The invention belongs to the field of superconducting motor applications, and in particular relates to a non-contact superconducting motor rotor winding temperature detection method based on the optical fiber interference principle. Background Art

[0002] Superconducting motors use the property of zero resistance of superconducting materials at critical temperature, and use superconducting tapes with stronger current carrying capacity to replace conventional copper wires to wind rotor excitation windings. They can generate a strong magnetic field under the same volume and current, and have the advantages of high efficiency, high power density, small size, light weight, good stability, etc. Therefore, they have broad application prospects in many fields such as aerospace, ship electric propulsion, industrial power generation, etc.

[0003] Superconductors can only work normally at critical temperatures. Usually, the superconducting excitation winding is placed in a low-temperature dewar and cooled with a cooling medium to keep its temperature at the critical temperature. During the operation of the superconducting motor, the temperature of the superconducting rotor excitation winding directly affects the performance and operating safety of the motor. Even a slight temperature change may seriously affect the working state of the winding or even cause quenching, which will greatly reduce the working life and safety of the equipment. Therefore, accurate temperature detection of the rotor winding of the superconducting motor is the key to ensure its efficient and stable operation.

[0004] Common motor rotor temperature detection methods, such as thermocouple method and infrared temperature measurement method, will encounter measurement difficulties, reduced accuracy, slow response, electromagnetic interference and other problems when facing the closed space, strong magnetic field and extreme low temperature working conditions of superconducting motor rotors. Therefore, it is necessary to design a temperature detection technology with high measurement accuracy and sensitivity for superconducting motor rotor windings for the stable operation and wide application of superconducting motors. This technology can not only solve the limitations of existing measurement methods, but also provide solid technical support and guarantee for the stable and safe operation of superconducting motors. Summary of the invention

[0005] The purpose of the present invention is to propose a non-contact superconducting motor rotor winding temperature detection method based on the principle of optical fiber interference. This method can overcome the limitations of existing measurement methods, accurately measure the temperature of each pole rotor winding, and has the advantages of high detection accuracy, high sensitivity, and strong reliability.

[0006] The core idea of ​​the present invention is to use the change in the number of light and dark fringes in the interference image to reflect the temperature change of the rotor winding of the superconducting motor. The measurement system includes a plurality of equal-length measurement optical fibers and reference optical fibers, wherein the measurement optical fibers are closely arranged on the surface of each pole superconducting excitation winding in a serpentine shape, and the reference optical fibers are surrounded by each pole superconducting excitation winding. The head ends of the measurement optical fibers and reference optical fibers corresponding to the same winding are connected to a spectrometer. When the rotor rotates, light is injected through the light-transmitting window on the cryogenic dewar, enters the two optical fibers through the spectrometer, and interferes through the focusing lens at the end. The temperature of each pole winding can be obtained by calculating the optical path difference by detecting the change in the number of light and dark fringes in the interference image.

[0007] The technical solution of the present invention is as follows:

[0008] A non-contact superconducting motor rotor winding temperature detection method based on the principle of optical fiber interference is characterized in that the measurement system includes a light source, a spectrometer, a plurality of optical fibers of the same length, a focusing lens, a photodetector, a signal amplifier, a data acquisition card and a data processor.

[0009] Wherein, a light-transmitting window is opened on each side of the cryogenic dewar of the superconducting motor rotor, the light source is arranged outside the light-transmitting window of the cryogenic dewar, the multiple optical fibers of equal length are divided into measuring optical fibers and reference optical fibers, the measuring optical fibers are closely arranged on the surface of each superconducting excitation winding in a serpentine shape, the reference optical fibers surround each superconducting excitation winding, and the head ends of the measuring optical fibers and the reference optical fibers corresponding to the same excitation winding are connected to the spectrometer; the focusing lens is arranged outside the light-transmitting window of the cryogenic dewar, the photodetector receives the interference light signal of the focusing lens and converts it into an electrical signal, which is amplified by the signal amplifier and input into the data acquisition card, and processed and analyzed by the data processor.

[0010] During the rotation of the superconducting motor rotor, when the superconducting excitation windings of each pole pass through the light-transmitting window on the low-temperature Dewar, the light emitted by the light source enters the Dewar through the light-transmitting window and is divided into two beams by the beam splitter and enters the measuring optical fiber and the reference optical fiber. It is then emitted from the end of the optical fiber and meets in the focusing lens to interfere and produce alternating light and dark interference fringes. The photodetector converts the received interference light signal into an electrical signal. The data processor detects the change in the number of light and dark fringes in the interference image of the superconducting excitation windings of each pole by analyzing the electrical signal to obtain the optical path difference of the output light of the measuring optical fiber and the reference optical fiber. The temperature of the measuring optical fiber can be calculated from the optical path difference, thereby obtaining the temperature of the superconducting excitation windings of each pole.

[0011] The light source is a solid laser, a gas laser, a semiconductor laser or other light-emitting device that can emit space laser.

[0012] The optical splitter divides the light emitted by the light source into two beams which enter the measuring optical fiber and the reference optical fiber respectively, and the splitting ratio is 1:1.

[0013] The excitation winding of the superconducting motor rotor is wound with superconducting tape, superconducting wire or composite superconducting conductor, and is cooled by immersion, air cooling or conduction cooling.

[0014] The non-contact optical fiber interferometric temperature measurement system is used to detect the temperature of the superconducting motor rotor winding, including the following steps:

[0015] (1): Inject cooling medium into the cryogenic dewar to put the motor rotor into a superconducting state, then start the light source, and the light will enter the motor rotor through the light-transmitting window on the cryogenic dewar.

[0016] (2): Start the superconducting motor, the rotor starts to rotate and accelerates to the rated speed. At this time, the temperature of the windings on each pole of the motor rotor rises, and the temperature of the measuring optical fiber arranged on the windings also rises accordingly, and the refractive index changes. The temperature of the reference optical fiber surrounding the windings remains unchanged, which leads to the difference in the refractive index of the measuring optical fiber and the reference optical fiber. When the windings of each pole rotate to the measurement position, the light emitted by the light source enters the beam splitter through the light-transmitting window. The light is divided into two beams in the beam splitter and enters two optical fibers respectively. The light is emitted at the end of the optical fiber through the light-transmitting window and enters the focusing lens to interfere. The photodetector converts the received interference light signal into an electrical signal and inputs it into the data acquisition card through the signal amplifier.

[0017] (3): Use the data processor to process the data collected by the data acquisition card. The detailed principle is as follows:

[0018] For the above-mentioned non-contact fiber optic interferometric temperature measurement system, when the optical path difference △s between the measuring fiber and the reference fiber corresponding to the same pole winding satisfies △s=mλ, the interference signal presents a bright fringe image and the electrical signal is a high level; when the optical path difference △s satisfies △s=(m+1 / 2)λ, the interference signal presents a dark fringe image and the electrical signal is a low level; wherein m is a positive integer and λ is the wavelength of light.

[0019] The optical path difference between the measurement fiber and the reference fiber corresponding to the same winding can be expressed as △

[0020] s=s1-s2=n1(T1)L1-n2(T2)L2, where s1 represents the optical path of light in the measuring fiber, s2 represents the optical path of light in the reference fiber, n1(T1) represents the refractive index of the measuring fiber at temperature T1, n2(T2) represents the refractive index of the reference fiber at temperature T2, L1 represents the length of the measuring fiber, and L2 represents the length of the reference fiber.

[0021] When the motor is not started, the temperature of the measuring optical fiber and the reference optical fiber corresponding to each pole winding is equal to T1=T2, and the length of the measuring optical fiber and the reference optical fiber is the same L1=L2, so △s=0. During the operation of the superconducting motor or when a fault occurs, the temperature of each pole winding rises, and the change of the temperature T1 of the measuring optical fiber arranged on the winding causes the change of the refractive index n1 and the optical path difference △s, which leads to the change of the light and dark fringes in the interference image and the change of the high and low levels in the electrical signal. By recording the change in the number of light and dark fringes in the interference image of each pole winding (the number of changes in the high and low levels in the electrical signal) to obtain the m value, the corresponding optical path difference △s can be obtained.

[0022] Substitute the optical path difference △s of each pole winding into the following formula to calculate the temperature T of each pole winding:

[0023]

[0024] Wherein: L is the length of the measuring optical fiber, n(T0) is the refractive index of the measuring optical fiber at temperature T0, T0 is the initial temperature before the superconducting motor rotor is started, α is the thermal expansion coefficient of the measuring optical fiber, β is the temperature coefficient of the measuring optical fiber, and both α and β are measured by the manufacturer during production.

[0025] The beneficial effects of the present invention are:

[0026] The present invention discloses a non-contact superconducting motor rotor winding temperature detection method based on the principle of optical fiber interference, which can accurately measure the temperature of each pole winding of the superconducting motor. Compared with the commonly used temperature measurement method, this method uses the characteristic that the refractive index of the optical fiber changes with temperature, and reflects the temperature change of the superconducting motor rotor winding by detecting the change in the number of light and dark stripes in the interference image. The measurement system includes a plurality of equal-length measurement optical fibers and reference optical fibers, the measurement optical fibers are closely arranged on the surface of each pole superconducting excitation winding in a serpentine shape, the reference optical fibers are surrounded by each pole superconducting excitation winding, and the head ends of the measurement optical fibers and the reference optical fibers corresponding to the same winding are connected to the spectrometer. When the rotor rotates, the light is injected into the two optical fibers through the light-transmitting window on the low-temperature dewar through the spectrometer, and interferes through the focusing lens at the end. The temperature of each pole winding can be obtained by calculating the optical path difference by detecting the change in the number of light and dark stripes in the interference image. The temperature of each pole winding can be measured during the high-speed rotation of the superconducting motor rotor, and has the advantages of high detection accuracy, high sensitivity, and strong reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Attached Figure 1 Schematic diagram of the temperature measurement system layout;

[0028] Description of reference numerals: 101-light source; 102-beam splitter; 103-reference optical fiber; 104-measurement optical fiber; 105-superconducting winding; 106-focusing lens; 107-motor rotor; 108-cryogenic dewar; 109-light transmission window 1; 110-light transmission window 2;

[0029] Attached Figure 2 This is a system connection block diagram of a non-contact superconducting motor rotor winding temperature detection method based on the principle of optical fiber interference;

[0030] Description of reference numerals: 201-light source; 202-beam splitter; 203-measurement optical fiber; 204-reference optical fiber; 205-focusing lens; 206-photodetector; 207-signal amplifier; 208-data acquisition card; 209-data processor; 210-superconducting winding; 211-cryogenic Dewar; DETAILED DESCRIPTION

[0031] The following will be combined with the accompanying drawings in the examples of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention provides a non-contact superconducting motor rotor winding temperature detection method based on the optical fiber interference principle. The present invention is further described below in conjunction with embodiments and drawings.

[0033] 1. As attached Figure 1 , is a schematic diagram of the temperature measurement system layout of the present invention, and the specific process is as follows:

[0034] There are two light-transmitting windows 109 and 110 on both sides of the cryogenic dewar 108. The light source 101 is arranged outside the light-transmitting window 109. The measuring optical fiber 104 is tightly arranged on the surface of each superconducting excitation winding 105 in a serpentine shape using a cryogenic adhesive, the reference optical fiber 103 is fixed around each superconducting excitation winding 105, the optical splitter 102 is fixed on the superconducting motor rotor 107 and connected to the head end of the measuring optical fiber 104 and the reference optical fiber 103, and the focusing lens 106 is arranged outside the light-transmitting window 110, so as to obtain the following. Figure 1 The temperature measurement system shown.

[0035] 2. As attached Figure 2, which is a system connection block diagram of a non-contact superconducting motor rotor winding temperature detection method based on the principle of optical fiber interference, and comprises a light source 201, a beam splitter 202 is arranged at the output end of the light source 201, two output ports of the beam splitter 202 are respectively connected to the input ports of two optical fibers of the same length, a measuring optical fiber 203 is closely arranged on the surface of a superconducting winding 210 in a serpentine shape, a reference optical fiber 204 surrounds the superconducting winding 210, a focusing lens 205 is arranged at the output ports of the two optical fibers, and then a photodetector 206 is connected to convert the optical signal into an electrical signal, which is then connected to a data processor 209 via a signal amplifier 207 and a data acquisition card 208.

[0036] During the rotation of the superconducting motor rotor, when each superconducting excitation winding 210 passes through the light-transmitting window on the cryogenic dewar 211, the light emitted by the light source 201 enters the cryogenic dewar 211 through the light-transmitting window and is divided into two beams by the beam splitter 202 and enters the measuring optical fiber 203 and the reference optical fiber 204, and then is emitted from the end of the optical fiber and meets in the focusing lens 205 to interfere and generate light and dark interference fringes. The photodetector 206 converts the received interference light signal into an electrical signal, which is amplified by the signal amplifier 207 and collected by the data acquisition card 208. The data processor 209 obtains the optical path difference of the outgoing light of the measuring optical fiber and the reference optical fiber by analyzing the electrical signal to detect the change in the number of light and dark fringes in the interference image of each superconducting excitation winding. The temperature of the measuring optical fiber can be calculated from the optical path difference, thereby obtaining the temperature of each superconducting excitation winding.

[0037] The light source 201 is a 1500nm band fiber laser with an output light intensity of 80mW and a line width of 10kHz. Other light-emitting devices such as solid lasers, gas lasers or semiconductor lasers that can emit space lasers can also be used.

[0038] The optical splitter 202 splits the light emitted by the light source into two beams which enter the measuring optical fiber and the reference optical fiber respectively, with a splitting ratio of 1:1.

[0039] The photoelectric detector 206 is a high-speed detector used to convert light and dark stripes in the optical signal into high and low levels in the electrical signal. It has a bandwidth of 800 MHz and can realize high-speed optical pulse signal detection. Other types of high-speed photoelectric detectors can also be used.

[0040] The data processor 209 is mainly used to process and display in real time the data collected by the data acquisition card 208. The system software written in the example of the present invention is based on the data acquisition card for processing.

[0041] The excitation winding 210 of the superconducting motor rotor is wound with superconducting tape, superconducting wire or composite superconducting conductor, and is cooled by immersion, air cooling or conduction cooling.

[0042] The non-contact optical fiber interferometric temperature measurement system is used to detect the temperature of the superconducting motor rotor winding, including the following steps:

[0043] (1): Inject cooling medium into the cryogenic dewar to put the motor rotor into a superconducting state, then start the light source, and the light will enter the motor rotor through the light-transmitting window on the cryogenic dewar.

[0044] (2): Start the superconducting motor, the rotor starts to rotate and accelerates to the rated speed. At this time, the temperature of the windings on each pole of the motor rotor rises, and the temperature of the measuring optical fiber arranged on the windings also rises accordingly, and the refractive index changes. The temperature of the reference optical fiber surrounding the windings remains unchanged, which leads to the difference in the refractive index of the measuring optical fiber and the reference optical fiber. When the windings of each pole rotate to the measurement position, the light emitted by the light source enters the beam splitter through the light-transmitting window. The light is divided into two beams in the beam splitter and enters two optical fibers respectively. The light is emitted at the end of the optical fiber through the light-transmitting window and enters the focusing lens to interfere. The photodetector converts the received interference light signal into an electrical signal and inputs it into the data acquisition card through the signal amplifier.

[0045] (3): Use the data processor to process the data collected by the data acquisition card. The detailed principle is as follows:

[0046] For the above-mentioned non-contact fiber optic interferometric temperature measurement system, when the optical path difference △s between the measuring fiber and the reference fiber corresponding to the same pole winding satisfies △s=mλ, the interference signal presents a bright fringe image and the electrical signal is a high level; when the optical path difference △s satisfies △s=(m+1 / 2)λ, the interference signal presents a dark fringe image and the electrical signal is a low level; wherein m is a positive integer and λ is the wavelength of light.

[0047] The optical path difference between the measurement fiber and the reference fiber corresponding to the same winding can be expressed as △

[0048] s=s1-s2=n1(T1)L1-n2(T2)L2, where s1 represents the optical path of light in the measuring fiber, s2 represents the optical path of light in the reference fiber, n1(T1) represents the refractive index of the measuring fiber at temperature T1, n2(T2) represents the refractive index of the reference fiber at temperature T2, L1 represents the length of the measuring fiber, and L2 represents the length of the reference fiber.

[0049] When the motor is not started, the temperature of the measuring optical fiber and the reference optical fiber corresponding to each pole winding is equal to T1=T2, and the length of the measuring optical fiber and the reference optical fiber is the same L1=L2, so △s=0. During the operation of the superconducting motor or when a fault occurs, the temperature of each pole winding rises, and the change of the temperature T1 of the measuring optical fiber arranged on the winding causes the change of the refractive index n1 and the optical path difference △s, which leads to the change of the light and dark fringes in the interference image and the change of the high and low levels in the electrical signal. By recording the change in the number of light and dark fringes in the interference image of each pole winding (the number of changes in the high and low levels in the electrical signal) to obtain the m value, the corresponding optical path difference △s can be obtained.

[0050] Substitute the optical path difference △s of each pole winding into the following formula to calculate the temperature T of each pole winding:

[0051]

[0052] Wherein: L is the length of the measuring optical fiber, n(T0) is the refractive index of the measuring optical fiber at temperature T0, T0 is the initial temperature before the superconducting motor rotor is started, α is the thermal expansion coefficient of the measuring optical fiber, β is the temperature coefficient of the measuring optical fiber, and both α and β are measured by the manufacturer during production.

[0053] The above description is only an example of the implementation mode of the solenoid-shaped superconducting magnet of the present invention, and is not intended to limit the protection scope of the present invention. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention. For example, the light source can be a laser of other bands, infrared laser, etc.; other shapes of static or rotating superconducting magnets such as D-type, racetrack type, etc.; and the superconducting material can be wire, strip or composite conductor, etc., all of which are covered within the protection scope of the present invention.

Claims

1. A non-contact superconducting motor rotor winding temperature detection method based on the principle of optical fiber interference, characterized in that: The measuring system includes a light source, a spectrometer, a plurality of optical fibers of the same length, a focusing lens, a photodetector, a signal amplifier, a data acquisition card and a data processor.

2. The method according to claim 1, characterized in that A light-transmitting window is opened on both sides of the cryogenic dewar of the superconducting motor rotor, the light source is arranged outside the light-transmitting window of the cryogenic dewar, the multiple optical fibers of equal length are divided into measuring optical fibers and reference optical fibers, the measuring optical fibers are closely arranged on the surface of each superconducting excitation winding in a serpentine shape, the reference optical fibers surround each superconducting excitation winding, and the head ends of the measuring optical fibers and the reference optical fibers corresponding to the same excitation winding are connected to the spectrometer; the focusing lens is arranged outside the light-transmitting window of the cryogenic dewar, the photodetector receives the interference light signal of the focusing lens and converts it into an electrical signal, which is amplified by the signal amplifier and input into the data acquisition card, and processed and analyzed by the data processor. During the rotation of the superconducting motor rotor, when the superconducting excitation windings of each pole pass through the light-transmitting window on the cryogenic dewar, the light emitted by the light source enters the cryogenic dewar through the light-transmitting window and is divided into two beams by the beam splitter and enters the measuring optical fiber and the reference optical fiber. Then, the light is emitted from the end of the optical fiber and meets in the focusing lens to interfere and produce light and dark interference fringes. The photodetector converts the received interference light signal into an electrical signal. The data processor detects the change in the number of light and dark fringes in the interference image of the superconducting excitation windings of each pole by analyzing the electrical signal to obtain the optical path difference of the output light of the measuring optical fiber and the reference optical fiber. The temperature of the measuring optical fiber can be calculated from the optical path difference, thereby obtaining the temperature of the superconducting excitation windings of each pole.

3. The method according to claim 1, characterized in that The light source is a solid laser, a gas laser, a semiconductor laser or other light-emitting device that can emit space laser.

4. The method according to claim 1, characterized in that The optical splitter splits the light emitted by the light source into two beams which enter the measuring optical fiber and the reference optical fiber respectively, with a splitting ratio of 1:

1.

5. The method according to claim 1, characterized in that The excitation winding of the superconducting motor rotor is wound by superconducting tape, superconducting wire or composite superconducting conductor, and is cooled by immersion, air cooling or conduction cooling.

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