CN201063055Y - Circuit for monitoring three-phase four-wire power failure - Google Patents

Abstract

The utility model relates to a power fault detecting circuit, in particular to a three-phase four-wire system power fault detecting circuit that is used for a dual power automatic transfer switch. The power fault detecting circuit comprises a three-phase four-wire system unbalanced voltage and phase failure detecting circuit, a power failure detecting circuit and a single-chip microcomputer; the three-phase four-wire system unbalanced voltage and phase failure detecting circuit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1 and a bidirectional photo coupler D1; the power failure detecting circuit comprises a transformer T1, a rectifying bridge D2, a resistor R6, a resistor R7 and a capacitor C2. No matter how the three-phase power is loaded (resistance, capacitance and inductance) or wired, the detecting circuit can give off an alarm for unbalanced voltage, phase failure and power failure of the power, thereby ensuring accurate and reliable fault detecting and judging.

Description

Three-phase four-wire power supply fault monitoring circuit

technical field

The utility model relates to a power supply failure monitoring circuit, in particular to a three-phase four-wire system power supply failure monitoring circuit used for dual power supply automatic transfer switches.

technical background

At present, the application field of dual power automatic transfer switch is very wide. Since the input power grid will fail during normal operation, the monitoring of power failure should be accurate and reliable. However, the problem generally existing in the existing power failure monitoring circuit is: when there is a failure of three-phase power supply phase failure, three-phase voltage unbalance or power loss of three-phase power supply, the monitoring circuit cannot accurately monitor and judge its failure. Therefore, the reliability is poor.

Contents of the invention

In view of the above-mentioned problems in the prior art, the utility model provides a three-phase four-wire system power supply fault monitoring circuit for a dual-power automatic transfer switch. Regardless of the three-phase power supply with any load (resistive, capacitive, inductive) and any wiring mode of the load, the monitoring circuit can effectively realize the alarm of the voltage imbalance, phase failure and power failure of the power supply, ensuring monitoring And judge its fault accurately and reliably.

The technical solution adopted by the utility model is: a three-phase four-wire system power supply failure monitoring circuit, which is characterized in that it includes a three-phase four-wire system voltage unbalance and phase failure monitoring circuit, a power failure monitoring circuit and a single-chip microcomputer. The three-phase voltage unbalance and phase failure monitoring circuit includes resistors R1, R2, R3, R4, R5, capacitor C1 and bidirectional photocoupler D1; the power failure monitoring circuit includes transformer T1, rectifier bridge D2, resistors R6, R7 and capacitor C2.

The beneficial effects of the utility model are: adopting the above-mentioned technical scheme, the utility model has the characteristics of simple circuit, low cost and high reliability of monitoring and judging power failure.

Description of drawings

Fig. 1 is the electrical schematic diagram of the utility model and is used as abstract accompanying drawing.

Detailed ways

The working principle is described in detail as follows: In the normal working state of the three-phase power supply, the phase difference of the three-phase AC L1-N, L2-N, L3-N AC voltage 220V is 120°, the phasor sum of the voltage at the UP terminal is zero, and the photosensitive sensor of the photocoupler The voltage at the input terminal of the emitting diode is 0V, the current flowing through the emitter of the bidirectional photocoupler D1 is very small, and the DC voltage VD1 is generated through the resistor R5 and the capacitor C1. Unbalanced voltage value, power supply has no phase failure or unbalanced fault alarm. At the same time, L1-N in the three-phase AC phase line outputs AC voltage through transformer T1, rectifies and filters through rectifier bridge D2 and resistors R6, R7 divides the voltage and outputs to single chip AD2. The voltage is higher than the fault undervoltage alarm value, because AD1, AD2 Both are within the normal range, and the single-chip microcomputer outputs the normal signal of the three-phase power supply.

If the three-phase power supply loses power, although the voltage output to the microcontroller AD1 is normal, but AD2 is lower than the fault undervoltage alarm value, the microcontroller outputs an alarm signal at this time. If the three-phase voltage is unbalanced, the photosensitive emitting diode of the bidirectional photocoupler D1 There is an AC voltage at the input terminal, and the signal is amplified by the phototransistor to generate VD1 voltage. After the AD conversion of the single-chip microcomputer, if the AD value is greater than the set alarm value, the single-chip microcomputer outputs an alarm signal.

With reference to accompanying drawing, describe the utility model in detail.

The utility model includes a three-phase four-wire voltage unbalance and phase failure monitoring circuit, a power failure monitoring circuit and a single-chip microcomputer. The three-phase voltage unbalance and phase failure monitoring circuit includes resistors R1, R2, R3, R4, R5, capacitor C1 and A bidirectional photocoupler D1, wherein one end of the resistors R1, R2, and R3 is respectively connected to three AC phase lines L1, L2, and L3, and the other ends of the resistors R1, R2, and R3 are connected in parallel to each other in the bidirectional photocoupler D1. One end of the two photosensitive emitting diodes and one end of the resistor R4, the other end of the two photosensitive emitting diodes in the bidirectional photocoupler D1 are respectively connected to the other end of the resistor R4 and the N terminal of the three-phase power supply, and the collector in the bidirectional photocoupler D1 The pole is connected to +5V power supply, the emitter is connected to one end of the resistor R5 and the capacitor C1 and the input terminal AD1 of the single chip microcomputer, and the other end of the resistor R5 and the capacitor C1 is connected to the ground; the power loss monitoring circuit includes a transformer T1, a rectifier bridge D2, Resistors R6, R7 and capacitor C2, wherein the AC phase line L1 and N line are respectively connected to the primary of the transformer T1, the secondary of the transformer T1 is connected to the input terminal of the rectifier bridge D2, the output terminal of the rectifier bridge D2 is connected to one end of the resistor R6, and the resistor The other end of R6 is connected to one end of resistor R7 and capacitor C2 and the input end AD2 of the single chip microcomputer, and the other end of resistor R7, capacitor C2 and rectifier bridge D2 is connected to ground.

The utility model single-chip microcomputer can adopt any one in PIC16F877 and PIC16F72 model.

Claims (2)

1. a three-phase four-wire system power supply fault monitoring circuit, is characterized in that, comprises three-phase four-wire system voltage unbalance and phase failure monitoring circuit, power failure monitoring circuit and single-chip microcomputer, described three-phase voltage imbalance and failure phase monitoring circuit The phase monitoring circuit includes resistors (R1), (R2), (R3), (R4), (R5), capacitors (C1) and bidirectional optocoupler (D1), wherein the resistors (R1), (R2), ( One end of R3) is respectively connected to three AC phase lines (L1), (L2), (L3), and the other ends of resistors (R1), (R2), (R3) are connected in parallel and respectively connected to a bidirectional photocoupler (D1) One end of the two photosensitive emitting diodes and one end of the resistor (R4), the other end of the two photosensitive emitting diodes in the bidirectional photocoupler (D1) are respectively connected to the other end of the resistor (R4) and the three-phase power supply (N) Terminal, the collector in the bidirectional photocoupler (D1) is connected to +5V power supply, the emitter is connected to one end of the resistor (R5) and capacitor (C1) and the input terminal (AD1) of the single-chip microcomputer, resistor (R5) and capacitor (C1) The other end is connected to the ground; the power loss monitoring circuit includes a transformer (T1), a rectifier bridge (D2), a resistor (R6), (R7) and a capacitor (C2), wherein the AC phase line (L1) and N The wires are respectively connected to the primary of the transformer (T1), the secondary of the transformer (T1) is connected to the input terminal of the rectifier bridge (D2), the output terminal of the rectifier bridge (D2) is connected to one end of the resistor (R6), and the other end of the resistor (R6) Connect one end of the resistor (R7) and the capacitor (C2) to the input terminal (AD2) of the single chip microcomputer, connect the resistor (R7), the capacitor (C2) and the other output terminal of the rectifier bridge (D2) to ground. 2. The three-phase four-wire power supply fault monitoring circuit as claimed in claim 1, wherein the single-chip microcomputer can adopt any one of PIC16F877 and PIC16F72 models.

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