An impedance detection method for a circuit breaker and its contact mechanism

Abstract

An impedance detection method for a circuit breaker and its contact mechanism, including a measurement circuit and at least one energized circuit. The two ends of the measurement circuit are connected to the first terminal and the second terminal of the contact mechanism. The measurement circuit includes a current sensor, a first voltage sensor, a second voltage sensor, a controller, and an isolation circuit; the current sensor transmits the sensed current signal to the controller, the first voltage sensor transmits the sensed voltage of the first terminal to the controller, and the second voltage sensor transmits the sensed voltage of the second terminal to the controller. The isolation circuit is used to prevent the measurement circuit from forming a current loop, and the controller calculates the impedance of the contact mechanism based on the current signal, the first voltage signal, and the second voltage signal. In the present invention, the impedance of the contact mechanism is detected through the measurement circuit, and the isolation circuit prevents the measurement circuit from forming a current loop, avoiding the potential hazard of electric leakage.

Description

Technical Field

[0001] The present invention relates to low-voltage electrical appliances, and particularly to an impedance detection method for a circuit breaker and its contact mechanism. Background Art

[0002] A low-voltage circuit breaker, also known as an automatic air switch or an automatic air circuit breaker, is an electrical appliance that has both the function of a manual switch and can automatically perform undervoltage, overvoltage, overload, and short-circuit protection. It can be used to distribute electric energy, start an asynchronous motor infrequently, and protect power supply lines and motors, etc. When they encounter serious overload, short-circuit, or undervoltage faults, it can automatically cut off the circuit, and its function is equivalent to the combination of a fuse switch and an over- and under-thermal relay, etc.

[0003] The contact mechanism is an important part of a low-voltage circuit breaker. It controls the energization or de-energization of the circuit by closing or opening. However, each closing and opening of the contact mechanism will cause attenuation of the contact mechanism, resulting in an increase in the impedance of the circuit breaker path, further causing an increase in power consumption and a decrease in power transmission efficiency. As the power consumption continues to increase, it will eventually lead to the failure of the low-voltage circuit breaker. At present, existing low-voltage circuit breakers cannot measure the conduction impedance of the contact mechanism of the circuit breaker in real time. The main reason is that the measurement circuit cannot be isolated from the circuit of the circuit breaker. A tiny current generated by the measurement circuit during operation will flow through the load, easily causing a leakage risk and posing a safety hazard. Therefore, the conduction impedance of the contact mechanism cannot be measured in real time, and thus the working state of the circuit breaker cannot be accurately detected and the life of the circuit breaker cannot be predicted. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a circuit breaker with a simple structure that can measure contact impedance and an impedance detection method for its contact mechanism.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A circuit breaker includes a measurement circuit and at least one energized circuit. Each energized circuit includes a set of contact mechanisms for controlling the on / off of the energized circuit. The two ends of the measurement circuit are respectively connected to the first terminal and the second terminal of the contact mechanism. The measurement circuit includes a current sensor, a first voltage sensor, a second voltage sensor, a controller, and an isolation circuit;

[0007] The current sensor is connected to the first terminal of the contact mechanism, and the first voltage sensor is connected to the first terminal of the contact mechanism. The current sensor transmits a current signal to the controller, and the first voltage sensor transmits a first voltage signal to the controller. The second voltage sensor is connected to the second terminal of the contact mechanism and transmits a second voltage signal to the controller. The isolation circuit is connected to the controller to prevent the measurement circuit from forming a current loop. The controller calculates the impedance of the contact mechanism based on the obtained current signal, first voltage signal, and second voltage signal.

[0008] Preferably, the isolation circuit is connected between the second voltage sensor and the controller. The second voltage sensor transmits the second voltage signal to the controller through the isolation circuit. The current sensor and the first voltage sensor are respectively connected to the controller and directly transmit the current signal and the first voltage signal to the controller.

[0009] Preferably, the current sensor and the first voltage sensor are respectively connected to the isolation circuit. The current sensor and the first voltage sensor respectively transmit the current signal and the first voltage signal to the controller through the isolation circuit. The second voltage sensor is connected to the controller and directly transmits the second voltage signal to the controller.

[0010] Preferably, the isolation circuit is further connected to an analog-to-digital conversion circuit. The current sensor and the first voltage sensor are respectively connected to the isolation circuit through the analog-to-digital conversion circuit.

[0011] Preferably, the measurement circuit further includes a controllable current source driven by the controller. The controllable current source is connected in each phase of the energized circuit and can increase the current in the energized circuit under the drive of the controller.

[0012] Preferably, the controllable current source includes a driving controller and a controllable circuit controlled by the driving controller. The two ends of the controllable circuit are respectively connected to the second terminal and the neutral line of the energized circuit. The controllable circuit includes a first conducting element, a resistor, and a second conducting element connected in sequence. Under the drive of the driving controller, the first conducting element and the second conducting element are turned on, and the driving controller adjusts the current in the controllable circuit according to the voltage across the resistor.

[0013] Preferably, the measurement circuit further includes one or more power supplies for providing power to the measurement circuit.

[0014] Preferably, the current sensor is a Hall current sensor, a transformer, or a resistor. The first voltage sensor and the second voltage sensor are both one or more combinations of a Hall current sensor, a transformer, or a resistor. The isolation circuit is composed of one or more isolation devices, and the controller is a single-chip microcomputer.

[0015] Preferably, the measurement circuit further includes two power supplies for providing operating power to the measurement circuit. One power supply powers the current sensor and the first voltage sensor, and the other power supply powers the second voltage sensor.

[0016] Preferably, the measurement circuit includes a current transformer, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a controller, a drive controller, a first field-effect transistor, a second field-effect transistor, an isolation circuit, an analog-to-digital conversion circuit, a first power supply, and a second power supply;

[0017] The current transformer serves as the current sensor. The primary coil of the current transformer is connected in series to the first terminal of the contact mechanism, and the secondary coil of the current transformer is connected to the input terminal of the analog-to-digital conversion circuit. The first resistor and the second resistor serve as the first voltage sensor. One end of the first resistor is connected to one end of the primary coil of the current transformer, and the other end of the first resistor is respectively connected to one end of the second resistor and the input terminal of the analog-to-digital conversion circuit. The other end of the second resistor is connected to the zero line of the energized circuit. The output terminal of the analog-to-digital conversion circuit is connected to the input terminal of the isolation circuit, and the output terminal of the isolation circuit is connected to the input terminal of the controller. The third resistor and the fourth resistor serve as the second voltage sensor. One end of the third resistor is connected to the second terminal of the contact mechanism, and the other end of the third resistor is connected to one end of the fourth resistor and the input terminal of the controller. The other end of the fourth resistor and one power supply terminal of the controller are connected to the zero line of the energized circuit;

[0018] The output terminal of the controller is connected to the input terminal of the drive controller. The G poles of the first field-effect transistor and the second field-effect transistor are connected to the output terminal of the drive controller. The S poles of the first field-effect transistor and the second field-effect transistor are respectively connected to both ends of the fifth resistor. The D pole of the first field-effect transistor is connected to the second terminal of the contact mechanism, and the D pole of the second field-effect transistor is connected to the zero line of the energized circuit;

[0019] The two power supply terminals of the first power supply are respectively connected to the first terminal and the zero line of the energized circuit, and the output terminal of the first power supply is connected to the power supply terminal of the analog-to-digital conversion circuit. The two power supply terminals of the second power supply are respectively connected to the second terminal and the zero line of the energized circuit, and the output terminal of the second power supply is respectively connected to the power supply terminals of the drive controller and the controller.

[0020] An impedance detection method for the contact mechanism in a circuit breaker, including the circuit breaker as described above. When the contact mechanism is closed, the controller of the circuit breaker obtains the current I flowing through the contact mechanism through a current sensor. The controller respectively obtains the first voltage V1 at the first terminal of the contact mechanism and the second voltage V2 at the second terminal through a first voltage sensor and a second voltage sensor. The controller calculates and stores the impedance value of the contact mechanism according to the impedance Z = (V1 - V2) / I of the contact mechanism.

[0021] Furthermore, the controller obtains the impedance change value of the contact mechanism by comparing the impedance values when the contact mechanism is closed for the nth time and the (n - 1)th time, and judges the working condition of the circuit breaker and predicts the life of the contact mechanism based on this; where n is an integer greater than or equal to 1.

[0022] A circuit breaker of the present invention can detect the impedance of the contact mechanism in each energized circuit through a measuring circuit. The isolation circuit in the measuring circuit prevents the measuring circuit from forming a current loop, avoiding the generation of current flowing through the load in the measuring circuit and forming a leakage hazard of the circuit breaker.

[0023] In addition, the isolation circuit is connected to the controller. The first voltage sensor or the second voltage sensor transmits a voltage signal to the controller through the isolation circuit, isolating the second voltage sensor from the first voltage sensor and the current sensor, and further preventing the measuring circuit from forming a complete current loop.

[0024] In addition, the measuring circuit is also provided with a controllable current source, which outputs a controllable current under the drive of the controller to increase the current flowing through the contact mechanism and improve the measurement accuracy; in addition, the measuring circuit is also provided with a power supply for providing a working power supply.

[0025] An impedance detection method for the contact mechanism in a circuit breaker of the present invention, based on the above circuit breaker, the controller calculates and obtains the impedance value of the contact mechanism by obtaining the current, the first voltage and the second voltage of the contact mechanism. The method is reasonable and simple, and has a high accuracy.

[0026] In addition, by comparing with the impedance value of the contact mechanism obtained in the previous measurement, the working state of the contact mechanism can be judged and the life of the contact mechanism can be predicted based on this. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of a circuit breaker of the present invention;

[0028] Figure 2 is a schematic diagram of the first embodiment of a circuit breaker of the present invention;

[0029] Figure 3 is a schematic diagram of the second embodiment of a circuit breaker of the present invention;

[0030] Figure 4 It is the circuit diagram of the second embodiment in a circuit breaker of the present invention;

[0031] Figure 5 It is the schematic diagram of the third embodiment in a circuit breaker of the present invention (the power supply is omitted);

[0032] Figure 6 It is the schematic diagram of the third embodiment in a circuit breaker of the present invention;

[0033] Figure 7 It is the waveform diagram (pulse type) of the current generated by the controllable current source and the current generated by the energized circuit in a circuit breaker of the present invention;

[0034] Figure 8 It is the waveform diagram (continuous type) of the current generated by the controllable current source and the current generated by the energized circuit in a circuit breaker of the present invention. Specific embodiments

[0035] The following combines the appended Figures 1 to 8 Given embodiments to further illustrate the specific embodiments of an impedance detection method for a circuit breaker and its contact mechanism of the present invention. The impedance detection method for a circuit breaker and its contact mechanism of the present invention is not limited to the descriptions of the following embodiments.

[0036] A circuit breaker includes a measurement circuit and at least one energized circuit phase. Each energized circuit phase includes a set of contact mechanisms for controlling the on / off of the energized circuit. The measurement circuit is respectively connected to each energized circuit phase, and both ends of the measurement circuit are respectively connected to the first connection terminal and the second connection terminal of a set of contact mechanisms. The measurement circuit includes a current sensor, a first voltage sensor, a second voltage sensor, a controller, and an isolation circuit;

[0037] The current sensor is connected to the first connection terminal of the contact mechanism, and the first voltage sensor is connected to the first connection terminal of the contact mechanism. The current sensor transmits the sensed current signal in the energized circuit to the controller, and the first voltage sensor transmits the voltage at the first connection terminal as a first voltage signal to the controller. The second voltage sensor is connected to the second connection terminal of the contact mechanism and transmits the voltage at the second connection terminal as a second voltage signal to the controller. The isolation circuit is connected to the controller to prevent the measurement circuit from forming a current loop. The controller calculates the impedance of the contact mechanism based on the obtained current signal, first voltage signal, and second voltage signal.

[0038] For a circuit breaker of the present invention, the impedance of the contact mechanism in each energized circuit phase can be detected through the measurement circuit. The isolation circuit in the measurement circuit prevents the measurement circuit from forming a current loop, avoiding the generation of current flowing through the load in the measurement circuit and forming a potential leakage hazard of the circuit breaker.

[0039] Combination Figures 1-2 An embodiment of the first circuit breaker is provided. In this embodiment, the circuit breaker is a single-phase circuit breaker. The energized circuit of the circuit breaker includes a live wire and a neutral wire. The contact mechanism of the energized circuit is connected to the live wire. Of course, a set of contact mechanisms can also be provided on the neutral wire. In this embodiment, the contact mechanism connected to the live wire is marked as 1 in Figure 1 ; The current sensor and the first voltage sensor in the measurement circuit are both connected to the first terminal of the contact mechanism. In this embodiment, the first terminal is the incoming line terminal of the circuit breaker, marked as terminal A in the figure. The current sensor directly transmits the sensed current signal in the energized circuit to the controller. The first voltage sensor is connected to the first terminal of the contact mechanism through the current sensor. The two input terminals of the first voltage sensor are respectively connected to the live wire and the neutral wire. The first voltage sensor directly transmits the sensed voltage of the first terminal ( Figure 1 , 2 marked as V1 in

[0040] ) as the first voltage signal directly to the controller; The second voltage sensor is connected to the second terminal of the contact mechanism. The two input terminals of the second voltage sensor are respectively connected to the live wire and the neutral wire. In this embodiment, it is the outgoing line terminal of the circuit breaker, marked as terminal B in the figure. The isolation circuit is connected between the second voltage sensor and the controller. The second voltage sensor transmits the sensed voltage of the second terminal (marked as V2 in the figure) as the second voltage signal to the controller through the isolation circuit. The controller calculates the impedance of the contact mechanism according to the obtained current signal, first voltage signal, and second voltage signal. Specifically, it is the ratio of the difference between the first voltage signal and the second voltage signal to the current signal. Since the isolation circuit isolates the second voltage sensor from the controller, the first voltage sensor, and the current sensor, the measurement circuit cannot form a complete current loop, so no current flowing through the load will be generated, avoiding electric leakage. Preferably, the measurement circuit further includes a controllable current source driven by the controller. When the current obtained by the controller through the current transformer in the energized circuit is small, the small current is not conducive to accurately measuring the impedance of the contact mechanism. The controller drives the controllable current source to output current to increase the current in the energized circuit. In this way, the requirement for the sensitivity of the current sensor can be reduced, and the measurement result is more accurate. The additional current generated by the controllable current source can be pulsed (see Figure 7 ), or continuous (see Figure 8 ). The controllable current source is connected to the second terminal of the contact mechanism, that is, the outgoing line terminal of the circuit breaker or the load side.

[0041] Furthermore, the measurement circuit further includes a power supply for providing a working power supply for the measurement circuit. In Figure 2In this case, the number of power supplies is two. One power supply supplies power to the current sensor and the first voltage sensor, and the other power supply supplies power to the second voltage sensor. Any one of the two power supplies can be used to supply power to other components such as the controller. In the figure, the first power supply supplies power to the current sensor, the first voltage sensor, and the controller, and the second power supply supplies power to the second voltage sensor, the isolation circuit, and the controllable current source. The two power supplies can directly draw power from the energized circuit, and of course, they can also be batteries.

[0042] In this embodiment, the current sensor is a Hall current sensor, a transformer, or a resistor. The first voltage sensor and the second voltage sensor are both one or more combinations of a Hall current sensor, a transformer, or a resistor. The isolation circuit consists of one or more isolation devices, and the isolation devices can be selected as optocouplers or transformers, etc. The controller has certain logical operation capabilities and storage functions, and is preferably a single-chip microcomputer.

[0043] Combined Figures 3-4 Provide a second embodiment of the circuit breaker. The same as the first embodiment, the circuit breaker in this embodiment is also a single-phase circuit breaker. The energized circuit of the circuit breaker also includes a live wire and a neutral wire. The contact mechanism is connected to the live wire and is also marked as 1 in Figure 3 、 4 ; The current sensor is connected to the first terminal of the contact mechanism, which is also marked as the A terminal in Figure 3 、 4 . The first voltage sensor is connected to the first terminal. One input terminal of the first voltage sensor is connected to the live wire of the first terminal of the contact mechanism through the current sensor, and the other input terminal is connected to the neutral wire of the energized circuit. The current sensor and the first voltage sensor are respectively connected to the isolation circuit. The current sensor transmits the sensed current signal in the energized circuit (marked as I in Figure 3 ) to the controller through the isolation circuit. The first voltage sensor transmits the sensed voltage at the first terminal (marked as V1 in Figure 3 ) as the first voltage signal to the controller through the isolation circuit. The two ends of the second voltage sensor are respectively connected to the second terminal and the controller. The second sensor transmits the sensed voltage at the second terminal (marked as V2 in Figure 3 ) as the second voltage signal directly to the controller. The same as the first embodiment, the controller calculates the impedance of the contact mechanism according to the obtained current signal, the first voltage signal, and the second voltage signal. Since the isolation circuit isolates the second voltage sensor and the controller from the first voltage sensor and the current sensor, the measurement circuit cannot form a complete current loop, so no current flowing through the load will be generated, avoiding electric leakage.

[0044] In this embodiment, a controllable current source is preferably further provided. The controllable current source generates a controllable additional current under the drive of the controller. The additional current can be a pulsed current or a continuous current. The controllable current source is started when the controller measures a low current through the current sensor, and the controllable current source is arranged at the second terminal of the contact mechanism. Thus, when the current flowing through the energized circuit is small, the controller drives the controllable current source to generate an additional current, thereby sequentially reducing the requirement for the sensitivity of the current sensor and improving the measurement accuracy.

[0045] Specifically, the controllable current source includes a drive controller and a controllable circuit controlled by the drive controller. The two ends of the controllable circuit are respectively connected to the second terminal of the contact mechanism and the zero line of the energized circuit. The controllable circuit includes a first conduction element, a resistor, and a second conduction element connected in sequence. Under the drive of the drive controller, the first conduction element and the second conduction element are turned on to allow a current to flow through the controllable circuit, and the drive controller adjusts the current in the controllable circuit according to the voltage across the resistor.

[0046] Preferably, the measurement circuit further includes an analog-to-digital conversion circuit. The current sensor and the first voltage sensor are respectively connected to the isolation circuit through the analog-to-digital conversion circuit. The analog-to-digital conversion circuit converts the voltage signal transmitted by the current sensor into a digital signal, and then the isolation circuit transmits the current value to the controller; the first voltage sensor converts the obtained voltage into a small signal and transmits it to the analog-to-digital conversion circuit, and then the analog-to-digital conversion circuit converts it into a digital signal and the isolation circuit transmits the voltage value to the controller.

[0047] Further, the measurement circuit further includes one or more power supplies for providing a working power supply for the measurement circuit. In this embodiment, two power supplies are also provided. The first power supply is used to supply power to the current sensor, the first voltage sensor, the analog-to-digital conversion circuit, and the isolation circuit, and the second power supply is used to supply power to the second voltage sensor, the controller, and the drive controller in the controllable current source.

[0048] In this embodiment, the current sensor is a Hall current sensor, a transformer, or a resistor. The first voltage sensor and the second voltage sensor are both one or more combinations of a Hall current sensor, a transformer, or a resistor; the isolation circuit is composed of one or more isolation devices, and the isolation device can be selected as an optocoupler or a transformer, etc.; the controller has a certain logical operation ability and a storage function, preferably a single-chip microcomputer; the analog-to-digital conversion circuit can be a circuit including an analog-to-digital conversion chip, such as a circuit composed of ADC0809CCVX, and the drive controller can be a circuit including a chip, such as a circuit composed of a HEF4011 chip. The first conduction element and the second conduction element are preferably field effect transistors.

[0049] Combined withFigure 4 Provide the connection mode of the measurement circuit in this embodiment. The measurement circuit includes a current transformer T1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a controller, a drive controller, a first field-effect transistor M1, a second field-effect transistor M2, an isolation circuit, an analog-to-digital conversion circuit, a first power supply, and a second power supply;

[0050] The current transformer T1 serves as a current sensor. The primary coil of the current transformer T1 is connected in series to the first terminal of the contact mechanism, and the secondary coil of the current transformer T1 is connected to the input terminal of the analog-to-digital conversion circuit. The first resistor R1 and the second resistor R2 serve as a first voltage sensor. One end of the first resistor R1 is connected to one end of the primary coil of the current transformer T1, so that the first resistor R1 is connected to the first terminal of the contact mechanism through the primary coil (in practical applications, the primary coil of the current transformer is the live wire, and its impedance can be ignored, or one end of the first resistor R1 can be directly connected to the first terminal of the contact mechanism). The other end of the first resistor R1 is respectively connected to one end of the second resistor R2 and the input terminal of the analog-to-digital conversion circuit. The other end of the second resistor R2 is connected to the zero line of the energized circuit; the output terminal of the analog-to-digital conversion circuit is connected to the input terminal of the isolation circuit, and the output terminal of the isolation circuit is connected to the input terminal of the controller; the third resistor R3 and the fourth resistor R4 serve as a second voltage sensor. One end of the third resistor R3 is connected to the second terminal of the contact mechanism, the other end of the third resistor R3 is connected to one end of the fourth resistor R4 and the input terminal of the controller, and the other end of the fourth resistor R4 and a power supply terminal of the controller are connected to the zero line of the energized circuit;

[0051] The output terminal of the controller is connected to the input terminal of the drive controller. The G poles of the first field-effect transistor M1 and the second field-effect transistor M2 are connected to the output terminal of the drive controller. The S poles of the first field-effect transistor M1 and the second field-effect transistor M2 are respectively connected to both ends of the fifth resistor R5. The D pole of the first field-effect transistor M1 is connected to the second terminal of the contact mechanism, and the D pole of the second field-effect transistor M2 is connected to the zero line of the energized circuit;

[0052] The two power supply terminals of the first power supply are respectively connected to the first terminal and the zero line of the energized circuit, and the output terminal of the first power supply is connected to the power supply terminal of the analog-to-digital conversion circuit; the two power supply terminals of the second power supply are respectively connected to the second terminal and the zero line of the energized circuit, and the output terminal of the second power supply is respectively connected to the power supply terminals of the drive controller and the controller.

[0053] Its working principle is as follows: When the contact mechanism closes, current flows through the primary coil of the current transformer T1. A corresponding voltage is generated in the secondary coil of the current transformer T1. The current is converted into a digital signal by the analog-to-digital conversion and the current value is transmitted to the controller through the isolation circuit; the first resistor R1 and the second resistor R2 convert the voltage V1 between the live wire and the neutral wire at the first terminal into a small signal and transmit it to the analog-to-digital conversion circuit, which is converted into a digital signal and transmitted to the controller through the isolation circuit; the third resistor R3 and the fourth resistor R4 convert the voltage V2 between the live wire and the neutral wire at the second terminal of the contact mechanism into a small signal and transmit it to the controller. The controller calculates the impedance value of the contact mechanism based on the current signal, the first voltage, and the second voltage.

[0054] In addition, when the current transformer T1 detects that the current is too small, the controllable current source will be started. Under the drive of the controller, the controller outputs a high potential to turn on the first field-effect transistor M1 and the second field-effect transistor M2. Current flows through the controllable circuit composed of the first field-effect transistor M1, the fifth resistor R5, and the second field-effect transistor M2. A corresponding voltage is generated across the fifth resistor R5. The drive controller adjusts the current flowing through the first field-effect transistor M1 and the second field-effect transistor M2 according to the voltage across the fifth resistor R5 to make the flowing current controlled.

[0055] Combined with Figures 5-6 Provide a third embodiment of the circuit breaker. In this embodiment, the circuit breaker is a three-phase four-wire circuit breaker, including three-phase power-on circuits. The three-phase power-on circuits respectively have an A-phase live wire, a B-phase live wire, and a C-phase live wire. A set of contact mechanisms are connected to each phase of the live wire. In this embodiment, a current sensor is connected to the first terminal of each phase of the contact mechanism. The first voltage sensor is respectively connected to the first terminals of the three sets of contact mechanisms through three current sensors. The three current sensors are respectively connected to the controller to transmit current signals to the controller. Among them, the current of the A-phase power-on circuit is IA, the current of the B-phase power-on circuit is IB, and the current of the C-phase power-on circuit is IC; the first voltage sensor respectively transmits the voltage of the first terminal of the three sets of contact mechanisms to the controller. In the figure, V1A, V1B, and V1C respectively represent the first voltage signals of the three-phase power-on circuits; the second voltage sensor is respectively connected to the second terminals of the three sets of contact mechanisms and transmits the second voltage signals of the three-phase power-on circuits to the controller through the isolation circuit. In the figure, V2A, V2B, and V2C respectively represent.

[0056] Preferably, it further includes three controllable current sources. The controllable current sources are respectively connected in a phase of the power-on circuit and can generate additional current in each phase of the power-on circuit under the drive of the controller. Its working principle refers to the second embodiment. Further, the same as the first embodiment and the second embodiment, this embodiment also includes two power supplies that provide working power for the measurement circuit.

[0057] An impedance detection method for the contact mechanism in a circuit breaker, including the circuit breaker as described above. When the contact mechanism is closed, the controller obtains the current I flowing through the contact mechanism through a current sensor. The controller respectively obtains the first voltage V1 at the first terminal of the contact mechanism and the second voltage V2 at the second terminal of the contact mechanism through a first voltage sensor and a second voltage sensor. The controller calculates and stores the impedance value of the contact mechanism according to the impedance Z = (V1 - V2) / I. The method is simple and accurate.

[0058] Furthermore, the controller obtains the impedance change of the contact mechanism by comparing the impedance values when the contact mechanism is closed for the nth time and the (n - 1)th time, and accordingly judges the working condition of the contact mechanism and predicts the service life of the contact mechanism; where n is an integer greater than or equal to 1.

[0059] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A circuit breaker, characterized in that: it includes a measurement circuit and at least one energized circuit. Each energized circuit includes a set of contact mechanisms for controlling the on / off of the energized circuit. The two ends of the measurement circuit are respectively connected to the first terminal and the second terminal of the contact mechanism. The measurement circuit includes a current sensor, a first voltage sensor, a second voltage sensor, a controller, and an isolation circuit; the current sensor is connected to the first terminal of the contact mechanism, the first voltage sensor is connected to the first terminal of the contact mechanism. The current sensor transmits a current signal to the controller, the first voltage sensor transmits a first voltage signal to the controller. The second voltage sensor is connected to the second terminal of the contact mechanism and transmits a second voltage signal to the controller. The isolation circuit is connected to the controller to prevent the measurement circuit from forming a current loop. The controller calculates the impedance of the contact mechanism based on the obtained current signal, first voltage signal, and second voltage signal; the isolation circuit is connected between the second voltage sensor and the controller. The second voltage sensor transmits the second voltage signal to the controller through the isolation circuit. The current sensor and the first voltage sensor are respectively connected to the controller and directly transmit the current signal and the first voltage signal to the controller; or, the current sensor and the first voltage sensor are respectively connected to the isolation circuit. The current sensor and the first voltage sensor respectively transmit the current signal and the first voltage signal to the controller through the isolation circuit. The second voltage sensor is connected to the controller and directly transmits the second voltage signal to the controller. The isolation circuit is also connected to an analog-to-digital conversion circuit. The current sensor and the first voltage sensor are respectively connected to the isolation circuit through the analog-to-digital conversion circuit. The current sensor is a Hall current sensor, a transformer, or a resistor; the measurement circuit further includes two power supplies for providing operating power to the measurement circuit. One power supply supplies power to the current sensor and the first voltage sensor, and the other power supply supplies power to the second voltage sensor.

2. A circuit breaker according to claim 1, characterized in that: the measurement circuit further includes a controllable current source driven by the controller. The controllable current source is connected in each energized circuit and can increase the current of the energized circuit under the drive of the controller.

3. A circuit breaker according to claim 2, characterized in that: the controllable current source includes a drive controller and a controllable circuit controlled by the drive controller. The two ends of the controllable circuit are respectively connected to the second terminal and the neutral wire of the energized circuit. The controllable circuit includes a first conduction element, a resistor, and a second conduction element connected in sequence. Under the drive of the drive controller, the first conduction element and the second conduction element conduct. The drive controller adjusts the current in the controllable circuit according to the voltage across the resistor.

4. A circuit breaker according to claim 2, characterized in that: both the first voltage sensor and the second voltage sensor are one or a combination of more than one of a Hall current sensor, a transformer, or a resistor; the isolation circuit is composed of one or more isolation devices, and the controller is a single-chip microcomputer.

5. A circuit breaker according to claim 1, characterized in that: the measurement circuit includes a current transformer, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a controller, a drive controller, a first field effect transistor, a second field effect transistor, an isolation circuit, an analog-to-digital conversion circuit, a first power supply and a second power supply; the current transformer serves as a current sensor, the primary coil of the current transformer is connected in series to the first terminal of the contact mechanism, the secondary coil of the current transformer is connected to the input terminal of the analog-to-digital conversion circuit, the first resistor and the second resistor serve as a first voltage sensor, one end of the first resistor is connected to one end of the primary coil of the current transformer, the other end of the first resistor is respectively connected to one end of the second resistor and the input terminal of the analog-to-digital conversion circuit, and the other end of the second resistor is connected to the zero line of the energized circuit; the output terminal of the analog-to-digital conversion circuit is connected to the input terminal of the isolation circuit, and the output terminal of the isolation circuit is connected to the input terminal of the controller; the third resistor and the fourth resistor serve as a second voltage sensor, one end of the third resistor is connected to the second terminal of the contact mechanism, the other end of the third resistor is connected to one end of the fourth resistor and the input terminal of the controller, and the other end of the fourth resistor and a power supply terminal of the controller are connected to the zero line of the energized circuit; the output terminal of the controller is connected to the input terminal of the drive controller, the G poles of the first field effect transistor and the second field effect transistor are connected to the output terminal of the drive controller, the S poles of the first field effect transistor and the second field effect transistor are respectively connected to both ends of the fifth resistor, the D pole of the first field effect transistor is connected to the second terminal of the contact mechanism, and the D pole of the second field effect transistor is connected to the zero line of the energized circuit; the two power supply terminals of the first power supply are respectively connected to the first terminal and the zero line of the energized circuit, and the output terminal of the first power supply is connected to the power supply terminal of the analog-to-digital conversion circuit; the two power supply terminals of the second power supply are respectively connected to the second terminal and the zero line of the energized circuit, and the output terminal of the second power supply is respectively connected to the power supply terminals of the drive controller and the controller.

6. An impedance detection method for a contact mechanism in a circuit breaker, characterized in that: it includes the circuit breaker according to any one of claims 1-5. When the contact mechanism is closed, the controller of the circuit breaker obtains the current I flowing through the contact mechanism through the current sensor, the controller respectively obtains the first voltage V1 at the first terminal of the contact mechanism and the second voltage V2 at the second terminal of the contact mechanism through the first voltage sensor and the second voltage sensor, and the controller calculates the impedance value according to the impedance Z=(V1 - V2) / I of the contact mechanism.

7. An impedance detection method for a contact mechanism in a circuit breaker according to claim 6, characterized in that: the controller obtains the impedance change value of the contact mechanism by comparing the impedance values when the contact mechanism is closed for the nth time and the (n - 1)th time, and judges the working condition of the circuit breaker and predicts the life of the contact mechanism accordingly; where n is an integer greater than or equal to 1.

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