Current transformer
By adding auxiliary windings to the ring core of the current transformer and adding signal transmission and reception units to the control circuit board, the self-detection and diagnosis of the current transformer are realized, solving the problem of cumbersome detection and diagnosis of the existing detection process.
Patent Information
- Application Number
- CN202421793487.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-26
- Publication Date
- 2025-06-13
- Estimated Expiration
- 2034-07-26
AI Technical Summary
The detection process of existing current transformers is cumbersome and requires additional equipment to be used for detection.
A current transformer is designed, including a magnetic ring assembly and a control circuit board, and self-detection and diagnosis are achieved by adding auxiliary windings to the ring core and signal transmission unit and signal reception unit on the control circuit board.
The self-detection and diagnosis of current transformers can be achieved without external equipment, greatly simplifying the detection process.
Smart Images
Figure CN222979772U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of detection equipment, and more specifically, to a current transformer. Background Art
[0002] In the circuits of power generation, transformation, transmission, distribution and power consumption, the magnitudes of currents vary widely, ranging from several amperes to tens of thousands of amperes. For the convenience of measurement, protection and control, when measuring the current in the above circuits, it is necessary to first convert the current in the above circuits into a relatively unified current. In addition, the voltages on the above circuits are generally relatively high, and it will be very dangerous to measure directly. A current transformer can play the roles of current transformation and electrical isolation. Based on the principle of electromagnetic induction, it converts the large current on the primary side into a small current on the secondary side to measure the current on the circuit.
[0003] In some important occasions, to ensure the accuracy of electrical parameter acquisition, it is also necessary to diagnose and judge the current transformer itself. However, the existing detection of current transformers requires the use of additional equipment (such as standard transformers and transformer calibrators, etc.), and the detection process is relatively cumbersome. Summary of the Utility Model
[0004] The technical problem to be solved by the utility model is to provide a new current transformer for the problem that the existing detection of the current transformer itself is relatively cumbersome.
[0005] The technical solution of the utility model to solve the above technical problem is to provide a current transformer, including:
[0006] A magnetic ring assembly, the magnetic ring assembly includes an annular magnetic core, a main winding and an auxiliary winding. The main winding and the auxiliary winding are respectively wound around the annular magnetic core, and the main winding is evenly distributed along the circumferential direction of the annular magnetic core;
[0007] A control circuit board, on which a control unit, a signal receiving unit and a signal sending unit are integrated; the control unit includes an instruction output end for outputting detection instructions and a signal input end for receiving detection signals; the input end of the signal sending unit is electrically connected to the instruction output end of the control unit, and the output end is electrically connected to the auxiliary winding, and generates an analog voltage with a corresponding frequency and amplitude according to the input detection instruction and then outputs it; the input end of the signal receiving unit is electrically connected to the main winding, and the output end is electrically connected to the signal input end of the control unit, and converts and outputs the received analog voltage.
[0008] As a further improvement of the present utility model, the control unit includes a main control chip and peripheral circuits, and the main control chip includes an ADC input pin and a DAC output pin. The ADC input pin constitutes the signal input end of the control unit, and the DAC output pin constitutes the instruction output end of the control unit.
[0009] As a further improvement of the present utility model, the signal sending unit includes a first amplifier and a triode. The positive input end of the first amplifier is electrically connected to the DAC output pin of the main control chip. The base of the triode is electrically connected to the output end of the first amplifier. The emitter of the triode is grounded. The collector of the triode is electrically connected to one end of the auxiliary winding, and the other end of the auxiliary winding is connected to a DC voltage source.
[0010] As a further improvement of the present utility model, the control circuit board includes a reference voltage source. The signal sending unit includes a first voltage dividing resistor and a second voltage dividing resistor. The first voltage dividing resistor and the second voltage dividing resistor are connected in series between the DAC output pin of the main control chip and the output end of the reference voltage source, and the connection point of the first voltage dividing resistor and the second voltage dividing resistor is electrically connected to the positive input end of the first amplifier.
[0011] As a further improvement of the present utility model, the signal receiving unit includes a second amplifier and a transformer. The primary winding of the transformer is connected in series between the two ends of the main winding. The positive input end and the negative input end of the second amplifier are respectively connected to the two ends of the secondary winding of the transformer. The output end of the second amplifier is connected to the ADC input pin of the main control chip.
[0012] As a further improvement of the present utility model, the control circuit board further includes a reference voltage source. The signal receiving unit includes a first current limiting resistor and a second current limiting resistor. One end of the secondary winding of the transformer is electrically connected to the negative input end of the second amplifier via the first current limiting resistor, and the other end of the secondary winding of the transformer is electrically connected to the positive input end of the second amplifier via the second current limiting resistor. And the end of the secondary winding connected to the second current limiting resistor is electrically connected to the output end of the reference voltage source.
[0013] As a further improvement of the present utility model, the central angle corresponding to the part of the toroidal core around which the auxiliary winding is wound is less than 30°.
[0014] As a further improvement of the present utility model, the frequency of the voltage output by the signal sending unit is greater than 3 kHz.
[0015] As a further improvement of the present utility model, the number of turns of the main winding is greater than the number of turns of the auxiliary winding.
[0016] The utility model has the following beneficial effects: By adding an auxiliary winding on the toroidal core and adding a signal sending unit on the control circuit board, the signal sending unit outputs a voltage signal to the auxiliary winding to generate an induced current in the main winding, and then by detecting the above-mentioned induced current, the self-detection and diagnosis of the current transformer are greatly facilitated. Description of the Drawings
[0017] Figure 1 is a schematic structural diagram of a current transformer provided by an embodiment of the utility model.
[0018] Figure 2 is a structural block diagram of a control circuit board in a current transformer provided by an embodiment of the utility model.
[0019] Figure 3 is a schematic circuit diagram of a control unit in a current transformer provided by an embodiment of the utility model.
[0020] Figure 4 is a schematic circuit diagram of a signal sending unit in a current transformer provided by an embodiment of the utility model.
[0021] Figure 5 is a schematic circuit diagram of a signal receiving unit in a current transformer provided by an embodiment of the utility model.
[0022] Figure 6 is a schematic circuit diagram of a reference voltage source in a current transformer provided by an embodiment of the utility model. Detailed Embodiments
[0023] In order to make the objectives, technical solutions and advantages of the utility model clearer, the following further details the utility model in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the utility model and are not used to limit the utility model.
[0024] As Figure 1 shown, it is a schematic structural diagram of a current transformer provided by an embodiment of the utility model. This current transformer can be used to detect the current flowing through a wire. The current transformer of this embodiment includes a magnetic ring assembly and a control circuit board 20. The above magnetic ring assembly and control circuit board 20 can be fixed in the same housing (this housing can include two cavities respectively for fixing the magnetic ring assembly and the control circuit board 20), and the wiring terminals are led out of the housing by the control circuit board 20, so as to realize the power supply input and signal output of the current transformer, etc.
[0025] The above magnetic ring assembly includes a toroidal magnetic core 11, a main winding 12, and an auxiliary winding 13. Among them, the toroidal magnetic core 11 can be processed from ferromagnetic materials and has a through hole for the wire under test to pass through. The main winding 12 and the auxiliary winding 13 are respectively wound around the toroidal magnetic core 11, and the main winding 12 is evenly distributed along the circumference of the toroidal magnetic core 11, that is, the main winding 12 covers the entire circumference of the toroidal magnetic core 11. Thus, when the wire under test is at any position within the through hole of the toroidal magnetic core 11, the main winding 12 can generate a strong induced current. The auxiliary winding 13 can be wound around one of the arc segments of the toroidal magnet 11. Specifically, the toroidal magnetic core 11 can be in a circular ring shape. In practical applications, the toroidal magnetic core 11 can also be in an elliptical ring shape or other existing ring shapes. Similarly, the main winding 12 and the auxiliary winding 13 can be wound around the toroidal magnetic core 11 in any existing manner, which will not be elaborated here.
[0026] The control circuit board 20 may include a printed circuit board and electronic components soldered to the printed circuit board, and the electronic components on the printed circuit board form a control unit 21, a signal sending unit 22, and a signal receiving unit 23 through the conductive lines on the printed circuit board, as Figure 2 shown. The above control unit 21 includes an instruction output terminal for outputting detection instructions and a signal input terminal for receiving detection signals; the input terminal of the signal sending unit 22 is electrically connected to the instruction output terminal of the control unit 21, and the output terminal is electrically connected to the auxiliary winding 13. After converting the detection instruction input from its input terminal into a voltage (analog signal) with a corresponding frequency and amplitude, it is output through its output terminal; the input terminal of the signal receiving unit 23 is electrically connected to the main winding 12, and the output terminal is electrically connected to the signal input terminal of the control unit 21. After converting (such as amplifying) the analog voltage received at its input terminal, it is output through its output terminal.
[0027] When performing self-diagnosis using the above current transformer, the control unit 21 can output a detection instruction, and the signal sending unit 22 generates a voltage with a corresponding frequency and amplitude according to the detection instruction and outputs it to the auxiliary winding 13. Correspondingly, an alternating magnetic field is generated in the toroidal magnetic core 11. At the same time, an induced current is formed in the main winding 12 under the action of the changing magnetic field in the toroidal magnetic core 11. The signal receiving unit 23 preliminarily processes the induced current formed in the main winding 12 and then outputs it to the control unit 21. The control unit 21 analyzes the waveform and characteristics of the output signal from the signal receiving unit 23 and forms a corresponding diagnosis result.
[0028] For the above current transformer, by adding an auxiliary winding 13 on the toroidal core 11 and adding a signal sending unit 22 on the control circuit board 20, the signal sending unit 22 outputs a voltage signal to the auxiliary winding 13 to generate an induced current in the main winding 12, and then by detecting the above induced current, the detection of the self-state of the current transformer can be realized without external devices (such as a reference transformer, a transformer calibrator, etc.), which greatly facilitates the self-detection and diagnosis of the current transformer.
[0029] In particular, the number of turns of the main winding 12 is greater than that of the auxiliary winding 13. For example, the number of turns of the main winding 12 is more than 5 times that of the auxiliary winding, so that the signal output on the main winding 12 is easier to be detected.
[0030] Combined Figure 3 As shown, the above control unit 21 includes a main control chip U3 and its peripheral circuits. Among them, the main control chip U3 includes an ADC input pin ADC_IN1 and a DAC output pin DAD1_OUT. The ADC input pin ADC_IN1 constitutes the signal input end of the control unit 21, and the DAC output pin DAD1_OUT constitutes the instruction output end of the control unit 21. The above main control chip U3 may include a digital-to-analog conversion circuit, and generate a detection instruction according to the setting through the digital-to-analog conversion circuit (the detection instruction may specifically be a sine wave, and the main control chip U3 can adjust the frequency and amplitude of the sine wave according to different settings), and output the above detection signal through the DAC output pin DAD1_OUT; the main control chip U3 may also include an analog-to-digital conversion circuit, and convert the analog signal input through the ADC input pin ADC_IN1 into a digital signal through the analog-to-digital conversion circuit, and then perform corresponding operations on the above digital signal, and finally form a corresponding detection value and output it. The above main control chip U3 may specifically adopt an STM32H743VIT6 chip. Of course, in practical applications, the main control chip U3 may also adopt other chips with similar functions, which will not be elaborated here.
[0031] As Figure 4As shown, in an embodiment of the present utility model, the above signal sending unit 22 includes a first interface H1, a second interface H2, a first amplifier U4, and a triode Q1, and is electrically connected to the control unit 21 through the first interface H1 and electrically connected to the auxiliary winding 13 through the second interface H2. The positive input terminal of the first amplifier U4 is directly or indirectly connected to the first interface H1 and is electrically connected to the DAC output pin DAD1_OUT of the main control chip through the first interface H1. The triode Q1 may specifically be an NPN type triode, and the base of the triode Q1 is electrically connected to the output terminal of the first amplifier U4. The emitter of the triode Q1 is grounded via a resistor R11, and the collector of the triode Q1 is connected to the second interface H2. The above second interface H2 is also electrically connected to a DC voltage source 5V2, that is, the collector of the triode Q1 is electrically connected to one end IN- of the auxiliary winding 13 through the second interface H2, and the other end IN+ of the auxiliary winding 13 is connected to the DC voltage source 5V2 through the second interface H2.
[0032] The detection instruction input through the first interface H1 (i.e., output from the DAC output pin DAD1_OUT of the main control chip U3) is amplified by the first amplifier U4 and then biased and amplified by the triode Q1 to form an analog signal. Specifically, the above first amplifier U4 may adopt NCS20061SN2T1G. In practical applications, the first amplifier U4 may also adopt other amplifiers, and the signal sending unit 22 may further include circuits such as voltage stabilization and filtering to improve the quality of its output voltage, which will not be elaborated here.
[0033] In an embodiment of the present utility model, the above control circuit board 20 further includes a reference voltage source as Figure 6 shown. Specifically, the reference voltage source can convert the input voltage into a stable 1.25V DC voltage and output it. Correspondingly, the above signal sending unit 22 includes a first voltage dividing resistor R13 and a second voltage dividing resistor R14. The first voltage dividing resistor R13 and the second voltage dividing resistor R14 are connected in series between the DAC output pin DAC1_OUT1 of the main control chip U3 and the output terminal of the reference voltage source, and the connection point of the first voltage dividing resistor R13 and the second voltage dividing resistor R14 is electrically connected to the positive input terminal of the first amplifier U4. By the above method, the output voltage of the signal sending unit 22 can be within a certain preset range, thereby improving the accuracy of the self-check of the current transformer.
[0034] As Figure 5As shown, in an embodiment of the present invention, the signal receiving unit 23 includes a second amplifier U1 and a transformer. The primary winding of the transformer is serially connected between the two ends OUT+ and OUT- of the main winding 12. The positive input terminal and the negative input terminal of the second amplifier U1 are respectively connected to the two ends of the secondary winding of the transformer, and the output terminal of the second amplifier U1 is connected to the ADC input pin ADC_IN1 of the main control chip U3.
[0035] Since the amplitude of the voltage corresponding to the induced current formed by the main winding 12 is small, through the above structure, the analog voltage output from the two ends OUT+ and OUT- of the main winding 12 is first amplified by the transformer for AC amplification, and then further amplified by the second amplifier U1 and output to the main control chip U3, thereby improving the detection accuracy. Specifically, the second amplifier U1 can adopt NCS20061SN2T1G. In actual applications, the second amplifier U1 can also adopt other amplifiers, and the signal receiving unit 23 can also include circuits such as voltage regulation and filtering to improve the quality of its output voltage, which will not be elaborated here.
[0036] Similarly, the signal receiving unit 23 can also be connected to a reference voltage source. Specifically, the signal receiving unit 23 includes a first current limiting resistor R4 and a second current limiting resistor R9. One end of the secondary winding of the transformer is electrically connected to the negative input terminal of the second amplifier U1 via the first current limiting resistor R4, and the other end of the secondary winding of the transformer is electrically connected to the positive input terminal of the second amplifier U1 via the second current limiting resistor R9, and the end of the secondary winding connected to the second current limiting resistor R9 is electrically connected to the output terminal of the reference voltage source. By the above method, the output voltage of the signal receiving unit 23 can be within a certain preset range, thereby improving the accuracy of the self-check of the current transformer.
[0037] To avoid the influence of the auxiliary winding 13 on the main winding 12, in an embodiment of the present invention, the central angle corresponding to the part of the toroidal core 11 wound with the auxiliary winding 13 is less than 30°.
[0038] The self-diagnosis process of the above current transformer can be carried out simultaneously with the detection of the measured wire, that is, the current transformer is "online" detected. At this time, in order to ensure that the detection signal injected through the auxiliary winding 13 does not interfere with the normal detection of the main winding 12, a frequency that is not related to the signal frequency of the main winding 12 needs to be selected. Usually, the signal of the main winding 12 includes alternating current signals with frequencies in the ranges of 1.5 kHz to 3 kHz, 50 Hz, and 25 Hz. Therefore, a detection signal frequency that is not related to these frequencies can be selected. For example, the frequency of the voltage output by the signal sending unit 22 is preferably greater than 3 kHz. Of course, in actual applications, the current transformer can also be "offline" detected, such as the detection before the current transformer is put into use.
[0039] The amplitude of the voltage output by the signal sending unit 22 can be selected according to the input requirements and sensitivity of the current transformer.
[0040] As described above, only the preferred specific embodiments of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.
Claims
1. A current transformer, characterized in that: include: A magnetic ring assembly, the magnetic ring assembly comprising an annular magnetic core, a main winding and an auxiliary winding, the main winding and the auxiliary winding are respectively wound on the annular magnetic core, and the main winding is evenly distributed along the circumference of the annular magnetic core; A control circuit board, wherein a control unit, a signal receiving unit and a signal sending unit are integrated on the control circuit board; the control unit comprises an instruction output terminal for outputting a detection instruction and a signal input terminal for receiving a detection signal; the input terminal of the signal sending unit is electrically connected to the instruction output terminal of the control unit, and the output terminal is electrically connected to the auxiliary winding, and an analog voltage of corresponding frequency and amplitude is generated according to the input detection instruction and then outputted; the input terminal of the signal receiving unit is electrically connected to the main winding, and the output terminal is electrically connected to the signal input terminal of the control unit, and the received analog voltage is converted and then outputted.
2. The current transformer according to claim 1, characterized in that: The control unit includes a main control chip and a peripheral circuit, and the main control chip includes an ADC input pin and a DAC output pin, and the ADC input pin constitutes a signal input end of the control unit, and the DAC output pin constitutes a command output end of the control unit.
3. The current transformer according to claim 2, characterized in that: The signal sending unit includes a first amplifier and a transistor, the non-inverting input terminal of the first amplifier is electrically connected to the DAC output pin of the main control chip, the base of the transistor is electrically connected to the output terminal of the first amplifier, the emitter of the transistor is grounded, the collector of the transistor is electrically connected to one end of the auxiliary winding, and the other end of the auxiliary winding is connected to a DC voltage source.
4. The current transformer according to claim 3, characterized in that: The control circuit board includes a reference voltage source, and the signal sending unit includes a first voltage-dividing resistor and a second voltage-dividing resistor, the first voltage-dividing resistor and the second voltage-dividing resistor are connected in series between a DAC output pin of a main control chip and an output end of the reference voltage source, and a connection point between the first voltage-dividing resistor and the second voltage-dividing resistor is electrically connected to a non-inverting input end of the first amplifier.
5. The current transformer according to claim 2, characterized in that: The signal receiving unit includes a second amplifier and a transformer, the primary winding of the transformer is connected in series between the two ends of the main winding, the positive input terminal and the negative input terminal of the second amplifier are respectively connected to the two ends of the secondary winding of the transformer, and the output terminal of the second amplifier is connected to the ADC input pin of the main control chip.
6. The current transformer according to claim 5, characterized in that: The control circuit board also includes a reference voltage source, the signal receiving unit includes a first current limiting resistor and a second current limiting resistor, one end of the secondary winding of the transformer is electrically connected to the inverting input terminal of the second amplifier via the first current limiting resistor, the other end of the secondary winding of the transformer is electrically connected to the non-phase input terminal of the second amplifier via the second current limiting resistor, and the end of the secondary winding connected to the second current limiting resistor is electrically connected to the output terminal of the reference voltage source.
7. The current transformer according to any one of claims 1 to 6, characterized in that: The central angle of the portion of the annular magnetic core wound with the auxiliary winding is smaller than 30°.
8. The current transformer according to any one of claims 1 to 6, characterized in that: The frequency of the voltage output by the signal sending unit is greater than 3 kHz.
9. The current transformer according to any one of claims 1 to 6, characterized in that: The number of turns of the main winding is greater than the number of turns of the auxiliary winding.