Low-voltage high-current test device and control method thereof

Abstract

The application provides a low-voltage large-current test device and a control method thereof, and belongs to the technical field of current test. The test device comprises a man-machine interface unit, an industrial control computer, a closed-loop control and acquisition unit, a programmed voltage source, a logic control unit and a multi-magnetic circuit current generating device. The man-machine interface unit and the industrial control computer are in bidirectional communication. The industrial control computer is electrically connected with the closed-loop control and acquisition unit, the programmed voltage source and the logic control unit respectively, and is used for data processing and control scheduling. The output end of the programmed voltage source is connected with the logic control unit, and the output end of the logic control unit is connected with the multi-magnetic circuit current generating device. The closed-loop control and acquisition unit is electrically connected with the industrial control computer and the multi-magnetic circuit current generating device respectively. The application can connect the test loop according to the phase angle of the setting requirement, test the current protection function of the test product, and has the characteristics of accurate phase angle, rapid reaction, low cost and simple maintenance.

Description

Technical Field

[0001] This application belongs to the field of current testing technology and relates to a low-voltage high-current current source device that can set the test current closing angle and control multiple magnetic circuits. It is used to detect the current protection function operation accuracy and performance of low-voltage electrical appliances through the low-voltage current source provided by the testing device. Specifically, it is a low-voltage high-current testing device and its control method. Background Technology

[0002] Low-voltage high-current devices are mainly used in the testing of the current performance of low-voltage electrical appliances. Low-voltage electrical appliances primarily distribute electrical energy and protect circuits in power distribution networks, preventing damage from overloads, short circuits, and other faults. Especially after assembly, low-voltage electrical components require overload and short-circuit protection functional tests, and their accuracy and reliability are extremely important. Generally, low-voltage high-current testing is used after assembly or during routine testing. If the product performance cannot be accurately calibrated, it can easily lead to failure to provide timely and accurate protection for power lines and equipment in the event of overloads or short circuits, resulting in significant economic losses and personal injury accidents. Conventional testing methods involve providing a low-voltage high-current to the main circuit, connecting the product under test, and testing whether its protection disconnection time meets the operating characteristics. However, for AC low-voltage electrical components, general devices cannot control the phase angle of the connected current, and cannot simulate the protection characteristics to ensure they meet product requirements under the most severe peak fault conditions, resulting in inaccurate evaluation and testing. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this application provides a low-voltage high-current testing device and its control method. The device allows for arbitrary setting of the closing angle, is convenient, simple, and reliable, while also improving economic efficiency, reducing the probability of current characteristic failure in low-voltage electrical appliances, and enhancing testing accuracy. To achieve the above objectives, the following technical solutions are adopted: A low-voltage high-current testing device includes a human-machine interface unit, an industrial control computer, a closed-loop control and acquisition unit, a programmable voltage source, a logic control unit, and a multi-magnetic circuit current generator. The human-machine interface unit communicates bidirectionally with the industrial control computer to issue control commands and display the operating status. The industrial control computer is electrically connected to the closed-loop control and acquisition unit, the programmable voltage source, and the logic control unit, respectively, and is used for data processing and control scheduling. The output terminal of the programmable voltage source is connected to the logic control unit, and the programmable voltage source is electrically connected to the industrial control computer. The industrial control computer controls the output amplitude of the programmable voltage source. The output terminal of the logic control unit is connected to the multi-magnetic circuit current generator. The logic control unit is electrically connected to the industrial control computer. The industrial control computer controls the primary side of the multi-magnetic circuit current generator to form different series and parallel winding combination schemes. The closed-loop control and acquisition unit is electrically connected to the industrial control computer and the multi-magnetic circuit current generator, respectively, and acquires the voltage and current at the primary and secondary output terminals to form a closed-loop feedback regulation of the current / voltage parameters.

[0004] Furthermore, the multi-magnetic-circuit current generating device includes a primary side and a secondary side. The primary side includes multiple windings, each of which is connected in series or in parallel with an AC contactor of a logic control unit. The secondary side outputs low voltage and high current for testing.

[0005] Moreover, the logic control unit consists of multiple AC contactors. By changing the connection or disconnection of the AC contactors, different series and parallel winding schemes can be formed in the primary winding of the multi-magnetic circuit current generator.

[0006] Furthermore, the closed-loop control and acquisition unit includes a voltage transformer and a current transformer. The voltage transformer acquires the voltage signals of the primary and secondary sides of the multi-magnetic circuit current generator, and the current transformer acquires the current signals of the primary and secondary sides of the multi-magnetic circuit current generator.

[0007] Furthermore, the current signal is modulated by an operational amplifier and then connected to a data acquisition ADC analog-to-digital converter installed inside the industrial control computer to obtain the modulated current signal. The modulated current signal is then connected to the data acquisition card installed inside the industrial control computer through a current zero-crossing detection circuit to complete the zero-crossing acquisition of the current signal.

[0008] Furthermore, the voltage signal is connected to the data acquisition ADC analog-to-digital converter installed inside the industrial control computer through the voltage acquisition circuit to obtain the modulated voltage signal. The modulated voltage signal is then connected to the data acquisition card installed inside the industrial control computer through the voltage zero-crossing detection circuit to complete the zero-crossing acquisition of the voltage signal.

[0009] A control method for a low-voltage, high-current testing device includes the following steps: Step 1: Input relevant parameters through the human-machine interface. The system reads the settings, calculates the pre-connection current based on the output current, and converts it into a drive voltage value. Based on the capacity of the multi-magnetic circuit current generator and Table 1, select the drive winding scheme and proceed to Step 2. Step 2: Based on the selected winding scheme, drive the corresponding contactor of the logic control unit to complete the winding connection of the multi-magnetic circuit current generator, and proceed to Step 3. Step 3: Close the solid-state relay and output contactor to connect the input and output circuits, then proceed to step 4; Step 4: Based on the driving voltage value, drive the CNC voltage source to output current; Step 5: Collect input and output voltage, current and other parameters, and determine if they meet the expected turn-on current. If they do, disconnect the solid-state relay or output contactor and proceed to step 6; otherwise, calculate the drive voltage difference, update the drive value, and return to step 4. Step 6: Based on the collected input and output voltages, currents, frequencies, and zero-crossing points, calculate the phase difference between the input voltage and the output current, and convert it into a time constant t3. Proceed to Step 7. Step 7: Select the drive winding scheme according to the output current and Table 1 and drive it. Calculate the input power supply voltage drive value based on the drive scheme. Correct the actual CNC voltage source drive value according to the actual drive voltage value of the expected output current. Drive the voltage source, close the output circuit, and go to step 8. Step 8: Determine the zero-crossing point of the input voltage as the base point, wait for the t3 delay, and when the phase delay time is up, close the solid-state relay of the input circuit and proceed to step 9; Step 9: Calculate whether the numerical phase and current amplitude meet the output settings. If they do not meet the settings, proceed to step 10; otherwise, proceed to step 11. Step 10: Adjust the driving value of the digital control voltage source according to the output current ratio and fine-tune the drive, then proceed to Step 11; Step 11: Check if the main circuit has no current and the test circuit is disconnected; check if the drive protection time has expired. If not, return to step 9. If one of these conditions is met, disconnect the output circuit, clear the programmable voltage source drive, disconnect the solid-state relay, and exit.

[0010] In summary, the technical solutions provided in the embodiments of this application have the following technical effects or advantages: 1. This solution employs a method where, when the output phase is selected and a large current is closed, a small current of 10%-20% of the required current is first applied to the test sample. The actual input and output current waveforms are collected and imported into the software formula for automatic compensation and phase calibration. Finally, the required phase low-voltage large current is directly output. This solution uses a small current to connect without damaging the test sample. It also avoids the inconsistency between the test return impedance when setting the phase and the actual test sample impedance, which would cause the actual output phase deviation. This ensures that the set phase and the actual output phase are absolutely consistent, effectively avoiding excessive errors between the set phase and the actual phase.

[0011] 2. This solution adopts high-frequency signal acquisition and closed-loop control of voltage and current on the power supply side and output side to meet the requirements of static and dynamic output accuracy and current fluctuation.

[0012] 3. This solution uses a solid-state relay module without mechanical contacts to control the main power supply in the primary winding. The contactor controls the series, parallel, and short-circuit connections of the multi-magnetic circuit primary winding to achieve power-on without mechanical delay, while ensuring that the multi-magnetic circuit transformer can output 30%-300% of its rated current, meeting the requirements of a wide output current range and high accuracy. The three sets of multi-magnetic circuit windings are completely identical, and the contactor can directly combine the magnetic circuits to achieve the superposition of the output current multiple during output, which has the characteristics of low cost, high efficiency, and wide output range.

[0013] In summary, this invention utilizes a programmable voltage source, solid-state relays, contactors, and multi-magnetic circuit transformers, combined with zero-crossing acquisition and programmable algorithms, to remotely connect the experimental circuit according to the required phase angle, and test the current protection function of the test object. It features accurate phase angle, rapid response, low cost, and easy maintenance. Attached Figure Description

[0014] Figure 1 The schematic diagram of the experimental apparatus in this embodiment.

[0015] Figure 2 Electrical schematic diagram of the test device in this embodiment.

[0016] Figure 3 Schematic diagram of current signal and zero-crossing acquisition.

[0017] Figure 4 Schematic diagram of voltage signal and zero-crossing acquisition.

[0018] Figure 5 A schematic diagram of the phase calculation logic and the driving waveform curve.

[0019] Figure 6 Schematic diagram of the device system control logic.

[0020] Reference numerals: 101, Human-Machine Interface Unit; 102, Industrial Control Computer; 103, Closed-Loop Control and Acquisition Unit; 104, Multi-Magnetic Circuit Current Generator; 105, Logic Control Unit; 106, Programmable Voltage Source. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0022] A fully closed-loop, low-voltage high-current generating device with adjustable drive closing phase angle and its control method are disclosed, which are applied to a current device and its control method for detecting the current characteristics of low-voltage components.

[0023] This device includes a primary multi-magnetic-circuit current generator with three windings and a logic control unit for its magnetic circuit switching circuit; a digital voltage source device that provides power to the current generator; and a solid-state relay without mechanical contacts that disconnects and connects the power supply to the multi-magnetic-circuit current generator. The multi-magnetic circuit current generator includes a closed-loop control and acquisition unit circuit for the voltage and current at the power supply and output terminals, an industrial control calculation unit and a human-machine interface unit for calculating the amplitude and angle of the current and voltage, and a drive unit for driving the various electrical components to connect and disconnect.

[0024] like Figure 1 The schematic diagram of the experimental device shown in this embodiment illustrates the principle of the device, which includes an industrial control computer 102 as the processing core and an internally installed data acquisition and I / O driver card. The industrial control computer 102 acquires the device voltage, current, zero-crossing signal, and other statuses from the closed-loop control and acquisition unit 103 through the internal data acquisition card. The closed-loop control and acquisition unit 103 acquires the current and voltage signals of the primary and secondary output sides of the multi-magnetic circuit current generator 104 through current and voltage transformers. The industrial control computer 102 is connected to the human-machine interface unit 101 via a data cable to complete data display and parameter input. The industrial control computer 102 is connected to the programmable voltage source 106 via a communication interface through a data cable to set the voltage source output voltage, output, and disconnection. The industrial control computer 102 drives the contactors in the logic control unit 105 through the internal data acquisition card to complete the series and parallel connection of the primary windings of the multi-magnetic circuit current generator 104, forming various winding schemes.

[0025] Table 1 The I / O ports of the industrial control computer 102 data acquisition card are connected to the logic control unit 105 and the contactor auxiliary nodes in the device to collect the on / off status of control elements. This scheme uses the industrial control computer 102 to control the programmable voltage source 106 to provide a precise output voltage for the multi-magnetic circuit current generator 104. At the same time, the industrial control computer 102 adjusts the series and parallel combination of the primary winding of the multi-magnetic circuit current generator 104 through the logic control power supply. The secondary side of the multi-magnetic circuit current generator 104 outputs low voltage and high current for testing. The closed-loop control and acquisition unit in the control system collects the status of the contactor and other switching elements in the device. The output of the programmable voltage source 106, namely the primary input voltage, current, and frequency waveform of the multi-magnetic circuit current generator 104 and the secondary output voltage, current, and frequency waveform of the multi-magnetic circuit current generator 104, is transmitted to the industrial control computer 102 for calculation and judgment. The industrial control computer 102 judges the status and parameters, and adjusts the output of the programmable voltage source 106 through communication to complete the closed-loop control. Figure 2The diagram shown is the electrical schematic of the test device in this embodiment. The main circuit is divided into a control circuit, the primary side of the transformer, and the secondary side of the transformer. The control circuit realizes the switching and voltage regulation / switching control of the transformer windings.

[0026] The specific structure of the control loop includes a programmable voltage source 106 (U1), a current transformer CT1, a voltage transformer VT1, and a low-voltage circuit breaker QF1. Ports 1 and 2 of the QF1 low-voltage circuit breaker are connected to the power supply voltage. Ports 3 and 4 of the QF1 low-voltage circuit breaker are connected to the power input ports 1 and 2 of the programmable voltage source 106 (U1). Communication ports 5 and 6 of the programmable voltage source 106 (U1) are connected to the communication port 102 of the industrial control computer to complete data exchange. The voltage output interface 3 of the programmable voltage source 106 (U1) is connected to port 1 of the voltage transformer VT1, and port 1 of the current transformer CT1 is connected to the power input port VT1. The 106 (U1) programmable voltage source, with its 4-port connected to the VT1 voltage transformer, is connected to the VT1 voltage transformer, which in turn connects to the 1-ports of contactors KM12-NO1, KM8-NO, and KM4-NO. The CT1 current transformer, with its 2-port connected to the 3-port of the U2 solid-state relay and the 1-port of the KM1-NO1 relay, is connected to the 1-ports of the industrial control computer 102 data acquisition card. The computer controls the U2 relay to turn on and off. The 4-port of the U2 solid-state relay is connected to the 1-ports of contactors KM2-NO1, KM6-NO1, and KM10-NO1. The specific structure of the primary side of the transformer: Terminal 1 of the T1 (104) multi-magnetic circuit current generator is connected to port 2 of contactors KM2-NO1 and KM3-NO; Terminal 2 of the T1 (104) multi-magnetic circuit current generator is connected to port 1 of contactors KM3-NO1 and KM5-NO1, and port 2 of contactor KM4-NO1; Terminal 3 of the T1 (104) multi-magnetic circuit current generator is connected to port 2 of contactors KM5-NO1, KM6-NO1, and KM7-NO1; T 1 (104) The 4 terminals of the multi-magnetic circuit current generator are connected to the 1 port of KM73-NO1 and KM9-NO1 contactors and the 2 port of KM8-NO1 contactor. The 5 terminals of the T1 (104) multi-magnetic circuit current generator are connected to the 2 ports of KM9-NO1, KM10-NO1 and KM11-NO1 contactors. The 65 terminals of the T1 (104) multi-magnetic circuit current generator are connected to the 1 port of KM11-NO1 contactor and the 2 port of KM12-NO1 contactor. The specific structure of the transformer secondary side is as follows: Terminal 7 of the T1 (104) multi-magnetic circuit current generator is connected to the CT1 current transformer in direction 1; Terminal 8 of the T1 (104) multi-magnetic circuit current generator is connected to the KM13-NO1 contactor port 3, the VT2 voltage transformer port 1, the CT1 current transformer in direction 2 is connected to the VT2 voltage transformer port 2, the KM13-NO1 contactor port 1, the KM13-NO1 contactor port 2 is connected to the JP1 output port 1, and the KM13-NO1 contactor port 4 is connected to the JP1 output port 2.

[0027] This scheme uses a programmable voltage source to drive a multi-magnetic circuit current generator to produce low-voltage, high-current devices that can be connected to loads with different impedances for testing. By using a test pre-current method, it collects the current and voltage waveforms of the primary and secondary sides, compares and calculates them, and can actually convert them to obtain the secondary side output current waveform. It also uses a solid-state relay to drive the device, which can achieve fully dynamic closed-loop control and precise phase output.

[0028] like Figure 3 The diagram shows the current signal and zero-crossing acquisition principle. The secondary currents I- and I+ output by the current transformer are connected to ports 1 of Zener diodes D1 and D2, and ports 2 of resistors R1 and R2, respectively. Ports 2 of Zener diodes D1 and D2 are grounded. Ports 2 of the U3A integrated operational amplifier are connected to resistor R1, and terminals 2 of resistor R3. Ports 3 of the U3A integrated operational amplifier are connected to resistor R2, and terminals 2 of resistor R4. Port 8 of the U3A integrated operational amplifier is connected to the positive power supply of 10V. Port 4 of the U3A integrated operational amplifier is connected to the negative power supply of 10V. Terminal 1 of resistor R4 is grounded. Terminal 1 of the U3A integrated operational amplifier is connected to the first segment of resistor R3, and terminals 2 of resistors R5 and R8, and is connected to the ADC analog-to-digital sampling port U / I_1_ADC of the industrial control computer 102 data acquisition card. The U3B integrated operational amplifier's 5th port is connected to the R8 resistor's 1st port, the U3B integrated operational amplifier's 6th port is connected to the R7 resistor's 1st port, the R9 resistor's 2nd port, the R7 resistor's 2nd port is grounded, the U3B integrated operational amplifier's 7th port is connected to the R9 resistor's 1st port, and is connected to the industrial control computer 102 data acquisition card's ADC analog-to-digital sampling port U / I_1_ADC. The U4A integrated operational amplifier 1 port is connected to the R5 resistor 1 port, the U4A integrated operational amplifier 3 port is connected to the R6 resistor 1 port, the R6 resistor 2 port is grounded, the U4A integrated operational amplifier 5 port is connected to the positive power supply 10V, the U4A integrated operational amplifier 2 port is grounded, and the U4A integrated operational amplifier 4 port is connected to the rising edge triggered interrupt sampling port IF_ADC of the industrial control computer 102 data acquisition card. The diodes D1 and D2 clamp the input signal to prevent signal abrupt changes from damaging subsequent circuits. R1, R2, R3, R4, and U3A form an instrument operational amplifier to condition the signal with a bandwidth of ±10V. R1, R2, R3, R4, and U3B form a proportional operational amplifier to amplify the signal. The above two circuits complete the signal acquisition. The proportional operational amplifier is 4 times larger than the instrument operational amplifier to ensure full waveform acquisition. R5, R6, and U4A form a zero-crossing conversion circuit. When the current waveform crosses zero, it outputs a high level as the frequency acquisition signal. like Figure 4 The voltage signal and zero-crossing acquisition schematic diagram shows that the voltage UV of the secondary circuit output of the voltage transformer is connected to port 1 of resistor R9, port 2 of resistor R9 is connected to port 1 of resistor R10, port 2 of resistor R10 is connected to port 1 of resistor R11, port 2 of resistor R11 is connected to port 2 of capacitor C1, port 2 of resistor R12, port 2 of Zener diode D3, port 1 of operational amplifier U5A, port 2 of operational amplifier U5A is grounded, port 5 of operational amplifier U5A is connected to a positive 10V power supply, port 2 of operational amplifier U6A is grounded, and port 5 of operational amplifier U6A is connected to a positive 10V power supply. Connect port 5 to a positive 10V power supply. Connect port 3 of operational amplifier U5A to port 2 of resistor R13 and connect it to the ADC analog-to-digital sampling port UV_ADC of industrial control computer 102 data acquisition card. Connect port 1 of operational amplifier U6A to port 2 of resistor R13. Connect port 1 of operational amplifier U6A to port 1 of resistor R14. Connect port 2 of resistor R14 to ground. Connect port 1 of operational amplifier U6A to port 1 of resistor R14 and connect it to the rising edge triggered interrupt sampling port VF_ADC of industrial control computer 102 data acquisition card. R9, R10, R11, R12, C1, and U3A form a voltage acquisition circuit. Diode D1 clamps the input signal to prevent signal abrupt changes from damaging subsequent circuits. Finally, it is connected to the industrial control computer acquisition card through a voltage follower U3A. R13, R14, and U6A form a zero-crossing conversion circuit. When the current waveform crosses zero, it outputs a high level as a frequency acquisition signal. Combination Figure 5 As shown in Table 1, the implementation method of this solution is as follows: 1) The industrial control computer 102 receives the output current amplitude and phase angle from the human-machine interface unit 101; 2) The industrial control computer 102 calculates the current amplitude. 10% of the current amplitude is not less than 50A. Combined with the control logic control unit 105 in Table 1, the contactor completes the series and parallel connection of the primary winding of the multi-magnetic circuit current generator 104 to form a suitable circuit. 3) Close KM13-NO1 to drive the solid-state relay to close, send a communication command to drive the programmable voltage source 106 to output voltage, and turn on the power supply of the 104 multi-magnetic circuit current generator to output current. 4) The input current and voltage signals of the 104 multi-magnetic circuit current generator pass through the current transformer and are then... Figure 3 , Figure 4 The circuit input is to the industrial control computer 102; 5) The industrial control computer 102 calculates the input and output voltage, current, and frequency, such as... Figure 5 Input current waveform i0, voltage waveform u0, voltage frequency waveform fu0, and current frequency waveform fi0; output current waveform i1, voltage waveform u1, voltage frequency waveform fu1, and current frequency waveform fi1. First, calculate the input and output voltage and current amplitudes, and feed them back to the output voltage terminal of the communication driver programmable voltage source 106 to calibrate the output voltage. Second, compare the output current with the set value, and feed the difference back to the output voltage terminal of the communication driver programmable voltage source 106 to adjust the output, ensuring that the output current matches the set accuracy. After the output meets the set value, record the output voltage drive value Ut of the driver programmable voltage source 106 and record the primary winding scheme. Additionally, compare the input voltage frequency waveform with the output current frequency waveform to calculate the phase rise time difference, and substitute this time into the frequency period time to calculate the phase difference degree. 6) The industrial control computer 102 calculates and reads the set output phase, and uses the calculated phase deviation to obtain the zero-crossing delay drive time t3; 7) Based on the set current and the rated capacity of the programmable voltage source 106, and in conjunction with the contactor of the control logic control unit 105 in Table 1, the primary winding of the multi-magnetic circuit current generator 104 is connected in series and parallel to form a suitable circuit. 8) Based on the output set current, the first set current multiple, the primary winding scheme of the 104 multi-magnetic circuit current generator, and the recorded output voltage drive value Ut of the drive programmable voltage source 106, the output voltage drive value Ur of the programmable voltage source 106 for the set drive current is calculated. 9) Acquire the input voltage frequency of the 104 multi-magnetic circuit current generator, use the zero-crossing point as the driving start point, and delay for t3 time to drive the solid-state relay. The output waveform is as follows: Figure 5 Current waveform I2, voltage waveform u2, industrial control computer 102 drives solid-state relay and records output time, collects output current and dynamically adjusts programmable voltage source 106 drive value to ensure that it meets output current. 10) Wait for the circuit to automatically disconnect or for the protection time to expire to automatically disconnect.

[0029] like Figure 6 The control logic diagram and driving logic of the control system are as follows: 1) Input relevant parameters through the human-machine interface, the system reads the settings, calculates the pre-connection current based on the output current, and converts it into a drive voltage value. Based on the capacity of the multi-magnetic circuit current generator and Table 1, select the drive winding scheme and proceed to step 2. 2) Based on the selected winding scheme, drive the corresponding contactor of the logic control unit to complete the winding connection of the multi-magnetic circuit current generator, and proceed to step 3; 3) Close the solid-state relay and output contactor to connect the input and output circuits, then proceed to step 4. 4) Based on the driving voltage value, drive the digitally controlled voltage source to output current; 5) Collect input and output voltage, current and other parameters, and determine if they meet the expected turn-on current. If they do, disconnect the solid-state relay or output contactor and proceed to step 6; otherwise, calculate the drive voltage difference, update the drive value, and return to step 4. 6) Based on the collected input and output voltages, currents, frequencies, and zero-crossing points, calculate the phase difference between the input voltage and the output current, and convert it into a time constant t3, then proceed to step 7; 7) Select the drive winding scheme according to the output current and Table 1 and drive it. Calculate the input power supply voltage drive value based on the drive scheme. Correct the actual CNC voltage source drive value according to the actual drive voltage value of the expected output current. Drive the voltage source, close the output circuit, and go to step 8. 8) Determine the zero-crossing point of the input voltage as the base point, wait for t3 delay, and when the phase delay time is up, close the solid-state relay of the input circuit and proceed to step 9; 9) Calculate whether the numerical phase and current amplitude meet the output settings. If they do not meet the settings, proceed to step 10; if they do meet the settings, proceed to step 11. 10) Adjust the driving value of the digital control voltage source according to the output current ratio and fine-tune the drive, then proceed to step 11; 11) Check if the main circuit has no current and the test circuit is disconnected, and check if the drive protection time has expired. If not, return to step 9. If one of these conditions is met, disconnect the output circuit, clear the programmable voltage source drive, disconnect the solid-state relay, and exit.

[0030] The foregoing description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of other embodiments of this disclosure upon considering the specification and the disclosure of practical truth. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described in this disclosure. The specification and embodiments are considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

Claims

1. A low-voltage, high-current testing device, characterized in that, It includes a human-machine interface unit, an industrial control computer, a closed-loop control and acquisition unit, a programmable voltage source, a logic control unit, and a multi-magnetic circuit current generator. The human-machine interface unit communicates bidirectionally with the industrial control computer to issue control commands and display the operating status. The industrial control computer is electrically connected to the closed-loop control and acquisition unit, the programmable voltage source, and the logic control unit, respectively, and is used for data processing and control scheduling. The output terminal of the programmable voltage source is connected to the logic control unit, and the programmable voltage source is electrically connected to the industrial control computer. The industrial control computer controls the output amplitude of the programmable voltage source. The output terminal of the logic control unit is connected to the multi-magnetic circuit current generator. The logic control unit is electrically connected to the industrial control computer. The industrial control computer controls the primary side of the multi-magnetic circuit current generator to form different series and parallel winding combination schemes. The closed-loop control and acquisition unit is electrically connected to the industrial control computer and the multi-magnetic circuit current generator, respectively, and acquires the voltage and current at the primary and secondary output terminals to form a closed-loop feedback regulation of the current / voltage parameters.

2. The low-voltage high-current testing device according to claim 1, characterized in that, The multi-magnetic-circuit current generating device includes a primary side and a secondary side. The primary side includes multiple windings, each of which is connected in series or in parallel with an AC contactor of a logic control unit. The secondary side outputs low voltage and high current for testing.

3. The low-voltage high-current testing device according to claim 2, characterized in that, The logic control unit consists of multiple AC contactors. By changing the connection or disconnection of the AC contactors, different series and parallel winding schemes can be formed in the primary winding of the multi-magnetic circuit current generator.

4. The low-voltage high-current testing device according to claim 2, characterized in that, The closed-loop control and acquisition unit includes a voltage transformer and a current transformer. The voltage transformer acquires the voltage signals of the primary and secondary sides of the multi-magnetic circuit current generator, and the current transformer acquires the current signals of the primary and secondary sides of the multi-magnetic circuit current generator.

5. A low-voltage, high-current testing device according to claim 4, characterized in that, The current signal is modulated by an operational amplifier and then connected to the data acquisition ADC analog-to-digital converter installed inside the industrial control computer to obtain the modulated current signal. The modulated current signal is then connected to the data acquisition card installed inside the industrial control computer through the current zero-crossing detection circuit to complete the zero-crossing acquisition of the current signal.

6. The low-voltage high-current testing device according to claim 4, characterized in that, The voltage signal is passed through a voltage acquisition circuit and connected to a data acquisition ADC analog-to-digital converter installed inside the industrial control computer to obtain a modulated voltage signal. The modulated voltage signal is then passed through a voltage zero-crossing detection circuit and connected to a data acquisition card installed inside the industrial control computer to complete the zero-crossing acquisition of the voltage signal.

7. A control method for a low-voltage, high-current testing device, characterized in that, Includes the following steps: Step 1: Input relevant parameters through the human-machine interface. The system reads the settings, calculates the pre-connection current based on the output current, and converts it into a drive voltage value. Based on the capacity of the multi-magnetic circuit current generator and Table 1, select the drive winding scheme and proceed to Step 2. Step 2: Based on the selected winding scheme, drive the corresponding contactor of the logic control unit to complete the winding connection of the multi-magnetic circuit current generator, and proceed to Step 3. Step 3: Close the solid-state relay and output contactor to connect the input and output circuits, then proceed to step 4; Step 4: Based on the driving voltage value, drive the CNC voltage source to output current; Step 5: Collect input and output voltage, current and other parameters, and determine if they meet the expected turn-on current. If they do, disconnect the solid-state relay or output contactor and proceed to step 6; otherwise, calculate the drive voltage difference, update the drive value, and return to step 4. Step 6: Based on the collected input and output voltages, currents, frequencies, and zero-crossing points, calculate the phase difference between the input voltage and the output current, and convert it into a time constant t3. Proceed to Step 7. Step 7: Select the drive winding scheme according to the output current and Table 1 and drive it. Calculate the input power supply voltage drive value based on the drive scheme. Correct the actual CNC voltage source drive value according to the actual drive voltage value of the expected output current. Drive the voltage source, close the output circuit, and go to step 8. Step 8: Determine the zero-crossing point of the input voltage as the base point, wait for the t3 delay, and when the phase delay time is up, close the solid-state relay of the input circuit and proceed to step 9; Step 9: Calculate whether the numerical phase and current amplitude meet the output settings. If they do not meet the settings, proceed to step 10; otherwise, proceed to step 11. Step 10: Adjust the driving value of the digital control voltage source according to the output current ratio and fine-tune the drive, then proceed to Step 11; Step 11: Check if the main circuit has no current and the test circuit is disconnected; check if the drive protection time has expired. If not, return to step 9. If one of these conditions is met, disconnect the output circuit, clear the programmable voltage source drive, disconnect the solid-state relay, and exit.

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