Transformer resonance frequency measuring device and method based on second-order series oscillation method

Abstract

The application discloses a transformer resonance frequency measuring device and method based on a second-order series oscillation method, and the device comprises an energy storage battery, an energy storage switching switch, an energy storage capacitor, a test switch, a diode and a test device; the output end of the energy storage battery is connected in parallel with the energy storage capacitor through the energy storage switching switch; the energy storage capacitor is connected in parallel to the input end of a measured transformer winding through the test switch and the diode; the input end of the test device is connected to the input end of the measured transformer winding, and the control end of the test device is connected with the control end of the energy storage switching switch and the control end of the test switch respectively. The application utilizes the RLC second-order series equivalent circuit formed by the transformer winding loop, measures the frequency of the sinusoidal oscillation change of the voltage across the capacitor with time, and the frequency is the inherent frequency of the transformer.

Description

Technical Field

[0001] This invention belongs to the field of transformer frequency measurement, and specifically relates to a transformer resonant frequency measurement device and method based on the second-order series oscillation method. Background Technology

[0002] The resonant frequency is a core parameter for the efficient, safe, and compact operation of a resonant transformer. Proper utilization can significantly improve the performance of power equipment testing and industrial heating, but potential risks must be mitigated through precise control and protection measures. If the input frequency coincides with the transformer's natural frequency, it may cause overvoltage, overcurrent, or even insulation breakdown, requiring prevention through structural design, frequency control, or damping measures. Typically, transformer windings can be equivalent to an inductor L and a resistor R. After winding, a distributed capacitance C exists between the windings, thus forming a second-order RLC circuit connected in series. Summary of the Invention

[0003] In order to obtain the inherent resonant frequency of a transformer, this invention proposes a transformer resonant frequency measurement device and method based on the RLC second-order series oscillation method.

[0004] The technical solution of the present invention is as follows: A transformer resonant frequency measuring device based on the second-order series oscillation method includes: Energy storage batteries, energy storage switching switches, energy storage capacitors, test switches, diodes, and testing equipment; The output terminal of the energy storage battery is connected in parallel with the energy storage capacitor through the energy storage switching switch; The energy storage capacitor is connected in parallel to the input terminal of the transformer winding under test through the test switch and the diode. The input terminal of the testing device is connected to the input terminal of the transformer winding under test, and is used to acquire the voltage signal of the transformer winding under test; the control terminal of the testing device is connected to the control terminal of the energy storage switching switch and the control terminal of the test switch respectively, and is used to control the closing or opening of the energy storage switching switch and the test switch. When the energy storage switching switch is closed and the test switch is open, the energy storage battery charges the energy storage capacitor. When the energy storage switching switch is open and the test switch is closed, the energy storage capacitor applies a DC excitation signal to the winding of the transformer under test through the diode, causing the RLC second-order series equivalent circuit of the winding of the transformer under test to be in a zero-state response state. The voltage across the equivalent capacitor changes according to the oscillating discharge process.

[0005] Preferably, the capacitance value of the energy storage capacitor is in the range of 10μF to 100μF. If it is too large, it is easy to saturate and cause the oscillation waveform to be incomplete.

[0006] Preferably, the energy storage battery is a 12V lead-acid battery.

[0007] Preferably, the diode is a 10A diode.

[0008] Preferably, the energy storage switching switch is an AC contactor with a rated current of 16A.

[0009] Preferably, the test switch is an AC contactor with a rated current of 100A.

[0010] Preferably, the above-mentioned testing apparatus includes: The voltage divider circuit has its input terminal connected to both ends of the winding of the transformer under test. The microprocessor module has its analog-to-digital converter terminal connected to the output terminal of the voltage divider circuit; The display module has its input terminal connected to the input / output terminal of the microprocessor module; A storage module, the input of which is connected to the input / output terminals of the microprocessor module; A communication module, which is connected to the communication interface of the microprocessor module; The power module has its output terminal connected to the power terminal of the microprocessor module.

[0011] During testing, the oscillation frequency f is calculated by reading the period T of the oscillation waveform. The period T and frequency f are reciprocals of each other. However, in order to eliminate the influence between windings, the non-measuring winding and the secondary side need to be short-circuited during measurement in order to obtain the oscillation frequency of the primary side.

[0012] Preferably, the voltage divider circuit is a resistor voltage divider circuit, which uses two series resistors connected in parallel across the test winding of the test transformer to reduce the 12VAC voltage to 3VAC.

[0013] Preferably, the microprocessor module uses the STM32F103C8T6 chip, which is packaged in an LQFP-48 package. Compared to other microcontroller chips, the STM32F103C8T6 offers advantages such as high performance, low cost, and low power consumption. Internally, it includes 37 GPIO ports, two 12-bit ADC channels, one CAN bus, one IIC bus, and multiple SPI buses. Its internal clock frequency reaches up to 64MHz. Its compact size and rich functionality meet the functional requirements of this system. The microcontroller circuit is as follows: Figure 6 As shown, the entire microcontroller circuit consists of an STM32F103C8T6 chip and its peripheral circuits. The added crystal oscillator circuit is used to improve the clock accuracy of the entire system, providing a more reliable clock source for the microcontroller. The SW download circuit is used to download and debug embedded software programs in conjunction with the J-link tool, and the reset circuit is used to reset the microcontroller.

[0014] The display module uses a TJC4827T043_011X USART_HMI serial touchscreen as the human-machine interface tool. This screen allows for the design of a user interface (GUI) on a PC using its dedicated development software. The user interface primarily displays real-time and historical temperature data for each node, as well as alarm temperature information. The serial touchscreen communicates with the microcontroller via UART serial communication for function operation and parameter configuration. The serial touchscreen is powered by 5V and is connected to the microcontroller's I / O ports via the transmit (TX) and receive (RX) terminals.

[0015] The storage module uses the GD25Q16E FLASH memory to store temperature and electrical data. This chip is packaged in DIP-8, powered by a 3.3V power supply, has a built-in 16M bytes of storage capacity, 100,000 erase / write cycles, and a 20-year data retention period, meeting the actual application requirements of the system.

[0016] The communication module uses the NBIOT wireless communication module of WH-NB73-BA for data transmission between the data receiving device and the network server. WH-NB73-BA is powered by 5V DC and has a built-in SIM card slot for inserting SIM cards.

[0017] The power module uses the LM2596-5 buck switching integrated voltage regulator chip to achieve 12V-5V voltage conversion. The LM2596-5 has a fixed current output capability of 3A and a power conversion efficiency of up to 88%. It includes a 150KHz fixed frequency oscillator and a reference regulator with a reference voltage of 1.23V. Its built-in protection circuitry, current limiting, and thermal shutdown circuitry result in significantly less heat generation than similar linear regulator ICs during high current output. The 5V to 3.3V conversion is achieved using an AMS-1117 LDO (low dropout linear regulator). LDOs offer advantages such as low cost, low noise, and low quiescent current. Furthermore, LDOs require relatively few external components; only a few capacitors need to be connected in parallel at the input and output terminals.

[0018] This invention also provides a method for measuring the resonant frequency of a transformer based on a second-order series oscillation method, applied to the aforementioned device, comprising the following steps: S1: During testing, the test device disconnects the test switch; S2: The energy storage switching device closes the energy storage switch for more than 20 seconds to fully charge the energy storage capacitor. S3: The test device disconnects the energy storage switching switch; S4: The test device closes the test switch and simultaneously acquires the voltage signal across the two ends of the test transformer winding. The test time is less than 10 seconds. S5: The testing device reads the time between the two zero-crossing points of the voltage, which is half the cycle time T / 2 of the oscillation frequency. The oscillation frequency f can then be calculated using the relationship f=1 / T. The test data is stored, and the average value is taken after repeated testing. If there are no two zero-crossing points during measurement, it indicates that the energy storage capacitor C1 stores too much energy. The stored energy can be reduced by decreasing the capacitance value of energy storage capacitor C1.

[0019] The beneficial effects of this invention are: This invention mainly utilizes the RLC second-order series equivalent circuit formed by the transformer winding circuit. Under underdamped conditions, the voltage across the capacitor in the transformer winding equivalent circuit changes sinusoidally with time. By measuring the frequency of the sinusoidal oscillation of the voltage across the capacitor with time, this frequency is the natural frequency of the transformer. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the device of the present invention; Figure 2 It is an equivalent circuit for measuring the resonant frequency of a transformer based on the RLC second-order series oscillation method; Figure 3 This is a schematic diagram of the testing device. Figure 4 This is a waveform diagram of the voltage oscillation across the transformer windings; Figure 5 This is the wiring diagram for transformer winding testing; Figure 6 It is a microcontroller circuit; Figure 7 It is a human-computer interaction circuit; Figure 8 It is a FLASH storage circuit; Figure 9 It is an NB-IoT wireless communication module circuit; Figure 10 It is a 2V-5V voltage conversion circuit; Figure 11 It is a 5V-3.3V voltage conversion circuit. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0022] like Figure 1 , 2 As shown, a transformer resonant frequency measuring device based on the second-order series oscillation method includes: Energy storage batteries, energy storage switching switches, energy storage capacitors, test switches, diodes, and testing equipment; The output terminal of the energy storage battery is connected in parallel with the energy storage capacitor through the energy storage switching switch; The energy storage capacitor is connected in parallel to the input terminal of the transformer winding under test through the test switch and the diode. The input terminal of the testing device is connected to the input terminal of the transformer winding under test, and is used to acquire the voltage signal of the transformer winding under test; the control terminal of the testing device is connected to the control terminal of the energy storage switching switch and the control terminal of the test switch respectively, and is used to control the closing or opening of the energy storage switching switch and the test switch. When the energy storage switching switch is closed and the test switch is open, the energy storage battery charges the energy storage capacitor. When the energy storage switching switch is open and the test switch is closed, the energy storage capacitor applies a DC excitation signal to the winding of the transformer under test through the diode, causing the RLC second-order series equivalent circuit of the winding of the transformer under test to be in a zero-state response state. The voltage across the equivalent capacitor changes according to the oscillating discharge process.

[0023] Preferably, the capacitance value of the energy storage capacitor is in the range of 10μF to 100μF. If it is too large, it is easy to saturate and cause the oscillation waveform to be incomplete.

[0024] Preferably, the energy storage battery is a 12V lead-acid battery.

[0025] Preferably, the diode is a 10A diode.

[0026] Preferably, the energy storage switching switch is an AC contactor with a rated current of 16A.

[0027] Preferably, the test switch is an AC contactor with a rated current of 100A.

[0028] like Figure 3 As shown, the above-mentioned testing apparatus includes: The voltage divider circuit has its input terminal connected to both ends of the winding of the transformer under test. The microprocessor module has its analog-to-digital converter terminal connected to the output terminal of the voltage divider circuit; The display module has its input terminal connected to the input / output terminal of the microprocessor module; A storage module, the input of which is connected to the input / output terminals of the microprocessor module; A communication module, which is connected to the communication interface of the microprocessor module; The power module has its output terminal connected to the power terminal of the microprocessor module.

[0029] like Figure 4As shown, during the test, the oscillation frequency f is calculated by reading the period T of the oscillation waveform. The period T and the frequency f are reciprocals of each other. However, in order to eliminate the influence between the windings, the non-measuring winding and the secondary side need to be short-circuited during the measurement so that the primary side oscillation frequency can be obtained. Figure 5 In the diagram, A, B, and C are the three-phase input terminals of the test transformer, a, b, and c are the three-phase output terminals of the test transformer, and n is the neutral point of the test transformer.

[0030] Preferably, the voltage divider circuit is a resistor voltage divider circuit, which uses two series resistors connected in parallel across the test winding of the test transformer to reduce the 12VAC voltage to 3VAC.

[0031] like Figure 6 As shown, the microprocessor module described above uses the STM32F103C8T6 chip, which is packaged in an LQFP-48 package. Compared to other microcontroller chips, the STM32F103C8T6 offers advantages such as high performance, low cost, and low power consumption. Internally, it includes 37 GPIO ports, two 12-bit ADC channels, one CAN bus, one IIC bus, and multiple SPI buses. Its internal clock frequency reaches up to 64MHz. Its compact size and rich functionality meet the functional requirements of this system. The microcontroller circuit is shown below. Figure 6 As shown, the entire microcontroller circuit consists of an STM32F103C8T6 chip and its peripheral circuits. The added crystal oscillator circuit is used to improve the clock accuracy of the entire system, providing a more reliable clock source for the microcontroller. The SW download circuit is used to download and debug embedded software programs in conjunction with the J-link tool, and the reset circuit is used to reset the microcontroller.

[0032] The display module uses a TJC4827T043_011X USART_HMI serial touchscreen as the human-machine interface tool. This screen allows for the design of a user interface (GUI) on a PC using its dedicated development software. The user interface primarily displays real-time and historical temperature data for each node, as well as alarm temperature information. The serial touchscreen communicates with the microcontroller via UART serial communication for function operation and parameter configuration. The serial touchscreen is powered by 5V and is connected to the microcontroller's I / O ports via the transmit (TX) and receive (RX) terminals. The human-machine interface circuit is as follows: Figure 7 As shown.

[0033] The storage module uses a GD25Q16E FLASH memory to store temperature and electrical data. This chip is packaged in a DIP-8 package, operates on a 3.3V power supply, has a built-in 16MB storage capacity, 100,000 erase / write cycles, and a 20-year data retention period, meeting the practical application requirements of the system. The FLASH memory communicates with the microcontroller via SPI, and its hardware circuitry is as follows... Figure 8 As shown.

[0034] The communication module uses the WH-NB73-BA NB-IoT wireless communication module for data transmission between the data receiving device and the network server. The WH-NB73-BA is powered by 5V DC and has a built-in SIM card slot for inserting a SIM card. The NB-IoT wireless communication module circuit is as follows: Figure 9 As shown.

[0035] The power module uses the LM2596-5 buck switching integrated voltage regulator chip to achieve 12V-5V voltage conversion. The LM2596-5 has a fixed current output capability of 3A and a power conversion efficiency of up to 88%. Internally, it includes a 150kHz fixed-frequency oscillator and a reference regulator with a reference voltage of 1.23V. Furthermore, its built-in protection circuitry, current limiting, and thermal shutdown circuitry result in significantly less heat generation than similar linear voltage regulator ICs during high-current output. The 12V-5V voltage conversion circuit is as follows: Figure 10 As shown, a 5V to 3.3V converter is achieved using an AMS-1117 LDO (Low Dropout Linear Regulator). LDOs offer advantages such as low cost, low noise, and low quiescent current. Furthermore, LDOs require relatively few external components; only a few capacitors need to be connected in parallel at the input and output terminals. The circuit is shown below. Figure 11 As shown.

[0036] This invention also provides a method for measuring the resonant frequency of a transformer based on a second-order series oscillation method, applied to the aforementioned device, comprising the following steps: S1: During testing, the test device disconnects the test switch; S2: The energy storage switching device closes the energy storage switch for more than 20 seconds to fully charge the energy storage capacitor. S3: The test device disconnects the energy storage switching switch; S4: The test device closes the test switch and simultaneously acquires the voltage signal across the two ends of the test transformer winding. The test time is less than 10 seconds. S5: The testing device reads the time between the two zero-crossing points of the voltage, which is half the cycle time T / 2 of the oscillation frequency. The oscillation frequency f can then be calculated using the relationship f=1 / T. The test data is stored, and the average value is taken after repeated testing. If there are no two zero-crossing points during measurement, it indicates that the energy storage capacitor C1 stores too much energy. The stored energy can be reduced by decreasing the capacitance value of energy storage capacitor C1.

[0037] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A transformer resonant frequency measuring device based on the second-order series oscillation method, characterized in that, include: Energy storage batteries, energy storage switching switches, energy storage capacitors, test switches, diodes and test devices; The output terminal of the energy storage battery is connected in parallel with the energy storage capacitor through the energy storage switching switch; The energy storage capacitor is connected in parallel to the input terminal of the transformer winding under test through the test switch and the diode. The input terminal of the testing device is connected to the input terminal of the transformer winding under test, and is used to acquire the voltage signal of the transformer winding under test; the control terminal of the testing device is connected to the control terminal of the energy storage switching switch and the control terminal of the test switch respectively, and is used to control the closing or opening of the energy storage switching switch and the test switch. When the energy storage switching switch is closed and the test switch is open, the energy storage battery charges the energy storage capacitor; When the energy storage switching switch is open and the test switch is closed, the energy storage capacitor applies a DC excitation signal to the winding of the transformer under test through the diode, so that the RLC second-order series equivalent circuit of the winding of the transformer under test is in a zero-state response state, and the voltage across the equivalent capacitor changes according to the oscillating discharge process.

2. The transformer resonant frequency measuring device based on the second-order series oscillation method according to claim 1, characterized in that, The capacitance value of the energy storage capacitor ranges from 10μF to 100μF.

3. The transformer resonant frequency measuring device based on the second-order series oscillation method according to claim 1, characterized in that, The energy storage switching switch is an AC contactor with a rated current of 16A.

4. The transformer resonant frequency measuring device based on the second-order series oscillation method according to claim 1, characterized in that, The test switch is an AC contactor with a rated current of 100A.

5. The transformer resonant frequency measuring device based on the second-order series oscillation method according to claim 1, characterized in that, The testing apparatus includes: The voltage divider circuit has its input terminal connected to both ends of the winding of the transformer under test. The microprocessor module has its analog-to-digital converter terminal connected to the output terminal of the voltage divider circuit; The display module has its input terminal connected to the input / output terminal of the microprocessor module; A storage module, the input of which is connected to the input / output terminals of the microprocessor module; A communication module, which is connected to the communication interface of the microprocessor module; The power module has its output terminal connected to the power terminal of the microprocessor module.

6. The transformer resonant frequency measuring device based on the second-order series oscillation method according to claim 5, characterized in that, The voltage divider circuit is a resistor voltage divider circuit, used to step down the voltage signal across the winding of the transformer under test and then output it.

7. The transformer resonant frequency measuring device based on the second-order series oscillation method according to claim 5, characterized in that, The microprocessor module uses an STM32F103C8T6 chip.

8. A method for measuring the resonant frequency of a transformer based on a second-order series oscillation method, applied to the apparatus described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: The test device controls the test switch to disconnect; S2: The test device controls the energy storage switching switch to close, so that the energy storage battery charges the energy storage capacitor; S3: The test device controls the energy storage switching switch to open; S4: The test device controls the test switch to close, so that the energy storage capacitor applies a DC excitation signal to the winding of the transformer under test through the diode, and at the same time, it collects the voltage signal across the winding of the transformer under test. S5: The testing device reads the zero-crossing point of the acquired voltage signal, determines the oscillation half-cycle based on the time difference between two adjacent zero-crossing points, calculates the oscillation frequency, and stores the test data.

9. The method for measuring the resonant frequency of a transformer based on the second-order series oscillation method according to claim 8, characterized in that, In step S2, the closing duration of the energy storage switching switch is greater than 20 seconds, and in step S4, the time for acquiring the voltage signal is less than 10 seconds.

10. The method for measuring the resonant frequency of a transformer based on the second-order series oscillation method according to claim 8, characterized in that, In step S5, if two zero-crossing points cannot be obtained, the capacitance value of the energy storage capacitor is reduced and the measurement is repeated.

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