Secondary side open circuit protection device for current measuring devices

Abstract

The utility model relates to a kind of secondary side open-circuit protection device suitable for current measuring device.It includes: rectifying unit;Discharge circuit, including at least one discharge unit, discharge unit with the rectifying unit and the secondary side winding of current measuring device adaptive connection, wherein, the secondary side winding of current measuring device is in open-circuit state, and when the direct current voltage generated by rectifying unit can drive discharge circuit to enter discharge working state, the two ends of current measuring device secondary winding and discharge circuit adaptive connection are connected, to discharge the energy coupled by current measuring device secondary winding through discharge circuit;When the secondary side winding of current measuring device is in non-open-circuit state, the direct current voltage generated by rectifying unit cannot drive discharge circuit to enter discharge working state.The utility model can effectively realize secondary side open-circuit protection without affecting current measuring accuracy, improve the security and reliability of current measuring device.

Description

Technical Field

[0001] This utility model relates to an open circuit protection device, and more particularly to an open circuit protection device suitable for the secondary side of a current measuring device. Background Technology

[0002] In the field of current measurement, wound current transformers and current sensors have wide applications. Generally, wound current transformers are passive current measuring devices, while current sensors are active current measuring devices. The output signal of a current measuring device is current. Therefore, a current path must be formed for the current measuring device to work properly, and the secondary side of the current measuring device must not be open-circuited. However, during installation and use, due to negligence, poor wiring, and other reasons, it is difficult to completely avoid open circuits on the secondary side.

[0003] Winded current transformers and current sensors have a high number of turns on their secondary side. If the secondary side is open, high voltage may be coupled out. In addition to causing a series of safety problems, this may also damage the wound current transformer or the current sensor itself. In particular, the current sensor uses an active structure, that is, the current sensor is an active device. Generally, active devices have a withstand voltage limit. If the withstand voltage limit is exceeded, it will break down and cause permanent damage.

[0004] As can be seen from the above description, how to effectively achieve open-circuit protection on the secondary side for winding current transformers and current sensors is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a secondary side open circuit protection device suitable for current measuring devices. It can effectively achieve secondary side open circuit protection without affecting the accuracy of current measurement, thereby improving the safety and reliability of current measuring devices.

[0006] According to the technical solution provided by this utility model, a secondary side open-circuit protection device suitable for current measuring devices is provided, the secondary side open-circuit protection device comprising:

[0007] The rectifier unit is connected to the secondary winding of the current measuring device to rectify the energy coupled from the secondary winding of the current measuring device into a DC voltage.

[0008] The discharge circuit includes at least one discharge unit, which is adapted and connected to the secondary winding of the rectifier unit and the current measuring device.

[0009] When the secondary winding of the current measuring device is in an open circuit state, and the DC voltage generated by the rectifier unit can drive the discharge circuit to enter the discharge working state, the two ends of the secondary winding of the current measuring device are adapted to be connected to the discharge circuit so as to discharge the energy coupled by the secondary winding of the current measuring device through the discharge circuit.

[0010] When the secondary winding of the current measuring device is in a non-open circuit state, the DC voltage generated by the rectifier unit cannot drive the discharge circuit to enter the discharge working state.

[0011] The current measuring device is a wound current transformer or a current sensor, wherein...

[0012] When the current measuring device is a winding current transformer, the secondary winding of the winding current transformer forms the secondary winding of the current measuring device.

[0013] When the current measuring device is a current sensor, the feedback winding inside the current sensor forms the secondary winding of the current measuring device;

[0014] The two ends of the secondary winding of the current measuring device are respectively adapted to the rectifier unit and adapted to the discharge circuit through the rectifier unit.

[0015] When the current measuring device is a wound current transformer, the discharge unit includes a discharge voltage divider circuit and a voltage clamping switch circuit adapted and connected to the discharge voltage divider circuit, wherein,

[0016] The bleed circuit is connected to the rectifier unit through a bleed voltage divider circuit, and the DC voltage generated by the rectifier unit is divided by the bleed voltage divider circuit.

[0017] When the DC voltage divider drive voltage clamping switch circuit is in the conducting state, the discharge unit enters the discharge state. The voltage clamping switch circuit is adapted to connect to both ends of the secondary winding of the current measuring device, so as to discharge the energy coupled to the secondary winding of the current measuring device through the voltage clamping switch circuit.

[0018] The voltage clamping switch circuit includes an NPN transistor Q1 and a PNP transistor Q2, wherein,

[0019] The base of NPN transistor Q1 is connected to the bleeder voltage divider circuit to receive the DC voltage divided by the bleeder voltage divider circuit;

[0020] The emitter of NPN transistor Q1 is connected to the cathode of Zener diode D5, the anode of Zener diode D5 is connected to the first rectifier connection terminal of the rectifier unit, and the collector of NPN transistor Q1 is connected to one end of resistor R3 and the base of PNP transistor Q2.

[0021] The other end of resistor R3 and the emitter of PNP transistor Q2 are adapted to be connected to the second rectifier connection terminal of the rectifier unit, and the collector of PNP transistor Q2 is connected to the anode of Zener diode D5.

[0022] The voltage clamping switch circuit also includes a resistor R6 and a power switch Q3, wherein,

[0023] The collector terminal of the PNP transistor Q2 is connected to one end of the resistor R6 and the control terminal of the power switch Q3.

[0024] The other end of resistor R6 and the first connection terminal of power switch Q3 are adapted to be connected to the first rectification connection terminal of the rectifier unit, and the second connection terminal of power switch Q3 is adapted to be connected to the second rectification connection terminal of the rectifier unit.

[0025] The voltage clamping switch circuit also includes a resistor R4 and a Zener diode D6, wherein,

[0026] The base of the PNP transistor Q2 is connected to the collector of the NPN transistor Q1 through resistor R4.

[0027] The control terminal of the power switch Q3 is connected to the cathode of the Zener diode D6, and the anode of the Zener diode D6 is connected to the first connection terminal of the power switch Q3.

[0028] The power switch Q3 is a MOSFET device, an IGBT device, or a thyristor.

[0029] The voltage clamping switch circuit includes an NPN transistor Q5 and a PNP transistor Q4, wherein...

[0030] The base of the PNP transistor Q4 is connected to the bleeder voltage divider circuit to receive the DC voltage divided by the bleeder voltage divider circuit.

[0031] The emitter of PNP transistor Q1 is connected to the anode of Zener diode D7, the cathode of Zener diode D7 is connected to the second rectifier connection terminal of the rectifier unit, and the collector of PNP transistor Q4 is connected to one end of resistor R7 and the base of NPN transistor Q5.

[0032] The other end of resistor R7 and the emitter of NPN transistor Q5 are connected to the first rectifier connection terminal of the rectifier unit, and the collector of NPN transistor Q5 is connected to the cathode of Zener diode D7.

[0033] When the current measuring device is a current sensor, the second rectifier connection terminal of the rectifier unit is connected to the power supply V+ terminal, and the first rectifier connection terminal of the rectifier unit is connected to the power supply V- terminal.

[0034] When the discharge circuit includes a discharge unit, the discharge unit is adapted to be connected to the power supply V+ terminal and the power supply V- terminal;

[0035] When the bleeder circuit includes two bleeder units, one bleeder unit is adapted to the power supply V+ terminal to form a bleeder channel to the power supply V+ terminal, and the other bleeder unit is adapted to the power supply V- terminal to form a bleeder channel to the power supply V- terminal.

[0036] The rectifier unit includes diodes D1, D2, D3, and D4, wherein...

[0037] The anode of diode D1 is connected to the cathode of diode D2 and the first end of the secondary winding. The cathode of diode D4 is connected to the second end of the secondary winding and the anode of diode D3. The anodes of diode D4 and D2 are adapted to the discharge circuit, and the cathodes of diode D1 and D3 are adapted to the discharge circuit.

[0038] The advantages of this utility model are: the energy coupled by the secondary winding can be rectified by the rectifier unit. When the DC voltage generated by the rectifier can drive the discharge circuit to enter the discharge working state, the secondary winding can be adapted to the discharge circuit to discharge the coupling capacity of the secondary winding through the discharge circuit, so as to play the role of open circuit protection. The open circuit protection has a short start time, strong protection capability, and is safe and reliable.

[0039] Under normal operating conditions, the secondary winding is connected normally. The DC voltage generated by the rectifier unit cannot drive the discharge circuit to enter the discharge working state, which has no effect on the operation of the secondary winding and will not affect the measurement accuracy of the current measuring device.

[0040] The secondary side open circuit protection device should be placed inside the current measuring device, such as inside the winding current transformer or the current sensor, so that continuous and uninterrupted open circuit protection can be achieved regardless of the state of the external connection, which can avoid damage to itself and also avoid personal danger caused by high voltage coupling. Attached Figure Description

[0041] Figure 1 The circuit diagram of the first embodiment of the secondary side open circuit protection device of this utility model is shown when the current measuring device is a winding current transformer.

[0042] Figure 2 The circuit diagram of the second embodiment of the secondary side open circuit protection device of this utility model is shown when the current measuring device is a winding current transformer.

[0043] Figure 3The circuit diagram of the third embodiment of the secondary side open circuit protection device of this utility model is shown when the current measuring device is a winding current transformer.

[0044] Figure 4 The circuit diagram of the fourth embodiment of the secondary side open circuit protection device of this utility model is shown when the current measuring device is a winding current transformer.

[0045] Figure 5 The circuit diagram of the first embodiment of the secondary side open circuit protection device of this utility model is shown when the current measuring device is a current sensor.

[0046] Figure 6 The circuit diagram of the first embodiment of the secondary side open circuit protection device of this utility model is shown when the current measuring device is a current sensor. Detailed Implementation

[0047] The present invention will be further described below with reference to the specific accompanying drawings and embodiments.

[0048] To effectively achieve secondary side open-circuit protection and improve the safety and reliability of current measuring devices without affecting the accuracy of current measurement, this utility model provides a secondary side open-circuit protection device suitable for current measuring devices. Specifically, the secondary side open-circuit protection device includes:

[0049] The rectifier unit is connected to the secondary winding of the current measuring device to rectify the energy coupled from the secondary winding of the current measuring device into a DC voltage.

[0050] The discharge circuit includes at least one discharge unit, which is adapted and connected to the secondary winding of the rectifier unit and the current measuring device.

[0051] When the secondary winding of the current measuring device is in an open circuit state, and the DC voltage generated by the rectifier unit can drive the discharge circuit to enter the discharge working state, the two ends of the secondary winding of the current measuring device are adapted to be connected to the discharge circuit so as to discharge the energy coupled by the secondary winding of the current measuring device through the discharge circuit.

[0052] When the secondary winding of the current measuring device is in a non-open circuit state, the DC voltage generated by the rectifier unit cannot drive the discharge circuit to enter the discharge working state.

[0053] It should be noted that the current measuring device is a winding current transformer or a current sensor. The secondary side open circuit protection device of this utility model specifically refers to the open circuit protection of the secondary side of the winding current transformer or the open circuit protection of the secondary side of the current sensor. Specifically, the secondary side open circuit means that the secondary side is not properly connected and working. The situation of the secondary side open circuit is consistent with the prior art, and will not be described in detail here.

[0054] In practical implementation, when the current measuring device is a wound-type current transformer, the secondary winding of the wound-type current transformer forms the secondary winding of the current measuring device. Figures 1-4 The document illustrates several embodiments where the current measuring device is a wound current transformer, and open-circuit protection is provided for the secondary winding of the wound current transformer. Figures 1-4 L in the middle is the secondary winding.

[0055] When the current measuring device is a current sensor, since the current sensor is an active device, it feeds back the current through the feedback winding on the secondary side to cancel the magnetic flux generated by the bus current in the magnetic core, thus achieving a zero magnetic flux state. Therefore, the feedback winding based on the current sensor forms the secondary winding of the current measuring device. Figure 5 and Figure 6 The document illustrates some embodiments where the current measuring device is a current sensor, and the secondary winding of the current sensor is protected against open circuit. Figure 5 and Figure 6 In the diagram, T represents the magnetic core. A feedback winding is set on the secondary side of the magnetic core. The operation of the current sensor requires monitoring the magnetic flux state within the magnetic core. By setting a feedback winding on the secondary side of the magnetic core, the magnetic flux state of the current sensor is detected. The controller controls the power amplifier to generate a compensation current, which is then used to drive the feedback winding, thus achieving closed-loop current feedback.

[0056] As explained above, the secondary winding of the current measuring device couples with bus current energy; if the secondary side is open-circuited, a high voltage may be coupled out. In one embodiment of this invention, a rectifier unit is adapted and connected to the secondary winding of the current measuring device to rectify the energy coupled from the secondary winding, thereby generating a DC voltage. Figures 1-6 An embodiment of the rectifier unit is shown below, in conjunction with... Figures 1-6 The illustrated embodiments provide examples of the rectifier unit of this utility model.

[0057] In one embodiment of this utility model, the rectifier unit includes diodes D1, D2, D3, and D4, wherein...

[0058] The anode of diode D1 is connected to the cathode of diode D2 and the first end of the secondary winding. The cathode of diode D4 is connected to the second end of the secondary winding and the anode of diode D3. The anodes of diode D4 and D2 are adapted to the discharge circuit, and the cathodes of diode D1 and D3 are adapted to the discharge circuit.

[0059] Figures 1-4In the figure, the secondary winding L has a first end and a corresponding second end. The end corresponding to "1" is the first end of the secondary winding L, and the end corresponding to "2" is the second end of the secondary winding L. Figure 5 and Figure 6 The diagram shows the secondary winding of the current sensor. The end corresponding to "3" is the first end of the secondary winding, and the end corresponding to "4" is the second end of the secondary winding.

[0060] Specifically, the cathodes of diodes D1 and D3 are connected to form one end of the rectifier unit, and the anodes of diodes D2 and D4 are connected to form the second end of the rectifier unit. It should be understood that diodes D1, D2, D3, and D4 constitute the rectifier unit, and the rectification method using this unit is consistent with existing technology; the rectification process of the rectifier unit will not be elaborated here.

[0061] To achieve open-circuit protection, the secondary-side open-circuit protection device of this utility model should include a discharge circuit, which may include at least one discharge unit. Figures 1-5 The diagram illustrates an embodiment where a discharge unit is included within the discharge circuit. Figure 6 The diagram illustrates an embodiment of a discharge circuit including two discharge units; the number of discharge units in the discharge circuit will be explained below. Figures 1-6 Specific details are provided below. In practice, the discharge unit in the discharge circuit should be adapted and connected to the secondary winding of the rectifier unit and the current measuring device. When the discharge unit is connected to the rectifier unit, the DC voltage generated after rectification by the rectifier unit will be applied to the discharge unit, and the discharge unit can be driven to work using the DC voltage.

[0062] When the secondary winding of the current measuring device is in an open-circuit state, and the DC voltage can drive the discharge circuit into the discharge working state, the two ends of the secondary winding of the current measuring device can be adapted to connect with the discharge circuit. Thereafter, the energy coupled to the secondary winding of the current measuring device can be discharged through the discharge circuit, preventing damage to the current measuring device or injury to the human body caused by the coupled energy. Specifically, for the DC voltage to drive the discharge circuit into the discharge working state, the magnitude of the DC voltage must be at least greater than the discharge threshold voltage of the discharge circuit. That is, the discharge unit in the discharge circuit will only enter the discharge working state when the rectified DC voltage is greater than the discharge threshold voltage of the discharge unit within the discharge circuit. Otherwise, the discharge unit is in a non-working state, meaning that the energy coupled to the secondary winding cannot be discharged through the discharge unit.

[0063] When the bleeder circuit includes only one bleeder unit, the bleeder circuit enters the bleeder working state, which specifically means that the bleeder unit in the bleeder circuit enters the bleeder working state; while when the bleeder circuit includes multiple bleeder units, the bleeder circuit enters the bleeder working state, which generally means that at least one bleeder unit enters the bleeder working state.

[0064] It should be noted that when the secondary winding of the current measuring device is in a non-open circuit state, that is, when the secondary winding of the current measuring device is in normal connection condition, the DC voltage generated by the rectifier unit cannot drive the discharge current to enter the discharge operation state. In other words, the discharge units in the discharge circuit cannot enter the discharge operation state. Generally, when the secondary winding of the current measuring device is in a non-open circuit state, the DC voltage generated by the rectifier unit will generally be less than the discharge threshold voltage of the discharge unit, that is, it cannot drive the discharge unit to enter the discharge operation state.

[0065] It should be understood that when all discharge units in the discharge circuit are unable to enter the discharge working state, the normal operation of the secondary winding of the current measuring device will not be affected, and the current measurement accuracy of the current measuring device will not be affected. Therefore, this invention can effectively achieve secondary open-circuit protection without affecting the current measurement accuracy, thus improving the safety and reliability of the current measuring device.

[0066] In one embodiment of this utility model, when the current measuring device is a wound current transformer, the discharge unit includes a discharge voltage divider circuit and a voltage clamping switch circuit adapted and connected to the discharge voltage divider circuit, wherein...

[0067] The bleed circuit is connected to the rectifier unit through a bleed voltage divider circuit, and the DC voltage generated by the rectifier unit is divided by the bleed voltage divider circuit.

[0068] When the DC voltage divider drive voltage clamping switch circuit is in the conducting state, the discharge unit enters the discharge state. The voltage clamping switch circuit is adapted to connect to both ends of the secondary winding of the current measuring device, so as to discharge the energy coupled to the secondary winding of the current measuring device through the voltage clamping switch circuit.

[0069] In practice, when the discharge circuit includes multiple discharge units, the discharge units can generally adopt the same circuit configuration. However, different circuit configurations can also be used, depending on the specific requirements. Specifically, the discharge unit may include a discharge voltage divider circuit and a voltage clamping switch circuit. Figures 1-4The figure shows an embodiment of a bleed voltage divider circuit. The bleed voltage divider circuit may include resistor R1 and resistor R2. One end of resistor R1 is connected to the first end of the rectifier unit, and the other end of resistor R1 is connected to one end of resistor R2 and a voltage clamping switch circuit. The other end of resistor R2 is connected to the second end of the rectifier unit. That is, voltage division can be performed through the resistor voltage divider network formed by resistors R1 and R2.

[0070] The required discharge threshold voltage can be set through the voltage clamping switch circuit. The voltage clamping switch circuit compares the DC voltage divider with the discharge threshold voltage. When the DC voltage divider is greater than the discharge threshold voltage, the voltage clamping switch circuit is in the conducting state, thus enabling the discharge unit to enter the discharge state. Otherwise, the discharge unit cannot enter the discharge state. When the voltage clamping switch circuit is in the conducting state, the energy coupled to the secondary winding of the current measuring device can be discharged through the voltage clamping switch circuit. Conversely, when the discharge unit cannot enter the discharge state, the energy coupled to the secondary winding of the current measuring device cannot be discharged through the voltage clamping switch circuit.

[0071] In one embodiment of this utility model, the voltage clamping switch circuit includes an NPN transistor Q1 and a PNP transistor Q2, wherein...

[0072] The base of NPN transistor Q1 is connected to the bleeder voltage divider circuit to receive the DC voltage divided by the bleeder voltage divider circuit;

[0073] The emitter of NPN transistor Q1 is connected to the cathode of Zener diode D5, the anode of Zener diode D5 is connected to the first rectifier connection terminal of the rectifier unit, and the collector of NPN transistor Q1 is connected to one end of resistor R3 and the base of PNP transistor Q2.

[0074] The other end of resistor R3 and the emitter of PNP transistor Q2 are adapted to be connected to the second rectifier connection terminal of the rectifier unit, and the collector of PNP transistor Q2 is connected to the anode of Zener diode D5.

[0075] Figure 3 The diagram illustrates one embodiment of a voltage clamping switch circuit. As shown, resistor R3 and the emitter of PNP transistor Q2 are connected to the first terminal of the rectifier unit, while the anode of Zener diode D5 and the collector of PNP transistor Q2 are connected to the second terminal of the rectifier unit. Specifically, Zener diode D5 provides a regulated voltage Vz. Figure 3 The discharge threshold voltage set in the voltage clamping switch circuit is Vz+V Q1be , where V Q1be This is the threshold voltage of the NPN transistor Q1. Generally, V Q1beApproximately 0.7V. When the DC voltage divider voltage is greater than the discharge threshold voltage, NPN transistor Q1 turns on, and the collector voltage of NPN transistor Q1 drops, triggering PNP transistor Q2 to turn on. When PNP transistor Q2 turns on, the two ends of the secondary winding of the current measuring device are connected through PNP transistor Q2 to form a discharge circuit, so that the energy coupled to the secondary winding can be discharged through PNP transistor Q2.

[0076] In one embodiment of this utility model, the voltage clamping switch circuit further includes a resistor R6 and a power switch Q3, wherein...

[0077] The collector terminal of the PNP transistor Q2 is connected to one end of the resistor R6 and the control terminal of the power switch Q3.

[0078] The other end of resistor R6 and the first connection terminal of power switch Q3 are adapted to be connected to the first rectification connection terminal of the rectifier unit, and the second connection terminal of power switch Q3 is adapted to be connected to the second rectification connection terminal of the rectifier unit.

[0079] Figure 1 Another embodiment of the voltage clamping switch circuit of this utility model is shown in the figure, and... Figure 3 Compared to the embodiment shown, a power switch Q3 and a resistor R6 are added. The power switch Q3 can be a MOSFET, an IGBT, or a silicon controlled rectifier (SCR), and has a very low on-resistance, allowing it to handle very high currents, especially transient currents. Figure 3 The diagram illustrates an embodiment where the power switch Q3 uses an NMOS transistor. When the power switch Q3 uses an NMOS transistor, the drain terminal of the NMOS transistor serves as the first connection terminal of the power switch Q3, and the source terminal of the NMOS transistor serves as the second connection terminal of the power switch Q3.

[0080] Figure 1 The working principle of the medium voltage clamping switch circuit can be referred to the above. Figure 3 The difference in the medium voltage clamping switch circuit is that after the PNP transistor Q2 is turned on, a voltage is formed across the resistor R6, which triggers the power switch Q3 to turn on. By utilizing the operating characteristics of the power switch Q3, the reliability of the coupling energy can be improved.

[0081] In one embodiment of this utility model, the voltage clamping switch circuit further includes a resistor R4 and a Zener diode D6, wherein...

[0082] The base of the PNP transistor Q2 is connected to the collector of the NPN transistor Q1 through resistor R4.

[0083] The control terminal of the power switch Q3 is connected to the cathode of the Zener diode D6, and the anode of the Zener diode D6 is connected to the first connection terminal of the power switch Q3.

[0084] Figure 2 The figure shows an embodiment of the voltage clamping switch circuit of this utility model, which has Figure 1 Compared to the embodiment shown, a resistor R4 and a Zener diode D6 are added. The resistor R4 limits the current, and the Zener diode D6 limits the gate voltage of the power switch Q3, so that the gate voltage of the power switch Q3 does not exceed the Zener voltage of the Zener diode D6. This can prevent the power switch Q3 from being damaged due to excessively high gate voltage.

[0085] In one embodiment of this utility model, the voltage clamping switch circuit includes an NPN transistor Q5 and a PNP transistor Q4, wherein...

[0086] The base of the PNP transistor Q4 is connected to the bleeder voltage divider circuit to receive the DC voltage divided by the bleeder voltage divider circuit.

[0087] The emitter of PNP transistor Q1 is connected to the anode of Zener diode D7, the cathode of Zener diode D7 is connected to the second rectifier connection terminal of the rectifier unit, and the collector of PNP transistor Q4 is connected to one end of resistor R7 and the base of NPN transistor Q5.

[0088] The other end of resistor R7 and the emitter of NPN transistor Q5 are connected to the first rectifier connection terminal of the rectifier unit, and the collector of NPN transistor Q5 is connected to the cathode of Zener diode D7.

[0089] Figure 4 The diagram shows a fourth embodiment of the voltage clamping switch circuit. For details, please refer to the above description of the working process, which will not be repeated here.

[0090] In one embodiment of this utility model, when the current measuring device is a current sensor, the second rectifier connection terminal of the rectifier unit is connected to the power supply V+ terminal, and the first rectifier connection terminal of the rectifier unit is connected to the power supply V- terminal.

[0091] When the discharge circuit includes a discharge unit, the discharge unit is adapted to be connected to the power supply V+ terminal and the power supply V- terminal;

[0092] When the bleeder circuit includes two bleeder units, one bleeder unit is adapted to the power supply V+ terminal to form a bleeder channel to the power supply V+ terminal, and the other bleeder unit is adapted to the power supply V- terminal to form a bleeder channel to the power supply V- terminal.

[0093] It should be understood that current sensors are active devices and require an external power input to power power amplifiers and other components, thus meeting the operational requirements of active devices. The compensation current during current sensor operation is generated by the power amplifier. Figure 5 and Figure 6 PA in this diagram refers to the power amplifier. The power amplifier has two power supply terminals: V+ and V-. The V+ terminal is connected to the first terminal of the rectifier unit, and the V- terminal is connected to the second terminal. The power amplifier is also connected to an external power source via these terminals. The output terminal of the power amplifier is connected to the first terminal of the secondary winding, and the second terminal of the secondary winding serves as the current output port for the current sensor. Furthermore, the current sensor requires the cooperation of an induction winding and a controller to generate a drive signal to control the power amplifier and achieve a zero-flux state within the induction winding. The induction winding includes a small winding to the left of the T-shaped section, used to detect the magnetic flux state of the core, such as... Figure 5 and Figure 6 As shown, the specific working principle of the current sensor is consistent with existing technology, and will not be elaborated here.

[0094] Figure 5 An embodiment with a discharge unit within the discharge circuit is shown. Figure 5 The first terminal of the rectifier unit is connected to the second terminal of the rectifier unit through capacitor C1. Figure 5 The venting unit in the middle can adopt the above-mentioned Figures 1-4 Any of the circuit configurations is available; the specific configuration can be selected based on the needs. Figure 5 When the discharge unit is in discharge mode, it can discharge and limit the voltage between the power supply V+ terminal and the power supply V- terminal, thus preventing damage to the power amplifier and controller.

[0095] Figure 6 An embodiment with two discharge units within the discharge circuit is shown. Figure 6 In the circuit, the power supply V+ terminal is connected to one end of capacitor C3 and discharge unit 1, while the other end of capacitor C3 and discharge unit 1 are both grounded. The power supply V- terminal is connected to one end of capacitor C4 and discharge unit 2, while the other end of capacitor C4 and discharge unit 2 are both grounded. Figure 5 Unlike the previous embodiment, the power supply V+ terminal and the power supply V- terminal can be discharged independently to avoid the situation where there is no overvoltage between the power supply V+ terminal and the power supply V- terminal, but only the power supply V+ terminal or the power supply V- terminal is overvoltage.

[0096] When the discharge unit adopts the above-described circuit configuration, for discharge unit 1, the second terminal of the rectifier unit and the corresponding connection node of the second terminal of the rectifier unit should be grounded, such as... Figure 1In the illustrated embodiment, the source terminal of power switch Q3 should be grounded. For discharge unit 2, the connection node corresponding to the first terminal of the rectifier unit and the connection node corresponding to the first terminal of the rectifier unit should be grounded, such as... Figure 1 In the illustrated embodiment, the drain terminal of the power switch Q3 should be grounded.

[0097] It should be noted that the secondary side open circuit protection device of this utility model should be placed inside the current measuring device, such as inside the winding current transformer and the current sensor, so that continuous and uninterrupted open circuit protection can be achieved regardless of the state of the external connection, which can avoid damage to itself and also avoid personal danger caused by high voltage coupling.

Claims

1. A secondary-side open-circuit protection device suitable for current measuring devices, characterized in that, The secondary side open-circuit protection device includes: The rectifier unit is connected to the secondary winding of the current measuring device to rectify the energy coupled from the secondary winding of the current measuring device into a DC voltage. The discharge circuit includes at least one discharge unit, which is adapted and connected to the secondary winding of the rectifier unit and the current measuring device. When the secondary winding of the current measuring device is in an open circuit state, and the DC voltage generated by the rectifier unit can drive the discharge circuit to enter the discharge working state, the two ends of the secondary winding of the current measuring device are adapted to be connected to the discharge circuit so as to discharge the energy coupled by the secondary winding of the current measuring device through the discharge circuit. When the secondary winding of the current measuring device is in a non-open circuit state, the DC voltage generated by the rectifier unit cannot drive the discharge circuit to enter the discharge working state.

2. The secondary side open-circuit protection device suitable for current measuring devices according to claim 1, characterized in that: The current measuring device is a wound current transformer or a current sensor, wherein... When the current measuring device is a winding current transformer, the secondary winding of the winding current transformer forms the secondary winding of the current measuring device. When the current measuring device is a current sensor, the feedback winding inside the current sensor forms the secondary winding of the current measuring device; The two ends of the secondary winding of the current measuring device are respectively adapted to the rectifier unit and adapted to the discharge circuit through the rectifier unit.

3. The secondary side open-circuit protection device suitable for current measuring devices according to claim 2, characterized in that: When the current measuring device is a wound current transformer, the discharge unit includes a discharge voltage divider circuit and a voltage clamping switch circuit adapted and connected to the discharge voltage divider circuit, wherein, The bleed circuit is connected to the rectifier unit through a bleed voltage divider circuit, and the DC voltage generated by the rectifier unit is divided by the bleed voltage divider circuit. When the DC voltage divider drive voltage clamping switch circuit is in the conducting state, the discharge unit enters the discharge state. The voltage clamping switch circuit is adapted to connect to both ends of the secondary winding of the current measuring device, so as to discharge the energy coupled to the secondary winding of the current measuring device through the voltage clamping switch circuit.

4. The secondary side open-circuit protection device suitable for current measuring devices according to claim 3, characterized in that: The voltage clamping switch circuit includes an NPN transistor Q1 and a PNP transistor Q2, wherein, The base of NPN transistor Q1 is connected to the bleeder voltage divider circuit to receive the DC voltage divided by the bleeder voltage divider circuit; The emitter of NPN transistor Q1 is connected to the cathode of Zener diode D5, the anode of Zener diode D5 is connected to the first rectifier connection terminal of the rectifier unit, and the collector of NPN transistor Q1 is connected to one end of resistor R3 and the base of PNP transistor Q2. The other end of resistor R3 and the emitter of PNP transistor Q2 are adapted to be connected to the second rectifier connection terminal of the rectifier unit, and the collector of PNP transistor Q2 is connected to the anode of Zener diode D5.

5. The secondary side open-circuit protection device suitable for current measuring devices according to claim 4, characterized in that: The voltage clamping switch circuit also includes a resistor R6 and a power switch Q3, wherein, The collector terminal of the PNP transistor Q2 is connected to one end of the resistor R6 and the control terminal of the power switch Q3. The other end of resistor R6 and the first connection terminal of power switch Q3 are adapted to be connected to the first rectification connection terminal of the rectifier unit, and the second connection terminal of power switch Q3 is adapted to be connected to the second rectification connection terminal of the rectifier unit.

6. The secondary side open-circuit protection device suitable for current measuring devices according to claim 5, characterized in that: The voltage clamping switch circuit also includes a resistor R4 and a Zener diode D6, wherein, The base of the PNP transistor Q2 is connected to the collector of the NPN transistor Q1 through resistor R4. The control terminal of the power switch Q3 is connected to the cathode of the Zener diode D6, and the anode of the Zener diode D6 is connected to the first connection terminal of the power switch Q3.

7. The secondary side open-circuit protection device suitable for current measuring devices according to claim 5, characterized in that: The power switch Q3 is a MOSFET device, an IGBT device, or a thyristor.

8. The secondary side open-circuit protection device suitable for current measuring devices according to claim 3, characterized in that: The voltage clamping switch circuit includes an NPN transistor Q5 and a PNP transistor Q4, wherein... The base of the PNP transistor Q4 is connected to the bleeder voltage divider circuit to receive the DC voltage divided by the bleeder voltage divider circuit. The emitter of PNP transistor Q1 is connected to the anode of Zener diode D7, the cathode of Zener diode D7 is connected to the second rectifier connection terminal of the rectifier unit, and the collector of PNP transistor Q4 is connected to one end of resistor R7 and the base of NPN transistor Q5. The other end of resistor R7 and the emitter of NPN transistor Q5 are connected to the first rectifier connection terminal of the rectifier unit, and the collector of NPN transistor Q5 is connected to the cathode of Zener diode D7.

9. The secondary side open-circuit protection device suitable for current measuring devices according to claim 2, characterized in that: When the current measuring device is a current sensor, the second rectifier connection terminal of the rectifier unit is connected to the power supply V+ terminal, and the first rectifier connection terminal of the rectifier unit is connected to the power supply V- terminal. When the discharge circuit includes a discharge unit, the discharge unit is adapted to be connected to the power supply V+ terminal and the power supply V- terminal; When the bleeder circuit includes two bleeder units, one bleeder unit is adapted to the power supply V+ terminal to form a bleeder channel to the power supply V+ terminal, and the other bleeder unit is adapted to the power supply V- terminal to form a bleeder channel to the power supply V- terminal.

10. The secondary side open-circuit protection device suitable for a current measuring device according to any one of claims 1 to 9, characterized in that: The rectifier unit includes diodes D1, D2, D3, and D4, wherein... The anode of diode D1 is connected to the cathode of diode D2 and the first end of the secondary winding. The cathode of diode D4 is connected to the second end of the secondary winding and the anode of diode D3. The anodes of diode D4 and D2 are adapted to the discharge circuit, and the cathodes of diode D1 and D3 are adapted to the discharge circuit.

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