Mutual inductor open circuit prevention circuit for primary and secondary split type current protection equipment

Abstract

The utility model discloses a mutual inductor open circuit prevention circuit for primary and secondary split type current protection equipment, which is characterized by comprising a mutual inductor T1, a mutual inductor forward output open circuit protection circuit and a mutual inductor reverse output open circuit protection circuit, the primary side of the mutual inductor T1 is electrically connected with the input end, the secondary side of the mutual inductor T1 is electrically connected with the mutual inductor forward output open circuit protection circuit and the mutual inductor reverse output open circuit protection circuit, and the mutual inductor forward output open circuit protection circuit is electrically connected with output ends of the mutual inductor reverse output open circuit protection circuit. According to the utility model, the technical problems of circuit damage and personal danger caused by open circuit of the body mutual inductor when the existing primary and secondary split type current protection equipment is replaced in an electrified manner, and low control precision and timeliness of the protection circuit are solved.

Description

Technical Field

[0001] This utility model relates to the field of power distribution technology, and in particular to an open-circuit protection circuit for current transformers used in primary and secondary split-type current protection equipment. Background Technology

[0002] The primary and secondary split-type current protection equipment includes devices such as the new type of intelligent low-voltage circuit breaker with a primary and secondary split structure as defined by the State Grid. This type of low-voltage intelligent circuit breaker integrates the primary unit (mainly consisting of mechanical, electrical, and necessary sensing components) and the secondary unit (mainly consisting of control, protection, and communication electronic circuits) into two separate housings. The primary and secondary units are assembled using a modular method, and the secondary unit can be independently plugged in and replaced. The communication module supports hot-swapping. When the secondary unit of the aforementioned low-voltage intelligent circuit breaker is replaced while energized, the current transformer in the main body will open-circuit, and the open-circuit voltage will reach over 200V. This high voltage can damage the secondary unit circuitry and may even pose a risk of personal injury to maintenance personnel. Currently, many current transformer open-circuit protection designs primarily employ structural short-circuit and electronic circuit control. The structural short-circuit method involves short-circuiting the secondary output section of the transformer with metal springs when the secondary component detaches from the structural springs or other mechanisms. This method is simple but slow to close, suffers from brief open circuits, and occupies significant space. The current mainstream circuit control principle uses thyristors to short-circuit the open circuit for protection. However, the thyristors can only close the open-circuit protection at zero crossing, resulting in low timing accuracy. Capacitors and Zener diodes are generally used to generate drive signals and start-up control thresholds. Capacitors have low accuracy and vary with environmental conditions, leading to low voltage accuracy in the open-circuit protection circuit's start-up control. Furthermore, adding capacitors to the circuit increases parasitic capacitance, affecting the measurement accuracy of the subsequent sampling circuit of the current transformer.

[0003] Patent application CN202120077281.6 discloses an open-circuit protection circuit for a current transformer, including the secondary coil of the current transformer and a bidirectional thyristor. The secondary coil of the current transformer is used to connect the T1 and G terminals of the bidirectional thyristor to trigger the circuit. The T1 and T2 terminals of the bidirectional thyristor are used to short-circuit the secondary coil of the current transformer. A capacitor is connected between the G terminal and the T2 terminal of the bidirectional thyristor. This solution draws power from the capacitor, which is related to the material properties of the capacitor itself and has a large degree of variability. This can lead to low control accuracy or voltage instability. Furthermore, the thyristor uses a zero-crossing dielectric, resulting in low control accuracy and failing to meet the requirements of high precision and high timeliness. Therefore, there is an urgent need to propose an open-circuit protection circuit for the current transformer in a separate primary and secondary current protection device to solve the technical problems of circuit damage and personal danger caused by the open circuit of the main current transformer during live replacement of existing separate primary and secondary current protection devices, as well as the low control accuracy and timeliness of the protection circuit. Utility Model Content

[0004] The main purpose of this utility model is to propose an open-circuit protection circuit for the current transformer in a primary and secondary split-type current protection device. This aims to solve the technical problems of circuit damage and personal danger caused by the open circuit of the main current transformer when the primary and secondary split-type current protection device is replaced under energized conditions, as well as the low control accuracy and timeliness of the protection circuit.

[0005] To achieve the above objectives, this utility model provides a transformer open-circuit protection circuit for a primary and secondary split-type current protection device. The transformer open-circuit protection circuit includes: a transformer T1, a forward output open-circuit protection circuit, and a reverse output open-circuit protection circuit. The primary side of the transformer T1 is electrically connected to its input terminal, and the secondary side of the transformer T1 is electrically connected to both the forward output open-circuit protection circuit and the reverse output open-circuit protection circuit. The forward output open-circuit protection circuit is electrically connected to each output terminal of the reverse output open-circuit protection circuit.

[0006] In one preferred embodiment, the forward output open-circuit protection circuit of the current transformer includes a diode D4, a MOSFET Q1, an adjustable voltage regulator D2, a resistor R1, and a forward output voltage divider circuit of the current transformer. The anode of the diode D4 is connected to the drain of the MOSFET Q1, the reverse output open-circuit protection circuit of the current transformer, pin 2 of the adjustable voltage regulator D2, and the forward output voltage divider circuit of the current transformer. The cathode of the diode D4 is connected to the current transformer and the reverse output open-circuit protection circuit of the current transformer. The source of the MOSFET Q1 is connected to the reverse output open-circuit protection circuit of the current transformer, the resistor R1, the forward output voltage divider circuit of the current transformer, and the output terminal. The gate of the MOSFET Q1 is connected to the resistor R1 and pin 1 of the adjustable voltage regulator D2. Pin 3 of the adjustable voltage regulator D2 is connected to the forward output voltage divider circuit of the current transformer.

[0007] In one preferred embodiment, the forward output voltage divider circuit of the current transformer includes resistors R2 and R3; one end of resistor R2 is connected to the source of MOSFET Q1, the other end of resistor R2 is connected to pin 3 of adjustable voltage regulator D2 and resistor R3 respectively, and the other end of resistor R3 is connected to the anode of diode D4.

[0008] In one preferred embodiment, the MOS transistor Q1 is a P-channel MOS transistor.

[0009] In one preferred embodiment, the forward output voltage of the current transformer forward output open-circuit protection circuit is:

[0010]

[0011] Among them, V outpV is the positive output voltage of the current transformer. ref1 The reference voltage for the adjustable regulated power supply D2 is given by R2 and R3, respectively. df1 This is the forward voltage drop of diode D4.

[0012] In one preferred embodiment, the reverse output open-circuit protection circuit of the current transformer includes a diode D1, a MOSFET Q2, an adjustable voltage regulator D3, a resistor R5, and a reverse output voltage divider circuit of the current transformer. The anode of the diode D1 is connected to the forward output open-circuit protection circuit of the current transformer, the drain of the MOSFET Q2, pin 2 of the adjustable voltage regulator D3, and the reverse output voltage divider circuit of the current transformer. The cathode of the diode D1 is connected to the current transformer and the forward output open-circuit protection circuit of the current transformer. The source of the MOSFET Q2 is connected to the forward output open-circuit protection circuit of the current transformer, the resistor R5, the reverse output voltage divider circuit of the current transformer, and the output terminal. The gate of the MOSFET Q2 is connected to pin 1 of the adjustable voltage regulator D3 and the resistor R5. Pin 3 of the adjustable voltage regulator D3 is connected to the reverse output voltage divider circuit of the current transformer.

[0013] In one preferred embodiment, the reverse output voltage divider circuit of the current transformer includes resistors R4 and R6; one end of resistor R4 is connected to the anode of diode D1, the other end of resistor R4 is connected to pin 3 of adjustable voltage regulator D3 and resistor R6 respectively, and the other end of resistor R6 is connected to the source of MOSFET Q2.

[0014] In one preferred embodiment, the MOS transistor Q2 is a P-channel MOS transistor.

[0015] In one preferred embodiment, the reverse output voltage of the current transformer reverse output open-circuit protection circuit is:

[0016]

[0017] Among them, V outq V is the reverse output voltage of the current transformer. ref2 The reference voltage for the adjustable voltage regulator D3 is given by R4 and R5, respectively. df2 This is the forward voltage drop of diode D1.

[0018] In the above-described technical solution of this utility model, the transformer open-circuit protection circuit for a primary and secondary split-type current protection device includes: a transformer T1, a forward output open-circuit protection circuit for the transformer, and a reverse output open-circuit protection circuit for the transformer. The primary side of the transformer T1 is electrically connected to the input terminal, and the secondary side of the transformer T1 is electrically connected to both the forward output open-circuit protection circuit and the reverse output open-circuit protection circuit. The forward output open-circuit protection circuit is electrically connected to each output terminal of the reverse output open-circuit protection circuit. This utility model solves the technical problems of existing primary and secondary split-type current protection devices where an open circuit in the main transformer during live replacement leads to circuit damage and personal injury, as well as low control accuracy and timeliness of the protection circuit.

[0019] In this invention, dual MOSFETs are used as short-circuit switches, which have a fast response speed and are not affected by zero crossing, resulting in high control accuracy. A high-precision adjustable voltage regulator is used for feedback control, which provides fast open-circuit protection. The open-circuit clamping voltage of the current transformer is set by configuring forward and reverse output voltage divider circuits, which ensures high voltage setting accuracy. The entire circuit does not require filtering or energy storage capacitors, and the measurement accuracy is not affected by the addition of parasitic capacitance. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 This is a first schematic diagram of an open-circuit protection circuit for a primary and secondary split-type current protection device according to an embodiment of the present invention.

[0022] Figure 2 This is a second schematic diagram of an open-circuit protection circuit for a primary and secondary split-type current protection device according to an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram of the output waveform of the current transformer without the current transformer anti-open circuit circuit in an embodiment of this utility model;

[0024] Figure 4 A schematic diagram of the output waveform of the current transformer with an anti-open-circuit circuit in an embodiment of this utility model.

[0025] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Furthermore, the technical solutions of the various embodiments of this utility model can be combined with each other, but only if they are based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the protection scope claimed by this utility model.

[0028] See Figures 1-4 According to one aspect of this utility model, this utility model provides an open-circuit protection circuit for a primary and secondary split-type current protection device for a current transformer. The open-circuit protection circuit for the current transformer for the primary and secondary split-type current protection device includes: a current transformer T1, a forward output open-circuit protection circuit for the current transformer, and a reverse output open-circuit protection circuit for the current transformer. The primary side of the current transformer T1 is electrically connected to its input terminal, and the secondary side of the current transformer T1 is electrically connected to both the forward output open-circuit protection circuit and the reverse output open-circuit protection circuit. The forward output open-circuit protection circuit is electrically connected to each output terminal of the reverse output open-circuit protection circuit.

[0029] Specifically, in this embodiment, the current transformer T1 is a current transformer. The input terminal connected to the primary side of the current transformer T1 is Iin, which represents the input current signal, and the output terminal is Iout, which represents the output secondary signal of the current transformer.

[0030] Specifically, in this embodiment, the transformer forward output open-circuit protection circuit includes a diode D4, a MOSFET Q1, an adjustable voltage regulator D2, a resistor R1, and a transformer forward output voltage divider circuit. The anode of the diode D4 is connected to the drain of the MOSFET Q1, the transformer reverse output open-circuit protection circuit, pin 2 of the adjustable voltage regulator D2, and the transformer forward output voltage divider circuit. The cathode of the diode D4 is connected to the transformer and the transformer reverse output open-circuit protection circuit. The source of the MOSFET Q1 is connected to the transformer reverse output open-circuit protection circuit, the resistor R1, the transformer forward output voltage divider circuit, and the output terminal. The gate of the MOSFET Q1 is connected to the resistor R1 and pin 1 of the adjustable voltage regulator D2. Pin 3 of the adjustable voltage regulator D2 is connected to the transformer forward output voltage divider circuit.

[0031] Specifically, in this embodiment, the forward output voltage divider circuit of the current transformer includes resistors R2 and R3; one end of resistor R2 is connected to the source of MOSFET Q1, and the other end of resistor R2 is connected to pin 3 of adjustable voltage regulator D2 and resistor R3, respectively; the other end of resistor R3 is connected to the anode of diode D4; the reverse output voltage divider circuit of the current transformer includes resistors R4 and R6; one end of resistor R4 is connected to the anode of diode D1, and the other end of resistor R4 is connected to pin 3 of adjustable voltage regulator D3 and resistor R6, respectively. The other end of resistor R6 is connected to the source of MOSFET Q2. The open-circuit output voltage of the current transformer is set by adjusting the resistance values ​​of resistors R2, R3, R4, and R6. The resistance value of resistor R2 is equal to the resistance value of resistor R4, and the resistance value of resistor R3 is equal to the resistance value of resistor R6. The forward and reverse clamping voltages of the forward and reverse output voltage divider circuits of the current transformer are the same. The open-circuit clamping voltage of the current transformer is set by setting the forward and reverse output voltage divider circuits of the current transformer, resulting in high voltage setting accuracy.

[0032] Specifically, in this embodiment, resistors R2 and R3 are connected to the reference terminal of the adjustable voltage regulator D2. When the voltage divided by resistors R2 and R3 is higher than the reference voltage V of the adjustable voltage regulator D2... ref1 When the voltage is low, the A and K terminals of the adjustable voltage regulator D2 are turned on, which means pins 2 and 1 of the adjustable voltage regulator D2 are turned on, and MOSFET Q1 is turned on; when the voltage divided by resistors R2 and R3 is lower than the reference voltage V of the adjustable voltage regulator D2... ref1 When the voltage regulator D2 is in operation, its A and K terminals are cut off, meaning pins 2 and 1 of the adjustable voltage regulator D2 are also cut off, thus turning off the MOSFET Q1. The forward output voltage of the current transformer forward output open-circuit protection circuit is:

[0033]

[0034] Among them, V outp V is the positive output voltage of the current transformer. ref1 The reference voltage for the adjustable regulated power supply D2 is given by R2 and R3, respectively. df1 This is the forward voltage drop of diode D4.

[0035] Specifically, in this embodiment, the transformer reverse output open-circuit protection circuit includes a diode D1, a MOSFET Q2, an adjustable voltage regulator D3, a resistor R5, and a transformer reverse output voltage divider circuit. The anode of the diode D1 is connected to the transformer forward output open-circuit protection circuit, the drain of the MOSFET Q2, pin 2 of the adjustable voltage regulator D3, and the transformer reverse output voltage divider circuit. The cathode of the diode D1 is connected to the transformer and the transformer forward output open-circuit protection circuit. The source of the MOSFET Q2 is connected to the transformer forward output open-circuit protection circuit, the resistor R5, the transformer reverse output voltage divider circuit, and the output terminal. The gate of the MOSFET Q2 is connected to pin 1 of the adjustable voltage regulator D3 and the resistor R5. Pin 3 of the adjustable voltage regulator D3 is connected to the transformer reverse output voltage divider circuit.

[0036] Specifically, in this embodiment, resistors R4 and R6 are connected to the reference terminal of the adjustable voltage regulator D3. When the voltage divided by resistors R4 and R6 is higher than the reference voltage V of the adjustable voltage regulator D3... ref2 When the voltage is low, the A and K terminals of the adjustable voltage regulator D3 are turned on, which means pins 2 and 1 of the adjustable voltage regulator D3 are turned on, and MOSFET Q2 is turned on; when the voltage divided by resistors R4 and R6 is lower than the reference voltage V of the adjustable voltage regulator D3... ref2 When the voltage is turned off, the A and K terminals of the adjustable voltage regulator D3 are cut off, which also means the 2 and 1 pins of the adjustable voltage regulator D3 are cut off, and the MOSFET Q2 is cut off; the reverse output voltage of the current transformer reverse output open circuit protection circuit is:

[0037]

[0038] Among them, V outq V is the reverse output voltage of the current transformer. ref2 The reference voltage for the adjustable voltage regulator D3 is given by R4 and R5, respectively. df2 This is the forward voltage drop of diode D1.

[0039] Specifically, in this embodiment, MOSFET Q2 is a P-channel MOSFET, MOSFET Q1 is a P-channel MOSFET, MOSFET Q1 and diode D4 form a forward open-circuit current short-circuit path, and MOSFET Q2 and diode D1 form a reverse open-circuit current short-circuit path. Since the current carrying capacity of the body diodes of MOSFETs Q1 and Q2 is limited, diodes D1 and D4 are connected in parallel to increase the current carrying capacity.

[0040] Specifically, in this embodiment, see Appendix Figure 3 For a schematic diagram of the output waveform of a current transformer without an open-circuit protection circuit, please refer to the appendix. Figure 4The diagram shows the output waveform of the current transformer anti-open-circuit circuit as described in this invention. The voltage output by the current transformer is: V outq ≤V out ≤V outp When the secondary unit is detached from the main body, the circuit of this invention limits the output voltage of the current transformer to below a safe voltage, avoiding damage to the secondary unit circuit caused by high voltage and personal injury to maintenance personnel. This invention uses a simple electronic circuit, is small in size, and uses dual MOS transistors as short-circuit switches, resulting in fast response speed and no impact from zero crossings, thus achieving high control accuracy. It uses a high-precision adjustable voltage regulator as feedback control, providing fast open-circuit protection. Furthermore, it sets the open-circuit clamping voltage of the current transformer by setting forward and reverse output voltage divider circuits, ensuring high voltage setting accuracy. Notably, the current transformer open-circuit protection circuit of this invention does not require filtering or energy storage capacitors, thus avoiding the increase of parasitic capacitance that could affect measurement accuracy.

[0041] The above are merely preferred embodiments of this utility model and do not limit the patent scope of this utility model. Any equivalent structural transformations made based on the inventive concept of this utility model and the contents of this utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this utility model.

Claims

1. An open circuit prevention circuit for a transformer of a secondary split type current protection device, characterized by, The transformer T1, the transformer forward output open circuit protection circuit and the transformer reverse output open circuit protection circuit; the primary side of the transformer T1 is electrically connected with the input end, the secondary side of the transformer T1 is electrically connected with the transformer forward output open circuit protection circuit and the transformer reverse output open circuit protection circuit respectively, and the transformer forward output open circuit protection circuit is electrically connected with the transformer reverse output open circuit protection circuit. The transformer forward output open circuit protection circuit comprises a diode D4, a MOS tube Q1, an adjustable voltage stabilizing source D2, a resistor R1 and a transformer forward output voltage dividing circuit; the anode of the diode D4 is connected with the drain of the MOS tube Q1, the transformer reverse output open circuit protection circuit, the 2th pin of the adjustable voltage stabilizing source D2 and the transformer forward output voltage dividing circuit respectively, the cathode of the diode D4 is connected with the transformer and the transformer reverse output open circuit protection circuit respectively, the source of the MOS tube Q1 is connected with the transformer reverse output open circuit protection circuit, the resistor R1, the transformer forward output voltage dividing circuit and the output end respectively, the gate of the MOS tube Q1 is connected with the resistor R1 and the 1th pin of the adjustable voltage stabilizing source D2 respectively, and the 3th pin of the adjustable voltage stabilizing source is connected with the transformer forward output voltage dividing circuit.

2. An open circuit prevention circuit for a transformer of a secondary split type current protection device according to claim 1, characterized in that, The transformer forward output voltage dividing circuit comprises a resistor R2 and a resistor R3; one end of the resistor R2 is connected with the source of the MOS tube Q1, the other end of the resistor R2 is connected with the 3th pin of the adjustable voltage stabilizing source D2 and the resistor R3 respectively, and the other end of the resistor R3 is connected with the anode of the diode D4.

3. An open circuit prevention circuit for a transformer of a secondary split current protection device according to claim 2, characterized in that, The MOS tube Q1 is a P-channel MOS tube.

4. The open circuit prevention circuit for a transformer of a two-part current protection device according to claim 2, characterized in that, The forward output voltage of the transformer forward output open circuit protection circuit is:

5. The open circuit prevention circuit for a transformer of a two-part current protection device according to claim 3, characterized in that, The transformer reverse output open circuit protection circuit comprises a diode D1, a MOS tube Q2, an adjustable voltage stabilizing source D3, a resistor R5 and a transformer reverse output voltage dividing circuit; the anode of the diode D1 is connected with the transformer forward output open circuit protection circuit, the drain of the MOS tube Q2, the 2th pin of the adjustable voltage stabilizing source D3 and the transformer reverse output voltage dividing circuit respectively, the cathode of the diode D1 is connected with the transformer and the transformer forward output open circuit protection circuit respectively, the source of the MOS tube Q2 is connected with the transformer forward output open circuit protection circuit, the resistor R5, the transformer reverse output voltage dividing circuit and the output end respectively, the gate of the MOS tube Q2 is connected with the 1th pin of the adjustable voltage stabilizing source D3 and the resistor R5 respectively, and the 3th pin of the adjustable voltage stabilizing source D3 is connected with the transformer reverse output voltage dividing circuit. Wherein, V outp is the forward output voltage of the transformer, V ref1 is the reference voltage of the adjustable voltage regulator D2, R2 and R3 are the resistance values of the resistor R2 and the resistor R3, respectively, V df1 is the forward conduction voltage drop of the diode D4.

6. A circuit for preventing opening of a transformer for a primary and secondary split current protection device according to any of claims 1-5, characterized in that, The transformer reverse output voltage dividing circuit comprises a resistor R4 and a resistor R6; one end of the resistor R4 is connected with the anode of the diode D1, the other end of the resistor R4 is connected with the 3th pin of the adjustable voltage stabilizing source D3 and the resistor R6 respectively, and the other end of the resistor R6 is connected with the source of the MOS tube Q2.

7. An open circuit prevention circuit for a transformer of a secondary split current protection device according to claim 6, characterized in that, The MOS tube Q2 is a P-channel MOS tube.

8. An open circuit prevention circuit for a transformer of a secondary split current protection device according to claim 6, wherein The reverse output voltage of the transformer reverse output open circuit protection circuit is:

9. An open circuit prevention circuit for a transformer of a secondary split current protection device according to claim 7, wherein ​ Wherein, V outq is the reverse output voltage of the transformer, V ref2 is the reference voltage of the adjustable voltage regulator D3, R4 and R5 are the resistance values of the resistor R4 and the resistor R5, respectively, V df2 is the forward conduction voltage drop of the diode D1.

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