A circuit for live detection of an ac device

Abstract

The utility model relates to a circuit for live detection of alternating current equipment belongs to electrical control technical field. Single -phase alternating current detection circuit is by resistance R1, R2, R3, R4, rectifier module U1, voltage stabilizing diode D1, filter capacitor C1, photocoupler U2, emitting diode D2, D3, triode D4 is constituteed, three -phase alternating current detection circuit can use three same single -phase alternating current detection circuit constitutes. The utility model mainly has the advantages of simple and efficient circuit, can convert the live signal into the signal that PLC or embedded application system identifies, and is convenient for access to various control systems, adopts the strong and weak electric isolation technology, avoids the strong electric to sneak into weak electric system, and will weak electric equipment damage, can see whether the equipment is live through the emitting diode on the circuit, can replace low voltage test pen detection.

Description

Technical Field

[0001] This utility model belongs to the field of electrical control technology. It is a circuit for detecting live signals of single-phase AC equipment or three-phase AC equipment and converting live signals into signals that can be recognized by PLC or embedded application systems. Background Technology

[0002] In PLC or embedded application system development, it is sometimes necessary to detect whether single-phase or three-phase AC equipment is energized, and use the detected signal as a calculation condition for the PLC or embedded application system. For example, in the development of remote power outage and restoration systems, circuit breakers equipped with electric operating mechanisms can easily achieve remote opening and closing control of the circuit breaker. If combined with a voltage detection circuit, the detected equipment energization signal can be transmitted to the PLC or embedded application system, enabling remote voltage detection of the equipment. This meets the technical requirement that power outages for equipment maintenance must be performed with voltage detection, which can significantly shorten the power outage and restoration time during factory equipment maintenance, reduce workload, and improve maintenance efficiency.

[0003] Chinese patent CN220752299U, "A Contactor Main Contact Adhesion Detection Device," detects DC current, and the detected signal can only be provided to an MCU with a DC 3.3V level. CN104698259A, "A Live Detection Circuit Suitable for Three-Phase Power Systems," is used for three-phase live indication. The input uses a sensing unit, which is driven by a tri-color LED and a thyristor driver. Utility Model Content

[0004] The present invention aims to provide a live detection circuit for single-phase AC equipment or three-phase AC equipment. This circuit can convert the live signal of the equipment into a signal that can be recognized by a PLC or embedded application system, and use it as a calculation condition for the PLC or embedded application system.

[0005] The technical solution of this utility model:

[0006] A circuit for live detection of AC equipment is disclosed. The single-phase AC detection circuit comprises resistors R1, R2, R3, and R4, a rectifier module U1, a Zener diode D1, a filter capacitor C1, an optocoupler U2, LEDs D2 and D3, and a transistor D4. Resistor R1, rectifier module U1, Zener diode D1, filter capacitor C1, LED D2, and optocoupler U2 constitute the input section of the single-phase AC detection circuit. The phase line input terminal L-In is connected to the AC input terminal AC1 of rectifier module U1 via a step-down resistor R1, and the neutral line input terminal N-In is connected to the AC input terminal AC2 of rectifier module U1. A Zener diode D1 and a filter capacitor C1 are connected in parallel between the output terminals DC+ and DC- of rectifier module U1. The DC+ terminal of rectifier module U1 is connected to the anode of LED D2, the cathode of D2 is connected to input terminal 1 of optocoupler U2, and the DC- terminal of rectifier module U1 is connected to input terminal 2 of optocoupler U2. The output terminal 3 of optocoupler U2 is connected to one end of two resistors R2 and R3. The other end of R2 is connected to the collector of PNP transistor D4 and leads out the digital output signal terminal Digital-Output. The other end of R3 is connected to the base of PNP transistor D4. The emitter of transistor D4 is connected to the positive terminal VCC of the power supply. The output terminal 4 of optocoupler U2 is connected to the negative terminal GND of the power supply.

[0007] Furthermore, the three-phase AC detection circuit is constructed using the same three single-phase AC detection circuits described above.

[0008] The beneficial effects of this utility model are as follows: It provides a circuit for live detection of single-phase or three-phase AC equipment, which has three main advantages: First, the circuit is simple and efficient, and can convert live signals into signals that can be recognized by PLCs or embedded application systems, making it convenient to connect to various control systems; Second, it adopts strong and weak current isolation technology to prevent strong current from entering the weak current system and damaging the weak current equipment; Third, the light-emitting diodes on the circuit can be used to see whether the equipment is live, which can replace the low-voltage test pen for voltage testing. Attached Figure Description

[0009] Figure 1 This is an electrical schematic diagram of a circuit used for live detection of single-phase AC equipment.

[0010] Figure 2 This is a diagram showing the connection between a circuit for live detection of AC equipment and a circuit breaker with remote closing / opening function.

[0011] Figure 3 This is a circuit diagram showing the connection between a circuit used for live detection of AC equipment and the digital input module of a PLC.

[0012] In the diagram: R1, R2, R3, R4 - resistors; U1 - rectifier module; U2 - optocoupler; D1 - Zener diode; D2, D3 - LEDs; D4 - transistor; C1 - capacitor; QF - circuit breaker with remote closing / opening function; U3 - Siemens digital input module DI 16x24VDC BA. Detailed Implementation

[0013] A circuit for live detection of AC equipment. The phase and neutral lines of the power supply of the equipment under test are connected to the input side of this invention. The circuit converts the AC voltage signal into a digital signal that can be recognized by a PLC or microcontroller, allowing the PLC or microcontroller to perform program calculations. The following description uses single-phase AC detection as an example, with reference to the accompanying drawings, for further explanation. Three-phase AC detection can use three identical circuits.

[0014] A device live detection circuit, whose hardware mainly consists of resistors R1, R2, R3, R4, rectifier module U1, Zener diode D1, filter capacitor C1, optocoupler U2, light-emitting diodes D2 and D3, transistor D4 and other components.

[0015] like Figure 1 The diagram shows the electrical schematic of a live detection circuit for a device: The phase line input terminal L-In is connected to the AC input terminal AC1 of the rectifier module U1 via a step-down resistor R1. The neutral line input terminal N-In is connected to the AC input terminal AC2 of the rectifier module U1. A Zener diode D1 and a filter capacitor C1 are connected in parallel between the output terminals DC+ and DC- of the rectifier module U1. The DC+ terminal of the rectifier module U1 is connected to the anode of the light-emitting diode D2, and the cathode of D2 is connected to input terminal 1 of the optocoupler U2. The DC- terminal of the rectifier module U1 is connected to input terminal 2 of the optocoupler U2. The output terminal 3 of the optocoupler U2 is connected to one end of two resistors R2 and R3. The other end of R2 is connected to the collector of a PNP transistor D4, and a digital output signal terminal Digital-Output is led out. The other end of R3 is connected to the base of the PNP transistor D4. The emitter of the transistor D4 is connected to the positive terminal VCC of the power supply. The output terminal 4 of the optocoupler U2 is connected to the negative terminal GND of the power supply. The Digital-Output signal terminal is also connected to a light-emitting diode D3 and a resistor R4 connected in series with it. The other end of R4 is connected to the negative terminal GND of the power supply.

[0016] Taking the detection of whether there is power at the output terminal of the circuit breaker and the sending of the power signal to the Siemens digital input module DI 16x24VDC BA, order number 6ES7521-1BH10-0AA0 as an example, the application method of this utility model is explained, which is similar to the connection and application method of a microcontroller.

[0017] Figure 2As shown: A device live detection circuit is connected to a circuit breaker with remote closing / opening function. The incoming terminal of the circuit breaker QF is connected to the phase line L and the neutral line N of the power supply. In addition to the output terminal of the circuit breaker QF being connected to the electrical equipment, the phase line input terminal L-In and the neutral line input terminal N-In of the device live detection circuit are also connected to it.

[0018] Figure 3 The diagram shows a circuit for connecting a device live detection circuit to a Siemens PLC (Programmable Logic Controller) digital input module U3. The digital output signal terminal Digital-OutPut of the device live detection circuit is connected to channel DIx of the PLC's digital input module U3. The M terminal of the digital input module U3 is connected to the negative terminal GND of the power supply.

[0019] The voltage level of the power supply should match the rated voltage of the PLC's digital input module. For example, if the rated voltage of the digital input module is DC24V, then the voltage level of the power supply VCC should also be DC24V.

[0020] When a circuit breaker QF with remote closing / opening function is remotely operated and placed in the closed state, the output terminals of QF are energized. Then, there is an AC 220V voltage between the phase line input terminals L-In and N-In of the energized detection circuit of a device. This voltage is stepped down by resistor R1 and then connected to the AC input terminal of rectifier module U1. After the voltage at the output terminal of rectifier module U1 is regulated by Zener diode D1 and filtered by capacitor C1, a stable DC voltage is obtained. This voltage will cause LED D2 to light up, indicating that the output terminals of circuit breaker QF are energized. Simultaneously, the input terminal of optocoupler U2 is energized, and its output terminal 3 outputs a low level. The base of PNP transistor D4 receives a low level and transitions from cutoff to conduction. The digital output signal terminal Digital-Output of a device energization detection circuit changes from low to high. This signal is sent to channel DIx of the digital input module U3 of the PLC (Programmable Logic Controller) for PLC program calculations. For example, it may indicate on the human-machine interface that circuit breaker QF has closed and is energized, or be converted into a program interlocking condition. LED D3 is also illuminated, indicating that the energized signal at the QF output terminal has been converted into a signal recognizable by the PLC, indicating normal operation.

[0021] When a circuit breaker QF with remote closing / opening function is remotely operated and placed in the open state, the output terminals of QF are not energized. Therefore, there is no AC voltage between the phase line input terminals L-In and N-In of the energized detection circuit, LED D2 is off, indicating that the output terminals of circuit breaker QF are not energized. The output terminal 3 of optocoupler U2 outputs a high level, and the base of PNP transistor D4 receives a high level and changes from conducting to cutoff. The digital output signal terminal Digital-Output of the energized detection circuit changes from high to low, and the channel DIx of the digital input module U3 of the PLC (Programmable Logic Controller) receives a low level, indicating that circuit breaker QF has been opened.

Claims

1. A circuit for performing live detection on AC equipment, characterized in that: The single-phase AC current detection circuit consists of resistors R1, R2, R3, and R4, rectifier module U1, Zener diode D1, filter capacitor C1, optocoupler U2, LEDs D2 and D3, and transistor D4. Resistor R1, rectifier module U1, Zener diode D1, filter capacitor C1, LED D2, and optocoupler U2 constitute the input section of the single-phase AC current detection circuit. The phase line input terminal L-In is connected to the AC input terminal AC1 of rectifier module U1 via a step-down resistor R1, and the neutral line input terminal N-In is connected to the AC input terminal AC2 of rectifier module U1. A Zener diode D1 and filter capacitor C1 are connected in parallel between the output terminals DC+ and DC- of rectifier module U1. The DC- of rectifier module U1... The + terminal is connected to the anode of LED D2, the cathode of D2 is connected to input terminal 1 of optocoupler U2, and the DC- terminal of rectifier module U1 is connected to input terminal 2 of optocoupler U2. Optocoupler U2, LED D3, transistor D4, and resistors R2, R3, and R4 constitute the output part of the circuit. The output terminal 3 of optocoupler U2 is connected to one end of two resistors R2 and R3. The other end of R2 is connected to the collector of PNP transistor D4 and leads out the digital output signal terminal Digital-Output. The other end of R3 is connected to the base of PNP transistor D4. The emitter of transistor D4 is connected to the positive terminal VCC of the power supply. The output terminal 4 of optocoupler U2 is connected to the negative terminal GND of the power supply.

2. The circuit for detecting liveness of AC equipment according to claim 1, characterized in that: The three-phase AC detection circuit is constructed using three identical single-phase AC detection circuits as described above.

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