Combination switch open-phase protection circuit
The phase loss protection circuit, composed of a power transformer, rectifier bridge, phase loss detection unit, voltage transformer and microcontroller, solves the problems of installation complexity and increased cost when switching between three-phase three-wire and three-phase four-wire systems, and achieves flexible adaptation and efficient phase loss protection.
Patent Information
- Application Number
- CN202422535186.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-21
- Publication Date
- 2025-10-28
- Estimated Expiration
- 2034-10-21
AI Technical Summary
When switching between three-phase three-wire and three-phase four-wire systems, the phase loss protection circuit of the existing composite switch requires the introduction of an additional neutral wire, which leads to complicated installation, increased costs and safety hazards. Moreover, the existing connection method is not convenient to adapt to different application scenarios.
The phase loss protection circuit, composed of a power transformer, rectifier bridge, phase loss detection unit, voltage transformer, small signal amplification unit, and microcontroller, determines the phase loss status by monitoring the voltage signals of phases A and B and phases B and C. It eliminates the need for a neutral wire, simplifying the installation process and reducing costs.
It achieves flexible adaptation between three-phase three-wire and three-phase four-wire systems, simplifies the installation process, reduces wire and production costs, and improves the accuracy and reliability of phase loss protection.
Smart Images
Figure CN223487849U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of composite switch technology, and in particular to a composite switch phase loss protection circuit. Background Technology
[0002] In power quality systems, composite switches are used as switching devices to control the connection and disconnection between the power grid and reactive power compensation capacitors. Since composite switches have the characteristic of no inrush current when switching on and off, and their price is lower than that of thyristor modules, they are very suitable for applications where the switching frequency requirement is not high.
[0003] Composite switches have protective functions, such as phase loss protection and no-load prohibition of operation. Phase loss protection usually uses voltage transformer isolation sampling. The sampled small signal is processed and sent to the microcontroller. When a phase is lost, the microcontroller immediately issues a control command to disconnect the switch. If there is no phase loss protection function, the composite switch will not open when a phase loss occurs. Since the composite switch is in the closed state, a current surge will occur when the power grid is restored, which will impact the power grid and damage the relay contacts inside the composite switch.
[0004] In the prior art, such as the appendix to the specification... Figure 1-2 As shown, voltage transformers are typically connected with one phase line and the other with the neutral line N. This connection method is quite common in many cases. However, in practical applications, when the compensation cabinet uses a three-phase three-wire system instead of a three-phase four-wire system, this connection method will bring many inconveniences. In order to enable the transformer to work normally, an additional neutral line needs to be connected. This process is not only cumbersome and increases the complexity and workload of installation, but may also bring new safety hazards and increased costs due to the introduction of the neutral line. Therefore, in order to better adapt to different application scenarios, composite switches need to be improved to a form without neutral line access in order to improve their versatility and practicality.
[0005] Therefore, we propose a composite switch phase loss protection circuit. Utility Model Content
[0006] The purpose of this invention is to address the shortcomings of existing technologies. In existing technologies, current transformers are typically connected with one end to the phase line and the other end to the neutral line (N). This connection method is generally applicable in many situations. However, in practical applications, when the compensation cabinet uses a three-phase three-wire system instead of a three-phase four-wire system, this connection method will cause many inconveniences. In order to enable the current transformer to work normally, an additional neutral line needs to be connected. This process is not only cumbersome and increases the complexity and workload of installation, but may also bring new safety hazards and increased costs due to the introduction of the neutral line. Therefore, in order to better adapt to different application scenarios, composite switches need to be improved to a form without neutral line access in order to improve their versatility and practicality.
[0007] In order to achieve the above purpose, the present invention adopts the following technical solutions:
[0008] A composite switch phase loss protection circuit includes:
[0009] A power transformer is used to receive phase A voltage UA and phase B voltage UB.
[0010] The rectifier bridge is used to rectify the AC power output from the power transformer into DC power, which is then sent to the voltage regulator circuit and the phase loss detection unit.
[0011] The phase loss detection unit receives the signal output from the rectifier bridge and performs real-time monitoring of the power transformer branch connecting phases A and B.
[0012] Voltage transformers are used to accurately acquire phase B and phase C voltage signals.
[0013] The small-signal amplification unit is used to enhance the output signal strength of the voltage transformer.
[0014] The microcontroller is used to integrate two signals and determine phase loss.
[0015] As a preferred embodiment of this utility model, the output terminal of the power transformer is connected to a rectifier bridge. The rectifier bridge rectifies the AC power output from the power transformer into DC power, which is then sent to the voltage regulator circuit to provide a relatively stable DC power supply for subsequent circuits.
[0016] Another path is sent to the phase loss detection unit, which monitors the rectified DC signal to determine whether phases A and B are missing, and outputs a logic signal to the microcontroller.
[0017] As a preferred embodiment of this utility model, the phase loss detection unit receives the signal output by the rectifier bridge and performs real-time monitoring of the power transformer branch connecting phases A and B.
[0018] When phases A and B are powered normally, the power transformer outputs a specific voltage signal, which is rectified by the rectifier bridge and forms a corresponding electrical signal characteristic in the phase loss detection unit.
[0019] If a phase A or phase B is lost, the output of the power transformer will change, which will lead to abnormalities in the rectified signal. The phase loss detection unit can keenly capture these changes and accurately determine whether it is a phase A loss, a phase B loss, or neither phase A nor phase B is lost.
[0020] As a preferred embodiment of this utility model, the microcontroller receives the logic signal output from the phase loss detection unit and the AC signal output from the small signal amplification unit after sampling and amplification by the voltage transformer. By comprehensively analyzing and processing these two signals, the microcontroller can accurately determine whether there is a phase loss in phases A, B, and C.
[0021] As a preferred embodiment of this utility model, the voltage transformer is connected to phases B and C, and the AC voltage of phases B and C is sampled. Due to its specific transformation ratio, it can convert high voltage into a small signal suitable for subsequent circuit processing.
[0022] As a preferred embodiment of this utility model, the small signal amplification unit sends the amplified AC signal to the microcontroller for sampling, providing the microcontroller with a clear and accurate input signal. The microcontroller can perform sampling calculations based on this signal to determine whether phases B and C are missing. Without the amplification and processing of the signal by the small signal amplification unit, the microcontroller may not be able to accurately detect the phase loss, thus affecting the realization of the phase loss protection function.
[0023] Compared with the prior art, the beneficial effects of this utility model are:
[0024] In this invention, a power transformer is connected to phases A and B, and a voltage transformer is connected to phases B and C. The power transformer is treated as a current transformer, and a comparator is used to monitor the secondary voltage of the transformer. If phase A is missing, the secondary voltage of the power transformer is abnormal. If phase B is missing, the outputs of both the power transformer and the voltage transformer are abnormal. If phase C is missing, the output of the voltage transformer is abnormal. Therefore, there is no need to connect a neutral wire, making installation more convenient, reducing wire costs, reducing the number of current transformers, and lowering production costs. Attached Figure Description
[0025] Figure 1 A prior art comparison circuit block diagram of a composite switch phase loss protection circuit provided for this utility model;
[0026] Figure 2 A prior art circuit diagram of a composite switch phase loss protection circuit provided for this utility model;
[0027] Figure 3 A circuit block diagram of a composite switch phase loss protection circuit provided by this utility model;
[0028] Figure 4 A schematic diagram of the circuit principle of a composite switch phase loss protection circuit provided by this utility model. Detailed Implementation
[0029] The technical solutions of the present utility model will be clearly and completely described below with reference to the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.
[0030] To facilitate understanding of this utility model, a more comprehensive description of this utility model will be provided below with reference to relevant embodiments, and several embodiments of this utility model will be given. However, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of this utility model more thorough and complete.
[0031] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.
[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0033] Example
[0034] like Figure 3 As shown, this utility model provides a technical solution: a composite switch phase loss protection circuit, comprising: a power transformer for receiving phase A voltage UA and phase B voltage UB; a rectifier bridge for rectifying the AC output of the power transformer into DC power and sending it to a voltage regulator circuit and a phase loss detection unit respectively; a phase loss detection unit for receiving the signal output of the rectifier bridge and performing real-time monitoring of the power transformer branch connecting phases A and B; a voltage transformer for accurately acquiring phase B and C voltage signals; a small signal amplification unit for increasing the output signal strength of the voltage transformer; and a microcontroller for integrating the two signals and determining the phase loss.
[0035] The power transformer is connected to phases A and B, and the voltage transformer is connected to phases B and C. The power transformer is treated as a current transformer, and a comparator is used to monitor the secondary voltage of the transformer. If phase A is missing, the secondary voltage of the power transformer is abnormal. If phase B is missing, the outputs of both the power transformer and the voltage transformer are abnormal. If phase C is missing, the output of the voltage transformer is abnormal. Therefore, there is no need to connect a neutral wire, making installation more convenient, reducing wiring costs, reducing the number of current transformers, and lowering production costs.
[0036] The output of the power transformer is connected to a rectifier bridge. The rectifier bridge rectifies the AC power output from the power transformer into DC power, which is then sent to the voltage regulator circuit to provide a relatively stable DC power supply for subsequent circuits.
[0037] Another path is sent to the phase loss detection unit, which monitors the rectified DC signal to determine whether phases A and B are missing, and outputs a logic signal to the microcontroller.
[0038] The phase loss detection unit receives the signal output from the rectifier bridge and performs real-time monitoring of the power transformer branch connecting phases A and B;
[0039] When phases A and B are powered normally, the power transformer outputs a specific voltage signal, which is rectified by the rectifier bridge and forms a corresponding electrical signal characteristic in the phase loss detection unit.
[0040] If a phase A or phase B is lost, the output of the power transformer will change, which will lead to abnormalities in the rectified signal. The phase loss detection unit can keenly capture these changes and accurately determine whether it is a phase A loss, a phase B loss, or neither phase A nor phase B is lost.
[0041] The microcontroller receives the logic signal output from the phase loss detection unit and the AC signal output from the small signal amplification unit after sampling and amplification by the voltage transformer. By comprehensively analyzing and processing these two signals, the microcontroller can accurately determine whether there is a phase loss in phases A, B, and C.
[0042] The voltage transformer is connected to phases B and C and samples the AC voltage of phases B and C. Due to its specific transformation ratio, it can convert high voltage into a small signal suitable for subsequent circuit processing.
[0043] The small signal amplification unit sends the amplified AC signal to the microcontroller for sampling, providing the microcontroller with a clear and accurate input signal. The microcontroller can perform sampling calculations based on this signal to determine whether phases B and C are missing. Without the amplification and processing of the signal by the small signal amplification unit, the microcontroller may not be able to accurately detect the phase loss, thus affecting the realization of the phase loss protection function.
[0044] Its specific implementation principle is as shown in the attached instruction manual. Figure 4 As shown:
[0045] Phase A voltage UA is connected to pin 1 of transformer T1, and phase B voltage UB is connected to pin 3 of transformer T1. Pin 2 of transformer T1 is connected to pin 2 of rectifier bridge DB1, and pin 4 of transformer T1 is connected to pin 1 of rectifier bridge DB1.
[0046] Pin 3 of rectifier bridge DB1 is connected to the voltage regulator circuit and the cathode of Zener diode Z1. The anode of diode Z1 is connected to one end of resistor R82. The other end of resistor R82 is connected to the positive terminal of capacitor C9, one end of resistor R84, one end of resistor R83, and pin 7 of integrated circuit U4. The negative terminal of capacitor C9, the other end of resistor R84, and the other end of resistor R83 are all connected to ground.
[0047] The power supply VCC is connected to one end of resistor R85 and one end of resistor R86. The other end of resistor R85 is connected to the other end of resistor R86. One end of resistor R87 is connected to pin 6 of integrated circuit U4. The other end of resistor R87 is connected to ground.
[0048] Pin 1 of integrated circuit U4 is connected to the cathode of diode D7. The anode of diode D7 is connected to the microcontroller and one end of resistor R88. The other end of resistor R88 is connected to the power supply VCC. Pin 3 of integrated circuit U4 is connected to the power supply VCC, and pin 12 of integrated circuit U4 is connected to ground.
[0049] Phase B voltage UB is connected to pin 3 of voltage transformer TVA via resistor R17, and phase C voltage UC is connected to pin 4 of voltage transformer TVA via resistor R18. Pin 1 of voltage transformer TVA is connected to one end of resistor R19, one end of capacitor C26, and pin 5 of integrated circuit U5. Pin 2 of voltage transformer TVA is connected to the other end of resistor R19, the other end of capacitor C26, one end of resistor R20, one end of capacitor C29, pin 1 and pin 2 of integrated circuit U5, and the other end of capacitor C29 is connected to ground.
[0050] The other end of resistor R20 is connected to pin 6 of integrated circuit U5 and one end of resistor R21. The other end of resistor R21 is connected to pin 7 of integrated circuit U5 and one end of resistor R22. The other end of resistor R22 is connected to the microcontroller and capacitor C27. The other end of capacitor C27 is connected to ground. Power supply VCC is connected to one end of resistor R8. The other end of resistor R8 is connected to pin 3 of integrated circuit U5, one end of resistor R9, and one end of capacitor C28. The other ends of resistor R9 and capacitor C28 are connected to ground. Pin 8 of integrated circuit U5 is connected to power supply VCC, and pin 4 of integrated circuit U5 is connected to ground.
[0051] Please continue to refer to the instruction manual appendix. Figure 4 Integrated circuit U4 is LM339, and integrated circuit U5 is LM258;
[0052] When phases A, B, and C are operating normally, the power transformer branch is as follows:
[0053] The potential of pin 7 of integrated circuit U4 is higher than that of pin 6. Pin 1 of integrated circuit U4 is at a high level. The microcontroller detects and determines that there is no phase loss in phases A and B.
[0054] Voltage transformer branch:
[0055] The output signal amplitude at pin 7 of integrated circuit U5 is within the normal range, and the microcontroller's sampling and calculation results indicate that phases B and C are not missing. Therefore, the microcontroller does not operate.
[0056] When phase A suddenly loses a phase during operation, the power transformer branch:
[0057] When the potential of pin 7 of integrated circuit U4 is lower than that of pin 6, pin 1 of integrated circuit U4 flips to a low level. The microcontroller detects the low level and determines that there is a phase loss in phases A and B. Because the capacitance of capacitor C9 is small, the potential of pin 7 of integrated circuit U4 drops rapidly. However, the capacitance of the filter capacitor in the voltage regulator circuit is large, so the microcontroller can issue a cut-off command in time before the power is lost to disconnect the relay.
[0058] When phase B suddenly loses a phase during operation, the power transformer branch:
[0059] When the potential of pin 7 of integrated circuit U4 is lower than that of pin 6, pin 1 of integrated circuit U4 flips to a low level. The microcontroller detects the low level and determines that there is a phase loss in phases A and B.
[0060] Voltage transformer branch: The output signal amplitude of pin 7 of integrated circuit U5 is too low. The microcontroller's sampling and calculation results indicate that phases B and C are missing. Since both detection paths are abnormal, the microcontroller quickly issues a disconnect command to disconnect the relay.
[0061] When phase C suddenly loses a phase during operation, the power transformer branch:
[0062] The potential of pin 7 of integrated circuit U4 is higher than that of pin 6. Pin 1 of integrated circuit U4 is at a high level. The microcontroller detects and determines that phases A and B are not missing. Voltage transformer branch: The output signal amplitude of pin 7 of integrated circuit U5 is low. The microcontroller's sampling and calculation results determine that phases B and C are missing.
[0063] At this point, the microcontroller issues a cut-off command to disconnect the relay.
[0064] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A composite switch phase loss protection circuit, characterized in that, include: A power transformer is used to receive phase A voltage UA and phase B voltage UB. The rectifier bridge is used to rectify the AC power output from the power transformer into DC power, which is then sent to the voltage regulator circuit and the phase loss detection unit. The phase loss detection unit receives the signal output from the rectifier bridge and performs real-time monitoring of the power transformer branch connecting phases A and B. Voltage transformers are used to accurately acquire phase B and phase C voltage signals. The small-signal amplification unit is used to enhance the output signal strength of the voltage transformer. The microcontroller is used to integrate two signals and determine phase loss.
2. The composite switch phase loss protection circuit according to claim 1, characterized in that: The output of the power transformer is connected to a rectifier bridge. The rectifier bridge rectifies the AC power output from the power transformer into DC power, which is then sent to the voltage regulator circuit to provide a relatively stable DC power supply for subsequent circuits. Another path is sent to the phase loss detection unit, which monitors the rectified DC signal to determine whether phases A and B are missing, and outputs a logic signal to the microcontroller.
3. The composite switch phase loss protection circuit according to claim 1, characterized in that: The phase loss detection unit receives the signal output from the rectifier bridge and performs real-time monitoring of the power transformer branch connecting phases A and B; When phases A and B are powered normally, the power transformer outputs a specific voltage signal, which is rectified by the rectifier bridge and forms a corresponding electrical signal characteristic in the phase loss detection unit. If a phase A or phase B is lost, the output of the power transformer will change, which will lead to abnormalities in the rectified signal. The phase loss detection unit can keenly capture these changes and accurately determine whether it is a phase A loss, a phase B loss, or neither phase A nor phase B is lost.
4. The composite switch phase loss protection circuit according to claim 1, characterized in that: The microcontroller receives the logic signal output from the phase loss detection unit and the AC signal output from the small signal amplification unit after sampling and amplification by the voltage transformer. By comprehensively analyzing and processing these two signals, the microcontroller can accurately determine whether there is a phase loss in phases A, B, and C.
5. A composite switch phase loss protection circuit according to claim 1, characterized in that: The voltage transformer is connected to phases B and C and samples the AC voltage of phases B and C. Due to its specific transformation ratio, it can convert high voltage into a small signal suitable for subsequent circuit processing.
6. The composite switch phase loss protection circuit according to claim 1, characterized in that: The small signal amplification unit sends the amplified AC signal to the microcontroller for sampling, providing the microcontroller with a clear and accurate input signal. The microcontroller can perform sampling calculations based on this signal to determine whether phases B and C are missing. Without the amplification and processing of the signal by the small signal amplification unit, the microcontroller may not be able to accurately detect the phase loss, thus affecting the realization of the phase loss protection function.