KR20090097038A - Coil Drive Circuit of Magnetic Contactor - Google Patents

Abstract

The present invention is to provide a coil drive circuit of a magnetic contactor that can be set by varying the trip voltage in the magnetic contactor, comprising: a voltage detector for detecting and outputting a voltage on a circuit to which the magnetic contactor is connected; A control unit for outputting a coil driving signal to open the magnetic contactor when the detected voltage is smaller than the reference voltage by comparing the detected voltage on the circuit output by the voltage detecting unit with an adjustable reference voltage, wherein the control unit is configured for the comparison. A comparator and a variable resistor connected to a reference input of said comparator for adjustment of a reference voltage; And a switching device for driving control of the drive coil such that the drive coil is excited or elemental.

Description

Coil Driving Circuit for Magnetic Contactor {COIL DRIVING CIRCUIT FOR MAGNETIC CONTACTOR}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic contactor, and more particularly, to a coil driving circuit of a magnetic contactor which allows a user to set a trip reference voltage in a variable manner.

A magnetic contactor is a switch for supplying or cutting off power to a load device such as an electric motor, and thus, a magnetic contactor is widely used as a main component of a factory automation system because it is possible to control the opening and closing of power supply or interruption through a control signal line.

In such a magnetic contactor, a function of protecting a load device by detecting a power supply voltage when the power supply voltage is lowered and cutting off the power supply (called an under voltage trip function) is required. May be used in addition to the magnetic contactor.

When there is a voltage sag caused by lightning, etc., it may be determined as normal and the operation of the load device may not be stopped.In case of undervoltage, the operation of the load device may be stopped according to the reference undervoltage value set. It may be. That is, the magnitude of the instantaneous voltage drop managed for each installation site of the factory automation system may be different, and thus, the user needs to be able to set the reference voltage of the low voltage trip of the magnetic contactor according to the load device.

However, in the related art, there is a problem in that it is impossible to set a trip reference voltage for a trip operation of the magnetic contactor according to the characteristics of the user's site.

Accordingly, the present invention solves the problems of the prior art, and an object of the present invention is to provide a coil drive circuit of a magnetic contactor in which a user can vary and set a trip reference voltage for a trip operation in the magnetic contactor.

An object of the present invention, in the coil drive circuit of the magnetic contactor for exciting control of the drive coil for opening and closing the magnetic contactor,

A voltage detector for detecting and outputting a voltage on a circuit to which the magnetic contactor is connected;

A control unit for outputting a coil driving signal to open the magnetic contactor when the detected voltage is smaller than the reference voltage by comparing the detected voltage on the circuit output by the voltage detecting unit with an adjustable reference voltage, wherein the control unit is configured for the comparison. A comparator and a variable resistor connected to a reference input of said comparator for adjustment of a reference voltage; And

It can be achieved by providing a coil drive circuit of a magnetic contactor according to the present invention, characterized in that it comprises a switching element for driving control of the drive coil so that the drive coil is excited or element. .

In the coil drive circuit of the magnetic contactor according to the present invention, since the user sets the reference voltage for the undervoltage trip operation in a variable manner, the reference voltage can be set appropriately for the site and the load device, so that the load device is stopped due to unnecessary trips. Can be prevented, and in the case of a low voltage sensitive load device, an appropriate reference voltage can be set to be protected when a low voltage occurs.

The object of the present invention and the constitution and effects of the present invention to achieve the same will be more clearly understood by the following description of the preferred embodiment of the present invention with reference to the accompanying drawings.

1 is a circuit block diagram showing the overall configuration of the coil drive circuit of the magnetic contactor according to the present invention, Figure 2 is a partial circuit block diagram showing the configuration of the coil opening and closing control in more detail in FIG.

In Fig. 1, the drive coil 6a for opening and closing the magnetic contactor, that is, the coil drive circuit of the magnetic contactor according to the present invention for exciting control of a trip coil, has a filter section 1. And a rectifier 2, a voltage detector 3, a constant voltage circuit 4, a controller 5 and a coil driver 6.

The filter unit 1 is a circuit for removing a noise signal that may be mixed into an AC power supply, and may be configured as, for example, a low pass filter circuit capable of removing a high frequency noise signal.

The rectifying section 2 is a rectifying circuit section for converting an AC power supply into a DC power supply, and may be composed of, for example, a well-known diode bridge circuit.

The voltage detector 3 detects and outputs a voltage on a circuit to which the magnetic contactor is connected, that is, a voltage on AC R, S, and T. The voltage detection unit 3 may be specifically configured as, for example, a displacement transformer.

The constant voltage circuit unit 4 is provided to supply a constant reference voltage to the control unit 5 even when the power supply voltage of the AC power source changes. In other words, supplying the constant voltage by the constant voltage circuit unit 4 is a trip determination and coil drive signal generation circuit unit of the subsequent step of determining a low voltage trip when the power supply voltage of the AC power supply changes and becomes a low voltage. This is to prevent the occurrence of an error in the trip determination and to obtain a reliable trip control operation by providing a constant reference voltage to the open / close control unit 5a invariably. The constant voltage circuit section 4 may, for example, consist of a circuit section of a Zener diode and / or a capacitor, as is well known.

The controller 5 compares the detected voltage on the circuit output by the voltage detector 3 (see Vdet in FIG. 2) with the adjustable reference voltage (see Vref in FIG. 2), and when the detected voltage is smaller than the reference voltage, A coil drive signal is output to open the magnetic contactor. To this end, as shown in FIG. 2, the control unit 5 includes a coil opening and closing control unit 5a, a pulse width modulation unit 5b, and an inrush time and operation control circuit unit 5c.

Here, as shown in FIG. 2, the detailed configuration of the coil opening and closing control unit 5a includes a comparator 5a-1 and a reference voltage Vref for comparing the detected voltage Vdet with the adjustable reference voltage Vref. Variable resistor R2 connected to the reference input terminal (+ input terminal) of the comparator 5a-1. In the circuit of the coil opening / closing control section 5a, reference numeral R1 is a voltage establishing resistor for establishing a reference voltage, and diode D1 is a reversing prevention diode.

The coil opening / closing control unit 5a compares the detection voltage Vdet on the circuit with the adjustable reference voltage Vref and determines that the detection voltage is smaller than the reference voltage to determine a low voltage state to open the electromagnetic contactor. Outputs

The pulse width modulation section 5b is connected to the output terminal of the coil opening and closing control section 5a, and if the following first switching element 6b is opened and closed control according to the coil drive signal (i.e., the coil drive signal for tripping) Output a low potential signal to control the first switching element to an open position and high to control the first switching element to an on position if there is no coil drive signal for tripping; By outputting a potential signal, the drive coil 6a can be controlled to be excited or demagnetized, and a constant holding current can be supplied to the drive coil 6a even when the applied voltage changes by the pulse width control of the switching control signal. Will be.

The inrush time and the operation control circuit unit 5c control the opening and closing of the second switching element 6c for controlling the on or off operation of the first switching element 6b, but depending on the instantaneous (temporary) undervoltage condition. When the detection voltage Vdet from the voltage detector 3 is lower than the reference voltage Vref even after a preset delay time to prevent a trip malfunction, the second switching element 6c is controlled to the open position and is set in advance. After the delay time, if the detected voltage Vdet from the voltage detector 3 is greater than the reference voltage Vref, the second switching element 6c is controlled to the closed position. That is, the inrush time and the operation control circuit section 5c control the second switching element 6c so that the output of the coil drive signal according to the undervoltage trip determination of the coil opening and closing control section 5a becomes effective after a predetermined delay time. As a negative portion, it may be composed of a delay circuit by a resistor and a capacitor and a second comparator circuit. Here, the second comparator circuit may be configured in the same manner as the configuration of the comparator circuit shown in FIG. 2, or may be configured with a fixed resistance of a resistance value connected to the reference voltage input terminal of the comparator.

The first switching element 6b is controlled to open and close according to the output signal from the pulse width modulation unit 5b, and is driven through the rectifying unit 2 at the closed position of the first switching element 6b. By making the circuit of the power supply supplied to 6a into a closed circuit, the drive coil 6a is excited or the rectifying section 2 is opened in the open position of the first switching element 6b. The drive coil 6a is drive-controlled (aka excitation control) so that the drive coil 6a is made an element by making an open circuit of a power supply circuit supplied to the drive coil 6a through the open circuit.

The first switching element 6b and the second switching element 6c may be formed of a semiconductor element capable of opening and closing control such as a transistor and a thyristor.

The operation of the coil driving circuit of the magnetic contactor according to the preferred embodiment of the present invention configured as described above will be described with reference to FIGS. 1 and 2.

In Fig. 1, the power signal from the AC power supply to the load side is converted to DC power through the rectifying section 2 and supplied to the trip coil 6a in a state where noise is removed through the filter section 1. The voltage detecting section 3 is connected to the line from the filter section 1 to the rectifying section 2 and detects the voltage value of the power signal from the AC power supply to the load side. The signal of the detection voltage Vdet indicating the voltage value of the power signal from the AC power supply detected by the voltage detection section 3 to the load side is applied to the negative input terminal of the comparator 5a-1 of FIG. The comparator 5a-1 compares the reference voltage Vref and the detected voltage Vdet obtained from the resistor R1 with respect to the DC constant voltage from the constant voltage circuit section 4 and the divided voltage by the variable resistor R2. If the detection voltage Vdet is smaller than the voltage Vref, this means that the voltage supplied from the AC power supply to the load side is undervoltage condition lower than the reference voltage preset by the user through adjustment of the variable resistor R2. Therefore, at this time, the comparator 5a-1 outputs a coil driving signal to open the magnetic contactor. The output of the coil driving signal may be represented as a signal output having a high potential. The detection voltage Vdet rather than the reference voltage Vref. ) Is greater than or equal to Means that the voltage supplied from the AC power supply to the load side is a normal state which is higher than or equal to a reference voltage preset by the user through adjustment of the variable resistor R2, and thus the magnetic contactor is opened from the comparator 5a-1. There is no output of the coil drive signal, and the absence of the output of the coil drive signal may be represented by the signal output of the low potential from the comparator 5a-1.

Subsequently, the pulse width modulation section 5b is connected to the output terminal of the coil opening and closing control section 5a, and controls the opening and closing control of the following first switching element 6b according to the coil driving signal (i.e., if the coil driving signal is present, Outputting a low potential signal to control the first switching element to the off position and outputting a high potential signal to control the first switching element to the on position if there is no coil drive signal. Control 6a) to be small or excited. At this time, the pulse width control of the switching control signal can supply a constant output current to the drive coil 6a even if the applied voltage changes.

In addition, at this time, the inrush time and the operation control circuit unit 5c detect the voltage Vdet from the voltage detector 3 even after a preset delay time to prevent a trip malfunction due to an instantaneous undervoltage condition. When lower, the second switching element 6c is controlled to the open position, and if the detected voltage Vdet from the voltage detector 3 is greater than the reference voltage Vref after the preset delay time, the second switching element ( 6c) is controlled to the on position.

When the second switching element 6c is switched to the open position due to the inrush time and the closing position control signal of the operation control circuit section 5c, that is, off, the circuit of current flows through the trip coil 6a. Since it opens, the trip coil 6a is demagnetized, so that the movable contact is separated from the fixed contact by the elastic force of the return spring, which is not shown in accordance with the element of the trip coil 6a, but is attached to the electromagnetic contactor, thereby tripping, i.e., breaking the circuit. This is done.

If the detected voltage Vdet of the power supply line from the AC power supply to the load device is greater than the reference voltage Vref for a predetermined delay time or more, the inrush time and the operation control circuit section 5c and the second switching element 6c are closed. In the on position, the pulse width modulator 5b controls the first switching element 6b to the closed position according to the coil drive signal from the coil opening and closing control section 5a, thereby driving the drive. As the circuit supplied with the coil 6a becomes a closed circuit, the driving coil 6a is excited, thus overcoming the elastic force of the return spring placed on the electromagnetic contactor and driving the movable contact to contact the fixed contact, thereby driving the load device from the load device. The circuit in the furnace becomes a closed circuit so that the load device can be operated.

1 is a circuit block diagram showing the overall configuration of the coil drive circuit of the magnetic contactor according to the present invention,

FIG. 2 is a partial circuit block diagram illustrating a configuration of a coil opening and closing control unit in FIG. 1 in more detail.

* Explanation of symbols on the main parts of the drawings

1: filter part 2: rectification part

3: voltage detection section 4: constant voltage circuit section

5: control part 5a: coil opening and closing control part

5a-1: comparator

5b: pulse width modulation section 5c: inrush time and operation control circuit section

6: coil drive part 6a: drive coil (excitation coil)

6b: first switching element 6c: second switching element

6d: flywheel diode

Claims (4)

In the coil drive circuit of the magnetic contactor for exciting control of the drive coil for opening and closing the magnetic contactor, A voltage detector for detecting and outputting a voltage on a circuit to which the magnetic contactor is connected; A control unit for outputting a coil driving signal to open the magnetic contactor when the detected voltage is smaller than the reference voltage by comparing the detected voltage on the circuit output by the voltage detecting unit with an adjustable reference voltage, wherein the control unit is configured for the comparison. A comparator and a variable resistor connected to a reference input of said comparator for adjustment of a reference voltage; And And a switching element for controlling the drive coil to drive or excite the drive coil. The method of claim 1, The control unit,  A coil opening / closing control unit which compares a detection voltage on a circuit with an adjustable reference voltage and determines a undervoltage condition when the detection voltage is smaller than the reference voltage to output a coil driving signal to open the magnetic contactor; A pulse width modulation circuit connected to an output terminal of the coil opening and closing control unit, controlling on or off of the switching element according to a coil driving signal from the coil opening and closing control unit, and supplying a constant holding current to the driving coil; Coil drive circuit of a magnetic contactor, characterized in that configured. The method of claim 2, A second switching element for controlling an on or off operation of the switching element; And In order to prevent a trip malfunction when an instantaneous undervoltage occurs, an inrush time and an operation control circuit unit for controlling the second switching element on or off are added to delay the predetermined time delay of the coil driving according to the undervoltage determination of the coil switching controller. Coil drive circuit of a magnetic contactor comprising a. The method of claim 1, And a constant voltage circuit unit for supplying a constant reference voltage to the control unit even when the power supply voltage changes.

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