Air gap sensor of water-turbine generator set
By installing waveguide sensors in the stator ventilation slots of hydro-generator units, electromagnetic waves are used to measure air gaps, solving the problem of traditional sensors being prone to loosening and falling off. This achieves high-precision and stable air gap monitoring, ensuring the safety of the unit.
Patent Information
- Application Number
- CN202511578012.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-31
- Publication Date
- 2026-01-16
AI Technical Summary
The air gap sensors of existing hydro-generator units are installed on the inner wall of the stator, which are prone to loosening or falling off, resulting in inaccurate measurements and difficulty in maintenance. Furthermore, the capacitance signal cannot be transmitted over long distances, affecting the safety of the unit and the accuracy of the measurements.
A waveguide sensor installed in the stator ventilation slot is designed to measure the air gap by transmitting and receiving electromagnetic waves, calculate the gap using a microwave signal source and antenna, and locate it using a key phase sensor. The sensor is fixed in the stator ventilation slot to prevent positional displacement and detachment.
It improves measurement accuracy and anti-interference ability, ensures sensor stability and safety, avoids safety hazards caused by traditional sensors due to positional displacement or detachment, and achieves high-precision air gap monitoring.
Smart Images
Figure CN121346709A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of measurement technology, and in particular to an air gap sensor for a hydro-generator set. Background Technology
[0002] The air gap between the stator and rotor of a hydro-generator unit is a crucial electromagnetic parameter during operation, directly impacting the generator's performance. Factors such as manufacturing processes, installation, operating conditions, and the effects of electromagnetic and centrifugal forces on the stator and rotor components can cause uneven air gaps between the stator and rotor, affecting their electrical and mechanical properties, causing unit vibration, and even leading to stator-rotor collision accidents due to reduced air gaps. Real-time online monitoring of the air gap in hydro-generator units helps power plant personnel constantly monitor the generator's operating status, track changes in the generator's magnetic poles, accurately locate the magnetic pole numbers and corresponding positions of the maximum and minimum air gaps, and determine the stator-rotor eccentricity, ensuring the normal and safe operation of the hydro-generator.
[0003] Currently, hydro-generator units typically employ capacitive plate measurement technology. This requires adhesively fixing the capacitive plate sensor probe to the inner wall of the stator. A data acquisition unit then obtains the probe signal and converts it into an analog signal. This analog signal is transmitted to a condition monitoring device for acquisition and analysis, and combined with key phase sensor signals for positioning. This method places high demands on sensor grounding; in cases of non-equipotentiality, the measurement results are unsatisfactory, and data reliability is insufficient. Furthermore, because capacitive signals cannot be transmitted over long distances, the direct installation distance between the data acquisition unit and the sensor probe is limited.
[0004] Because the sensors need to be attached to the inner wall of the stator, after long-term use, some units may experience sensor probes loosening or falling off due to adhesive aging, which may cause serious safety hazards to the unit operation. After the sensors are damaged, they are also difficult to maintain and replace. At the same time, the sensor probes have a certain thickness, and the sensors are easily scratched by the rotor during the unit installation and testing process. For retrofitted units, the small gap between the stator and rotor makes installation and maintenance difficult. Summary of the Invention
[0005] Purpose of the invention: This invention provides an air gap sensor for hydro-generator sets, which can be directly installed in the stator ventilation hole and measures the air gap based on electromagnetic waves, making it safe and stable.
[0006] Technical solution: The air gap sensor for a hydro-generator set provided by this invention includes: The waveguide installed in the ventilation slot of the stator of the unit is inserted from the outer periphery of the stator of the unit. The central axis of the waveguide is parallel to the radial direction of the rotor of the unit. A partition is provided inside the waveguide to divide the waveguide into mutually isolated transmitting signal branches and receiving signal branches. The partition is arranged along the length of the waveguide. The transmitting signal branch is equipped with a transmitting antenna and a microwave signal source at the end away from the unit rotor, and the receiving signal branch is equipped with a receiving antenna at the end away from the unit rotor. The transmitting antenna, microwave signal source and receiving antenna are connected to the controller and the external unit key phase sensor. The microwave signal source transmits the signal to the surface of the unit rotor. The echo from the rotor surface is received by the receiving antenna. The controller calculates the air gap based on the transmitted signal and the echo signal, and simultaneously acquires the signal from the external unit key phase sensor to locate the position of the unit stator and unit rotor corresponding to the measured air gap.
[0007] Furthermore, the waveguide has an oxygen-free copper shell, which is isolated by a copper foil isolation layer to form a transmitting signal branch and a receiving signal branch. Both the transmitting signal branch and the receiving signal branch are filled with alumina ceramic.
[0008] Furthermore, the inner wall of the oxygen-free copper shell is plated with a silver film, and the roughness of the silver film is less than 0.5 micrometers.
[0009] Furthermore, the oxygen-free copper outer shell and the copper foil isolation layer are integrally formed.
[0010] Furthermore, the controller includes interconnected signal transmitting and receiving circuit boards and signal conditioning and signal processing unit circuit boards.
[0011] Furthermore, the extended end of the waveguide is provided with a metal shell, and the signal transmitting and receiving circuit board and the signal conditioning and signal processing unit circuit board are both located inside the metal shell. The transmitting antenna, microwave signal source and receiving antenna are integrated on the signal transmitting and receiving circuit board.
[0012] Furthermore, the extended end of the waveguide extends into the interior of the metal casing, and the connection between the waveguide and the metal casing is welded and sealed.
[0013] Furthermore, the metal casing is provided with a key phase sensor connection port, which is connected to the external unit key phase sensor and the receiving circuit board for signal conditioning. The signal transmitting and receiving circuit board and the signal conditioning and signal processing unit circuit board are connected to power supply and signal transmission cables, which extend out of the metal casing.
[0014] Furthermore, the waveguide is provided with a distance adjustment component on its exterior, which is installed in the stator ventilation slot of the unit.
[0015] Furthermore, the distance adjustment component includes a fixed plate and an adjusting plate. The fixed plate is movably sleeved on the waveguide and fixed to the outside of the stator core. The adjusting plate is fixedly sleeved on the waveguide. The fixed plate and the adjusting plate are connected by an adjusting screw and fixed by a locking nut. The distance between the adjusting plate and the fixed plate is adjusted by the adjusting screw.
[0016] Furthermore, the signal emitted by the microwave signal source to the rotor surface of the unit includes a sawtooth wave whose frequency changes linearly with time and two single-frequency continuous waves with a fixed small frequency difference emitted synchronously with the sawtooth wave. Among them, the sawtooth wave that changes linearly with time is used to roughly measure the air gap between the stator and the rotor of the unit. After the sawtooth wave is emitted to the surface of the rotor, the rough air gap between the stator and the rotor surface is determined according to the echo signal of the sawtooth wave and the time-frequency difference ∆f1 between the sawtooth waves. Two fixed-frequency continuous waves, f1 and f2, are used, with f1 > f2. The precise phase value is determined by the frequency difference ∆f2. Based on the phase difference between the transmitted and received signals of the single-frequency wave with frequency f1 within the coarse measurement air gap range, the air gap between the stator and rotor of the unit is accurately measured.
[0017] Beneficial effects: Compared with the prior art, the significant advantages of this invention are: it uses the combination of electromagnetic wave emission and echo frequency difference to calculate the air gap, which has high measurement accuracy and strong anti-interference ability. At the same time, by fixing the sensor to the ventilation slot of the stator of the unit, rather than the surface of the stator, it is more conducive to connecting external equipment. There is no risk of position displacement or even falling off during motor operation, which ensures equipment safety and measurement accuracy. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the sensor structure of the present invention; Figure 2 This is a schematic diagram of the sensor installation location for the present invention; Figure 3 This is a schematic diagram of the sensor at different depth positions according to the present invention. Detailed Implementation
[0019] This embodiment provides, for example Figure 1 and 2 The air gap sensor of the hydro-generator unit shown includes: a waveguide 1 installed in the ventilation slot of the stator of the unit, inserted from the outer periphery of the stator of the unit, the central axis of the waveguide 1 being parallel to the radial direction of the rotor of the unit, and a partition for dividing the waveguide 1 into a mutually isolated transmitting signal branch 2 and receiving signal branch 3, the partition being arranged along the length direction of the waveguide 1.
[0020] The waveguide 1 has an oxygen-free copper shell 101. The inner wall of the oxygen-free copper shell 101 is plated with a silver film with a thickness of not less than 10 micrometers, a roughness of less than 0.5 micrometers, a width of not more than 9 millimeters, and a height of not more than 5 millimeters. It is smaller than the size of the unit's ventilation slot and is easy to install.
[0021] The oxygen-free copper shell 101 is isolated by a copper foil isolation layer 102 to form a transmitting signal branch 2 and a receiving signal branch 3. Both the transmitting signal branch 2 and the receiving signal branch 3 are filled with alumina ceramic, the dielectric constant of the alumina ceramic is not less than 9, and the thickness of the copper foil isolation layer 102 is 0.5mm.
[0022] The oxygen-free copper outer shell 101 and the copper foil isolation layer 102 are integrally formed without gaps in the middle. The waveguide has a waveguide frequency band of 60GHz~100GHz and a transmission loss of no more than 0.08dB / cm.
[0023] The transmitting signal branch (2) is equipped with a transmitting antenna (4) and a microwave signal source (5) at the end furthest from the unit rotor. The receiving signal branch (3) is equipped with a receiving antenna (6) at the end furthest from the unit rotor. The transmitting antenna 4, the microwave signal source 5, and the receiving antenna 6 are connected to the signal transmitting and receiving circuit board 7. The signal transmitting and receiving circuit board 7 is connected to the signal conditioning and signal processing unit circuit board 8, and is connected to the power supply and signal transmission cable 9 and the external unit key phase sensor. The microwave signal source 5 transmits the signal to the surface of the unit rotor. The echo from the rotor surface is received by the receiving antenna 6, which can avoid signal interference. The signal conditioning and signal processing unit processes the transmitted signal and the echo signal for signal modulation and demodulation, calculates the air gap measurement value, synchronously acquires the signal from the external unit key phase sensor, and locates the position of the unit stator and unit rotor corresponding to the measured air gap.
[0024] The extended end of the waveguide 1 is provided with a metal casing 10. The signal transmitting and receiving circuit board 7 and the signal conditioning and signal processing unit circuit board 8 are both located inside the metal casing 10. The transmitting antenna 4, the microwave signal source 5 and the receiving antenna 6 are integrated on the signal transmitting and receiving circuit board 7 to ensure the shielding and grounding of the internal circuit.
[0025] The extended head of the waveguide 1 extends into the interior of the metal housing 10, and the connection between the waveguide 1 and the metal housing 10 is welded and sealed.
[0026] The metal casing 10 is equipped with a key phase sensor connection port 11, which is connected to the external unit key phase sensor and the receiving circuit board 7 for signal conditioning. The rotor position corresponding to the current air gap measurement signal is located by the unit key phase signal.
[0027] The power supply and signal transmission cable 9 enters through the metal casing 10, providing power to the internal system and transmitting the processed data to the external status monitoring system.
[0028] The waveguide 1 is provided with a distance adjustment component 12 on the outside. The waveguide 1 is fixed to the stator ventilation slot by the distance adjustment component 12, and the length of the waveguide 1 inserted into the stator ventilation slot is adjusted according to the stator thickness.
[0029] The distance adjustment component 12 specifically includes a fixed plate 1201 and an adjusting plate 1202. The fixed plate 1201 is movably sleeved on the waveguide 1 and fixed to the outside of the stator core. The adjusting plate 1202 is fixedly sleeved on the waveguide 1. The fixed plate 1201 and the adjusting plate 1202 are connected by an adjusting screw 1203 and fixed by a locking nut 1204. The insertion length of the waveguide is consistent with the thickness of the stator, and its end is flush with the inner side of the stator.
[0030] like Figure 3 As shown, the distance between the adjustable disk 1202 and the fixed disk 1201 is adjusted by adjusting the screw 1203, thereby controlling the length of the sensor waveguide inserted into the stator ventilation slot.
[0031] Microwave signal source 5 synchronously sends a sawtooth wave whose frequency changes linearly with time and two single-frequency continuous waves with a fixed small frequency difference to the rotor surface of the unit. Among them, the sawtooth wave that changes linearly with time is used to roughly measure the air gap between the stator and the rotor of the unit. After the sawtooth wave is emitted to the surface of the rotor, the echo signal is received. There is a frequency difference ∆f1 between the echo signal and the emitted signal. The frequency difference is proportional to the emission distance. By measuring the frequency difference, the air gap from the emission end to the rotor surface can be roughly measured. Two fixed-frequency continuous waves, f1 and f2, with f1 > f2 and a frequency difference of ∆f2, are used to precisely measure the air gap between the rotors. The single-frequency wave with frequency f1 is used to accurately measure the phase difference between the transmitted wave and the echo signal within the coarse measurement range, while ∆f2 is used to determine the precise phase value.
Claims
1. A hydroelectric generator set air gap sensor, characterized by, The application relates to a waveguide (1) installed in a ventilation groove of a generator stator, which is inserted from the outer periphery of the generator stator, the central axis of the waveguide (1) is radially parallel to the generator rotor, and a partition plate is arranged in the waveguide (1) to divide the waveguide (1) into a transmitting signal branch (2) and a receiving signal branch (3) which are arranged in isolation. One end of the transmitting signal branch (2) away from the generator rotor is provided with a transmitting antenna (4) and a microwave signal source (5), and one end of the receiving signal branch (3) away from the generator rotor is provided with a receiving antenna (6); the transmitting antenna (4), the microwave signal source (5) and the receiving antenna (6) are connected with a controller and an external generator key sensor. The microwave signal source (5) transmits signals to the surface of the generator rotor, the rotor surface echoes to the receiving antenna (6) for receiving, the controller calculates the air gap according to the transmitting signals and the echo signals, synchronously acquires the signals of the external generator key sensor, and positions the position of the measured air gap corresponding to the generator stator and the generator rotor. The waveguide (1) is an oxygen-free copper shell (101), the oxygen-free copper shell (101) is isolated by a copper foil isolation layer (102) to form the transmitting signal branch (2) and the receiving signal branch (3), and the transmitting signal branch (2) and the receiving signal branch (3) are both filled with alumina ceramics.
2. The hydroelectric generator unit air gap sensor of claim 1, wherein: The inner wall of the oxygen-free copper shell (101) is plated with a silver film, and the roughness of the silver film is less than 0.5 microns.
3. The hydroelectric generator air gap sensor of claim 2, wherein: The oxygen-free copper shell (101) and the copper foil isolation layer (102) are integrally formed.
4. The hydroelectric generator air gap sensor of claim 2, wherein: The controller comprises a signal transmitting and receiving circuit board (7) and a signal conditioning and signal processing unit circuit board (8) which are connected with each other.
5. The hydroelectric generator air gap sensor of claim 1, wherein: The extending head end of the waveguide (1) is provided with a metal shell (10), the signal transmitting and receiving circuit board (7) and the signal conditioning and signal processing unit circuit board (8) are arranged in the metal shell (10), and the transmitting antenna (4), the microwave signal source (5) and the receiving antenna (6) are integrated on the signal transmitting and receiving circuit board (7).
6. The hydroelectric generator air gap sensor of claim 5, wherein: The extending head end of the waveguide (1) extends into the interior of the metal shell (10), and the connecting position of the waveguide (1) and the metal shell (10) is welded and sealed.
7. The hydroelectric generator air gap sensor of claim 6, wherein: The metal shell (10) is provided with a key sensor connecting port (11), the key sensor connecting port (11) is connected with the external generator key sensor and the receiving circuit board (7) respectively, the signal transmitting and receiving circuit board (7) and the signal conditioning and signal processing unit circuit board (8) are connected with a power supply and signal transmission cable (9), and the power supply and signal transmission cable (9) extends out of the metal shell (10).
8. The hydroelectric generator air gap sensor of claim 6, wherein: A distance adjusting component (12) is arranged outside the waveguide (1) and is installed in the ventilation groove of the generator stator through the distance adjusting component (12).
9. The hydroelectric generator air gap sensor of claim 1, wherein: 10. The hydroelectric generator air gap sensor of claim 8, wherein: The distance adjusting component (12) comprises a fixed disc (1201) and a distance adjusting disc (1202), the fixed disc (1201) is movably sleeved on the waveguide (1) and fixed outside the stator core, the distance adjusting disc (1202) is fixedly sleeved on the waveguide (1), the fixed disc (1201) and the distance adjusting disc (1202) are connected through an adjusting screw (1203) and fixed through a locking nut (1204), and the distance adjusting disc (1202) adjusts the distance with the fixed disc (1201) through the adjusting screw (1203).
11. The hydroelectric generator air gap sensor of claim 1, wherein: The signal emitted by the microwave signal source (5) to the surface of the rotor of the machine set comprises a sawtooth wave with a linearly changed frequency over time and two single-frequency continuous waves with a fixed small frequency difference synchronously emitted with the sawtooth wave; The sawtooth wave with a linearly changed frequency over time is used for coarsely measuring the air gap between the stator and the rotor of the machine set, after the sawtooth wave is emitted to the surface of the rotor of the machine set, the coarse air gap from the stator to the surface of the rotor of the machine set is determined according to the time-frequency difference Δf1 between the echo signal of the sawtooth wave and the sawtooth wave; The two single-frequency continuous waves are f1 and f2 respectively, and f1>f2, the accurate phase value is determined through the frequency difference Δf2, and the air gap between the stator and the rotor of the machine set is accurately measured according to the phase difference between the emitted signal and the received signal of the single-frequency wave with the frequency f1 in the range of the coarse air gap.