CN2924542Y - Three-phase three-wire system line voltage detecting circuit - Google Patents

Abstract

A three-phase three wire voltage detection circuit can be applied to intelligent protection equipment such as motor control and protection equipment. The utility model comprises a signal detection circuit and a signal processing circuit. The signal detection circuit is connected with a three-phase power supply and a signal processing circuit. The signal processing circuit is connected with A/D sampling point. The utility model is characterized in that the signal detection circuit comprises a resistance R1 and a resistance R4 that are connected with A phase of power supply in series, the connecting point of the resistance R1 and the resistance R4 is A1 point; a resistance R2 and a resistance R5 are connected with B phase of power supply in series, the connecting point of the resistance R2 and the resistance R5 is B1 point; a resistance R3 and a resistance R6 are connected with C phase of power supply in series, the connecting point of the resistance R2 and the resistance R5 is C1 point; three phase are connected in a star-shape and form a neutral point E1. The utility model has the advantages of simple circuit, small size, and high reliability.

Description

A kind of three-phase three-wire system line voltage detecting circuit

Technical field

The utility model relates to a kind of three-phase three-wire system line voltage detecting circuit, is used for intelligent protection equipment such as Motor Control protection.

Background technology

Existing three-phase three-wire system voltage detecting adopts the transformer step-down to detect usually, and promptly winding of transformer connects the power supply three-phase line voltage respectively, and Secondary Winding connects operational amplifier, by being exported by operational amplifier after the transformer step-down.Because winding of transformer is directly proportional with its number of turn respectively with the Secondary Winding both end voltage, by winding is set one time, the number of turn of Secondary Winding obtains the different step-down ratios of transformer front and back voltage.This Device Testing precision is subjected to the influence of Transformer Winding technology and working temperature, so accuracy of detection is low, and the cost height, and volume is bigger than normal, does not meet the development trend of intelligent electrical apparatus equipment high precision miniaturization.

Summary of the invention

The purpose of this utility model is to overcome the deficiencies in the prior art, provides a kind of circuit simple, the three-phase three-wire system line voltage detecting circuit that accuracy of detection is high.

The purpose of this utility model is achieved like this: a kind of three-phase three-wire system line voltage detecting circuit, it comprises signal deteching circuit, signal processing circuit, signal deteching circuit is connected with signal processing circuit with three-phase supply, signal processing circuit is connected with the A/D thief hatch, it is characterized in that signal deteching circuit comprises resistance R 1, connect power supply A phase after the R4 series connection, resistance R 1, the R4 tie point is the A1 point, resistance R 2, R5 series connection back connecting resistance B phase, resistance R 2, the R5 tie point is the B1 point, resistance R 3, R6 series connection back connection circuit C phase, resistance R 3, the R6 tie point is the C1 point, the star-like connection of three-phase forms neutral point E1.

Signal processing circuit comprises an end and the A1 point of resistance R 8, one end of resistance R 11 connects, one end of the other end and resistance R 13,1 of duodiode D1,2 ends, 3 pin of operational amplifier U1A connect, one end of resistance R 10 and B1 point, one end of resistance R 7 connects, one end of the other end and resistance R 14,1 of duodiode D2,2 ends, 5 pin of operational amplifier U1B connect, one end of resistance R 12 and C1 point, one end of resistance R 9 connects, one end of the other end and resistance R 15,1 of duodiode D3,2 ends, 10 pin of operational amplifier U1C connect, resistance R 13, R14, the other end of R15 is connected with neutral point E1,3 ends of the other end of resistance R 11 and duodiode D3,9 pin of operational amplifier U1C, one end of resistance R 18 connects, 3 ends of the other end of resistance R 7 and duodiode D1,2 pin of operational amplifier U1A, one end of resistance R 16 connects, 3 ends of the other end of resistance R 9 and duodiode D2,6 pin of operational amplifier U1B, one end of resistance R 17 connects, resistance R 16, R17, the other end of R18 respectively with 1 pin of operational amplifier U1A, 7 pin of U1B, 8 pin of U1C connect and difference output line voltage signal U _AB', U _BC', U _CA', 4 pin of operational amplifier U1A are connected with direct supply VCC, the 11 pin ground connection of operational amplifier U1A.

Compared with prior art, in the signal deteching circuit by the three-phase power line star-like connection behind the high withstand voltage resistance of connecting respectively, by the resistance step-down, operational amplifier carries out difference and amplifies, the three-phase high-voltage signal is changed into the line voltage signal that meets sampling request, replace prior art by the input that the transformer step-down realizes, avoided Transformer Winding to be subjected to temperature, technogenic influence to cause the low unfavorable factor of accuracy of detection greatly.The utility model circuit is simple, therefore has little, the high reliability features of volume.

Description of drawings

Fig. 1 is a theory diagram of the present utility model.

Fig. 2 is an electrical schematic diagram of the present utility model.

Embodiment

In Fig. 1, signal deteching circuit is used for the three-phase high-voltage conversion of signals is become low-voltage signal, and signal processing circuit is used for detected low-voltage signal difference amplification is obtained the line voltage signal.The line voltage signal send A/D thief hatch, thereby calculates power supply three-phase line voltage value by CPU.

In Fig. 2, resistance R 1, R4 and A power supply series connection mutually, resistance R 2, R5 and B power supply series connection mutually, resistance R 3, R6 and C power supply series connection mutually, the star-like connection of three-phase then forms neutral point E1.The A1 point number of winning the confidence minute two-way connects operational amplifier U1A in-phase input end 3 pin behind one tunnel resistance in series R8, connect operational amplifier U1C inverting input 9 pin behind the resistance in series R11 of another road.From the B1 point number of winning the confidence minute two-way, connect operational amplifier U1B in-phase input end 5 pin behind one tunnel resistance in series R10, connect operational amplifier U1A in-phase input end 2 pin behind the resistance in series R7 of another road.From the C1 point number of winning the confidence minute two-way, connect operational amplifier U1C in-phase input end 10 pin behind one tunnel resistance in series R12, connect operational amplifier U1B inverting input 6 pin behind the resistance in series R9 of another road.Operational amplifier U1 adopts TLV2254.Neutral point E1 respectively resistance in series R13, R14, R15, after connect operational amplifier U1A, U1B, U1C in-phase input end 3 pin, 5 pin, 10 pin, the two ends of duodiode D1, D2, D3 are connected with positive inverting input 3 pin, 2 pin, 5 pin, 6 pin, 10 pin, 9 pin of operational amplifier U1A, U1B, U1C respectively.Resistance R 16, R17, R18 are connected on respectively between inverting input 2 pin, 6 pin, 9 pin and output terminal 1 pin, 7 pin, 8 pin of operational amplifier U1A, U1B, U1C.

Neutral point E1 is reference signal voltage V _ErfNeutral point E1 connects in-phase input end 3 pin, 5 pin, 10 pin of operational amplifier U1A, U1B, U1C respectively behind resistance in series R13, R14, the R15, purpose is to raise the measuring basis voltage of difference channel, makes through the signal after the difference amplification to become the dc pulse signal that meets Chip Microcomputer A/D sampling request.A phase voltage U _AForm a low-voltage signal U by resistance R 1 step-down at the A1 point _A', B phase voltage U _BForm a low-voltage signal U by resistance R 2 step-downs at the B1 point _B', C phase voltage U _CForm a low-voltage signal U by resistance R 3 step-downs at the C1 point _C'; resistance R 7, R8, R13, R16 and operational amplifier U1A form differential amplifier circuit; resistance R 9, R10, R14, R17 and operational amplifier U1B form differential amplifier circuit; resistance R 11, R12, R15, R18 and operational amplifier U1C form differential amplifier circuit; duodiode D1, D2, D3 play a protective role, and prevent the too high damage operational amplifier of difference amplification input terminal voltage.Low-voltage signal U _B', U _A' send operational amplifier U1A to carry out difference amplification, U _B' send operational amplifier U1A inverting input 2 pin, U _A' send operational amplifier U1A in-phase input end 3 pin, the reference voltage of operational amplifier U1A is V _Erf, promptly operational amplifier U1A output end voltage is $-\frac{R_{16}}{R_7}(U_B\text{'}-U_A\text{'})=\frac{R_{16}}{R_7}(U_A\text{'}-U_B\text{'})$ , line voltage computing formula is ${\stackrel{\·}{U}}_{\mathrm{AB}}={\stackrel{\·}{U}}_A-{\stackrel{\·}{U}}_B,{\stackrel{\·}{U}}_{\mathrm{BC}}={\stackrel{\·}{U}}_B-{\stackrel{\·}{U}}_C,$ ${\stackrel{\·}{U}}_{\mathrm{CA}}={\stackrel{\·}{U}}_C-{\stackrel{\·}{U}}_A,$ So $U_{\mathrm{AB}}\text{'}=\frac{R_{16}}{R_7}(U_A\text{'}-U_B\text{'}),$ In like manner two output end signals of operational amplifier U1B, U1C are respectively $U_{\mathrm{AB}}\text{'}=\frac{R_{17}}{R_9}(U_B\text{'}-U_c\text{'}),$ $U_{\mathrm{CA}}\text{'}=\frac{R_{18}}{R_{11}}(U_C\text{'}-U_A\text{'}).$ Operational amplifier U1A, U1B, the line voltage signal of three output terminal 1 pin of U1C, 7 pin, 8 pin send A/D thief hatch, calculates power supply three-phase line voltage value by CPU.

Claims (2)

1, a kind of three-phase three-wire system line voltage detecting circuit, it comprises signal deteching circuit, signal processing circuit, signal deteching circuit is connected with signal processing circuit with three-phase supply, signal processing circuit is connected with the A/D thief hatch, it is characterized in that connecing power supply A phase after signal deteching circuit comprises resistance R 1, R4 series connection, resistance R 1, R4 tie point are the A1 point, resistance R 2, R5 series connection back connecting resistance B phase, resistance R 2, R5 tie point are the B1 point, resistance R 3, R6 series connection back connection circuit C phase, and resistance R 3, R6 tie point are the C1 point, the star-like connection of three-phase forms neutral point E1.

2, a kind of three-phase three-wire system line voltage detecting circuit according to claim 1, it is characterized in that signal processing circuit comprises an end and the A1 point of resistance R 8, one end of resistance R 11 connects, one end of the other end and resistance R 13,1 of duodiode D1,2 ends, 3 pin of operational amplifier U1A connect, one end of resistance R 10 and B1 point, one end of resistance R 7 connects, one end of the other end and resistance R 14,1 of duodiode D2,2 ends, 5 pin of operational amplifier U1B connect, one end of resistance R 12 and C1 point, one end of resistance R 9 connects, one end of the other end and resistance R 15,1 of duodiode D3,2 ends, 10 pin of operational amplifier U1C connect, resistance R 13, R14, the other end of R15 is connected with neutral point E1,3 ends of the other end of resistance R 11 and duodiode D3,9 pin of operational amplifier U1C, one end of resistance R 18 connects, 3 ends of the other end of resistance R 7 and duodiode D1,2 pin of operational amplifier U1A, one end of resistance R 16 connects, 3 ends of the other end of resistance R 9 and duodiode D2,6 pin of operational amplifier U1B, one end of resistance R 17 connects, resistance R 16, R17, the other end of R18 respectively with 1 pin of operational amplifier U1A, 7 pin of U1B, 8 pin of U1C connect and difference output line voltage signal U _AB', U _BC', U _CA', 4 pin of operational amplifier U1A are connected with direct supply VCC, the 11 pin ground connection of operational amplifier U1A.