Single core measuring ac and dc leakage current system

Abstract

The utility model provides a single iron core measures ac leakage current system, it has solved leakage current detection circuit cost higher problem, it includes power module, power module is connected with measurement circuit and MCU module, measurement circuit has two groups of operational amplifier follower, one group of operational amplifier follower is connected through sampling resistance R9 with the one end of the measurement coil that is wound on annular core, the other end of measurement coil is connected through another group of operational amplifier follower with the PWM pin of MCU module, the ADC pin of MCU module is connected on sampling resistance R9. The utility model has good leakage detection effect, lower cost and the like advantages.

Description

Technical Field

[0001] This utility model belongs to the field of current detection technology, specifically relating to a single-core AC / DC leakage current measurement system. Background Technology

[0002] With the continuous development of power technology, the number of various power electronic devices such as electric vehicles, smart homes, and photovoltaic inverters is increasing daily. Under this trend, the safe operation of electrical equipment is becoming increasingly important. Leakage current, which is an unexpected current that should not occur under normal operating conditions, can be caused by various factors such as aging insulation materials, wiring errors, or external environmental factors. The presence of leakage current can negatively impact system efficiency and may also lead to serious safety accidents such as fires and electric shocks. However, current AC / DC leakage current detection methods also have many shortcomings: zero-sequence current detection methods based on the principle of electromagnetic induction cannot be directly used for DC detection; current detection methods based on the principle of dual-core magnetic modulation can measure AC / DC current, but are easily affected by temperature, have complex circuits, and are too costly; and magnetic modulation AC / DC leakage current detection methods based on Fourier transform, although using a single core, are computationally too complex, require high MCU processing capabilities, and remain costly.

[0003] To address the shortcomings of existing technologies, people have conducted long-term explorations and proposed various solutions. For example, Chinese patent literature discloses an AC leakage current detector [201721110527.5], which includes a robotic arm. The robotic arm includes a first electric valve, a second electric valve, a first support, a second support, an AC / DC conversion module, and a control platform. The AC / DC conversion module includes an AC / DC conversion circuit, which includes an induction coil, a fuse, several capacitors, a rectifier bridge, a protective resistor, an inductor coil, and an iron core. The control platform includes a comparator circuit, an alarm circuit, and several buttons. The comparator circuit includes an operational amplifier, a constant voltage DC power supply, and a grounding terminal. The alarm circuit includes a field-effect transistor, a first resistor, a second resistor, a capacitor, a first transistor, a second transistor, a step-up transformer, a buzzer, a DC power supply, and a unipolar device.

[0004] The above solution has solved the problem of leakage current detection to some extent, but it still has many shortcomings, such as complex circuitry and high cost. Summary of the Invention

[0005] The purpose of this invention is to address the above-mentioned problems by providing a reasonably designed and low-cost single-core AC / DC leakage current measurement system.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a single-core AC / DC leakage current measurement system, including a power supply module, the power supply module being connected to a measurement circuit and an MCU module, the measurement circuit having two sets of operational amplifier followers, one set of operational amplifier followers being connected to one end of a measurement coil wound on a toroidal iron core through a sampling resistor R9, the other end of the measurement coil being connected to the PWM pin of the MCU module through another set of operational amplifier followers, and the ADC pin of the MCU module being connected to the sampling resistor R9.

[0007] In the above-mentioned single-core AC / DC leakage current measurement system, the measurement circuit includes an operational amplifier chip IC3. The operational amplifier chip IC3 is connected to a grounded capacitor C12. The operational amplifier chip IC3, together with resistors R7 and R11, forms two sets of operational amplifier followers. One set of operational amplifier followers is connected to the PWM pin of the MCU module through resistor R6, and the other set of operational amplifier followers is connected to a filter capacitor C11 and is connected to the measurement coil through a sampling resistor R9.

[0008] In the above-mentioned single-core AC / DC leakage current measurement system, the measurement circuit has a 2.5V reference power supply consisting of resistors R8 and R10 and capacitor C10.

[0009] In the above-mentioned single-core AC / DC leakage current measurement system, the operational amplifier chip IC3 is connected to interface J2.

[0010] In the above-mentioned single-core AC / DC leakage current measurement system, the MCU module includes a chip IC2, which is connected to resistors R12, R13, R14, R15 and capacitor C7.

[0011] In the above-mentioned single-core AC / DC leakage current measurement system, the MCU module has a 2.5V reference power supply consisting of resistor R2 and capacitor C5.

[0012] In the above-mentioned single-core AC / DC leakage current measurement system, the IC2 chip is model HC32F005.

[0013] In the above-mentioned single-core AC / DC leakage current measurement system, the power supply module includes a voltage regulator chip IC1, which is connected to filter capacitors C1, C2, C3, and C4, and a diode D1.

[0014] In the above-mentioned single-core AC / DC leakage current measurement system, the voltage regulator IC1 is model 7550.

[0015] In the single-core AC / DC leakage current measurement system described above, the MCU module update rate is 10ms.

[0016] Compared with existing technologies, the advantages of this utility model are as follows: it uses a single iron core to realize AC and DC current detection based on magnetic modulation, which simplifies the circuit and reduces the overall cost; it has a wide measurement range, with AC measurement range of 50 to 20KHz. Since the ADC conversion frequency is much higher than the leakage current frequency, it can keenly capture the magnetic field changes caused by external current and finally feed back the voltage on the sampling resistor; the update speed is up to 10ms, and the MCU can detect the magnitude of external leakage current in real time and detect leakage current in a timely manner. Attached Figure Description

[0017] Figure 1 This is a structural block diagram of the present invention;

[0018] Figure 2 This is a circuit diagram of the power module of this utility model;

[0019] Figure 3 This is a circuit diagram of the measuring circuit of this utility model;

[0020] Figure 4 This is a circuit diagram of the MCU module of this utility model;

[0021] In the diagram, the components are: power supply module 1, measurement circuit 2, MCU module 3, measurement coil 4, and toroidal iron core 5. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1-4 As shown, a single-core AC / DC leakage current measurement system includes a power supply module 1, which is connected to a measurement circuit 2 and an MCU module 3. The measurement circuit 2 has two sets of operational amplifier followers. One set of operational amplifier followers is connected to one end of a measurement coil 4 wound on a toroidal iron core 5 through a sampling resistor R9. The other end of the measurement coil 4 is connected to the PWM pin of the MCU module 3 through another set of operational amplifier followers. The ADC pin of the MCU module 3 is connected to the sampling resistor R9.

[0024] After external power is input, MCU module 3 generates a PWM signal. When current flows through measuring coil 4, coil 4 suppresses the current and gradually saturates, presenting a curve. When external current passes through measuring coil 4, it superimposes with the current signal generated by MCU module 3, causing the curve to deviate. Based on the characteristics of the coil, MCU module 3, after a delay during each rising and falling edge interrupt, continuously converts the voltage across sampling resistor R9 via ADC, takes the average value, and records it into the rising edge array and falling edge array respectively.

[0025] Specifically, the measurement circuit 2 includes an operational amplifier chip IC3. The operational amplifier chip IC3 is connected to a grounded capacitor C12. The operational amplifier chip IC3, together with resistors R7 and R11, forms two sets of operational amplifier followers. One set of operational amplifier followers is connected to the PWM pin of the MCU module 3 through resistor R6, and the other set of operational amplifier followers is connected to a filter capacitor C11 and is connected to the measurement coil 4 through a sampling resistor R9.

[0026] Specifically, measurement circuit 2 has a 2.5V reference power supply consisting of resistors R8 and R10 and capacitor C10.

[0027] Before measuring the current, a calibration is required when no current flows through the toroidal core 5. The zero-point value is obtained by averaging the rising edge array and the falling edge array and saving it to the chip's FLASH memory.

[0028] A DC current is passed through the toroidal core 5. The average value of the rising edge array is taken and then subtracted from the zero point value calculated in the previous step to obtain the difference. The current coefficient corresponding to each point difference is calculated and saved to the chip FLASH.

[0029] When measuring current, record several average values ​​over a period of time. After completion, compare each value in the array with the zero value. If fluctuations are found, it is considered to be alternating current; otherwise, it is considered to be direct current.

[0030] If it is direct current, average all the data in the value, subtract the zero value, and finally multiply by a coefficient to get the magnitude of the direct current; if the current is alternating current, calculate the difference between the maximum and minimum values ​​in the array, multiply the difference by a coefficient to calculate the maximum current, and then pass the calculated value through the array.

[0031] Furthermore, the operational amplifier chip IC3 is selected as the RS8522 model, but it can also be replaced with other equivalent operational amplifier chips.

[0032] Furthermore, the MCU module 3 includes a chip IC2, which is connected to resistors R12, R13, R14, R15 and capacitor C7.

[0033] In addition, MCU module 3 has a 2.5V reference power supply consisting of resistor R2 and capacitor C5.

[0034] Meanwhile, chip IC2 is connected to interface J2, and chip IC2 can also be replaced with other MCU chips with modulation output function and ADC conversion function.

[0035] As can be seen, the power module 1 includes a voltage regulator chip IC1, which is connected to filter capacitors C1, C2, C3, and C4, and a diode D1.

[0036] It is clear that the voltage regulator IC1 is model 7550, but it can also be replaced with other equivalent 5V voltage regulator chips.

[0037] Preferably, the update rate of MCU module 3 is 10ms.

[0038] In summary, the principle of this embodiment is as follows: the measuring coil 4 is wound on the toroidal iron core 5 as the excitation winding, and a sampling resistor R9 is connected in series. The MCU module 3 outputs a square wave excitation voltage with positive and negative symmetry at a specific frequency, so that the toroidal iron core 5 is in a magnetic saturation state. When leakage current passes through, the excitation magnetic field is no longer symmetrical, thereby causing the detection current waveform to deviate. The voltage signal on the sampling resistor R9 is continuously sampled for a period of time. By comparing the voltage sampling value of the deviation signal with the zero-point voltage sampling value, it is determined whether there is fluctuation, thus distinguishing between AC and DC current. Finally, the actual current is calculated from the amplitude of the voltage sampling value.

[0039] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

[0040] Although this document frequently uses terms such as power module 1, measurement circuit 2, MCU module 3, measurement coil 4, and toroidal core 5, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of this invention; interpreting them as any additional limitation would contradict the spirit of this invention.

Claims

1. A single-core AC / DC leakage current measurement system, comprising a power supply module (1), wherein the power supply module (1) is connected to a measurement circuit (2) and an MCU module (3), wherein the measurement circuit (2) has two sets of operational amplifier followers, characterized in that, One set of operational amplifier followers is connected to one end of the measurement coil (4) wound on the toroidal iron core (5) through the sampling resistor R9. The other end of the measurement coil (4) is connected to the PWM pin of the MCU module (3) through another set of operational amplifier followers. The ADC pin of the MCU module (3) is connected to the sampling resistor R9.

2. The single-core AC / DC leakage current measurement system according to claim 1, characterized in that, The measurement circuit (2) includes an operational amplifier chip IC3. The operational amplifier chip IC3 is connected to a grounded capacitor C12. The operational amplifier chip IC3, together with resistor R7 and resistor R11, forms two sets of operational amplifier followers. One set of operational amplifier followers is connected to the PWM pin of the MCU module (3) through resistor R6. The other set of operational amplifier followers is connected to a filter capacitor C11 and is connected to the measurement coil (4) through a sampling resistor R9.

3. A single-core AC / DC leakage current measurement system according to claim 2, characterized in that, The measurement circuit (2) has a 2.5V reference power supply consisting of resistors R8 and R10 and capacitor C10.

4. A single-core AC / DC leakage current measurement system according to claim 2, characterized in that, The operational amplifier chip IC3 mentioned above is model RS8522.

5. A single-core AC / DC leakage current measurement system according to claim 1, characterized in that, The MCU module (3) includes a chip IC2, which is connected to resistors R12, R13, R14, R15 and capacitor C7.

6. A single-core AC / DC leakage current measurement system according to claim 5, characterized in that, The MCU module (3) has a 2.5V reference power supply consisting of resistor R2 and capacitor C5.

7. A single-core AC / DC leakage current measurement system according to claim 5, characterized in that, The chip IC2 is connected to interface J2.

8. A single-core AC / DC leakage current measurement system according to claim 1, characterized in that, The power module (1) includes a voltage regulator chip IC1, which is connected to filter capacitors C1, C2, C3, and C4, and a diode D1.

9. A single-core AC / DC leakage current measurement system according to claim 8, characterized in that, The voltage regulator chip IC1 mentioned is model 7550.

10. A single-core AC / DC leakage current measurement system according to claim 1, characterized in that, The update rate of the MCU module (3) is 10ms.

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