Online program-controlled excitation power supply with quench protection for high-temperature superconducting magnet

Abstract

An on-line program control excitation power supply with quench protection for a high-temperature superconducting magnet comprises a single-chip microcomputer for receiving control data, outputting control voltage through digital-to-analog conversion (DAC) of the single-chip microcomputer, and magnetizing a magnet coil through current stepping; a sampling signal is output to the liquid crystal screen to display corresponding voltage and current values in real time after being processed by the single-chip microcomputer analog-to-digital conversion ADC; voltage signals at the two ends of the magnet coil are sampled and returned to the single-chip microcomputer to be processed, when high voltage occurs, it is judged that the voltage signals are abnormal voltage signals, quench protection is carried out, the single-chip microcomputer outputs control signals to cut off connection between the magnet coil and the excitation power source, and residual energy of the magnet coil is released through the high-power thyristor. The provided excitation power supply has the characteristics of high power, high stability, good repeatability and good linearity; performing numerical control stepping output, gradually applying current to the superconducting coil, and slowly establishing a magnetic field; effective quench protection is achieved, and it is guaranteed that a magnet coil is not damaged by quench.

Description

Technical Field

[0001] This utility model relates to the field of superconducting magnet technology, specifically to an in-line controlled excitation power supply with quench protection for high-temperature superconducting magnets. Background Technology

[0002] Excitation, also known as magnetization, refers to the process by which a superconducting magnet system gradually applies current to a superconducting coil under the action of a magnet power supply, thereby establishing a predetermined magnetic field. Successful excitation requires a complete control system, and a high-precision dedicated excitation power supply is an important component of this system.

[0003] Queue failure is the process of electromagnetic energy being converted into heat energy. The increase in temperature causes a localized area of ​​the coil to return to a normal state, meaning that the coil at that point experiences resistance. If current is continuously applied, it will heat the superconducting coil, potentially causing the localized temperature rise to burn the coil's insulation or even damage the entire magnet. Effective quench protection is necessary.

[0004] Existing excitation power supplies can only apply current and do not have quench protection. Magnet excitation types are divided into closed and non-closed types. A closed circuit means that the excitation power supply can be removed after the magnet excitation is completed, and the magnet itself can realize the circuit energy storage. A non-closed circuit means that the excitation power supply needs to be connected continuously to form a circuit. Summary of the Invention

[0005] To address the problems existing in the aforementioned background technology, this utility model proposes an in-line controlled excitation power supply with quench protection for high-temperature superconducting magnets, which can meet the requirements of high-precision excitation power supply and effective quench protection. This utility model can be used for both closed and non-closed types of magnets. When quenching occurs due to external factors during excitation or when no one is operating the system, the excitation power supply can be immediately disconnected under the quench protection mechanism. Simultaneously, through the quench protection diode, electrical energy is released, reducing the generation of heat inside the magnet. This utility model combines power supply and quench protection, making operation simpler and protection more comprehensive.

[0006] The in-line controlled excitation power supply for high-temperature superconducting magnets with quench protection includes a microcontroller that receives control data, outputs control voltage through the microcontroller's digital-to-analog converter (DAC), and magnetizes the magnet coil through current stepping; the sampled signal is processed by the microcontroller's analog-to-digital converter (ADC) and output to the LCD screen to display the corresponding voltage and current values ​​in real time.

[0007] The voltage signal across the sampling magnet coil is returned to the microcontroller for processing. When a high voltage is detected, it is identified as an abnormal voltage signal, triggering quench protection. The microcontroller outputs a control signal to disconnect the magnet coil from the excitation power supply and releases the residual energy of the magnet coil through a high-power thyristor.

[0008] Furthermore, control data is input to the microcontroller via the keyboard.

[0009] Furthermore, the output control voltage of the DAC is acquired through the ADC channel of the microcontroller, and the voltage value acquired by the ADC and the set output voltage value of the DAC are displayed on the LCD module.

[0010] Furthermore, the voltage across the magnet coil is acquired through the microcontroller's ADC channel, processed, and compared with preset data to perform corresponding operations.

[0011] Furthermore, during quench protection, the microcontroller's I / O port outputs a high-level signal to control the relay to engage, disconnecting the excitation power supply and the magnet coil.

[0012] Furthermore, a high-power diode is connected in reverse parallel at the output of the excitation power supply to short-circuit the output and release energy.

[0013] The beneficial effects achieved by this utility model are as follows: (1) The excitation power supply has the characteristics of high power, high stability, repeatability and good linearity. (2) The numerical control stepping output gradually applies current to the superconducting coil and slowly establishes the magnetic field. (3) Effective quench protection ensures that the magnet coil is not damaged by quench. Attached Figure Description

[0014] Figure 1 This is a system schematic diagram of the excitation power supply in an embodiment of this utility model.

[0015] Figure 2 This is a circuit diagram of the NMOS in an embodiment of the present invention.

[0016] Figure 3 This is a schematic diagram of the internal structure of the NMOS in an embodiment of the present invention.

[0017] Figure 4 This is a schematic diagram of the current control circuit of the MOS transistor in an embodiment of this utility model.

[0018] Figure 5 This is a circuit diagram of the quench protection in an embodiment of the present invention. Detailed Implementation

[0019] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings.

[0020] refer to Figure 1The excitation power supply is based on a microcontroller. Keyboard input controls the data (including the target excitation current, the estimated excitation time, and the current step size in amperes per minute). The microcontroller converts the digital signal to analog signal to change the control voltage, thereby achieving step-preset output settings (e.g., how many amperes the current increases per minute in minutes), and thus realizing numerical control output. The sampled signal is processed by the microcontroller's A / D converter and then output to the LCD screen to display the output voltage and current values ​​in real time.

[0021] Current equals voltage divided by resistance (I=U / R), where R is the resistance of the magnet coil. In the ideal superconducting state, the resistance is 0, but in reality it is a few milliohms. When the voltage U increases, the resistance R remains constant, and the current I increases. Electrical energy is converted into magnetic energy, and the magnetic field strength increases accordingly.

[0022] During the quench process, a high voltage will appear at both ends of the magnet coil. The microcontroller processes the sampled voltage signal and judges it as an abnormal voltage signal. The microcontroller outputs a control signal to cut off the connection between the magnet coil and the excitation power supply. The quench is also a process of electromagnetic energy being converted into heat energy. After the connection is broken, the coil releases the residual energy through a high-power thyristor.

[0023] For NMOS characteristics, refer to Figures 2 to 3 When Vgs exceeds a certain value, the circuit will conduct, making it suitable for applications where the source is grounded (low-side drive). This only requires a gate voltage of 4V or 10V. As the gate voltage Vgs changes, the amount of charge induced in the channel also changes, and the width of the conductive channel changes accordingly. Consequently, the drain current ID changes with the gate voltage.

[0024] The basic method for precisely controlling the current in a MOSFET circuit is as follows: A control voltage (from the non-inverting input of the comparator) and a reference voltage (from the inverting input of the comparator) are simultaneously applied to the voltage comparator. The output of the comparator is then connected to the gate (G) pin of the MOSFET. If the control voltage is higher than the reference voltage, the MOSFET is controlled to conduct and output current. (Reference) Figure 4 Where Io = R3 * V / (R1 + R2 + R3)R4.

[0025] NMOS is a type of MOSFET. MOSFETs are used to control the excitation power supply. You can think of a MOSFET as a water flow switch. The control voltage is like the faucet handle. The higher the voltage, the more the faucet handle is turned on, and the greater the water flow. Similarly, the greater the current.

[0026] The microcontroller's internal DAC module outputs voltage via a keyboard control. The DAC's output voltage is acquired through an ADC channel, and the LCD module displays the voltage value acquired by the ADC and the DAC's set output voltage value. DAC stands for Digital-to-Analog Converter, which converts digital signals into analog signals. For example, if the excitation voltage is 2V, and the input "2V" is an analog signal via the touchscreen, the microcontroller will convert it to an analog 2V voltage for output.

[0027] while(1)

[0028] {

[0029] t++;

[0030] key = KEY_Scan(0);

[0031] if(key==WKUP_PRES)

[0032] {

[0033] if (dacval < 4000) dacval += 200; / / Input via touchscreen or keypad

[0034] DAC->DHR12R1=dacval; / / DAC analog-to-digital converter output

[0035] }else if(key==KEY1_PRES)

[0036] {

[0037] if (dacval > 200) dacval -= 200; / / Input via touchscreen or button

[0038] else dacval=0;

[0039] DAC->DHR12R1=dacval; / / DAC analog-to-digital converter output

[0040] }

[0041] if(t==10||key==KEY1_PRES||key==WKUP_PRES)

[0042] {

[0043] adcx=DAC->DHR12R1;

[0044] LCD_ShowxNum(94,150,adcx,4,16,0); / / Display register value

[0045] temp = (float)adcx * (3.3 / 4096); / / Calculate the voltage value

[0046] adcx=temp;

[0047] LCD_ShowxNum(94,170,temp,1,16,0); / / Display output voltage value position

[0048] emp-=adcx;

[0049] temp *=1000; / / Calculation

[0050] LCD_ShowxNum(110,170,temp,3,16,0X80); / / Display output voltage value position

[0051] adcx = Get_Adc_Average(ADC_CH1, 10); / / Voltage acquisition input port

[0052] temp = (float)adcx * (3.3 / 4096); / / Calculate the voltage value

[0053] adcx=temp;

[0054] LCD_ShowxNum(94,190,temp,1,16,0); / / Displays the position of the sampled voltage value

[0055] temp-=adcx;

[0056] temp *=1000; / / Calculation

[0057] LCD_ShowxNum(110,190,temp,3,16,0X80); / / Displays the position of the sampled voltage value

[0058] LED0 = !LED0;

[0059] t=0;

[0060] }

[0061] delay_ms(10);

[0062] }

[0063] }

[0064] The voltage across the magnet coil is acquired through the ADC channel of the microcontroller. After processing, it is compared with preset data. If the magnet fails to quench, the microcontroller system calculates and determines the result and takes appropriate action. The microcontroller's I / O port outputs a high-level signal to control the relay to engage and disconnect the excitation power supply from the magnet coil.

[0065] During the quench process, a high voltage will appear at both ends of the magnet. The voltage on the inductor inside the coil and the voltage on the resistor (the result of the quench) are opposite. This voltage that appears in the quench zone inside the coil often reaches hundreds or even thousands of volts, which can cause an electric arc between the turns. The quench protection connects a high-power diode in reverse parallel at the output of the excitation power supply to short-circuit the output and release energy.

[0066] void Get_voltage_Q(void)

[0067] {

[0068] if(adcxQ<1100) / / If the sampled voltage is less than 1100mV, it is determined to be a quench signal.

[0069] {

[0070] GPIO_SetBits(GPIOF,GPIO_Pin_3); / / Enable timeout protection on microcontroller's F3 port.

[0071] delay_ms(900);

[0072] delay_ms(900);

[0073] delay_ms(900);

[0074] delay_ms(900);

[0075] delay_ms(900); / / Timer

[0076] GPIO_ResetBits(GPIOF,GPIO_Pin_3); / / Disables timeout protection on microcontroller's F3 port.

[0077] }

[0078] }

[0079] Under normal circumstances, the coils of relay pins 1 and 4 are not energized, and the normally closed contacts of relay pins 3 and 5 are energized, forming a circuit between the magnet coil and the excitation power supply, which can excite and raise the field. When an abnormal situation occurs, a high-level signal is sent through the microcontroller's I / O port to make pins 3 and 4 of optocoupler U2 conduct, so that one pin of the relay is grounded, the relay coil is energized, and the normally open contacts of relay pins 2 and 5 are energized and energized, disconnecting the connection circuit between the magnet coil and the excitation power supply, thereby completing the abnormal protection.

[0080] The above description is only a preferred embodiment of the present utility model. The protection scope of the present utility model is not limited to the above embodiments. Any equivalent modifications or changes made by those skilled in the art based on the content disclosed in the present utility model should be included in the protection scope recorded in the claims.

Claims

1. A thread-controlled excitation power supply with overrun protection for high-temperature superconducting magnets, characterized in that: The excitation power supply includes a microcontroller that receives control data, outputs control voltage through the microcontroller's digital-to-analog converter (DAC), and magnetizes the magnet coil through current stepping; the sampled signal is processed by the microcontroller's analog-to-digital converter (ADC) and output to the LCD screen to display the corresponding voltage and current values ​​in real time. The keyboard input controls the data, including the target excitation current, the estimated excitation time, and the current step per minute. The control voltage is changed through the microcontroller's digital-to-analog conversion to achieve the step preset output setting. The current is increased by amperes in minutes, thereby achieving numerical control output. The voltage signal across the sampling magnet coil is returned to the microcontroller for processing. When a high voltage is detected, it is identified as an abnormal voltage signal, triggering quench protection. The microcontroller outputs a control signal to disconnect the magnet coil from the excitation power supply and releases the residual energy of the magnet coil through a high-power thyristor.

2. The in-line controlled excitation power supply with quench protection for high-temperature superconducting magnets according to claim 1, characterized in that: The output control voltage of the DAC is acquired by the ADC channel of the microcontroller, and the voltage value acquired by the ADC and the set output voltage value of the DAC are displayed on the LCD module.

3. The in-line controlled excitation power supply with quench protection for high-temperature superconducting magnets according to claim 1, characterized in that: The voltage across the magnet coil is acquired through the ADC channel of the microcontroller, processed, and compared with preset data to perform corresponding operations.

4. The in-line controlled excitation power supply with quench protection for high-temperature superconducting magnets according to claim 1, characterized in that: When quench protection is activated, the microcontroller's I / O port outputs a high-level signal to control the relay to engage, disconnecting the excitation power supply and the magnet coil.

5. The in-line controlled excitation power supply with quench protection for high-temperature superconducting magnets according to claim 1, characterized in that: A high-power diode is connected in reverse parallel at the output of the excitation power supply to short-circuit the output and release energy.

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