CN112117741A - Three-phase voltage input protection equipment - Google Patents

Abstract

The invention provides a three-phase voltage input protection device, comprising: a power supply circuit, a voltage comparison circuit, a three-phase power supply sampling circuit, a drive circuit and a relay circuit; the input end of the power supply circuit is connected to the L1 phase and the L2 phase of the three-phase power supply. connection, the output end of the power supply circuit is connected with the input end of the voltage comparison circuit, wherein the positive power supply VCC provides the DC working voltage for the subsequent circuit; the input end of the three-phase power supply sampling circuit is respectively connected with the three-phase of the three-phase power supply, The output ends of the voltage comparison circuit and the three-phase power supply sampling circuit are connected with the input ends of the drive circuit; the output ends of the drive circuit are connected with the input ends of the relay circuit, and the output ends of the relay circuit are respectively connected with the three-phase output ends. Three-phase connection of the power supply. The invention has the advantages of simple structure, low cost and high reliability, can solve the problems of high voltage, fluctuation and lack of phase of the three-phase power supply, and prolong the service life of the equipment.

Description

Three-phase voltage input protection device

technical field

The invention belongs to the technical field of electrical equipment, in particular to a three-phase voltage input protection circuit.

Background technique

In the three-phase power supply line, faults such as excessive voltage, fluctuation or lack of phase often occur, causing equipment damage. In addition, in actual use, if 220V is connected to 380V by mistake, the equipment will be instantly damaged. At present, most of the three-phase power protection devices on the market are complex in structure, high in cost, and cannot be applied well.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a three-phase voltage input protection device with simple structure, low cost and high reliability, which is used to solve the problem of excessive voltage, fluctuation and phase loss of the three-phase power supply. , and mistakenly connect 220V to 380V, etc., to prolong the service life of the equipment.

In order to achieve the above purpose and other related purposes, the present invention provides a three-phase voltage input protection device, including: a power supply circuit, a voltage comparison circuit, a three-phase power supply sampling circuit, a drive circuit and a relay circuit;

The input end of the power supply circuit is connected with the L1 phase and L2 of the three-phase power supply, and the output end of the power supply circuit is connected with the input end of the voltage comparison circuit, wherein the positive power supply VCC provides the DC working voltage for the subsequent circuit; the three The input ends of the phase power supply sampling circuit are respectively connected with the three phases of the three-phase power supply, the output ends of the voltage comparison circuit and the three-phase power supply sampling circuit are connected with the input end of the drive circuit; the output end of the drive circuit is connected to the relay The input ends of the circuit are connected, and the output ends of the relay circuit are respectively connected with the three phases of the three-phase power supply.

In an embodiment of the present invention, the power supply circuit includes a fuse F1, a fuse F2, a transformer T1, a rectifier bridge B1, a capacitor C1, a voltage regulator unit U1, a fast recovery rectifier tube D1, an inductor L1, and a capacitor C2;

The two AC input terminals of the transformer T1 are respectively connected in series with the fuse F1 and the fuse F2 and then connected to the L1 phase and the L2 phase of the three-phase power supply. The output terminal of the transformer T1 is connected to the AC input terminal of the rectifier bridge B1, and the positive pole of the output terminal of the rectifier bridge B1 is simultaneously It is connected to the first pin of the voltage stabilization unit U1 and the positive electrode of the capacitor C1, the negative electrode of the output end of the rectifier bridge B1, the negative electrode of the capacitor C1, the third pin and the fifth pin of the voltage stabilization unit U1 are all grounded, and the voltage stabilization unit U1 The second pin is simultaneously connected to the negative electrode of the fast recovery rectifier tube D1 and one end of the inductor L1, the other end of the inductor L1 is simultaneously connected to the positive electrode of the capacitor C2 and the fourth pin of the voltage regulator unit U1, and the negative electrode of the capacitor C2 is grounded.

In an embodiment of the present invention, the voltage comparison circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a diode D2, and a voltage comparator U2;

The resistor R1 is connected in series with the resistor R2, the intermediate node after the series connection is connected to the inverting input terminal of the voltage comparator U2, the other end of the resistor R1 is connected to the positive pole of the output terminal of the rectifier bridge B1, and the other end of the resistor R2 is grounded; the resistor R3 and the resistor R4 Connected in series, the middle node after the series is connected to the non-inverting input terminal of the voltage comparator U2, the other end of the resistor R3 is connected to the power supply VCC, the other end of the resistor R4 is grounded, the output terminal of the voltage comparator U2 is connected to the negative pole of the diode D2, the diode The positive pole of D2 is connected to the input terminal of the driving circuit.

In an embodiment of the present invention, the three-phase power supply sampling circuit includes a plurality of resistors, a diode D3, a diode D4, a diode D5, and a voltage comparator U3;

Resistor R5, resistor R6, and resistor R7 are connected in series, resistor R14 and resistor R15 are connected in series, the other end of resistor R5 is connected to L3 of the three-phase power supply, and the middle node of resistor R14 and resistor R15 is connected to the other end of resistor R7; resistor R8, Resistor R9, resistor R10 are connected in series, resistor R16 and resistor R17 are connected in series, the other end of resistor R8 is connected to L2 of the three-phase power supply, and the middle node of resistor R16 and resistor R17 is connected to the other end of resistor R10; resistor R11, resistor R12, The resistor R13 is connected in series, the resistor R18 and the resistor R19 are connected in series, the other end of the resistor R11 is connected to the L1 of the three-phase power supply, and the middle node of the resistor R18 and the resistor R19 is connected to the other end of the resistor R13; resistor R14, resistor R16, resistor R18 The other ends are connected together, the diode D3 and diode D4 are connected in antiparallel, and the other end is connected to the common end of the resistor R14, the resistor R16, and the resistor R18, and the other end is grounded; the resistor R20 and the resistor R23 are connected in series, and the intermediate node of the resistor R20 and the resistor R23 is connected to the The common terminals of resistor R14, resistor R16, and resistor R18 are connected, the other end of resistor R20 is connected to the non-inverting input terminal of voltage comparator U3, and the other end of resistor R23 is grounded; the other ends of resistor R15, resistor R17, and resistor R19 are connected together , the resistor R21 and the resistor R22 are connected in series, the middle node of the resistor R21 and the resistor R22 is connected to the common terminal of the resistor R15, the resistor R17 and the resistor R19, the other end of the resistor R21 is connected to the inverting input terminal of the voltage comparator U3, and the The other end is grounded; the output end of the voltage comparator U3 is connected to the cathode of the diode D5, and the anode of the diode D5 is connected to the input end of the drive circuit.

In an embodiment of the present invention, the driving circuit includes a resistor R24, a diode D6, a diode D7, a resistor R25, a resistor R26, a capacitor C3 and a transistor Q1;

One end of the resistor R24 is connected to the power supply VCC, the other end is connected to the anode of the diode D2, the diode D5 and the diode D6, the cathode of the diode D6 is connected to the anode of the diode D7, the cathode of the diode D7 is connected to one end of the resistor R25, and the resistor R26 is connected in parallel with the capacitor C3. , one end after parallel connection is connected with the base of the transistor Q1 and the other end of the resistor R25, the other end after parallel connection is grounded, the collector of the transistor Q1 is connected with the relay K2, and the emitter of the transistor Q1 is grounded.

In an embodiment of the present invention, the relay circuit includes a relay K1, a relay K2, and a diode D8;

The diode D8 is connected in reverse parallel to both ends of the coil interface of the relay K2. The positive pole of the coil interface of the relay K2 is connected to the power supply VCC, and the negative pole is connected to the collector of the transistor Q1; a group of contact interfaces of the relay K2 are connected in series with one end of the coil interface of the relay K1 and Between phases L3 of the three-phase power supply; the other end of the coil interface of the relay K1 is connected to the three-phase power supply L1, and the three groups of contact interfaces of the relay K1 are respectively connected to the three-phase of the three-phase power supply.

As mentioned above, the three-phase voltage input protection device of the present invention has the following beneficial effects: the present invention protects the circuit from excessive voltage, fluctuation or phase loss, and has a simple structure, low cost and high reliability.

The initial state of the three-phase voltage input protection device of the present invention is disconnected. After the three-phase power supply is connected, if the three-phase power supply voltage is normal, the voltage comparator U2 and the voltage comparator U3 output a high level to the drive circuit, and the drive circuit makes the relay circuit When the power is turned on, the relay is closed, and the device works normally.

If the 220V is connected to 380V by mistake, or the three-phase power supply voltage has overvoltage, fluctuation or phase failure, the voltage comparator U2 or the voltage comparator U3 outputs a low level to the drive circuit, and the drive circuit will de-energize the relay circuit and keep it off. open state.

The primary of the transformer T1 and the control terminal of the relay K1 of the present invention are respectively connected to the L1 phase, the L2 phase and the L3 phase of the three-phase power supply. , so that the protection device cannot close the relay K1 in the state of lack of phase, so as to realize the protection of lack of phase.

Description of drawings

FIG. 1 is a block diagram showing the structure of the three-phase voltage input protection device of the present invention.

FIG. 2 shows a circuit diagram of the three-phase voltage input protection device of the present invention.

Component label description

1. Power supply circuit; 2. Voltage comparison circuit; 3. Three-phase power supply sampling circuit; 4. Driving circuit; 5. Relay circuit.

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other under the condition of no conflict.

It should be noted that the drawings provided in the following embodiments are only used to illustrate the basic concept of the present invention in a schematic way, so the drawings only show the components related to the present invention rather than the number, shape and number of components in actual implementation. For dimension drawing, the type, quantity and proportion of each component can be changed at will in actual implementation, and the component layout may also be more complicated.

Referring to FIG. 1 , the present invention provides a three-phase voltage input protection device that is easy to use and can provide overvoltage protection, phase loss protection and voltage fluctuation protection. It includes: a power supply circuit 1, a voltage comparison circuit 2, a three-phase power supply sampling circuit 3, a drive circuit 4 and a relay circuit 5; the input end of the power supply circuit 1 is connected to the L1 and L2 phases of the three-phase power supply, and the power supply circuit The output end of 1 is connected with the input end of the voltage comparison circuit 2, wherein the positive power supply VCC provides a DC working voltage for the subsequent circuit; the input ends of the three-phase power supply sampling circuit 3 are respectively connected with the three-phase power supply of The output end of the comparison circuit 2 and the three-phase power supply sampling circuit 3 is connected with the input end of the drive circuit 4; the output end of the drive circuit 4 is connected with the input end of the relay circuit 5, and the output ends of the relay circuit 5 are respectively Three-phase connection to a three-phase power supply.

The initial state of the three-phase voltage input protection device of the present invention is disconnected. After the three-phase power supply is connected, if the three-phase power supply voltage is normal, the voltage comparators U2 and U3 output high level to the drive circuit 4, and the drive circuit makes the relay circuit 5 get If the 220V is connected to 380V by mistake, or the three-phase power supply voltage has overvoltage, fluctuation or phase failure fault, the voltage comparator U2 or the voltage comparator U3 outputs a low level to the drive circuit 4, The drive circuit 4 de-energizes the relay circuit 5, and the relay remains open.

Please refer to FIG. 2, the power supply circuit 1 includes a fuse F1, a fuse F2, a transformer T1, a rectifier bridge B1, a capacitor C1, a voltage regulator unit U1, a fast recovery rectifier tube D1, an inductor L1, and a capacitor C2;

In this embodiment, the voltage-stabilizing unit U1 adopts a voltage-stabilizing chip LM2575. The two AC input terminals of the transformer T1 are respectively connected in series with the fuse F1 and the fuse F2 and then connected to the L1 phase and the L2 phase of the three-phase power supply. The output terminal of the transformer T1 is connected to the AC input terminal of the rectifier bridge B1, and the positive pole of the output terminal of the rectifier bridge B1 is simultaneously It is connected to the first pin of the voltage stabilization unit U1 and the positive electrode of the capacitor C1, the negative electrode of the output end of the rectifier bridge B1, the negative electrode of the capacitor C1, the third pin and the fifth pin of the voltage stabilization unit U1 are all grounded, and the voltage stabilization unit U1 The second pin is simultaneously connected to the negative electrode of the fast recovery rectifier tube D1 and one end of the inductor L1, the other end of the inductor L1 is simultaneously connected to the positive electrode of the capacitor C2 and the fourth pin of the voltage regulator unit U1, and the negative electrode of the capacitor C2 is grounded.

The power circuit 1 takes the L1 phase and the L2 phase of the three-phase power supply, and the fuses F1 and F2 provide protection for the line. The input AC power is stepped down by the transformer T1, rectified by the rectifier bridge B1, and filtered by the capacitor C1, and then converted into DC power to provide the working voltage for the voltage stabilization unit U1. The power supply VCC output by the voltage stabilization unit U1 is stabilized and filtered to provide work for the subsequent circuits. Voltage.

Please refer to FIG. 2, the voltage comparison circuit 2 includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a diode D2, and a voltage comparator U2;

The resistor R1 is connected in series with the resistor R2, the intermediate node after the series connection is connected to the inverting input terminal of the voltage comparator U2, the other end of the resistor R1 is connected to the positive pole of the output terminal of the rectifier bridge B1, and the other end of the resistor R2 is grounded; the resistor R3 and the resistor R4 Connected in series, the middle node after the series is connected to the non-inverting input terminal of the voltage comparator U2, the other end of the resistor R3 is connected to the power supply VCC, the other end of the resistor R4 is grounded, the output terminal of the voltage comparator U2 is connected to the negative pole of the diode D2, the diode The positive pole of D2 is connected to the input terminal of the driving circuit.

After the power supply VCC is divided by resistors R3 and R4, it is input to the non-inverting input terminal of the voltage comparator U2 as a reference voltage. The DC power output from the rectifier bridge B1 is divided by the resistors R1 and R2 and then input to the inverting input terminal of the voltage comparator U2.

Please refer to FIG. 2, the three-phase power supply sampling circuit 3 includes a plurality of resistors, a diode D3, a diode D4, a diode D5, and a voltage comparator U3;

Resistor R5, resistor R6, and resistor R7 are connected in series, resistor R14 and resistor R15 are connected in series, the other end of resistor R5 is connected to L3 of the three-phase power supply, and the middle node of resistor R14 and resistor R15 is connected to the other end of resistor R7; resistor R8, Resistor R9, resistor R10 are connected in series, resistor R16 and resistor R17 are connected in series, the other end of resistor R8 is connected to L2 of the three-phase power supply, and the middle node of resistor R16 and resistor R17 is connected to the other end of resistor R10; resistor R11, resistor R12, The resistor R13 is connected in series, the resistor R18 and the resistor R19 are connected in series, the other end of the resistor R11 is connected to the L1 of the three-phase power supply, and the middle node of the resistor R18 and the resistor R19 is connected to the other end of the resistor R13; resistor R14, resistor R16, resistor R18 The other ends are connected together, the diode D3 and diode D4 are connected in antiparallel, and the other end is connected to the common end of the resistor R14, the resistor R16, and the resistor R18, and the other end is grounded; the resistor R20 and the resistor R23 are connected in series, and the intermediate node of the resistor R20 and the resistor R23 is connected to the The common terminals of resistor R14, resistor R16, and resistor R18 are connected, the other end of resistor R20 is connected to the non-inverting input terminal of voltage comparator U3, and the other end of resistor R23 is grounded; the other ends of resistor R15, resistor R17, and resistor R19 are connected together , the resistor R21 and the resistor R22 are connected in series, the middle node of the resistor R21 and the resistor R22 is connected to the common terminal of the resistor R15, the resistor R17 and the resistor R19, the other end of the resistor R21 is connected to the inverting input terminal of the voltage comparator U3, and the The other end is grounded; the output end of the voltage comparator U3 is connected to the cathode of the diode D5, and the anode of the diode D5 is connected to the input end of the drive circuit.

Resistors R5, R6, R7, R8, R9, R10, R11, R12, R13 are step-down current limiting resistors, resistors R14, R16, R18 and resistors R15, R17, R19 form two sets of zeroing circuits, resistors R20, R21, R22, R23 input voltage comparator U3 after stable reset signal.

In order to save space, the voltage comparator integrated chip LM393 can be used to realize the functions of the voltage comparators U2 and U3.

Referring to FIG. 2, the driving circuit 4 includes a resistor R24, a diode D6, a diode D7, a resistor R25, a resistor R26, a capacitor C3 and a transistor Q1;

One end of the resistor R24 is connected to the power supply VCC, the other end is connected to the anode of the diode D2, the diode D5 and the diode D6, the cathode of the diode D6 is connected to the anode of the diode D7, the cathode of the diode D7 is connected to one end of the resistor R25, and the resistor R26 is connected in parallel with the capacitor C3. , one end after parallel connection is connected with the base of the transistor Q1 and the other end of the resistor R25, the other end after parallel connection is grounded, the collector of the transistor Q1 is connected with the relay K2, and the emitter of the transistor Q1 is grounded.

The resistor R24 is the pull-up resistor of the output terminals of the voltage comparators U2 and U3. The power supply VCC is limited by the resistor R25, and then stepped down through the diodes D6 and D7 to provide the working voltage for the base of the transistor Q1.

Referring to Figure 2, the relay circuit 5 includes a relay K1, a relay K2, and a diode D8;

The diode D8 is connected in reverse parallel to both ends of the coil interface of the relay K2 to protect the relay K2 from being burned out. The positive pole of the relay K2 coil interface is connected to the power supply VCC, and the negative pole is connected to the collector of the transistor Q1; a group of contact interfaces of the relay K2 are connected in series between one end of the relay K1 coil interface and the L3 phase of the three-phase power supply; the relay K1 coil interface The other end is connected with the three-phase power supply L1, and the three groups of contact interfaces of the relay K1 are respectively connected with the three-phase power supply of the three-phase power supply.

In order to protect the equipment, the initial state of the three-phase voltage input protection equipment of the present invention is disconnected. After connecting to the three-phase power supply, if the input voltage of the three-phase power supply is within the normal range, the inverting input voltage value of the voltage comparator U2 is less than the reference voltage value, the output is high, and the diode D2 is turned off; if the phase of the three-phase power supply is normal, The input terminal of the voltage comparator U3 is zero, the output terminal is in a high-impedance state, and the diode D5 is turned off; at this time, the power supply VCC is limited by the resistor R25, and the diodes D6 and D7 are stepped down to provide voltage for the base of the transistor Q1, and Q1 is turned on. , After the coil of relay K2 is energized, the coil of relay K1 is energized, the coil of relay K1 is pulled in, the three-phase power line is connected, and the equipment works normally.

If the customer mistakenly connects 220V to 380V, or the input voltage has an overvoltage or fluctuation fault, the output end of the voltage comparator chip U2 is at a low level, and the diode D2 is turned on; when the input voltage is out of phase, the voltage comparator chip The output terminal of U3 is at low level, and the diode D5 is turned on; if either diode D2 or D5 is turned on, the voltage value of the power supply VCC will be pulled down, causing the transistor Q1 to be turned off, and the relay K2 will be disconnected after the coil is de-energized, and K2 is disconnected. Open causes the relay K1 coil to lose power and disconnect, cut off the line, and protect the equipment from damage due to voltage failure.

The primary of the transformer T1 and the control terminal of the relay K1 are respectively connected to the three-phase power supply. The relay K1 cannot be closed under the condition that the second phase loss protection is realized.

To sum up, the initial state of the three-phase voltage input protection device of the present invention is disconnected. After the three-phase power supply is connected, if the three-phase power supply voltage is normal, the output terminals of the voltage comparator U2 and the voltage comparator U3 output a high level to Drive circuit, the drive circuit makes the relay circuit energized, the relay is closed, and the equipment works normally; if the 220V is connected to 380V by mistake, or the three-phase power supply voltage has overvoltage, fluctuation or phase failure, the voltage comparator U2 and voltage comparator U3 The output terminal of the relay outputs a low level to the drive circuit, the drive circuit de-energizes the relay circuit, and the relay remains disconnected. The invention protects the voltage from being too high, fluctuates or lacks phase in the line, and has the advantages of simple structure, low cost and high reliability.

Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial application value.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (6)

1. A three-phase voltage input protection device, comprising: the power supply circuit, the voltage comparison circuit, the three-phase power supply sampling circuit, the drive circuit and the relay circuit;

the input end of the power supply circuit is connected with the L1 phase and the L2 phase of a three-phase power supply, the output end of the power supply circuit is connected with the input end of the voltage comparison circuit, and the positive power supply VCC provides direct-current working voltage for subsequent circuits; the input end of the three-phase power supply sampling circuit is respectively connected with three phases of a three-phase power supply, and the output ends of the voltage comparison circuit and the three-phase power supply sampling circuit are connected with the input end of the driving circuit; the output end of the driving circuit is connected with the input end of the relay circuit, and the output end of the relay circuit is respectively connected with three phases of a three-phase power supply.

2. A three-phase voltage input protection device according to claim 1, characterized in that: the power supply circuit comprises a fuse F1, a fuse F2, a transformer T1, a rectifier bridge B1, a capacitor C1, a voltage stabilizing unit U1, a fast recovery rectifier tube D1, an inductor L1 and a capacitor C2;

two alternating current input ends of a transformer T1 are connected with a fuse F1 and a fuse F2 in series and then connected with an L1 phase and an L2 phase of a three-phase power supply, an output end of the transformer T1 is connected with an alternating current input end of a rectifier bridge B1, an anode of an output end of the rectifier bridge B1 is connected with a first pin of a voltage stabilizing unit U1 and an anode of a capacitor C1, a cathode of an output end of the rectifier bridge B1, a cathode of a capacitor C1, a third pin and a fifth pin of the voltage stabilizing unit U1 are all grounded, a second pin of a voltage stabilizing unit U1 is connected with a cathode of a fast recovery rectifier tube D1 and one end of an inductor L1, the other end of the inductor L1 is connected with an anode of the capacitor C2 and a fourth pin of the voltage stabilizing unit U1, and a cathode of a capacitor C2 is grounded.

3. A three-phase voltage input protection device according to claim 1, characterized in that: the voltage comparison circuit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a diode D2 and a voltage comparator U2;

the resistor R1 is connected with the resistor R2 in series, the middle node after the series connection is connected with the inverting input end of the voltage comparator U2, the other end of the resistor R1 is connected with the anode of the output end of the rectifier bridge B1, and the other end of the resistor R2 is grounded; the resistor R3 is connected in series with the resistor R4, the middle node after series connection is connected with the non-inverting input end of the voltage comparator U2, the other end of the resistor R3 is connected with a power supply VCC, the other end of the resistor R4 is grounded, the output end of the voltage comparator U2 is connected with the cathode of the diode D2, and the anode of the diode D2 is connected with the input end of the driving circuit.

4. A three-phase voltage input protection device according to claim 1, characterized in that: the three-phase power supply sampling circuit comprises a plurality of resistors, a diode D3, a diode D4, a diode D5 and a voltage comparator U3;

the resistor R5, the resistor R6 and the resistor R7 are connected in series, the resistor R14 and the resistor R15 are connected in series, the other end of the resistor R5 is connected with the L3 of the three-phase power supply, and the middle node of the resistor R14 and the resistor R15 is connected with the other end of the resistor R7; the resistor R8, the resistor R9 and the resistor R10 are connected in series, the resistor R16 and the resistor R17 are connected in series, the other end of the resistor R8 is connected with the L2 of the three-phase power supply, and the middle node of the resistor R16 and the resistor R17 is connected with the other end of the resistor R10; the resistor R11, the resistor R12 and the resistor R13 are connected in series, the resistor R18 and the resistor R19 are connected in series, the other end of the resistor R11 is connected with the L1 of the three-phase power supply, and the middle node of the resistor R18 and the resistor R19 is connected with the other end of the resistor R13; the other ends of the resistor R14, the resistor R16 and the resistor R18 are connected together, one end of the diode D3 and the diode D4 is connected with the common end of the resistor R14, the resistor R16 and the resistor R18 after being connected in parallel in an opposite direction, and the other end of the diode D3 and the common end of the resistor R3583 and the resistor R18 are grounded; the resistor R20 and the resistor R23 are connected in series, the middle node of the resistor R20 and the resistor R23 is connected with the common end of the resistor R14, the resistor R16 and the resistor R18, the other end of the resistor R20 is connected with the non-inverting input end of the voltage comparator U3, and the other end of the resistor R23 is grounded; the other ends of the resistor R15, the resistor R17 and the resistor R19 are connected together, the resistor R21 and the resistor R22 are connected in series, a middle node of the resistor R21 and the resistor R22 is connected with a common end of the resistor R15, the resistor R17 and the resistor R19, the other end of the resistor R21 is connected with an inverted input end of the voltage comparator U3, and the other end of the resistor R22 is grounded; the output end of the voltage comparator U3 is connected with the cathode of the diode D5, and the anode of the diode D5 is connected with the input end of the driving circuit.

5. A three-phase voltage input protection device according to claim 1, characterized in that: the driving circuit comprises a resistor R24, a diode D6, a diode D7, a resistor R25, a resistor R26, a capacitor C3 and a triode Q1;

one end of the resistor R24 is connected with a power supply VCC, the other end of the resistor R24 is connected with the anodes of the diode D2, the diode D5 and the diode D6, the cathode of the diode D6 is connected with the anode of the diode D7, the cathode of the diode D7 is connected with one end of the resistor R25, the resistor R26 is connected with the capacitor C3 in parallel, one end of the resistor D6 is connected with the base of the triode Q1 and the other end of the resistor R25 in parallel, the other end of the resistor D7 is grounded, the collector of the triode Q1 is connected with the relay K2, and the emitter of.

6. A three-phase voltage input protection device according to claim 1, characterized in that: the relay circuit comprises a relay K1, a relay K2 and a diode D8;

the diode D8 is reversely connected in parallel at two ends of the coil interface of the relay K2, the anode of the coil interface of the relay K2 is connected with a power supply VCC, and the cathode is connected with the collector of the triode Q1; one group of contact interfaces of the relay K2 are connected in series between one end of a coil interface of the relay K1 and the L3 phase of the three-phase power supply; the other end of the coil interface of the relay K1 is connected with a three-phase power supply L1, and three groups of contact interfaces of the relay K1 are respectively connected with three phases of the three-phase power supply.

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