CN207926158U - AC power failure monitoring and protection circuit for thermal power plants - Google Patents

Abstract

The utility model relates to an alternating current power failure monitoring and protection circuit used in thermal power plants, which belongs to the field of power supply monitoring of power plants. The utility model aims to solve the problem of safety accidents caused by alternating current power failure. The utility model includes NE555 time base integrated circuit, comparator A, optocoupler, resistors R1~R4, adjustable resistor R5, diodes D1~D3, voltage stabilizing diodes Vs1~Vs2, electrolytic capacitor C1, capacitor C2 and light emitting diode VL; The AC power supply AC is rectified by the diode D1 into a DC power supply, which is photoelectrically isolated by the optocoupler and input to the comparator A. When the power is off, the comparator A outputs a low level to trigger the NE555, and the NE555 outputs a high level to start the light indicating circuit and subsequent Execute component actions to protect critical equipment.

Description

AC power failure monitoring and protection circuit for thermal power plants

technical field

The utility model belongs to the field of power monitoring of power plants, and relates to the monitoring and protection technology of AC power.

Background technique

The thermal power plant has two major functions of power generation and heating. There are many electrical equipment in the thermal power plant. Since there are many key equipment in the thermal power plant, and the key settings all have continuous and uninterrupted working characteristics, it is required that the power supply should also be continuously supplied. Power failure will have a great impact on many running devices, and the data during power failure cannot be saved in time; if power failure cannot be detected and dealt with in time, it may cause more serious safety accidents.

In most electrical equipment powered by AC power, when the input AC power fails, it is necessary to quickly detect the signal of AC input power failure, and perform necessary protection on the equipment to ensure the normal operation of the electrical equipment. Especially for key equipment, it is necessary to detect the signal of AC power failure as early as possible, and avoid abnormal operation of the equipment caused by detection circuit malfunction.

Contents of the invention

The purpose of the utility model is to provide an AC power failure monitoring and protection circuit used in thermal power plants to avoid safety accidents.

The AC power failure monitoring protection circuit for thermal power plants described in the utility model includes NE555 time base integrated circuit, comparator A, optocoupler, resistors R1~R4, adjustable resistor R5, diodes D1~D3, voltage regulator diodes Vs1~Vs2 , electrolytic capacitor C1, capacitor C2 and light emitting diode VL;

The optocoupler is composed of light-emitting diode D2 and phototransistor VT;

One end of the AC power supply AC is connected to the anode of the diode D2 of the optocoupler through the series diode D1 and resistor R1; the other end of the AC power supply AC is connected to the cathode of the diode D2;

The collector of the phototransistor VT is connected to +5V DC power supply, and the emitter of the phototransistor VT is connected to the cathode of the Zener diode Vs1 and the anode of the diode D3 at the same time; the anode of the Zener diode Vs1 is grounded;

The cathode of the diode D3 is simultaneously connected to the positive pole of the electrolytic capacitor C1 and one end of the resistor R2; the negative pole of the electrolytic capacitor C1 is grounded;

The other end of the resistor R2 is simultaneously connected to the non-inverting input terminal of the comparator A, a fixed end of the adjustable resistor R5 and its sliding end; the other fixed end of the adjustable resistor R5 is grounded;

The inverting input terminal of comparator A is connected to one end of resistor R3 and the cathode of Zener diode Vs2 at the same time, the anode of Zener diode Vs2 is grounded, and the other end of resistor R3 is connected to +5V DC power supply;

The output terminal of comparator A is connected to pin 2 and pin 6 of NE555 time base integrated circuit and one end of resistor R4 at the same time; pin 4 and pin 8 of NE555 time base integrated circuit and the other end of resistor R4 are connected to +5V DC power supply at the same time; NE555 Pin 5 of the time base integrated circuit is grounded through capacitor C2, pin 1 of the NE555 time base integrated circuit is grounded; pin 3 of the NE555 time base integrated circuit is connected to the anode of the light-emitting diode VL, and the cathode of the light-emitting diode VL is grounded.

Preferably, an intermediate relay KA is also included, the two ends of the coil of the intermediate relay KA are respectively connected to pin 3 of the NE555 time-base integrated circuit and the power ground, and the contacts of the intermediate relay KA are connected in series in the power supply circuit of the execution component.

Preferably, comparator A adopts LM393 dual voltage comparator integrated circuit.

Beneficial effects of the utility model: The circuit structure of the utility model is simple, built with several analog components, without program embedding, quickly and effectively detects the power failure of the AC power supply, and quickly gives an indication result, and makes the execution part act to protect the corresponding of electrical equipment.

Description of drawings

Fig. 1 is a schematic structural diagram of the AC power failure monitoring and protection circuit used in a thermal power plant according to the present invention.

Detailed ways

Specific Embodiment 1: For illustration in conjunction with FIG. 1 , the AC power failure monitoring and protection circuit for thermal power plants described in this embodiment includes NE555 time base integrated circuit, comparator A, optocoupler, resistors R1~R4, adjustable resistor R5, Diodes D1-D3, Zener diodes Vs1-Vs2, electrolytic capacitor C1, capacitor C2, light-emitting diode VL and intermediate relay KA;

The optocoupler is composed of light-emitting diode D2 and phototransistor VT;

One end of the AC power supply AC is connected to the anode of the diode D2 of the optocoupler through the series diode D1 and resistor R1; the other end of the AC power supply AC is connected to the cathode of the diode D2;

The collector of the phototransistor VT is connected to +5V DC power supply, and the emitter of the phototransistor VT is connected to the cathode of the Zener diode Vs1 and the anode of the diode D3 at the same time; the anode of the Zener diode Vs1 is grounded;

The cathode of the diode D3 is simultaneously connected to the positive pole of the electrolytic capacitor C1 and one end of the resistor R2; the negative pole of the electrolytic capacitor C1 is grounded;

The other end of the resistor R2 is simultaneously connected to the non-inverting input terminal of the comparator A, a fixed end of the adjustable resistor R5 and its sliding end; the other fixed end of the adjustable resistor R5 is grounded;

The inverting input terminal of comparator A is connected to one end of resistor R3 and the cathode of Zener diode Vs2 at the same time, the anode of Zener diode Vs2 is grounded, and the other end of resistor R3 is connected to +5V DC power supply;

The output terminal of comparator A is connected to pin 2 and pin 6 of NE555 time base integrated circuit and one end of resistor R4 at the same time; pin 4 and pin 8 of NE555 time base integrated circuit and the other end of resistor R4 are connected to +5V DC power supply at the same time; NE555 Pin 5 of the time base integrated circuit is grounded through capacitor C2, pin 1 of the NE555 time base integrated circuit is grounded; pin 3 of the NE555 time base integrated circuit is connected to the anode of the light-emitting diode VL, and the cathode of the light-emitting diode VL is grounded.

The two ends of the coil of the intermediate relay KA are respectively connected to pin 3 of the NE555 time-base integrated circuit and the power ground, and the contacts of the intermediate relay KA are connected in series in the power supply circuit of the actuator.

Working principle: AC power supply, such as 220V or 380V, is rectified by diode D1 to DC power supply, photoelectrically isolated by optocoupler, and the front and rear circuits are isolated by optocoupler, so that the subsequent circuit can effectively output trigger commands. Then it is smoothed by Vs1, D3, C1, R2, and R5 and then input to the "+" terminal of comparator A. The input value of the "-" terminal of comparator A is the value of Vs2. Adjust R5 so that the lowest point of the waveform at the "+" terminal is higher than The input value of "-" terminal is slightly higher than 0.1~0.2V. When the power supply is normal, comparator A outputs high level, NE555 pin 6 inputs high level, then its pin 3 outputs low level, and VL and KA have no action. When the AC power supply is cut off, the "+" terminal voltage of comparator A is lower than the "-" terminal voltage, comparator A outputs low level, then pin 2 of NE555 is connected to low level, NE555 is flipped internally, and 3 pin of NE555 Pin outputs high level, VL lights up to represent the power-off state. At the same time, the KA coil is energized, and the contacts of KA are connected in series in the power supply circuit of the executive component. When the KA coil is energized, its corresponding contacts will act. Make the executive components take corresponding actions to protect key equipment.

Although the embodiments disclosed in the present utility model are as above, the content described is only an embodiment adopted for the convenience of understanding the present utility model, and is not intended to limit the present utility model. Anyone skilled in the technical field to which the utility model belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the utility model, but the patent of the utility model The scope of protection must still be based on the scope defined in the appended claims.

Claims (3)

1. The AC power failure monitoring and protection circuit used in thermal power plants is characterized in that it includes NE555 time base integrated circuit, comparator A, optocoupler, resistors R1~R4, adjustable resistor R5, diodes D1~D3, voltage regulator diode Vs1 ~Vs2, electrolytic capacitor C1, capacitor C2 and light-emitting diode VL; The optocoupler is composed of light-emitting diode D2 and phototransistor VT; One end of the AC power supply AC is connected to the anode of the diode D2 of the optocoupler through the series diode D1 and resistor R1; the other end of the AC power supply AC is connected to the cathode of the diode D2; The collector of the phototransistor VT is connected to +5V DC power supply, and the emitter of the phototransistor VT is connected to the cathode of the Zener diode Vs1 and the anode of the diode D3 at the same time; the anode of the Zener diode Vs1 is grounded; The cathode of the diode D3 is simultaneously connected to the positive pole of the electrolytic capacitor C1 and one end of the resistor R2; the negative pole of the electrolytic capacitor C1 is grounded; The other end of the resistor R2 is simultaneously connected to the non-inverting input terminal of the comparator A, a fixed end of the adjustable resistor R5 and its sliding end; the other fixed end of the adjustable resistor R5 is grounded; The inverting input terminal of comparator A is connected to one end of resistor R3 and the cathode of Zener diode Vs2 at the same time, the anode of Zener diode Vs2 is grounded, and the other end of resistor R3 is connected to +5V DC power supply; The output terminal of comparator A is connected to pin 2 and pin 6 of NE555 time base integrated circuit and one end of resistor R4 at the same time; pin 4 and pin 8 of NE555 time base integrated circuit and the other end of resistor R4 are connected to +5V DC power supply at the same time; NE555 Pin 5 of the time base integrated circuit is grounded through capacitor C2, pin 1 of the NE555 time base integrated circuit is grounded; pin 3 of the NE555 time base integrated circuit is connected to the anode of the light-emitting diode VL, and the cathode of the light-emitting diode VL is grounded. 2. according to claim 1, the AC power failure monitoring and protection circuit used in thermal power plants is characterized in that it also includes an intermediate relay KA, and the two ends of the intermediate relay KA coil are respectively connected to 3 pins and power ground of the NE555 time base integrated circuit, The contacts of the intermediate relay KA are connected in series in the power supply circuit of the actuator. 3. The AC power failure monitoring and protection circuit for thermal power plants according to claim 1, wherein the comparator A adopts an LM393 dual-voltage comparator integrated circuit.