Insulation detection device for single-phase alternating current IT system

Abstract

The utility model discloses a single-phase AC IT system insulation detection device, comprising a power supply, and a voltage division circuit, a fault determination circuit, a signal isolation circuit and an MCU module which are powered by the power supply, the voltage division circuit is connected with a live line and a zero line of an output end of an IT system so as to form partial voltage with a ground insulation impedance of the IT system, and the MCU module is connected with the fault determination circuit and the signal isolation circuit. The output of the voltage division circuit is connected with the input of the signal isolation circuit through the fault judgment circuit, and the signal isolation circuit outputs an isolation signal to the MCU module. The AC insulation detection circuit does not need an independent signal source, is simple in circuit structure and low in cost, and can detect whether AC insulation is abnormal on line.

Description

Technical Field

[0001] This utility model relates to an insulation monitoring device for circuit systems, and in particular to an insulation detection device for a single-phase AC IT system. Background Technology

[0002] When supplying power to loads such as mines, field medical vehicles, and ships, high reliability and safety of the power supply are required. Using an IT system for power supply is a good choice. When an IT system fails, the fault current is small, and the metal casing of the electrical equipment will not generate a dangerous contact voltage. Therefore, the power supply can be left on, allowing the electrical equipment to continue operating. However, it is necessary to monitor the insulation performance online and notify the user through an alarm device, so as to promptly check and eliminate the fault.

[0003] Currently, online insulation testing of IT systems widely employs signal injection-based detection methods. This involves acquiring the voltage across a sampling resistor or the current on the IT system bus during signal injection. When the IT system experiences a short circuit to ground or insulation degradation, its insulation impedance to ground decreases, and the fault characteristic quantities in the voltage across the sampling resistor or the current on the IT system bus increase dramatically during signal injection, allowing for diagnostics. However, signal injection-based insulation testing of IT systems requires a dedicated signal source, and the system is complex.

[0004] Currently, there is also a demand for online insulation testing of IT systems in engineering vehicles. Utility Model Content

[0005] This invention addresses the technical problems existing in the prior art by providing an insulation testing device for a single-phase AC IT system.

[0006] The technical solution adopted by this utility model to solve its technical problem is: a single-phase AC IT system insulation detection device, including a power supply, and a voltage divider circuit, a fault judgment circuit, a signal isolation circuit and an MCU module powered by the power supply. The voltage divider circuit is connected to the live wire and the neutral wire of the IT system output terminal to form a voltage divider with the IT system's insulation impedance to ground. The output of the voltage divider circuit is connected to the input of the signal isolation circuit through the fault judgment circuit. The signal isolation circuit outputs an isolation signal to the MCU module.

[0007] Furthermore, the voltage divider circuit includes resistors R1, R2, R3, and R5. One end of resistor R2 is connected to the live wire of the IT system, and one end of resistor R5 is connected to the neutral wire of the IT system. The other ends of resistors R2, R5, and R1 are connected together to form the output of the voltage divider circuit. The other end of resistor R1 is connected to the power supply. Resistor R3 is connected between the live wire and the neutral wire of the IT system.

[0008] Furthermore, the voltage divider circuit also includes a voltage stabilizing capacitor C1, one end of which is connected to the output of the voltage divider circuit, and the other end is connected to ground.

[0009] Furthermore, it also includes a fault latching circuit, which is connected to the voltage divider circuit and the fault detection circuit to achieve fault latching.

[0010] Furthermore, the fault diagnosis circuit includes switching transistors Q1 and Q2, resistors R9 and R11. The first terminal of switching transistor Q1 is connected to the output of the voltage divider circuit, the third terminal of switching transistor Q1 is connected to the first terminal of switching transistor Q2 through resistor R9, the second terminal of switching transistor Q1 is connected to the power supply, the third terminal of switching transistor Q2 is connected to the input of the signal isolation circuit, and the second terminal of switching transistor Q2 is grounded. One end of resistor R9 is connected to the first terminal of switching transistor Q2, and the other end of resistor R9 is grounded.

[0011] Furthermore, the switching transistor Q1 is a PNP transistor, the switching transistor Q2 is an NPN transistor, the first terminal is the base, the third terminal is the collector, and the second terminal is the emitter.

[0012] Furthermore, it also includes a fault latching circuit, which includes a switch Q3, resistors R6, R8, and R10. The third terminal of the switch Q3 is connected to the output of the voltage divider circuit through resistor R6, the second terminal of the switch Q3 is grounded, the first terminal of the switch Q3 is connected to one end of resistor R8 and one end of resistor R10, the other end of resistor R8 is connected to the third terminal of the switch Q1, and the other end of resistor R10 is grounded. The fault latching circuit also includes a capacitor C2, one end of which is connected to the first terminal of the switch Q3, and the other end of the capacitor C2 is grounded.

[0013] Furthermore, the switching transistor Q3 is an NPN transistor, with its first terminal being the base, its third terminal being the collector, and its second terminal being the emitter.

[0014] Furthermore, the signal isolation circuit includes an optocoupler, resistors R4 and R7. The primary terminal 1 of the optocoupler constitutes the input of the signal isolation circuit and is connected to the power supply through resistor R4. The primary terminal 2 of the optocoupler is grounded. The secondary terminal 4 of the optocoupler is connected to the isolation signal pin of the MCU module and is connected to the VDD pin of the MCU module through resistor R7. The secondary terminal 3 of the optocoupler is connected to the VSS pin of the MCU module.

[0015] Furthermore, the MCU module includes an MCU chip and a capacitor C3. The VDD pin of the MCU chip is connected to the power supply, one end of the capacitor C3 is connected to the VDD pin of the MCU chip, and the other end of the capacitor C3 is connected to the VSS pin of the MCU chip.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. This utility model uses the power supply, voltage divider circuit, fault judgment circuit, signal isolation circuit and MCU module to form an IT system insulation detection device. It does not require an independent signal source, and the circuit structure is simple and low in cost. It can detect whether AC insulation is abnormal online.

[0018] 2. This utility model further sets up a fault latching circuit between the voltage divider circuit and the fault judgment circuit, which can realize fault latching and avoid the false impression of normal AC insulation due to external environmental factors after the AC insulation impedance of the IT system is abnormal, thereby avoiding the MCU module from making misjudgments.

[0019] 3. This utility model can be used with an inverter to shut down the inverter's AC output, effectively protecting electrical safety.

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments; however, the single-phase AC IT system insulation detection device of the present invention is not limited to the embodiments. Attached Figure Description

[0021] Figure 1 This is a circuit diagram of the voltage divider circuit, fault diagnosis circuit, signal isolation circuit, etc. of this utility model in the connected state;

[0022] Figure 2 This is the circuit diagram of the MCU module of this utility model;

[0023] In the diagram, 1 is the voltage divider circuit, 2 is the fault diagnosis circuit, 3 is the signal isolation circuit, 4 is the MCU module, and 5 is the fault latch circuit. Detailed Implementation

[0024] Please see Figure 1 , Figure 2As shown, this utility model discloses a single-phase AC IT system insulation detection device, including a power supply, and a voltage divider circuit 1, a fault judgment circuit 2, a signal isolation circuit 3, and an MCU module 4 powered by the power supply. The voltage divider circuit 1, the switching circuit, and the signal isolation circuit 3 are connected sequentially. The voltage divider circuit 1 is connected to the live wire and the neutral wire of the IT system output terminal to form a voltage divider with the ground insulation impedance RL1 of the IT system. The output of the voltage divider circuit 1 is connected to the input of the signal isolation circuit 3 through the fault judgment circuit 2. The signal isolation circuit 3 outputs an isolation signal to the MCU module 4 so that the MCU module 4 can determine whether there is an AC insulation abnormality based on the level of the isolation signal.

[0025] As a preferred embodiment, the present invention also includes a fault latching circuit 5, which is connected to the voltage divider circuit 1 and the fault judgment circuit 2 to achieve fault latching, thereby avoiding the false impression of normal AC insulation due to external environmental factors after the AC insulation impedance of the IT system is abnormal, thus avoiding misjudgment by the MCU module 4.

[0026] In this embodiment, the voltage divider circuit 1 includes multiple voltage divider resistors connected between the power supply and the live and neutral wires of the IT system. Specifically, as shown... Figure 1 As shown, the multiple voltage divider resistors are resistors R1, R2, R3, and R5. One end of resistor R2 is connected to the live wire of the IT system, and one end of resistor R5 is connected to the neutral wire of the IT system. The other ends of resistors R2, R5, and R1 are connected together to form the output of voltage divider circuit 1. The other end of resistor R1 is connected to the power supply. Resistor R3 is connected between the live wire and the neutral wire of the IT system. Thus, resistors R2, R3, and R5 are equivalent to a single resistor, and resistor R3 connects the live wire and the neutral wire of the IT system to facilitate simultaneous detection of the parallel impedance of the live wire and the neutral wire to ground. Furthermore, voltage divider circuit 1 also includes a voltage regulator capacitor C1, one end of which is connected to the output of voltage divider circuit 1, and the other end is connected to ground.

[0027] like Figure 1As shown, the fault diagnosis circuit 2 includes switching transistors Q1 and Q2, resistors R9 and R11. The first terminal of switching transistor Q1 is connected to the output of voltage divider circuit 1, the third terminal of switching transistor Q1 is connected to the first terminal of switching transistor Q2 through resistor R9, the second terminal of switching transistor Q1 is connected to the power supply, the third terminal of switching transistor Q2 is connected to the input of signal isolation circuit 3, and the second terminal of switching transistor Q2 is grounded. One end of resistor R9 is connected to the first terminal of switching transistor Q2, and the other end of resistor R9 is grounded. Specifically, in this embodiment, switching transistor Q1 is a PNP transistor, and switching transistor Q2 is an NPN transistor. The first terminals of switching transistors Q1 and Q2 are the base, the third terminals of switching transistors Q1 and Q2 are the collector, and the second terminals of switching transistors Q1 and Q2 are the emitter. In other embodiments, switching transistors Q1 and / or Q2 can be implemented using suitable MOSFETs.

[0028] like Figure 1 As shown, the fault latch circuit 5 includes a switching transistor Q3, resistors R6, R8, and R10. The third terminal of the switching transistor Q3 is connected to the output of the voltage divider circuit 1 through resistor R6, and the second terminal of the switching transistor Q3 is grounded. The first terminal of the switching transistor Q3 is connected to one end of resistor R8 and one end of resistor R10. The other end of resistor R8 is connected to the third terminal of the switching transistor Q3, and the other end of resistor R10 is grounded. The fault latch circuit 5 also includes a capacitor C2. One end of capacitor C2 is connected to the first terminal of the switching transistor Q3, and the other end of capacitor C2 is grounded. Specifically, the switching transistor Q3 is an NPN transistor, but it is not limited to this. In other embodiments, the switching transistor Q3 can be implemented using a suitable MOSFET. The first terminal of the switching transistor Q3 is the base, the third terminal of the switching transistor Q3 is the collector, and the second terminal of the switching transistor Q3 is the emitter.

[0029] In this embodiment, the signal isolation circuit 3 includes an optocoupler IC1, a resistor R4, and a resistor R7. The primary terminal 1 of the optocoupler IC1 forms the input of the signal isolation circuit 3 and is connected to the power supply through the resistor R4. The primary terminal 2 of the optocoupler IC1 is grounded. The secondary terminal 4 of the optocoupler IC1 is connected to the isolation signal pin of the MCU module 4 and is connected to the VDD pin of the MCU module 4 through the resistor R7. The secondary terminal 3 of the optocoupler IC1 is connected to the VSS pin of the MCU module 4.

[0030] like Figure 2 As shown, MCU module 4 includes MCU chip IC2 and capacitor C3. The VDD pin of MCU chip IC2 is connected to the power supply. One end of capacitor C3 is connected to the VDD pin of MCU chip IC2, and the other end of capacitor C3 is connected to the VSS pin of MCU chip IC2.

[0031] In this embodiment, the power supply includes a first power supply VCC and a second power supply VDD. The first power supply VCC powers the voltage divider circuit 1, the fault diagnosis circuit 2, and the signal isolation circuit 3. That is, the other end of resistor R1, the second terminal (i.e., emitter) of the switching transistor Q1, and one end of resistor R4 are respectively connected to the first power supply VCC. The supply voltage of the second power supply VDD is higher than that of the first power supply VCC, and the second power supply VDD powers the MCU module 4. That is, the VDD pin of the MCU chip is connected to the second power supply VDD.

[0032] This utility model discloses an insulation detection device for a single-phase AC IT system. Its working principle is as follows: When an abnormal AC insulation impedance occurs in the IT system, its insulation impedance to ground RL1 decreases, causing a drop in the voltage divider voltage across the voltage regulator C1. After the voltage divider voltage across C1 drops, when the switching transistor Q1 reaches its conduction threshold voltage, Q1 conducts, causing Q2 to also conduct. After Q2 conducts, pin 1 of the primary side of the optocoupler IC1 is turned off, causing pin 4 of the secondary side of IC1 to set the isolation signal ISO-Err high. The MUC chip IC2 detects the high ISO-Err signal, determines that there is an AC insulation abnormality, and outputs an alarm signal. After Q1 conducts, Q3 is simultaneously turned on, achieving fault latching and keeping both Q1 and Q2 in the conducting state, thus maintaining the ISO-Err signal high at pin 4 of the secondary side of IC1. Disconnecting the AC output after a fault occurs releases the fault latch.

[0033] When the AC insulation abnormality problem of the IT system is resolved, its insulation resistance to ground RL1 increases, the voltage across the voltage regulator C1 rises, causing switch Q1 to disconnect, followed by switches Q2 and Q3. The primary pin 1 of optocoupler IC1 is turned on high, causing the secondary pin 4 of optocoupler IC1 to set the isolation signal ISO-Err low. When MUC chip IC2 detects that the isolation signal ISO-Err is set low, it determines that the AC insulation is normal.

[0034] This utility model discloses an insulation detection device for a single-phase AC IT system. It does not require an independent signal source, has a simple circuit structure, low cost, and can detect whether AC insulation is abnormal online in real time.

[0035] The present invention relates to an insulation testing device for a single-phase AC IT system. The parts not covered herein are the same as or can be implemented using existing technologies.

[0036] The above embodiments are only used to further illustrate the single-phase AC IT system insulation detection device of this utility model. However, this utility model is not limited to the embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this utility model shall fall within the protection scope of this utility model.

Claims

1. An insulation testing device for a single-phase AC IT system, characterized in that: It includes a power supply, and a voltage divider circuit, a fault diagnosis circuit, a signal isolation circuit and an MCU module powered by the power supply. The voltage divider circuit is connected to the live wire and the neutral wire of the IT system output terminal to form a voltage divider with the ground insulation impedance of the IT system. The output of the voltage divider circuit is connected to the input of the signal isolation circuit through the fault diagnosis circuit. The signal isolation circuit outputs an isolation signal to the MCU module.

2. The single-phase AC IT system insulation testing device according to claim 1, characterized in that: The voltage divider circuit includes resistors R1, R2, R3, and R5. One end of resistor R2 is connected to the live wire of the IT system, and one end of resistor R5 is connected to the neutral wire of the IT system. The other ends of resistors R2, R5, and R1 are connected together to form the output of the voltage divider circuit. The other end of resistor R1 is connected to the power supply. Resistor R3 is connected between the live wire and the neutral wire of the IT system.

3. The single-phase AC IT system insulation testing device according to claim 2, characterized in that: The voltage divider circuit also includes a voltage stabilizing capacitor C1, one end of which is connected to the output of the voltage divider circuit and the other end is connected to ground.

4. The single-phase AC IT system insulation testing device according to claim 1, characterized in that: It also includes a fault latching circuit, which is connected to the voltage divider circuit and the fault detection circuit to achieve fault latching.

5. The single-phase AC IT system insulation testing device according to any one of claims 1-4, characterized in that: The fault diagnosis circuit includes switching transistors Q1 and Q2, resistors R9 and R11. The first terminal of switching transistor Q1 is connected to the output of the voltage divider circuit, the third terminal of switching transistor Q1 is connected to the first terminal of switching transistor Q2 through resistor R9, the second terminal of switching transistor Q1 is connected to the power supply, the third terminal of switching transistor Q2 is connected to the input of the signal isolation circuit, and the second terminal of switching transistor Q2 is grounded. One end of resistor R9 is connected to the first terminal of switching transistor Q2, and the other end of resistor R9 is grounded.

6. The single-phase AC IT system insulation testing device according to claim 5, characterized in that: The switching transistor Q1 is a PNP transistor, the switching transistor Q2 is an NPN transistor, the first terminal is the base, the third terminal is the collector, and the second terminal is the emitter.

7. The single-phase AC IT system insulation testing device according to claim 5, characterized in that: It also includes a fault latching circuit, which includes a switching transistor Q3, resistors R6, R8, and R10. The third terminal of the switching transistor Q3 is connected to the output of the voltage divider circuit through resistor R6, the second terminal of the switching transistor Q3 is grounded, the first terminal of the switching transistor Q3 is connected to one end of resistor R8 and one end of resistor R10, the other end of resistor R8 is connected to the third terminal of the switching transistor Q1, and the other end of resistor R10 is grounded. The fault latching circuit also includes a capacitor C2, one end of which is connected to the first terminal of the switching transistor Q3, and the other end of the capacitor C2 is grounded.

8. The single-phase AC IT system insulation testing device according to claim 7, characterized in that: The switching transistor Q3 is an NPN transistor. The first terminal of the switching transistor Q3 is the base, the third terminal of the switching transistor Q3 is the collector, and the second terminal of the switching transistor Q3 is the emitter.

9. The insulation testing device for a single-phase AC IT system according to claim 1, characterized in that: The signal isolation circuit includes an optocoupler, resistors R4 and R7. The primary terminal 1 of the optocoupler forms the input of the signal isolation circuit and is connected to the power supply through resistor R4. The primary terminal 2 of the optocoupler is grounded. The secondary terminal 4 of the optocoupler is connected to the isolation signal pin of the MCU module and is connected to the VDD pin of the MCU module through resistor R7. The secondary terminal 3 of the optocoupler is connected to the VSS pin of the MCU module.

10. The single-phase AC IT system insulation testing device according to claim 1 or 9, characterized in that: The MCU module includes an MCU chip and a capacitor C3. The VDD pin of the MCU chip is connected to the power supply. One end of the capacitor C3 is connected to the VDD pin of the MCU chip, and the other end of the capacitor C3 is connected to the VSS pin of the MCU chip.

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