Three-phase electric neutral current detection early warning circuit

Abstract

The embodiment of the utility model discloses a three-phase electric neutral line current detection early warning circuit, which is connected with a neutral line of a three-phase circuit and comprises a current transformer, a rectifier bridge, a current and voltage conversion processing unit, a reference voltage circuit and a plurality of early warning lamp control units, the current transformer comprises an annular iron core and a secondary winding wound on the secondary side of the annular iron core, the current transformer is arranged outside the neutral line in a sleeving mode, the secondary winding is connected with the rectifier bridge, and the positive electrode output end of the rectifier bridge is connected with the current and voltage conversion processing unit. The current and voltage conversion processing unit is connected with the reference voltage circuit and each early warning lamp control unit, the reference voltage circuit is connected with each early warning lamp control unit, each early warning lamp control unit comprises a first divider resistor and a second divider resistor which are connected in series, the resistance values of the first divider resistors of the early warning lamp control units are different, and the resistance values of the second divider resistors of the early warning lamp control units are different. The resistance values of the second divider resistors of the early warning lamp control units are different.

Description

Technical Field

[0001] The utility model relates to the technical field of power electronic circuits, in particular to a three-phase neutral line current detection and early warning circuit. Background Art

[0002] The three-phase four-wire system is a power supply method in an electric power system, which includes three phase wires (usually marked as A, B, and C) and a neutral wire (usually marked as N). This power supply method can provide two different voltages: line voltage (380V) and phase voltage (220V) to meet the different needs of users.

[0003] In the three-phase four-wire system, the circuit powered by the three-phase power supply is called a three-phase circuit. The three-phase power supply can provide three electromotive forces (or voltages) of equal magnitude, the same frequency, and a phase difference of 120°. In this power supply mode, when the three-phase load is balanced, the neutral line current is zero, but in practical applications, the three-phase balance is usually relative, and the imbalance is absolute, so the neutral line must be set to ensure the stable output of each phase voltage. However, the cross-sectional area of ​​the neutral line is not larger than that of the phase line. The current exceeding the phase line will inevitably cause the neutral line to overheat. Since there is usually no fuse on the neutral line, it cannot be automatically disconnected in the case of overcurrent. The excessive current on the neutral line poses a huge fire hazard. Moreover, when the neutral line is burned, the neutral point will shift, causing the load to burn. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide a three-phase neutral line current detection and early warning circuit to detect the current of the neutral line and give an early warning.

[0005] In order to solve the above technical problems, the purpose of the utility model is achieved through the following technical solutions: a three-phase neutral line current detection and warning circuit is provided, which is connected to the neutral line of the three-phase circuit. The three-phase neutral line current detection and warning circuit includes a current transformer, a rectifier bridge, a current-voltage conversion processing unit, a reference voltage circuit and a plurality of warning light control units. The current transformer includes a ring-shaped iron core and a secondary winding wound on the secondary side of the ring-shaped iron core. The current transformer is sleeved outside the neutral line. The secondary winding is connected to the rectifier bridge. The positive output end of the rectifier bridge is connected to the current-voltage conversion processing unit. The current-voltage conversion processing unit is connected to the reference voltage circuit and each warning light control unit. The reference voltage circuit is connected to each warning light control unit. Each warning light control unit includes a first voltage-dividing resistor and a second voltage-dividing resistor connected in series. The resistance value of the first voltage-dividing resistor of each warning light control unit is different, and the resistance value of the second voltage-dividing resistor of each warning light control unit is different.

[0006] The beneficial technical effect of the utility model is that the three-phase electric neutral line current detection and warning circuit of the utility model is connected to the neutral line of the three-phase circuit, and a current transformer including a ring-shaped iron core and a secondary winding wound on the secondary side of the ring-shaped iron core is provided, and the current transformer is sleeved outside the neutral line, so that when there is current in the neutral line, the secondary winding of the current transformer can generate an induced current, and the secondary winding is connected to a rectifier bridge, so that the AC induced current generated by the current transformer according to the AC signal of the neutral line is converted into a DC induced current through the rectifier bridge, and the positive output end of the rectifier bridge is connected to a current-voltage conversion processing unit, and the current-voltage conversion processing unit is connected to a reference voltage circuit and each warning light control unit, and the reference voltage circuit is connected to each warning light control unit, so that the DC induced current converted by the rectifier bridge is converted into a DC induced voltage through the current-voltage conversion processing unit and the processed output voltage is sent to the reference voltage circuit and each warning light control unit. The control unit does not require an additional power supply circuit. The electric energy induced by the current transformer can be used to power the three-phase neutral line current detection and warning circuit. Each warning light control unit includes a first voltage-dividing resistor and a second voltage-dividing resistor connected in series. The resistance value of the first voltage-dividing resistor of each warning light control unit is different, and the resistance value of the second voltage-dividing resistor of each warning light control unit is different, so that the corresponding conduction voltage of each warning light control unit is different. Then, the conduction of each warning light control unit corresponds to a different neutral line current. In conjunction with the reference voltage circuit, each warning light control unit can control the corresponding warning light control unit to work according to the voltage output by the current-voltage conversion processing unit, realize the detection of the neutral line current and issue a warning according to the neutral line current, so as to remind the user that the three-phase load balancing configuration operation is required to ensure the safety of electricity use, and the current range of the neutral line can be known according to the state of the warning light control unit. The practicability is strong and the overall circuit is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0008] Figure 1 A schematic diagram of a three-phase neutral current detection and warning circuit provided by an embodiment of the utility model;

[0009] Figure 2 A schematic diagram of the connection between the current transformer and the neutral line of the three-phase neutral line current detection and warning circuit provided by the embodiment of the utility model;

[0010] Figure 3 A circuit diagram of a three-phase neutral current detection and warning circuit provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0011] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0012] See also Figures 1 to 3 , Figure 1 A framework schematic diagram of a three-phase electrical neutral line current detection and warning circuit provided in an embodiment of the utility model, wherein the three-phase electrical neutral line current detection and warning circuit 10 is connected to the neutral line of the three-phase circuit, and the three-phase electrical neutral line current detection and warning circuit 10 includes a current transformer 11, a rectifier bridge BD1, a current-voltage conversion processing unit 12, a reference voltage circuit 13 and a plurality of warning light control units 14, wherein the current transformer 11 includes an annular core 111 and a secondary winding wound on the secondary side of the annular core 111, and the current transformer 11 is sleeved outside the neutral line so that the two ends of the neutral line pass through the through hole of the annular core 111, and the annular core 111 is a closed annular core 111, and the through hole is located in the middle of the annular core 111. The secondary winding is connected to the rectifier bridge BD1, wherein the two ends of the secondary winding are respectively connected to the first AC input terminal AC1 and the second AC input terminal AC2 of the rectifier bridge BD1, and the negative output terminal of the rectifier bridge BD1 is grounded; the positive output terminal of the rectifier bridge BD1 is connected to the current-voltage conversion processing unit 12, and the current-voltage conversion processing unit 12 is connected to the reference voltage circuit 13 and each warning light control unit 14, and the reference voltage circuit 13 is connected to each warning light control unit 14, each of the warning light control units 14 includes a first voltage-dividing resistor and a second voltage-dividing resistor connected in series, and the resistance value of the first voltage-dividing resistor of each warning light control unit 14 is different, and the resistance value of the second voltage-dividing resistor of each warning light control unit 14 is different, so that the corresponding conduction voltage of each warning light control unit 14 is different, and the conduction of each warning light control unit 14 corresponds to a different neutral line current, thereby realizing the detection and warning of the neutral line current.

[0013] Among them, each warning light control unit 14 is connected in parallel so that each warning light control unit 14 is relatively independent and does not interfere with each other. The current transformer 11 is a component that converts a large current on the primary side into a small current on the secondary side for measurement based on the principle of electromagnetic induction. The calculation result of the current of the neutral line divided by the number of turns of the secondary winding of the current transformer 11 is the value of the AC induced current of the secondary winding of the current transformer 11. The larger the current of the neutral line, the larger the AC induced current of the secondary winding. The connection between the neutral line and the current transformer 11 is as follows: Figure 2 As shown, Figure 2 The N line represents the neutral line, and the two ends of the secondary winding of the current transformer 11 are represented by 1 and 2 respectively. Figure 3 The circuit diagram of the interface is represented by two pins 1 and 2. The current of the neutral line can be calculated using formula (1):

[0014]

[0015] In the formula, I N Indicates the current in the neutral line, I a ,I b and I c They represent the current of each phase line in the three-phase line. When the three-phase line is electrically balanced, the current of each phase line is equal, and the current in the neutral line is zero.

[0016] The three-phase electrical neutral line current detection and warning circuit 10 is connected to the neutral line of the three-phase circuit, and a current transformer 11 including a ring-shaped iron core 111 and a secondary winding wound on the secondary side of the ring-shaped iron core 111 is provided, and the current transformer 11 is sleeved outside the neutral line, so that when there is current in the neutral line, the secondary winding of the current transformer 11 can generate an induced current, and the secondary winding is connected to the rectifier bridge BD1, so that the AC induced current generated by the current transformer 11 according to the AC signal of the neutral line is converted into a DC induced current through the rectifier bridge BD1, and the positive output end of the rectifier bridge BD1 is connected to the current-voltage conversion processing unit 12, and the current-voltage conversion processing unit 12 is connected to the reference voltage circuit 13 and each warning light control unit 14, and the reference voltage circuit 13 is connected to each warning light control unit 14, so that the DC induced current converted by the rectifier bridge BD1 is converted into a DC induced voltage through the current-voltage conversion processing unit 12 and the processed output voltage is sent to the reference voltage circuit 13 and each warning light control unit 14. The control unit 14 does not require an additional power supply circuit. The electric energy induced by the current transformer 11 can be used to power the three-phase neutral line current detection and warning circuit 10. Each warning light control unit 14 includes a first voltage-dividing resistor and a second voltage-dividing resistor connected in series. The resistance value of the first voltage-dividing resistor of each warning light control unit 14 is different, and the resistance value of the second voltage-dividing resistor of each warning light control unit 14 is different, so that the corresponding conduction voltage of each warning light control unit 14 is different, and the conduction of each warning light control unit 14 corresponds to a different neutral line current. In conjunction with the reference voltage circuit 13, each warning light control unit 14 can control the corresponding warning light control unit 14 to work according to the voltage output by the current-voltage conversion processing unit 12, realize the detection of the neutral line current and issue a warning according to the neutral line current, so as to remind the user to perform a three-phase load balancing configuration operation to ensure power safety, and the current range of the neutral line can be known according to the state of the warning light control unit 14. It is highly practical and the overall circuit is simple.

[0017] Specifically, in this embodiment, the current-voltage conversion processing unit 12 includes a connection resistor R2A, an electrolytic capacitor C2, a current limiting resistor R1 and a voltage zener diode ZD1, the connection resistor R2A and the electrolytic capacitor C2 are connected in parallel, the positive output end of the rectifier bridge BD1 is connected to one end of the connection resistor R2A and the positive electrode of the electrolytic capacitor C2, the other end of the connection resistor R2A and the negative electrode of the electrolytic capacitor C2 are both grounded, the positive electrode of the electrolytic capacitor C2 is connected to one end of the current limiting resistor R1, the other end of the current limiting resistor R1 is connected to the cathode of the voltage zener diode ZD1, and the anode of the voltage zener diode ZD1 is grounded. Among them, the DC induced current obtained after rectification by the rectifier bridge BD1 generates a DC induced voltage through the connection resistor R2A, the voltage value of the DC induced voltage is the product of the DC induced current and the connection resistor R2A, the DC induced voltage is proportional to the current of the neutral line, and the DC induced voltage can be detected to calculate the current of the neutral line. The DC induced voltage is a DC voltage. The electrolytic capacitor C2 is connected in parallel with the connection resistor R2A. Then, the voltage value of the electrolytic capacitor C2 is equal to the value of the DC induced voltage. The DC induced voltage passes through the current limiting resistor R1 to the Zener diode ZD1 to generate a power supply voltage for powering the warning light control unit 14. The Zener diode ZD1 is used to limit the output power supply voltage to a lower voltage. The DC induced voltage can be recorded as VCC, and the power supply voltage can be recorded as VCC2. When the current of the neutral line is large, the DC induced voltage is high, the Zener diode ZD1 is broken down, the current limiting resistor R1 and the Zener diode ZD1 become loads, and are connected in parallel with the connection resistor R2A to further limit the voltage value of the DC induced voltage to protect the rear components.

[0018] Specifically, in this embodiment, the current-voltage conversion processing unit 12 further includes a fourteenth diode D14, the fourteenth diode D14 is connected in parallel with the connection resistor R2A, the cathode of the fourteenth diode D14 is connected to the positive output end of the rectifier bridge BD1, and the anode of the fourteenth diode D14 is grounded. The fourteenth diode D14 can be provided to prevent the DC induced voltage from being disturbed by instantaneous changes in the power grid and generating an over-high voltage problem.

[0019] Specifically, in this embodiment, the reference voltage circuit 13 includes an eleventh resistor R11 and a reference voltage chip IC2, one end of the eleventh resistor R11 is connected to the positive electrode of the electrolytic capacitor C2, the other end of the eleventh resistor R11 is connected to the cathode end of the reference voltage chip IC2 and the reference end of the reference voltage chip IC2, the anode end of the reference voltage chip IC2 is grounded, and the reference end of the reference voltage chip IC2 is connected to each of the warning light control units 14 to provide a reference voltage for each warning light control unit 14. Among them, the reference voltage chip IC2 can use a three-terminal adjustable reference voltage chip of model TL432, and the reference voltage VREF is 1.25V. Of course, in some embodiments, the reference voltage chip IC2 can use a three-terminal adjustable reference voltage chip of model TL431, and the reference voltage VREF is 2.49V.

[0020] Specifically, in this embodiment, each of the warning light control units 14 further includes a comparator and a light emitting diode, one end of the first voltage-dividing resistor is connected to the positive electrode of the electrolytic capacitor C2, the other end of the first voltage-dividing resistor is connected to one end of the second voltage-dividing resistor and the inverting input end of the comparator, the other end of the second voltage-dividing resistor is grounded, the reference end of the reference voltage chip IC2 is connected to the in-phase input end of the comparator through an input resistor, the output end of the comparator is connected to the cathode of the light emitting diode through an output resistor, the anode of the light emitting diode is connected to the cathode of the voltage stabilizing diode ZD1 and the other end of the current limiting resistor R1, and the in-phase input end and output end of the comparator are electrically connected in series with a first resistor and a first diode. The output end of the comparator is used to drive the corresponding light emitting diode. The more light emitting diodes of the warning light control unit 14 that are lit, the greater the corresponding DC induced voltage, and the greater the corresponding neutral line current.

[0021] Specifically, in this embodiment, one end of the first resistor is electrically connected between the input resistor and the non-inverting input terminal of the comparator, the other end of the first resistor is connected to the anode of the first diode, and the cathode of the first diode is electrically connected between the output terminal of the comparator and the output resistor. The resistance value of the first resistor can be relatively large, so that when the first diode is turned on, current flows through the first resistor and the first diode, but the current is small, so that the voltage difference between the inverting input terminal and the non-inverting input terminal of the comparator becomes larger, so as to play a hysteresis function and prevent the light-emitting diode from continuously flickering when it is at a critical trigger current.

[0022] Based on the above design, when working, when there is current in the neutral line, the secondary winding of the current transformer 11 generates an induced current. Since the current in the neutral line is AC, the induced current is an AC induced current. The secondary winding of the current transformer 11 transmits the AC induced current to the rectifier bridge BD1 to obtain a DC induced current. The connection resistor R2A of the current-voltage conversion processing unit 12 converts the DC induced current to generate a DC induced voltage. The current-limiting resistor R1 and the voltage-stabilizing diode ZD1 of the current-voltage conversion processing unit 12 limit the DC induced voltage to a smaller power supply voltage and output it to each warning light control unit 14 for power supply. The current-voltage conversion processing unit 12 transmits the DC induced voltage to the reference voltage chip IC2 of the reference voltage circuit 13, and the DC induced voltage is transmitted to each warning light control unit 14 through the reference voltage chip IC2 of the reference voltage circuit 13. The voltage of the first voltage-dividing resistor and the second voltage-dividing resistor of the element 14 is input to the inverting input terminal of the corresponding comparator, and the non-inverting input terminal of the comparator obtains the reference voltage of the reference terminal of the reference voltage chip IC2. The resistance value of the first voltage-dividing resistor of each warning light control unit 14 is different and the resistance value of the second voltage-dividing resistor is also different, so that the voltage division of the DC induced voltage generated by the current induction conversion of the neutral line is different, and the comparator compares the reference voltage and the corresponding voltage division. When the voltage division is less than the reference voltage, the output terminal of the comparator outputs a high level, at which time the corresponding first diode is turned off, and the corresponding light-emitting diode is turned off and does not emit light; when the voltage division is not less than the reference voltage, the output terminal of the comparator outputs a low level, at which time the corresponding first diode is turned on, and the corresponding light-emitting diode is turned on and emits light. The larger the current of the neutral line, the larger the corresponding AC induced current, the larger the DC induced current, and thus the larger the DC induced voltage, so that the voltage division is also larger, and the more warning light control units 14 whose light-emitting diodes are lit, that is, the larger the current of the neutral line, the more warning light control units 14 are in the light-emitting warning working state where the light-emitting diodes are lit.

[0023] Specifically, in the present embodiment, the number of the warning light control units 14 is four, which can be respectively recorded as a first warning light control unit 14a, a second warning light control unit 14b, a third warning light control unit 14c and a fourth warning light control unit 14d. The current range of the neutral line corresponding to the first warning light control unit 14a can be not less than 10A and less than 30A, the current range of the neutral line corresponding to the second warning light control unit 14b can be not less than 30A and less than 55A, the current range of the neutral line corresponding to the third warning light control unit 14c can be not less than 55A and less than 80A, and the current range of the neutral line corresponding to the fourth warning light control unit 14d can be not less than 80A. When the current of the neutral line is not less than 80A, the light emitting diodes of the first warning light control unit 14a, the second warning light control unit 14b, the third warning light control unit 14c and the fourth warning light control unit 14d are all turned on and emit light; when the current of the neutral line is 55A-79A, the light emitting diodes of the first warning light control unit 14a, the second warning light control unit 14b and the third warning light control unit 14c are all turned on and emit light, while the light emitting diode of the fourth warning light control unit 14d is turned off and does not emit light; when the current of the neutral line is 30A-54A, the light emitting diodes of the first warning light control unit 14a and the second warning light control unit 14b are turned on and emit light. The diodes are all turned on and emit light, while the light-emitting diodes of the third warning light control unit 14c and the fourth warning light control unit 14d are all turned off and do not emit light; when the current of the neutral line is 10A-29A, the light-emitting diode of the first warning light control unit 14a is turned on and emits light, while the light-emitting diodes of the second warning light control unit 14b, the third warning light control unit 14c and the fourth warning light control unit 14d are all turned off and do not emit light; when the current of the neutral line is less than 10A, the light-emitting diodes of the first warning light control unit 14a, the second warning light control unit 14b, the third warning light control unit 14c and the fourth warning light control unit 14d are all turned off and do not emit light.

[0024] Correspondingly, the first voltage-dividing resistor, the second voltage-dividing resistor, the comparator, the first resistor, the first diode, the input resistor, the output resistor and the light-emitting diode of the first warning light control unit 14a are respectively recorded as R7, R9, IC1A, R5, D9, R8, R6 and D3; the first voltage-dividing resistor, the second voltage-dividing resistor, the comparator, the first resistor, the first diode, the input resistor, the output resistor and the light-emitting diode of the second warning light control unit 14b are respectively recorded as R13, R16, IC1B, R12, D7, R14, R10 and D4; The first voltage-dividing resistor, the second voltage-dividing resistor, the comparator, the first resistor, the first diode, the input resistor, the output resistor and the light-emitting diode of the third warning light control unit 14c are respectively recorded as R20, R21, IC3A, R17, D8, R19, R15 and D5; the first voltage-dividing resistor, the second voltage-dividing resistor, the comparator, the first resistor, the first diode, the input resistor, the output resistor and the light-emitting diode of the fourth warning light control unit 14d are respectively recorded as R26, R29, IC3B, R24, D10, R25, R18 and D6.

[0025] In summary, the three-phase electrical neutral line current detection and warning circuit of the utility model is connected to the neutral line of the three-phase circuit, and a current transformer including a ring-shaped iron core and a secondary winding wound on the secondary side of the ring-shaped iron core is provided, and the current transformer is sleeved outside the neutral line, so that when there is current in the neutral line, the secondary winding of the current transformer can generate an induced current, and the secondary winding is connected to the rectifier bridge, so that the AC induced current generated by the current transformer according to the AC signal of the neutral line is converted into a DC induced current through the rectifier bridge, and the positive output end of the rectifier bridge is connected to the current-voltage conversion processing unit, and the current-voltage conversion processing unit is connected to the reference voltage circuit and each warning light control unit, and the reference voltage circuit is connected to each warning light control unit, so that the DC induced current converted by the rectifier bridge is converted into a DC induced voltage through the current-voltage conversion processing unit and the processed output voltage is sent to the reference voltage circuit and each warning light control unit, without No additional power supply circuit is required. The electric energy induced by the current transformer can be used to power the three-phase neutral line current detection and warning circuit. Each warning light control unit includes a first voltage-dividing resistor and a second voltage-dividing resistor connected in series. The resistance value of the first voltage-dividing resistor of each warning light control unit is different, and the resistance value of the second voltage-dividing resistor of each warning light control unit is different, so that the corresponding conduction voltage of each warning light control unit is different. Then, the conduction of each warning light control unit corresponds to a different neutral line current. In conjunction with the reference voltage circuit, each warning light control unit can control the corresponding warning light control unit to work according to the voltage output by the current-voltage conversion processing unit, realize the detection of the neutral line current and issue a warning based on the neutral line current, so as to remind the user that a three-phase load balancing configuration operation is required to ensure electricity safety, and the current range of the neutral line can be known according to the state of the warning light control unit. It is highly practical and the overall circuit is simple.

[0026] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the utility model, and these modifications or replacements should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. A three-phase neutral line current detection and warning circuit, characterized in that: The three-phase electrical neutral line current detection warning circuit includes a current transformer, a rectifier bridge, a current-voltage conversion processing unit, a reference voltage circuit and a plurality of warning light control units. The current transformer includes a ring-shaped iron core and a secondary winding wound on the secondary side of the ring-shaped iron core. The current transformer is sleeved outside the neutral line. The secondary winding is connected to the rectifier bridge. The positive output end of the rectifier bridge is connected to the current-voltage conversion processing unit. The current-voltage conversion processing unit is connected to the reference voltage circuit and each warning light control unit. The reference voltage circuit is connected to each warning light control unit. Each warning light control unit includes a first voltage-dividing resistor and a second voltage-dividing resistor connected in series. The resistance value of the first voltage-dividing resistor of each warning light control unit is different, and the resistance value of the second voltage-dividing resistor of each warning light control unit is different.

2. The three-phase neutral current detection and warning circuit according to claim 1 is characterized in that: The current-to-voltage conversion processing unit includes a connecting resistor, an electrolytic capacitor, a current-limiting resistor and a voltage-stabilizing diode. The connecting resistor and the electrolytic capacitor are connected in parallel. The positive output end of the rectifier bridge is connected to one end of the connecting resistor and the positive electrode of the electrolytic capacitor. The other end of the connecting resistor and the negative electrode of the electrolytic capacitor are both grounded. The positive electrode of the electrolytic capacitor is connected to one end of the current-limiting resistor. The other end of the current-limiting resistor is connected to the cathode of the voltage-stabilizing diode. The anode of the voltage-stabilizing diode is grounded.

3. The three-phase neutral current detection and warning circuit according to claim 2 is characterized in that: The current-voltage conversion processing unit also includes a fourteenth diode, which is connected in parallel with the connection resistor, a cathode of the fourteenth diode is connected to the positive output end of the rectifier bridge, and an anode of the fourteenth diode is grounded.

4. The three-phase neutral current detection and warning circuit according to claim 2 is characterized in that: The reference voltage circuit includes an eleventh resistor and a reference voltage chip, one end of the eleventh resistor is connected to the positive electrode of the electrolytic capacitor, the other end of the eleventh resistor is connected to the cathode end of the reference voltage chip and the reference end of the reference voltage chip, the anode end of the reference voltage chip is grounded, and the reference end of the reference voltage chip is connected to each of the warning light control units.

5. The three-phase neutral current detection and warning circuit according to claim 4 is characterized in that: Each of the warning light control units also includes a comparator and a light emitting diode, one end of the first voltage-dividing resistor is connected to the positive electrode of the electrolytic capacitor, the other end of the first voltage-dividing resistor is connected to one end of the second voltage-dividing resistor and the inverting input end of the comparator, the other end of the second voltage-dividing resistor is grounded, the reference end of the reference voltage chip is connected to the non-inverting input end of the comparator through an input resistor, the output end of the comparator is connected to the cathode of the light emitting diode through an output resistor, the anode of the light emitting diode is connected to the cathode of the voltage-stabilizing diode and the other end of the current-limiting resistor, and a first resistor and a first diode are electrically connected in series between the non-inverting input end and the output end of the comparator.

6. The three-phase neutral line current detection and warning circuit according to claim 5, characterized in that: One end of the first resistor is electrically connected between the input resistor and the non-inverting input terminal of the comparator, the other end of the first resistor is connected to the anode of the first diode, and the cathode of the first diode is electrically connected between the output terminal of the comparator and the output resistor.

7. The three-phase neutral line current detection and warning circuit according to claim 1, characterized in that: The number of the warning light control units is four.

Images