阅读说明：本技术 一种电流互感器故障检测电路及检测方法 (Current transformer fault detection circuit and detection method ) 是由 胡志英 张琪 于 2020-07-22 设计创作，主要内容包括：本发明公开了一种电流互感器故障检测电路及检测方法,一种电流互感器故障检测电路包括：单片机、电流互感器、放大器、第一电容、第二电容、第一电阻、第二电阻及示波器；所述电流互感器的第一端与所述单片机、所述第一电容的第一端及所述第一电阻的第一端电连接,所述电流互感器的第二端与所述第一电容的第二端、所述放大器的同相输入端及所述第二电容的第一端电连接,所述第一电阻的第二端与所述第二电阻的第一端及所述放大器的反相输入端电连接,所述第二电阻的第二端与所述放大器的输出端、所述第二电容的第二端及所述示波器电连接。本发明有成本低廉及可靠性高的优点。(The invention discloses a current transformer fault detection circuit and a detection method, wherein the current transformer fault detection circuit comprises the following components: the single chip microcomputer, the current transformer, the amplifier, the first capacitor, the second capacitor, the first resistor, the second resistor and the oscilloscope are connected; the first end of the current transformer is electrically connected with the single chip microcomputer, the first end of the first capacitor and the first end of the first resistor, the second end of the current transformer is electrically connected with the second end of the first capacitor, the non-inverting input end of the amplifier and the first end of the second capacitor, the second end of the first resistor is electrically connected with the first end of the second resistor and the inverting input end of the amplifier, and the second end of the second resistor is electrically connected with the output end of the amplifier, the second end of the second capacitor and the oscilloscope. The invention has the advantages of low cost and high reliability.)

1. A current transformer fault detection circuit, comprising: the single chip microcomputer, the current transformer, the amplifier, the first capacitor, the second capacitor, the first resistor, the second resistor and the oscilloscope are connected; the first end of the current transformer is electrically connected with the single chip microcomputer, the first end of the first capacitor and the first end of the first resistor, the second end of the current transformer is electrically connected with the second end of the first capacitor, the non-inverting input end of the amplifier and the first end of the second capacitor, the second end of the first resistor is electrically connected with the first end of the second resistor and the inverting input end of the amplifier, and the second end of the second resistor is electrically connected with the output end of the amplifier, the second end of the second capacitor and the oscilloscope.

2. The current transformer fault detection circuit of claim 1, further comprising a first diode; the first end of the first diode is electrically connected with the output end of the amplifier, and the second end of the first diode is electrically connected with the second end of the second resistor.

3. A current transformer fault detection circuit according to claim 2, wherein said current transformer fault detection circuit further comprises a third resistor; the third resistor is connected in parallel with the first capacitor.

4. A current transformer fault detection circuit according to claim 3, wherein said current transformer fault detection circuit further comprises a fourth resistor; the first end of the fourth resistor is electrically connected with the single chip microcomputer, and the second end of the fourth resistor is electrically connected with the first end of the first capacitor.

5. The current transformer fault detection circuit according to claim 4, further comprising a fifth resistor; the first end of the fifth resistor is electrically connected with the first diode and the second resistor, and the second end of the fifth resistor is electrically connected with the oscilloscope.

6. A detection method, a current transformer fault detection circuit according to any one of claims 1 to 5, comprising:

respectively acquiring an excitation signal sent by the singlechip and a voltage signal sent by the current transformer;

the voltage signals comprise a first voltage signal in a normal state, a second voltage signal in a short-circuit state and a third voltage signal in an open-circuit state;

receiving the excitation signal and the voltage signal, amplifying the excitation signal and the voltage signal, and outputting the amplified excitation signal and the amplified voltage signal to an oscilloscope for waveform display;

in a normal state, the current transformer and the first capacitor generate LC resonance to generate a first voltage signal, and the amplifier amplifies the first voltage signal and outputs a sawtooth waveform;

in a short-circuit state, the second voltage signal is zero, the input voltage of the amplifier is zero, and the output voltage is zero;

and in an open circuit state, the third voltage signal is an excitation signal sent by the singlechip, the voltage at the output end of the amplifier is zero, and the oscilloscope displays the charge-discharge curve waveform of the second capacitor.

Technical Field

The invention relates to the technical field of current transformers, in particular to a fault detection circuit for a current transformer.

Background

The current transformer is widely applied to the fields of current detection and electrical fire detection. In the prior art, a method for detecting whether a current transformer fails includes: 1) the judgment is carried out by detecting the series resistor of the current transformer coil as a medium, and the method has the limitation that the current transformer and the resistor with the resistance value close to that of the current transformer coil cannot be distinguished, so that the judgment of a detection result is influenced; 2) the auxiliary winding is arranged on the current transformer, and a certain current is input to the auxiliary winding for judgment when a fault is detected, so that the method also has the defects of complex control, higher cost and the like. Therefore, the invention of a low-cost and high-reliability fault detection circuit for a current transformer is a problem to be solved urgently by technical personnel in the field.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a fault detection circuit for a current transformer, aiming at the above-mentioned defects in the prior art.

The invention discloses a current transformer fault detection circuit which comprises a single chip microcomputer, a current transformer, an amplifier, a first capacitor, a second capacitor, a first resistor, a second resistor and an oscilloscope, wherein the single chip microcomputer is connected with the current transformer; the first end of the current transformer is electrically connected with the single chip microcomputer, the first end of the first capacitor and the first end of the first resistor, the second end of the current transformer is electrically connected with the second end of the first capacitor, the non-inverting input end of the amplifier and the first end of the second capacitor, the second end of the first resistor is electrically connected with the first end of the second resistor and the inverting input end of the amplifier, and the second end of the second resistor is electrically connected with the output end of the amplifier, the second end of the second capacitor and the oscilloscope.

Preferably, a current transformer fault detection circuit further comprises a first diode; the first end of the first diode is electrically connected with the output end of the amplifier, and the second end of the first diode is electrically connected with the second end of the second resistor.

Preferably, the current transformer fault detection circuit further comprises a third resistor; the third resistor is connected in parallel with the first capacitor.

Preferably, the current transformer fault detection circuit further comprises a fourth resistor; the first end of the fourth resistor is electrically connected with the single chip microcomputer, and the second end of the fourth resistor is electrically connected with the first end of the first capacitor.

Preferably, the current transformer fault detection circuit further comprises a fifth resistor; the first end of the fifth resistor is electrically connected with the first diode and the second resistor, and the second end of the fifth resistor is electrically connected with the oscilloscope.

In a second aspect, the present invention further discloses a detection method, where the detection method includes the current transformer fault detection circuit described in the first aspect, and includes:

respectively acquiring an excitation signal sent by the singlechip and a voltage signal sent by the current transformer;

the voltage signals comprise a first voltage signal in a normal state, a second voltage signal in a short-circuit state and a third voltage signal in an open-circuit state;

receiving the excitation signal and the voltage signal, amplifying the excitation signal and the voltage signal, and outputting the amplified excitation signal and the amplified voltage signal to an oscilloscope for waveform display;

in a normal state, the current transformer and the first capacitor generate LC resonance to generate a first voltage signal, and the amplifier amplifies the first voltage signal and outputs a sawtooth waveform;

in a short-circuit state, the second voltage signal is zero, the input voltage of the amplifier is zero, and the output voltage is zero;

and in an open circuit state, the third voltage signal is an excitation signal sent by the singlechip, the voltage at the output end of the amplifier is zero, and the oscilloscope displays the charge-discharge curve waveform of the second capacitor.

The invention discloses a current transformer fault detection circuit and a detection method, which have the following beneficial effects that: the single chip microcomputer, the current transformer, the amplifier, the first capacitor, the second capacitor, the first resistor, the second resistor and the oscilloscope are connected; the first end of the current transformer is electrically connected with the single chip microcomputer, the first end of the first capacitor and the first end of the first resistor, the second end of the current transformer is electrically connected with the second end of the first capacitor, the non-inverting input end of the amplifier and the first end of the second capacitor, the second end of the first resistor is electrically connected with the first end of the second resistor and the inverting input end of the amplifier, and the second end of the second resistor is electrically connected with the output end of the amplifier, the second end of the second capacitor and the oscilloscope. In this embodiment, the amplifier is simultaneously connected to the single chip microcomputer and the current transformer, a CT _ TEST end of the single chip microcomputer is used for outputting an excitation signal, and the amplifier is used for amplifying an input voltage and outputting the amplified voltage to the oscilloscope for waveform display. The working states of the current transformers are different, so that the voltages output to the amplifier are different in magnitude. And obtaining the normal, short circuit and open circuit states of the current transformer through different waveform displays in the oscilloscope. The invention detects the short open circuit fault through the inductance characteristic of the current transformer, has simple control, low cost and high reliability, and can effectively eliminate the defects existing in the traditional detection means. The invention has the advantages of low cost and high reliability.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the present invention will be further described with reference to the accompanying drawings and embodiments, wherein the drawings in the following description are only part of the embodiments of the present invention, and for those skilled in the art, other drawings can be obtained without inventive efforts according to the accompanying drawings:

FIG. 1 is a circuit diagram of a current transformer fault detection circuit in accordance with a preferred embodiment of the present invention;

fig. 2 is a schematic diagram of waveforms of a current transformer in a normal state of the current transformer fault detection circuit according to the preferred embodiment of the present invention;

fig. 3 is a schematic diagram of waveforms in a short-circuit state of a current transformer of the current transformer fault detection circuit according to the preferred embodiment of the present invention;

fig. 4 is a schematic diagram of waveforms of a current transformer of the current transformer fault detection circuit in an open state according to the preferred embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without inventive step, are within the scope of the present invention.

Fig. 1 shows a preferred embodiment of the present invention, which includes a single chip microcomputer a1, a current transformer CT, an amplifier UA, a first capacitor C1, a second capacitor C2, a first resistor R3, a second resistor R4 and an oscilloscope a 2; a first end of the current transformer CT is electrically connected to the single chip microcomputer a1, a first end of the first capacitor C1, and a first end of the first resistor R3, a second end of the current transformer CT is electrically connected to a second end of the first capacitor C1, a non-inverting input end of the amplifier UA, and a first end of the second capacitor C2, a second end of the first resistor R3 is electrically connected to a first end of the second resistor R4 and an inverting input end of the amplifier UA, and a second end of the second resistor R4 is electrically connected to an output end of the amplifier UA, a second end of the second capacitor C2, and the oscilloscope UA. The invention has the advantages of low cost and high reliability. In this embodiment, the amplifier UA is connected to the single chip microcomputer a1 and the current transformer CT at the same time, a CT _ TEST end of the single chip microcomputer a1 is configured to output an excitation signal, and the amplifier UA is configured to amplify an input voltage and output the amplified voltage to the oscilloscope a2 for waveform display. The current transformer CT operates in different states, which results in different voltages being output to the amplifier UA. The normal, short circuit and open circuit states of the current transformer CT can be obtained by observing the difference of the waveforms in the oscilloscope a 2. The invention detects the short open circuit fault through the inductance characteristic of the current transformer, has simple control, low cost and high reliability, and can effectively eliminate the defects existing in the traditional detection means. The invention has the advantages of low cost and high reliability.

Preferably, the current transformer fault detection circuit further comprises a first diode D5; a first terminal of the first diode D5 is electrically connected to the output terminal of the amplifier UA, and a second terminal of the first diode D5 is electrically connected to a second terminal of the second resistor R4. It can be understood that, in the present embodiment, the first diode D5 is used for rectification filtering, so as to enhance the stability of the signal output.

Preferably, the current transformer fault detection circuit further comprises a third resistor R2; the third resistor R2 is connected in parallel with the first capacitor C1. It is understood that, in this embodiment, the third resistor R2 is used to discharge the stored energy of the first capacitor C1.

Preferably, the current transformer fault detection circuit further comprises a fourth resistor R1; the first end of the fourth resistor R1 is electrically connected with the singlechip A1, and the second end of the fourth resistor R1 is electrically connected with the first end of the first capacitor C1. It can be understood that, in this embodiment, the fourth resistor R1 is used to protect the CT _ TEST pin of the single chip microcomputer, so as to prevent high voltage damage.

Preferably, the current transformer fault detection circuit further comprises a fifth resistor R5; a first end of the fifth resistor R5 is electrically connected to the first diode D5 and the second resistor R4, and a second end of the fifth resistor R5 is electrically connected to the oscilloscope a 2.

In a preferred embodiment, referring to fig. 2, when the current transformer CT is normally connected between the first terminal CT + of the current transformer CT and GND, an excitation waveform is generated at the CT _ TEST terminal of the single chip, since the secondary terminal of the current transformer CT is a coil winding, which is equivalent to an inductor, the inductor and the first capacitor C1 form an LC resonant circuit, the inductor resonates to generate an induced voltage at the moment when an external current is turned off, and the induced voltage is amplified by the reverse input terminal of the amplifier to output a sawtooth wave signal as shown in fig. 2.

In a preferred embodiment, referring to fig. 3, when the first terminal CT + of the current transformer is short-circuited with GND, the voltage at the input terminal of the amplifier UA is 0V, and thus the voltage at the output terminal ADC is 0V, then the oscilloscope outputs the waveform signal shown in fig. 3.

In a preferred embodiment, referring to fig. 4, when the first terminal CT + of the current transformer is disconnected from GND, only the inverting input terminal of the amplifier UA has an excitation signal, the voltage at the input terminal of the amplifier satisfies a basic voltage division relationship, so that the output terminal ADC of the operational amplifier is 0V, and the voltage at the output terminal of the operational amplifier satisfies the charge-discharge curve of the capacitor of the second capacitor C2, and the oscilloscope outputs the waveform of the charge-discharge curve of the capacitor as shown in fig. 4.