KR100425218B1 - Coil operating circuit for electric contactor - Google Patents

Abstract

The present invention relates to a coil drive circuit of a magnetic contactor capable of stably maintaining a current flow of an excitation coil by maintaining a stable operation of a reverse electromotive area absorption circuit. A coil driving circuit of a magnetic contactor that generates a magnetic force between a movable core and a fixed core to maintain a constant induced electromotive force, the coil driving circuit comprising: a voltage drop unit for dropping an input voltage; a charging unit for charging a voltage by the voltage drop unit; A separation controller for controlling the separation speed between the movable core and the fixed core by discharging the charge of the charging unit at high speed in parallel with the voltage drop unit, a switching unit controlled by the charging unit, and a peak current flowing in the charging unit Limiting the charge protection unit for protecting the charging unit, and controlling the current of the switching unit A stress applied to the switching control unit, the first switching protection unit for preventing the switch from being burned out, the second switching protection unit for preventing damage due to the counter electromotive force of the switching unit, and the stress applied to the switching unit and the second switching protection unit. It is characterized in that it comprises a third switching protection to block and absorb the reverse electromotive force in the forward direction.

Description

Coil Driving Circuit for Magnetic Contactor {COIL OPERATING CIRCUIT FOR ELECTRIC CONTACTOR}

The present invention relates to a magnetic contactor, and more particularly to a coil drive circuit of a magnetic contactor.

In general, a magnetic contactor is a mechanical switching component controlled by an electromagnet, and refers to a device that connects a circuit between a power supply and a controlled load by operating a main pole of the magnetic contactor when the coil of the electromagnet is free.

Hereinafter, a coil driving circuit of a conventional magnetic contactor will be described.

1 is a block diagram illustrating a conventional coil driving circuit.

As shown, the coil drive circuit of the conventional magnetic contactor includes a rectifier 10 for rectifying the power input from the input terminal V1 to output a DC voltage, and a controller 12 for generating a control signal for driving the coil. The switching unit 13 turned on / off according to the control signal generated by the controller 12, the exciting coil 14 sucking the magnetic contactor, and the counter electromotive force generated by the coil 14 when the magnetic contactor is released. It is composed of a coil drive unit 15 for absorbing and shortening the release time.

The coil driver 15 may include a first diode D1 receiving power as an anode through the power input unit V1, a second diode D2 having an anode connected to a cathode of the first diode D1, and A third diode D3 having an anode connected to the cathode of the second diode D2, and one end connected to an anode of the first diode D1, and the other end connected to a cathode of the third diode D3 A transistor Q1 having an emitter connected to a capacitor C1, a cathode of the third diode D3, and one end connected to the capacitor C1, and one end connected to a base of the transistor Q1. A resistor R1 and a varistor TNR connected at both ends to an emitter and a collector of the transistor Q1, respectively.

The operation of the coil drive circuit of the conventional magnetic contactor configured as described above is as follows. First, when power is applied to the input terminal, the control unit 12 outputs a suction signal (One shot pulse) and a square wave sustain signal as shown in FIG. Then, the magnetic contactor is attracted at the output of the suction signal, and the suction state of the magnetic contactor is maintained at the output of the sustain signal. While the switching unit 13 is turned on by this holding signal, the capacitor C1 of the coil driving unit 15 is divided by the voltage drop of the first, second and third diodes D1, D2, and D3. As long as the charge is charged. Thereafter, when the switching unit 13 is turned off, the electric charge charged in the capacitor C1 is applied to the base of the transistor Q1 through the resistor R1, and accordingly the transistor Q1 is turned on. The current accumulated in the coil and the counter electromotive force generated when the coil is turned on / off during the period in which the switching unit 13 is turned on, flows back to the coil through the transistor Q1. At this time, since the complete discharge time of the capacitor C1 is longer than the OFF time of the switching unit 13, the switching unit 13 repeatedly performs on / off, so that a constant current flows in the coil, It will provide a constant holding force.

In this state, when the input power drops below the release voltage or when the power supply V1 is turned off, the control unit 12 outputs a release signal LOW. When the switching unit 13 is turned off, the capacitor C1 is turned off. The accumulated charge is applied to the base of the transistor Q1 through the resistor R1. Then, the transistor Q1 becomes conductive, and current accumulated in the excitation coil 14 flows through the coil 14 and the transistor Q1 during the conduction time. After that, when the charge accumulated in the capacitor C1 is consumed and no current is applied to the base of the transistor Q1, the transistor Q1 is turned off. At this time, the remaining current remaining in the coil is consumed through the varistor (TNR) and operates to release when the current falls below the suction holding force of the magnetic contactor.

However, the coil drive circuit of the conventional magnetic contactor has the following problems.

Capacitor C1 uses an electrolytic or tantalum capacitor, which leads to destruction of capacitor C1 when the allowable voltage or allowable ripple current is exceeded or a reverse voltage of 10% or more of the rated voltage is applied.

In addition, the varistor (TNR) is a cause of poor openness due to the deterioration of reliability and lifetime due to the continuous stress of the varistor (TNR) by the input voltage of the switching unit of several to several tens of kilohertz (KHz). Inability to perform the protection function causes the transistor Q1 to burn out and loses the function of the back EMF absorption circuit.

Accordingly, an object of the present invention is to provide a coil driving circuit of a magnetic contactor capable of stably maintaining a current flow of an excitation coil by maintaining a stable operation of a reverse electromotive force absorption circuit. do.

1 is a block diagram illustrating a conventional coil drive circuit.

FIG. 2 is a driving waveform diagram of the control unit of FIG. 1. FIG.

3 is a block diagram illustrating the coil driving circuit of the magnetic contactor according to the embodiment of the present invention;

4 is a detailed circuit diagram of FIG.

Explanation of symbols on the main parts of the drawings

100: rectifier 110: voltage drop

120: charging unit 130: departure control unit

140: switching unit 150: charge protection unit

160: switching control unit 170: first switching protection unit

180: second switching protection unit 190: third switching protection unit

200: control unit 300: coil driving unit

400: female coil

The coil drive circuit of the electromagnetic contactor of the present invention for achieving the above object, the magnetic contactor for generating a magnetic force between the movable core and the fixed core to maintain a constant induction electromotive force through the core by repeatedly charging and discharging the current flowing in the excitation coil In the coil drive circuit of the present invention, a voltage drop section for dropping an input voltage, a charging section for charging a voltage by the voltage drop section, and connected in parallel with the voltage drop section to discharge the charge of the charging section at a high speed, A release control unit for controlling the separation speed between the movable core and the fixed core, a switching unit controlled by the charging unit, a charging protection unit protecting the charging unit by limiting peak current flowing in the charging unit, and controlling the current of the switching unit. A switching control unit, a first switching protection unit for preventing burnout of the switching unit, and the switching unit And a third switching protection unit for preventing damage caused by electromotive force, and a third switching protection unit for blocking stress applied to the switching unit and the second switching protection unit and absorbing back electromotive force in the forward direction. It is done.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram illustrating a coil driving circuit of the magnetic contactor according to the embodiment of the present invention, and FIG. 4 is a detailed circuit diagram of FIG. 3.

First, as shown in FIG. 3, the coil driving circuit of the electromagnetic contactor according to the embodiment of the present invention rectifies the power input from the input terminal and outputs a DC voltage, and a control signal required for driving the coil. The control unit 200 for generating a, the excitation coil 400 for sucking the magnetic contactor, and the coil drive unit 300 for absorbing back EMF generated from the coil 400 when the magnetic contactor is released and shortens the release time do.

Here, the coil driver 300 is in parallel with the voltage drop unit 110 for dropping the input voltage, the charging unit 120 for charging the voltage by the voltage drop unit 110, and the voltage drop unit 110 in parallel. The release control unit 130 connected to discharge the charge of the charging unit 120 at a high speed to control the separation speed between the movable core and the fixed core, the switching unit 140 controlled by the charging unit 120, and the charging unit 120 The charging protection unit 150 to protect the charging unit 120 by limiting the peak current flowing through the), the switching control unit 160 for controlling the current of the switching unit 140, and to prevent burnout of the switching unit 140 Applied to the first switching protection unit 170, the second switching protection unit 180, and the switching unit 140 and the second switching protection unit 180 to prevent damage due to the counter electromotive force of the switching unit 140. A third switching protection unit 190 that blocks the stress and absorbs the counter electromotive force in the forward direction, The control unit 200 generates a control signal for driving the excitation coil to induce energy charging and generation of back electromotive force of the excitation coil.

At this time, the control unit 200 is composed of a switching element, the voltage drop unit 110 is a structure in which a plurality of diodes having an anode and a cathode connected in series, the departure control unit 130, the charge protection unit 150 and Each of the switching controllers 160 includes resistance elements, and the first switching protection unit 170 and the third switching protection unit 190 each include a diode, and the second switching protection unit 180 is a varistor. Preferably configured. The input voltage is a voltage in which an AC voltage is smoothed through a full-wave rectifier circuit.

Detailed circuit diagrams are as follows.

As shown in FIG. 4, the rectifying unit 100 smoothes the AC input voltage V1 through the first capacitor C1 through the full-wave rectification circuit, that is, the bridge circuit B composed of four diodes. To create. The input voltage V2 drops through the first, second, and third diodes D1, D2, and D3 connected in series constituting the voltage drop unit 110. The first, second, and third resistors R1, R2, and R3 having one end connected to the anode of the first diode D1 are connected in parallel. Each of the first, second, and third resistors R1, R2, and R3 represents the separation controller 130, the charge protector 150, and the switching controller 160 of FIG. 3.

Next, the other end of the second resistor R2 is connected to the (+) side of the second capacitor C2 and the (-) side is connected to the other end of the first resistor R1. The other end of the first resistor R1 is connected to the cathode of the third diode D3. In this case, the second capacitor C2 represents the charging unit 120 of FIG. 3.

Next, the other end of the third resistor R3 is connected to the base of the transistor TR1, and the emitter of the transistor TR1 is connected to the cathode of the third diode D3.

Next, a fourth diode D4 having an anode connected to the negative side of the second capacitor C2 and a cathode connected to the base of the transistor TR1 is provided. The fourth diode D4 represents the first switching protection unit 170 of FIG. 3.

Next, one end of the excitation coil 400 is connected to the cathode side of the third diode D3, and the other end thereof is connected to the switching element TR2 of the controller 200 of FIG. 3. In addition, the switching element TR2 is connected to the collector of the transistor TR1 and simultaneously to the anode of the fifth diode D5. The fifth diode D5 represents the third switching unit 190 of FIG. 3.

Next, the varistor TNR is coupled to the cathode of the fifth diode D5 and the cathode of the third diode D3. The varistor TNR represents the second switching protection unit 180 of FIG. 3.

Referring to the operation of the coil drive circuit of the electronic connector is configured as follows.

First, when the AC power supply V1 is applied, a voltage is applied to the excitation coil 400 through the first, second, and third diodes D1, D2, and D3 via the full-wave rectifying circuit B, and the controller If the control signal of the switching element TR2 of 200 is at the "high" level, the current flows through the excitation coil, and if the "low" level, the current does not flow through the excitation coil.

In the state where power is applied, a voltage equal to the potential difference (about 2.1 V) due to the voltage drop of the series diodes D1, D2, and D3 is applied to the base of the transistor TR1 through the second resistor R2. Charged at (C2), the base of transistor TR1 is always kept ON by this charged voltage. Therefore, the transistor TR1 is always in an operating state. When the control signal of the controller 200 is turned off, the counter electromotive force generated from the energy of the excitation coil 400 is changed from the fourth diode D4 to the transistor TR1. ¡Æ the excitation coil 400 circulates through the fourth diode D4 and discharges, and when the control signal of the controller 200 is turned on again, the current flows through the switching element TR2 to the excitation coil 400. Will flow. The excitation coil 400 is charged with energy while the switching element TR2 is on.

If the AC power supply voltage V1 is cut off, the energy charged in the excitation coil 400 is converted into an instantaneous reverse voltage and instantaneous counter electromotive force is generated at both ends of the excitation coil 400. At this moment, the counter electromotive force is discharged through the second resistor R2 and the third resistor R3 by the charge charged in the second capacitor C2 to turn on the transistor TR1 to turn on the fourth diode D4 → transistor. (TR1) → the excitation coil (400) → the fourth diode (D4) circulates to discharge. As such, the current flowing through the excitation coil 400 repeatedly generates charging and discharging and generates magnetic force between the movable core (not shown) and the fixed core (not shown) to maintain a constant induced electromotive force through the core (not shown). To function as a magnetic contactor.

When the AC power supply voltage V1 is cut off, the magnetic force disappears and falls between the movable core and the fixed core. At this time, the first resistor R1 quickly discharges the charge of the second capacitor C2, and thus the transistor. (TR1) is quickly turned OFF, which speeds up the speed of core drop.

The varistor TNR is a protection device for preventing the back electromotive force from damaging the transistor TR1. The varistor TNR maintains the potential between the collector and the emitter of the transistor TR1 below the varistor voltage to prevent burnout of the transistor TR1. do.

In addition, the fifth diode D5 blocks the stress applied to the collector of the transistor TR1 through the varistor TNR at the moment when the AC power supply voltage V1 is turned on, thereby blocking the varistor TNR and the transistor TR1. It serves as a protection and absorbs only back electromotive force in the forward direction.

The second resistor R2 serves to protect the second capacitor C2 by connecting the second capacitor C2 in series with a resistance value of several Ω. In addition, the fourth diode D4 serves to prevent burnout between the base and the emitter of the transistor TR1.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

The coil drive circuit of the magnetic contactor according to the present invention has the following effects.

The coil drive circuit of the electromagnetic contactor of the present invention can secure the reliability of the circuit by eliminating the cause of the functional degradation or loss of the capacitor, transistor, varistor affected by electrical stress, that is, back electromotive force.

Accordingly, by extending the life of the product, it is possible to solve the user's safety and loss of material costs, unnecessary time consumption.

Claims (8)

In the coil drive circuit of the magnetic contactor for generating a magnetic force between the movable core and the fixed core to maintain a constant induction electromotive force through the core by repeatedly charging and discharging the current flowing through the excitation coil, A voltage drop unit for dropping an input voltage; A charging unit for charging the voltage by the voltage drop unit; A separation control unit connected in parallel with the voltage drop unit to control a separation speed between the movable core and the fixed core by discharging the charge of the charging unit at a high speed; A switching unit controlled by the charging unit; A charge protection unit protecting the charging unit by limiting a peak current flowing in the charging unit; A switching control unit controlling a current of the switching unit; A first switching protection unit for preventing burnout of the switching unit; A second switching protection unit for preventing damage caused by counter electromotive force of the switching unit; And a third switching protection unit for blocking stresses applied to the switching unit and the second switching protection unit, and absorbing back electromotive force in the forward direction. The method of claim 1, And a control unit generating a control signal required for driving the excitation coil to induce energy charging and generation of back electromotive force of the excitation coil. The method of claim 2, The control unit coil contact circuit, characterized in that consisting of a switching element. The method of claim 1, The input voltage is a magnetic contactor coil drive circuit, characterized in that the AC voltage smoothed through the full-wave rectifier circuit. The method of claim 1, The voltage drop unit is a coil drive circuit of the magnetic contactor, characterized in that the structure having a plurality of diodes having an anode and a cathode connected in series. The method of claim 1, And the release control unit, the charge protection unit, and the switching control unit each comprise a resistance element. The method of claim 1, And the first switching protection unit and the third switching protection unit are each composed of a diode. The method of claim 1, The second switching protection unit is a coil drive circuit of the magnetic contactor, characterized in that composed of a varistor.