System for carrying out thermal cycle test on large coil

Abstract

The invention discloses a system for carrying out a thermal cycle test on a large coil, belongs to the technical field of coil thermal cycle tests, and solves the technical problem that existing test equipment cannot realize constant-rate heating / cooling. The system comprises a heating device, a refrigeration exhaust device, a controller, an overtemperature protector, a multipath temperature recorder, a computer and a test box body for installing a coil, the heating device is electrically connected with the coil, the refrigeration exhaust device is installed in the test box body, and a temperature control temperature sensor and an overtemperature protection temperature sensor are arranged in the coil. A plurality of first temperature sensors are arranged on the surface of the coil, the controller is electrically connected with the heating device, the refrigeration exhaust device, the overtemperature protector and the temperature control temperature sensor, the overtemperature protector is electrically connected with the overtemperature protection temperature sensor, the multi-channel temperature recorder is electrically connected with the first temperature sensors, and the computer is in communication connection with the controller and the multi-channel temperature recorder. The controller controls the heating device and the refrigeration exhaust device to work cooperatively to achieve constant-speed heating / cooling of the coil.

Description

Technical Field

[0001] The present invention relates to the technical field of coil thermal cycle testing, and more particularly, to a system for conducting thermal cycle testing on a large coil. Background Art

[0002] The coils (wire rods) used in large generators need to undergo thermal cycle tests, that is, heating and cooling cycle tests. They can only be used if they pass the tests to ensure the working life and stability of the large generators.

[0003] Patent publication CN112269081A discloses a multi-factor aging stress control platform for stator wire rods of large hydro-turbine generators, including a vibrator cement base, an intelligent signal generator, a power amplifier, an electric vibrator, a piezoelectric force sensor, a charge amplifier, a heating plate, a stator wire rod multi-factor aging stress control platform body, a whole stator wire rod, a high-voltage cable, a thermocouple, a temperature control box, a vibrator cooling system, a parallel welding block, a stator wire rod fixing bracket, a support insulator, a transformer and a vibrator ventilation slot.

[0004] The above control platform only heats the wire rod at a constant temperature, and does not force the wire rod to cool down, and cannot achieve constant rate heating / cooling. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art. The purpose of the present invention is to provide a system for conducting thermal cycle tests on large coils.

[0006] The technical solution of the present invention is: a system for conducting thermal cycle tests on large coils, comprising a heating device, a cooling and exhaust device, a controller, an over-temperature protector, a multi-channel temperature recorder, a computer, and a test box for installing the coil, the heating device is electrically connected to the coil, the cooling and exhaust device is installed in the test box, a temperature control temperature sensor and an over-temperature protection temperature sensor are embedded in the coil at intervals, a plurality of first temperature sensors are evenly spaced on the surface of the coil, the controller is electrically connected to the heating device, the cooling and exhaust device, the over-temperature protector, and the temperature control temperature sensor, the over-temperature protector is electrically connected to the over-temperature protection temperature sensor, the multi-channel temperature recorder is electrically connected to the first temperature sensor, and the computer is communicatively connected to the controller and the multi-channel temperature recorder.

[0007] As a further improvement, the test box includes a test platform for installing the coil, the test platform is covered with ventilation holes running through the upper and lower sides thereof, and the top of the test platform is provided with a connection socket for electrically connecting the coil.

[0008] Further, the top of the test platform is covered with a box cover, the periphery of the test platform is provided with a support frame, the middle of the top of the support frame is provided with a driving mechanism for driving the opening / closing of the box cover, and the controller is electrically connected with the driving mechanism.

[0009] Further, the test platform is provided with a guide rail in sliding connection with the box cover.

[0010] Further, the driving mechanism comprises a lead screw connected with the box cover, the top of the support frame is rotationally provided with a lead screw nut seat in threaded connection with the lead screw, and a motor for driving the rotation of the lead screw nut seat, and the controller is electrically connected with the motor.

[0011] Further, the driving mechanism is an electric push rod or a pneumatic cylinder or an electric oil cylinder or an electric hoist.

[0012] Further, the heating device comprises a variable frequency industrial power supply and a high-power transformer, the variable frequency industrial power supply is electrically connected with the high-power transformer and the connecting seat in sequence, and the controller is electrically connected with the variable frequency industrial power supply.

[0013] Further, the refrigeration and air exhaust device comprises an exhaust fan arranged on the top of the box cover and a supply fan arranged on the bottom of the test platform, and the controller is electrically connected with the exhaust fan and the supply fan.

[0014] Further, the refrigeration and air exhaust device further comprises a cooling coil arranged below the supply fan, the outside of the test box is provided with a refrigeration machine, the refrigeration machine sends cold air into the cooling coil through an axial flow fan, and the controller is electrically connected with the refrigeration machine and the axial flow fan.

[0015] Further, the connecting seats are electrically connected through soft copper plates, the soft copper plates are provided with second temperature sensors, the test box is provided with a plurality of third temperature sensors located at different positions, and the multi-channel temperature recorder is electrically connected with the second temperature sensors and the third temperature sensors.

[0016] Advantages

[0017] Compared with the prior art, the present application has the following advantages:

[0018] The present invention controls the heating device through a controller to supply power to the coil, causing the coil to self-heat. Simultaneously, PID control is implemented based on the temperature data fed back by the temperature control temperature sensor, thereby achieving constant rate heating of the coil. Furthermore, the temperature rise of the coil is monitored in real time by an over-temperature protector and an over-temperature protection temperature sensor. When the temperature exceeds the limit, compensatory cooling is activated or heating is stopped, and an audible and visual alarm is emitted, effectively protecting the coil. Based on the temperature data fed back by the temperature control temperature sensor, the present invention controls the air supply mechanism, the exhaust mechanism, and the refrigerator of the cold exhaust device through the controller PID, thereby achieving constant rate cooling of the coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a diagram of the architecture of the present invention;

[0020] Figure 2 This is the wiring diagram of the controller in the present invention;

[0021] Figure 3 This is a schematic diagram of the main structure of the test box in the present invention;

[0022] Figure 4 This is a schematic diagram of the left side structure of the test box in the present invention;

[0023] Figure 5 Schematic diagram of the structure of the electric push rod as the driving mechanism in the present invention;

[0024] Figure 6 It is a structural schematic diagram of the box cover in the present invention;

[0025] Figure 7 Schematic diagram of the ventilation holes and cooling coils of the test platform of the present invention;

[0026] Figure 8 This is a schematic diagram of the installation of the coil in the present invention.

[0027] Among them: 1- heating device, 2- cooling and exhaust device, 3- controller, 4- over-temperature protector, 5- multi-channel temperature recorder, 6- computer, 7- coil, 8- test box, 9- temperature control temperature sensor, 10- over-temperature protection temperature sensor, 11- first temperature sensor, 12- test platform, 13- ventilation hole, 14- connecting seat, 15- box cover, 16- support frame, 17- driving mechanism, 18- guide rail, 19- screw rod, 20- screw rod Nut seat, 21-motor, 22-variable frequency industrial power supply, 23-high power transformer, 24-exhaust fan, 25-supply fan, 26-cooling coil, 27-refrigeration machine, 28-axial flow fan, 29-soft copper plate, 30-second temperature sensor, 31-third temperature sensor, 32-alarm, 33-mounting hole, 34-connecting copper busbar, 35-connecting pipe, 36-support foot, 37-bottom cover, 38-slider, 39-conductor, 40-insulation layer. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the specific embodiments in the accompanying drawings.

[0029] See Figures 1 to 8 A system for conducting thermal cycle tests on large coils includes a heating device 1, a cooling and exhaust device 2, a controller 3, an over-temperature protector 4, a multi-channel temperature recorder 5, a computer 6, and a test box 8 for installing a coil 7 (i.e., a wire rod, the coil 7 is composed of a conductor 39 and an insulating layer 40). The heating device 1 is electrically connected to the coil 7, the cooling and exhaust device 2 is installed in the test box 8, and a temperature control temperature sensor 9 and an over-temperature protection temperature sensor 10 are embedded in the coil 7 at intervals. A plurality of first temperature sensors 11 are evenly spaced on the surface of the coil 7. The controller 3 is electrically connected to the heating device 1, the cooling and exhaust device 2, the over-temperature protector 4, the temperature control temperature sensor 9, the over-temperature protector 4 is electrically connected to the over-temperature protection temperature sensor 10, the multi-channel temperature recorder 5 is electrically connected to the first temperature sensor 11, and the computer 6 is communicatively connected to the controller 3 and the multi-channel temperature recorder 5.

[0030] like Figure 8 As shown, the present invention uses seven coils 7 (wire rods) connected in series. By utilizing the coils' own resistance, the coils 7 are then heated by applying voltage and high current through a heating device 1. The coils 7 are then cooled by forced ventilation through a refrigeration and exhaust device 2 to perform a hot and cold alternating cycle test. The temperature is raised from a low-temperature test temperature of 40°C to 155°C at an average rate of (2.5±1.0)°C / min, then lowered to 40°C, for 500 cycles or longer. Both the temperature control temperature sensor 9 and the over-temperature protection temperature sensor 10 are K-type thermocouple temperature sensors embedded in the center of the slot of the measuring coil 7 (the fourth of the seven series-connected coils 7). A first temperature sensor 11 is used for temperature monitoring. Temperature sampling points 1# to 49# are temperature monitoring points on the test specimen's insulation surface, i.e., the installation locations of the first temperature sensors 11. The first temperature sensors 11 are Pt100 thermal resistor temperature sensors, installed in the slot of each coil 7 (no less than three at equal intervals) and on the surface of the wire rod at the slot.

[0031] Specifically, the test box 8 includes a test platform 12 for mounting the coil 7. The bottom of the test platform 12 is provided with legs 36. The test platform 12 is provided with ventilation holes 13 extending through its upper and lower sides. The top of the test platform 12 is provided with a connection base 14 for electrically connecting the coil 7. The connection base 14 is a plate-like structure to increase the contact surface with the coil 7.

[0032] The top of the test platform 12 is covered with a box cover 15, which can reduce heat loss during the heating process. Preferably, the inner wall of the box cover 15 is provided with a heat preservation layer. The periphery of the test platform 12 is provided with a support frame 16. The middle of the top of the support frame 16 is provided with a driving mechanism 17 for driving the opening / closing of the box cover 15. The controller 3 is electrically connected to the driving mechanism 17.

[0033] The test platform 12 is provided with guide rails 18 which are slidably connected with the box cover 15. Specifically, the four corners of the test platform 12 are respectively provided with guide rails 18. The upper ends of the guide rails 18 are connected with the support frame 16. The box cover 15 is provided with sliding blocks 38 which are slidably connected with the guide rails 18. This can improve the stability of the up / down movement of the box cover 15.

[0034] In one embodiment, the driving mechanism 17 includes a lead screw 19 connected with the box cover 15. The top of the support frame 16 is rotatably provided with a lead screw nut seat 20 threadedly connected with the lead screw 19. An electric motor 21 is arranged to drive the rotation of the lead screw nut seat 20. The controller 3 is electrically connected to the electric motor 21. Specifically, the electric motor 21 drives the lead screw nut seat 20 through a worm and gear mechanism. That is, the electric motor 21 is connected with a worm. A worm wheel is fixedly sleeved on the periphery of the lead screw nut seat 20. The worm is engaged with the worm wheel.

[0035] In one embodiment, the driving mechanism 17 is an electric push rod, a pneumatic cylinder, an electric cylinder or an electric hoist.

[0036] The heating device 1 includes a variable frequency industrial power supply 22 and a high-power transformer 23. The variable frequency industrial power supply 22 is electrically connected to the high-power transformer 23 and the connecting seat 14 in sequence. The controller 3 is electrically connected to the variable frequency industrial power supply 22.

[0037] The heating is performed in a low-voltage and high-current internal heating mode of the coil 7 itself. The power supply is directly applied to the coil 7. The heating power is determined according to the resistance of the test sample. The resistance value of the coil 7 is generally close to 10 -3 Ω order of magnitude. Considering that the resistance value of the coil 7 and the joint of the coil 7 is high and the power consumption is large, the test voltage should not be too high. Generally, several volts to tens of volts are more appropriate. The test loop current should be controlled at 1.5*10 4 A. The heating power P can be roughly calculated according to the following formula:

[0038] Q=C·m·ΔT=C1·m1·ΔT+C2·m2·ΔT+… (1)

[0039]

[0040] Q=P·t (3)

[0041] In the formula:

[0042] C is the specific heat capacity of the test loop conductor.

[0043] m——test circuit conductor mass;

[0044] △T——the difference between the final temperature and the initial temperature of the test circuit conductor;

[0045] R——test circuit conductor resistance;

[0046] U——test voltage;

[0047] Q – Calories;

[0048] P——heating power;

[0049] t——time.

[0050] In this embodiment, the maximum output voltage is designed to be 24V, the current is 15,000A, and the power is 360kW. The components in the main test circuit are connected using flexible copper busbars 34, which are easy to bend. To minimize joint resistance, the connection between busbars 34 and coils 7 is secured with a special double-sided clamp (clamped by connectors 14 on both sides and locked with bolts).

[0051] The heating power is 360kW, and the design leaves a margin. It is calculated based on 400kW. If the input is powered by AB phase 380V, 400000 / 380 is approximately equal to 1000A. The power line must be connected with a copper busbar. The project is large and power switching devices are required to regulate the voltage, which is quite difficult.

[0052] The power supply uses a three-phase 380V supply. A variable-frequency industrial power supply inputs three-phase 380V and outputs a single-phase 1000V voltage. The input current becomes 350A, allowing for cable wiring (no copper busbars required). The output voltage is increased to 1000V, and the output current of the variable-frequency industrial power supply is also 350A, allowing for wiring. The variable-frequency industrial power supply can regulate the output voltage (0-1000V).

[0053] Parameters of high power transformer:

[0054] Input: 0-1000V;

[0055] Output: 0-24V;

[0056] Current: 0-15000A;

[0057] The voltage is adjustable in three levels.

[0058] The refrigeration and air exhaust device 2 comprises an air exhaust fan 24 arranged on the top of the box cover 15 and an air supply fan 25 arranged on the bottom of the test platform 12, and the controller 3 is electrically connected with the air exhaust fan 24 and the air supply fan 25. Forced ventilation cooling mode is adopted for test cooling, and during the temperature decreasing from 155℃ to 40℃, the temperature difference between the test sample and the environment is large, heat release is easy, and the cooling can be realized by circulating air blowing of the air exhaust fan 24 and the air supply fan 25 according to formula (1). Specifically, the number of the air exhaust fan 24 and the air supply fan 25 is both 4, and they are arranged on the top of the box cover 15 and the bottom of the test platform 12 in a uniform interval, so as to ensure that the air pressure and air speed of each part of the coil are uniform. The box cover 15 is provided with mounting holes 33 for mounting the air exhaust fan 24.

[0059] When the temperature of the test sample approaches the ambient temperature, the air cooling cannot achieve the average (2.5±1.0)℃ / min cooling rate, and a high-power refrigeration device is required. Therefore, the refrigeration and air exhaust device 2 in the embodiment further comprises a cooling coil 26 arranged below the air supply fan 25, and a refrigeration machine 27 is arranged outside the test box 8, and the refrigeration power is 8P. The refrigeration machine 27 sends cold air into the cooling coil 26 through an axial flow fan 28, and the controller 3 is electrically connected with the refrigeration machine 27 and the axial flow fan 28. Specifically, the cold air output end of the refrigeration machine 27 is connected with the cooling coil 26 through a connecting pipe 35, and the axial flow fan 28 is installed on the connecting pipe 35.

[0060] The bottom of the test platform 12 is provided with a bottom cover 37, and the air supply fan 25 and the cooling coil 26 are both installed in the bottom cover 37.

[0061] In order to ensure that the refrigeration device and the fan can be started and stopped controllably, the power supply is introduced through a contactor, and a thermal relay protection is connected in series in the main circuit to prevent the refrigeration device from being overloaded.

[0062] The controller 3 adopts an ALTEC temperature controller with PID adjustment function, and the controller 3 drives the heating device and the refrigeration device through PID control to realize constant-rate temperature rising and falling. The temperature control program is designed according to the temperature curve required by the test, and is divided into two programs of temperature rising and falling, which are respectively controlled and realized by PID adjustment. Each program is provided with parameters such as PID value, starting value, target value, temperature rising and falling rate, upper and lower limit value, and cycle number. The midpoint temperature 100℃ is determined by constant temperature self-tuning to select the PID value.

[0063] During temperature rising, the program temperature setting value is increased by 0.5℃ every 12 seconds according to the preset temperature rising rate, the temperature value T1 collected by the temperature control sensor 9 is compared with the setting value, and the control signal X0 is output to the heating device 1 according to the ratio of T1 to the setting value, so as to realize stepless power regulation heating. Cold end compensation is not required during the temperature rising process, and the refrigeration device is not started.

[0064] During cooling, the program temperature setpoint is set to decrease by 0.5°C every 12 seconds at a preset cooling rate. Considering that the ambient temperature may slow down near the target temperature of 40°C, the cooling device should be started at a starting point of 155°C and full cooling power. This ensures that the ambient temperature is as low as possible near the target value. If the cooling process is too rapid, the heating mode is adjusted to compensate. This means that the heating device 1 inputs a compensation current to the coil 7 for thermal compensation.

[0065] To prevent T1 from exceeding its upper and lower limits due to equipment failure or other factors, an over-temperature protection output signal, X3, is added to activate compensatory cooling or stop heating. To facilitate monitoring of program operation, six LED indicators indicate power supply, output terminals X0 through X3, program status, and communication port status. The system is equipped with a computer, and temperature signals can be transmitted to the computer via an RS232 serial communication interface for storage and graphing.

[0066] To prevent overheating, the over-temperature protector 4 is connected to an alarm 32. The over-temperature protector 4 compares the temperature value T2 collected by the over-temperature protection temperature sensor 10 with the set value of the over-temperature protector 4. When the temperature exceeds the limit, the controller 3 starts compensating cooling or stops heating. The over-temperature protector 4 controls the alarm 32 to emit an audible and visual alarm, which plays a role of redundant protection.

[0067] Furthermore, the connecting sockets 14 are electrically connected through a soft copper plate 29, the soft copper plate 29 is provided with a second temperature sensor 30, and a plurality of third temperature sensors 31 located at different positions are provided in the test box 8, and the multi-channel temperature recorder 5 is electrically connected to the second temperature sensor 30 and the third temperature sensor 31.

[0068] like Figure 8 As shown, the temperature sampling point T1 is the temperature control point (i.e., the temperature control temperature sensor 9), which uses a K-type thermocouple embedded in the copper conductor to collect temperature and transmit it to the temperature controller, which controls the entire test operation; the temperature sampling point T2 is the over-temperature protection temperature measurement point (i.e., the over-temperature protection temperature sensor 10), which uses a K-type thermocouple embedded in the copper conductor to collect temperature and transmit it to the over-temperature protector to prevent over-temperature; the temperature sampling points 1# to 49# are the temperature monitoring points on the insulation surface of the test piece (i.e., the first temperature sensor 11), which uses a Pt100 thermocouple. The resistor and square bracket are fixed on the surface of the test sample, and the sampling data is transmitted to the 64-channel temperature recorder; temperature sampling points 50# to 55# are the temperature monitoring points of the soft copper plate 29 (i.e., the second temperature sensor 30), and a Pt100 thermal resistor is directly inserted into the soft copper plate to collect the temperature and transmit it to the 64-channel temperature recorder; temperature sampling points 56# to 64# are the internal ambient temperature monitoring points of the test box 8 (i.e., the third temperature sensor 31), and Pt100 thermal resistors are distributed throughout the test box to monitor the temperature of each point in the box.

[0069] A 64-channel temperature recorder is used to display and store monitored temperature values. In order to facilitate observation and review of historical data, a computer 6 is configured in the system to communicate with the 64-channel temperature recorder and temperature controller to count all monitored data, automatically generate single or multiple curve graphs, and directly generate data reports for printing.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A system for conducting thermal cycle tests on large coils, characterized in that: The invention comprises a heating device (1), a refrigeration and exhaust device (2), a controller (3), an over-temperature protector (4), a multi-channel temperature recorder (5), a computer (6), and a test box (8) for installing a coil (7). The heating device (1) is electrically connected to the coil (7), the refrigeration and exhaust device (2) is installed in the test box (8), a temperature control temperature sensor (9) and an over-temperature protection temperature sensor (10) are embedded in the coil (7), and a plurality of first temperature sensors (11) are evenly spaced on the surface of the coil (7). The controller (3) is electrically connected to the heating device (1), the refrigeration and exhaust device (2), the over-temperature protector (4), and the temperature control temperature sensor (9), the over-temperature protector (4) is electrically connected to the over-temperature protection temperature sensor (10), the multi-channel temperature recorder (5) is electrically connected to the first temperature sensor (11), and the computer (6) is communicatively connected to the controller (3) and the multi-channel temperature recorder (5).

2. A system for conducting thermal cycle tests on large coils according to claim 1, characterized in that: The test box (8) includes a test platform (12) for mounting the coil (7), the test platform (12) is covered with ventilation holes (13) running through the upper and lower sides thereof, and a connection seat (14) for electrically connecting the coil (7) is provided on the top of the test platform (12).

3. A system for conducting thermal cycle tests on large coils according to claim 2, characterized in that: The top of the test platform (12) is covered with a box cover (15), a support frame (16) is provided on the periphery of the test platform (12), a driving mechanism (17) for driving the box cover (15) to open / close is provided in the middle of the top of the support frame (16), and the controller (3) is electrically connected to the driving mechanism (17).

4. A system for conducting thermal cycle tests on large coils according to claim 3, characterized in that: The test platform (12) is provided with a guide rail (18) slidably connected to the box cover (15).

5. The system for conducting thermal cycle tests on large coils according to claim 3, characterized in that: The driving mechanism (17) includes a screw rod (19) connected to the box cover (15), a screw rod nut seat (20) threadedly connected to the screw rod (19) is rotatably provided on the top of the support frame (16), and a motor (21) driving the screw rod nut seat (20) to rotate, and the controller (3) is electrically connected to the motor (21).

6. The system for conducting thermal cycle testing on large coils according to claim 3, characterized in that: The driving mechanism (17) is an electric push rod, a cylinder, an electric oil cylinder or an electric hoist.

7. The system for conducting thermal cycle testing on large coils according to claim 2, characterized in that: The heating device (1) comprises a variable frequency industrial power supply (22) and a high-power transformer (23); the variable frequency industrial power supply (22) is electrically connected to the high-power transformer (23) and the connection seat (14) in sequence; and the controller (3) is electrically connected to the variable frequency industrial power supply (22).

8. The system for conducting thermal cycle testing on large coils according to claim 3, characterized in that: The refrigeration and exhaust device (2) includes an exhaust fan (24) arranged on the top of the box cover (15) and a blower (25) arranged on the bottom of the test platform (12), and the controller (3) is electrically connected to the exhaust fan (24) and the blower (25).

9. The system for conducting thermal cycle tests on large coils according to claim 8, characterized in that: The refrigeration and exhaust device (2) also includes a cooling coil (26) arranged below the air supply fan (25), and a refrigerator (27) is provided on the outside of the test box (8). The refrigerator (27) sends cold air into the cooling coil (26) through an axial flow fan (28), and the controller (3) is electrically connected to the refrigerator (27) and the axial flow fan (28).

10. A system for conducting thermal cycle testing on a large coil according to any one of claims 2 to 9, characterized in that: The connecting seats (14) are electrically connected via a soft copper plate (29), the soft copper plate (29) is provided with a second temperature sensor (30), a plurality of third temperature sensors (31) located at different positions are provided in the test box (8), and the multi-channel temperature recorder (5) is electrically connected to the second temperature sensor (30) and the third temperature sensor (31).

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