CN2197673Y

CN2197673Y - Electronic current transformer

Info

Publication number: CN2197673Y
Application number: CN 94215052
Authority: CN
Inventors: 介国安
Original assignee: JIE GUO AN
Current assignee: JIE GUO AN
Priority date: 1994-06-20
Filing date: 1994-06-20
Publication date: 1995-05-17
Anticipated expiration: 2004-06-20

Abstract

The utility model discloses an electronic current transformer, which is provided with a flow divider of a three phase conducting metal sheet, the flow dividing signals are connected with the primary end of an isolation transformer, and the secondary end of the isolation transformer is connected with a current detecting amplifying circuit; signals are connected with a DC meter head after the signals pass through an attenuation circuit, a special digital switch and a resistor form a voltage dividing varistor to set the value of rated current; the set signals and the direct current detection signals are synchronously sent into an operational amplifier to compare, causing that a power switch is controlled to act; besides, the utility model is provided with an alarm circuit, an overcurrent protection circuit, a time delaying and cutoff control circuit, a short circuit protection circuit, etc. The utility model which replaces the transformer type current mutual inductor has the advantages of small volume, light weight, high precision, and overflowing short circuit alarming and protecting function.

Description

Electronic current transformer

The utility model relates to electric wiring measurement instrument, particularly electronic current transducer.

Current transformer in the past is the little electric current with the proportional numerical value of big current conversion in the alternating circuit, for a kind of dedicated transformer of the usefulness of measurement instrument and relay protection.Shortcoming is that volume is bigger, and precision is relatively poor.

The purpose of this utility model provides the novel electronic current transformer, and volume is little in light weight, precision height easy to use, and have functions such as overcurrent warning, overcurrent protection and short-circuit protection, and directly use the direct current gauge outfit, the scale linearity improves greatly.

The utility model is finished as follows: make the three-phase conductive metal sheet as shunt; shunting signal is connected with the elementary of isolating transformer; transformer secondary output connects the current detecting amplifying circuit; signal is connected with the direct current gauge outfit behind attenuator circuit; there is special-purpose digital switch to become potentiometer resistance simultaneously with resistor group; set load current value; setting signal and current detection signal are sent into the operational amplifier comparator circuit simultaneously; its controlled action of power switch as a result; also has the overcurrent warning circuit, current foldback circuit, delay cut-off control circuit and short-circuit protection circuit.

Said conductive metal sheet shunt is made by brass or red copper, and said current detection circuit is made up of sheet metal shunt, isolating transformer, operational amplifier, diode, potentiometer, resistance and electric capacity.

The utility model has following advantage than conventional art: the precision height, volume is little in light weight, and is easy to install, saves a large amount of silicon steel sheets and copper conductor.Also have overcurrent, short-circuit protection, overcurrent warning function, directly use the direct current gauge outfit, the scale linearity improves greatly.Extensively be used in the power supply occasion of Super-Current Measurement.

Further describe below in conjunction with accompanying drawing.

Fig. 1 is the electrical schematic diagram of electronic current transducer.

Fig. 2 is that electronic current transducer is used for the electrical schematic diagram that single-phase current detects.

With reference to Fig. 1, there are A, B, C three-phase conductive metal sheet shunt R in the left side _A, R _B, R _C, signal wire is drawn respectively and is connected with it, and with isolate transformation B ₁, B ₂, B ₃Elementary connection.The secondary connection current detecting amplifying circuit of isolating transformer, signal is connected with the direct current gauge outfit behind attenuator circuit.The right AK ₁, AK ₂, AK ₃, be that special-purpose digital switch becomes potentiometer resistance with resistor group, set load current value, setting signal and current detection signal are sent into operational amplifier relatively simultaneously, its controlled action of power switch as a result.Also have warning circuit, current foldback circuit, delay cut-off control circuit on the figure.

Shunt is made with brass or the flat plate of red copper.By metal shunt R _A, isolating transformer B ₃, operational amplifier JC ₃, diode D ₃, potentiometer W ₃, resistance R ₃, R ₆And capacitor C ₃Connection in series-parallel is formed A phase current testing circuit; R ₈, B ₂, JC ₂, D ₂, W ₂, R ₂, R ₅, and C ₂Form B phase current testing circuit; R _C, B ₁, JC ₁, D ₁, W ₁, R ₁, R ₄And C ₁Connection in series-parallel is formed C phase current testing circuit.With A is example: R mutually _AOn shunting signal through B ₃Isolate, again through JC ₃Amplify D ₃Rectification, C ₃Filtering becomes d. c. voltage signal, W ₃Be to adjust JC ₃Enlargement factor.The current detection signal of output is through W ₄, W ₅Or W ₆Be connected potentiometer W with the electric current gauge outfit with K switch ₄, W ₅, W ₆, transfer each phase current scale to use respectively.Just can find out the current value on the circuit-under-test on the electric current gauge outfit.On the figure, AK ₁, AK ₂, AK ₃, be special-purpose digital switch and resistance R ₂₅～R ₅₆Form potentiometer resistance, replace multiturn potentiometer, be used for setting the ratings of overcurrent.Principle of work is R ₅₇And D ₁₄Form mu balanced circuit, the normal voltage of output is supplied with the O end and the B end of potentiometer resistance hundred figure places, according to setting digital difference, in the needed partial pressure value of the C of units end output.

By JC ₅, JC ₆, JC ₇, D ₈, D ₉, D ₁₀, R ₉～R ₁₄Form current foldback circuit.JC ₈, D ₁₁, R ₁6, R ₂₆, R ₂₁, R ₁₉And C ₄Connection in series-parallel is formed overcurrent delay cut-off control circuit.Principle of work is to detect voltage signal that A, the B of output, C three-phase current signal set with potentiometer resistance respectively through JC ₅, JC ₆, JC ₇Compare, A, B, any phase current signal of C are greater than setting signal, and operational amplifier output is noble potential just, at this moment controls BG ₂, J ₂, adhesive sends overcurrent and reports to the police.Be overcurrent for fear of instantaneous overcurrent phenomenon mistake, this signal is again through R ₁₉And C ₄Discharge and recharge time-delay, the mutual JC that crosses again ₈Control BG ₁, J ₁Adhesive is cut off the power supply these road feed circuit automatically.

By JC ₄, R ₇, R ₈, D ₇, R ₁₇, R ₁₈Connection in series-parallel is formed short-circuit protection circuit.If this road supply line or load have short circuit phenomenon will cause circuital current greater than the ratings of setting more than 1.5 times.At this moment through R ₁₇, R ₁₈The mutual again JC that crosses of the signal of dividing potential drop decay ₄Compare the output short-circuit control signal with setting value, make BG ₁Conducting, J ₁Adhesive can make this road power supply outage automatically immediately, thereby the protection power-supply unit not suffered a loss not by time-delay like this.

With reference to Fig. 2,

Be to be used for the circuit that single-phase current detects. Also be that single-phase current detects, output has interchange, two kinds of signals of direct current.

Figure is a three-phase overcurrent short-circuit protection control circuit, can cooperate

Figure with

Figure uses.

Components and parts inventory: B among the figure ₁, B ₂, B ₃Isolating transformer; R _A, R _B, R _CMetal such as brass or red copper shunt; JC ₁～JC ₃Operational amplifier; W ₁～W ₃-1.5K Ω solid potentiometer; W ₄～W ₆1K Ω～6.8K Ω solid potentiometer; R ₁～R ₃200K Ω; R ₄～R ₁₇10K Ω; R ₁₈-5.1K Ω; R ₁₀-100～200K Ω; R ₂₀, R ₂₁, R ₂₃, R ₂₄10K Ω; R ₂₂-3K Ω; R ₂₅～R ₃₄300 Ω; R ₃₅～R ₄₅1.5K Ω; R ₄₆～R ₅₆7.5K Ω; R ₅₇-1.8K Ω, C ₁～C ₄The 220UF/25V electrochemical capacitor, D ₁～D ₁₃Diode, D ₁₄-voltage stabilizing diode, D ₁₄-light emitting diode, BG ₁, 9013 triodes, K-1 * 3 switches, J ₁J ₂-12v miniature relay,

Button toggle switch (individual position), AK ₂-special-purpose digital switch (ten), Special-purpose digital switch (hundred).The WY-stabilized voltage supply, A-electric current gauge outfit.Fig. 2 belongs to the derivation circuit, the big small difference of components and parts data and Fig. 1.

Claims

1, electronic current transducer; it is characterized in that having three-phase to lead the sheet metal shunt; signal wire; be connected with isolating transformer is elementary; be connected to the current detecting amplifying circuit on secondary; signal connects gauge outfit with direct current and connects behind attenuator circuit; the potentiometer resistance that while is made up of special-purpose digital switch and resistance; set load current value; setting signal and current detection signal are sent into the operational amplifier comparator circuit simultaneously; its controlled action of power switch as a result, and warning circuit current foldback circuit, delay cut-off control circuit and short-circuit protection circuit are arranged.

2, according to the said electronic current transducer of claim 1, it is characterized in that the conductive metal sheet shunt by brass or red copper making, said current detection circuit is by the sheet metal shunt.Isolating transformer, operational amplifier, diode, potentiometer, resistance and electric capacity are formed.

3, according to claim 1 or 2 said electronic current transducers, it is characterized in that potentiometer resistance is made up of with resistance the special-purpose digital switch of two or multidigit, the numerical value of setting is exported partial pressure value with potentiometer resistance and is equated.

4,, it is characterized in that said comparator circuit is by JC according to claim 1 or 2 said electronic current transducers ₅, JC ₆, JC ₇, R ₁₀, R ₁₂, R ₁₄, D ₈, D ₉, D ₁₀Form; Said current foldback circuit is by JC ₅, JC ₆, JC ₇, D ₈～D ₁₀, R ₉～R ₁₄Form; Said delay cut-off control circuit is by JC ₈, D ₁₁, R ₁₆, R ₂₆, R ₂₁, R ₁₉, and C ₄Form; Said short-circuit protection circuit is by JC ₄, R ₇, R ₈, D ₇, R ₁₇, R ₁₈Form.