KR100695766B1 - Control device of inverter - Google Patents

Abstract

The present invention relates to an inverter control device having a capacitor short detection section for protecting the inverter circuit.

The present invention is composed of an input unit for supplying electric power from the three-phase power source to the DC power source, an output unit for driving the motor, a control unit for controlling the voltage and current of the input unit and the output unit, and a control power supply unit for supplying power to the control unit In the inverter control device, the control unit receives a DC voltage and an output current from the DC voltage detector of the input unit and the output current detector of the output unit, respectively, to control the voltage and frequency desired by the user, and the output module of the pulse width modulation And a capacitor short detection section for monitoring whether a sudden change in the DC voltage occurs through the DC voltage detector.

Inverter, Controller, Capacitor

Description

Inverter Controller {CONTROL DEVICE OF INVERTER}

1 is a block diagram of a conventional inverter control apparatus.

2 is a configuration diagram of an inverter control apparatus of the present invention.

3 is an explanatory diagram for explaining the operation of the present invention.

(Explanation of the sign)

60 Rectifier 70 Output Module

80 Magnetic Contactor 90 Charge Resistance

100, 110 Capacitor 130 DC Voltage Detector

150 Current detector 160 Control power supply

170 Control calculator 180 Pulse width modulation generator

190 Capacitor short circuit detection

The present invention relates to an inverter control device for driving control of an induction motor, and more particularly, to an inverter control device having a capacitor short circuit detecting unit for protecting an inverter circuit from a flame and an explosion caused by a short circuit of a capacitor.

In general, an inverter is a device for controlling the operation of an induction motor. Inverters are widely used for industrial purposes as devices for variable speed driving of induction motors. In particular, the demand is gradually increasing in terms of industrial automation and energy saving. In the past, a variable speed system was constructed using a DC motor with easy speed and torque control. However, in recent years, due to the development of power electronic technology, induction motors have become inexpensive and maintenance-free while achieving almost the same control performance as DC motors. It was used.

Inverter devices for driving such motors have been able to drive motors of hundreds of horsepower or more due to the rapid development of semiconductor technology in the last two decades.

In general, the inverter is largely composed of an input unit, an output unit, and a control unit. As the capacity thereof increases, the capacity and size of components constituting the input unit and the output unit also increase.

Therefore, the damage of accidents caused by these parts is also increased, so it is increasingly complicated in terms of the control unit, and the protection function of failure for each part is increasing.

Hereinafter, the configuration of the conventional inverter control apparatus is as shown in FIG.

Referring to the configuration and operation of the inverter control apparatus according to Figure 1 as follows.

The inverter controller receives an input from the three-phase power source 10, the input unit 20 to make a DC power source, an output unit 30 for driving the induction motor 50 by converting the DC power source to an AC power source, and the input unit It consists of a control operation unit 170 for controlling the output unit to output a variable voltage, a variable frequency of power having a DC power source made in and a pulse width modulation generator 180 for outputting a pulse width modulation (PWM) signal The control part 40 and the control power supply part 160 which supplies power to the control part 40 are comprised.

The input unit 20 includes a rectifier 60 consisting of a three-phase rectifier diode bridge, a charging resistor 90 for preventing excessive inrush current from flowing during initial charging, and initial charging is completed to exclude the charging resistance. And a condenser (100, 110) for smoothing the power rectified by the rectifier (60). In addition, in the 400V class inverter, two capacitors are connected in series due to the breakdown voltage.

The output unit 30 is composed of an output module 70 consisting of six power switches and a current detector 150 for detecting the output current.

Next, the operation according to Fig. 1 is as follows.

The rectifier 60 receives power from an AC power source of three phases and rectifies it to serve as a DC power source. This rectified power is input to the capacitor bank through an initial charging section consisting of a charging resistor 90 and an electromagnetic contactor 80.

Since the magnetic contactor 80 is turned off at the initial stage when the three-phase AC power is turned on, the DC power rectified through the charging resistor 90 is input to the capacitors 100 and 110.

The control power supply unit 160 supplies the control power required to the control unit 40 by inputting the DC voltage stored in the condenser (100, 110).

The control operation unit 170 of the control unit 40 receives a DC voltage and an output current from the DC voltage detector 130 of the input unit 20 and the output current detector 150 of the output unit 30, respectively. A frequency is generated, and the voltage and the frequency are output through the pulse width modulation generator 180 to output the gate signal of the pulse width modulation to the output module 70.

In addition, when the initial power is turned on when the inverter power is turned on, the electromagnetic contactor 80 is turned on through an excitation signal of the electromagnetic contactor 80 so that the rectified power is smoothly introduced into the capacitors 100 and 110.

The output unit 30 converts the DC power into three-phase AC power by inputting a gate signal to the output module to supply the induction motor 50 with power of three-phase variable voltage and variable frequency. The output current signal of the motor is sent to the controller 40.

When a short circuit accident occurs in the condenser 100 or the condenser 110 in the conventional inverter device described above, an excessive voltage above the rated voltage is applied to the condenser that does not have a short circuit. For example, when a short circuit accident occurs at both ends of the capacitor 110, the capacitor 110 is discharged in an instant, so that power supplied through the rectifier 60 is introduced into the capacitor 100 without limiting the current. As such, when an excessive voltage is applied to a single capacitor due to a short circuit, the insulation of the insulator inside the capacitor is destroyed, a short circuit phenomenon occurs, gas may explode, or may cause a fire.

 Accordingly, an object of the present invention is to provide an inverter control device that detects a short circuit of a DC capacitor connected in series in an inverter control device and cuts off an excitation signal of the electromagnetic contactor by the detection signal.

In addition, another object of the present invention to provide an inverter control device that prevents the risk of explosion of the capacitor by the inrush current by controlling the input current input to the capacitor even if a short circuit occurs in one of the DC capacitors connected in series in the inverter controller. have.

Other objects and advantages of the present invention will be described below, which is not limited to the matters disclosed in the claims of the present invention and the disclosures of the embodiments thereof, but also to the broader ranges by means and combinations within the range that can be easily contemplated therefrom. Add that it will be included.

In order to achieve the above object, the present invention provides an input unit for supplying electric power from a three-phase power source to the DC power source, an output unit for driving the motor, a control unit for controlling the voltage and current of the input unit and the output unit, An inverter control device comprising a control power supply unit for supplying power, wherein the control unit receives a DC voltage and an output current from a DC voltage detector of an input unit and an output current detector of an output unit, respectively, and controls the control unit to control a desired voltage and frequency. And a pulse width modulation generator for outputting the gate signal of the pulse width modulation to the output module, and a capacitor short circuit detection unit for monitoring whether a sudden change in the DC voltage occurs through the DC voltage detector.

The capacitor short circuit detecting unit of the control unit detects the falling voltage for a predetermined time of the DC voltage as the falling slope (dv / dt), and is greater than the falling slope value, characterized in that the excitation signal of the magnetic contactor is turned off.

The capacitor short detection unit detects a DC voltage value through an AD converter and detects a short circuit of a capacitor connected in series. When the detected value is equal to or greater than a reference value, the magnetic contactor 80 is turned off through an excitation signal of the electromagnetic contactor. It is characterized by generating a signal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, when it is determined that the detailed description of related known functions or known configurations or obvious matters to those skilled in the art may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

2 is a block diagram of an inverter control apparatus according to an embodiment of the present invention.

As shown in FIG. 2, the inverter control apparatus according to the embodiment of the present invention receives an input from the three-phase power source 10, the input unit 20 to make a direct current power source, and converts the direct current power source into an alternating current power source. 50 and an output unit 30 for driving the control unit 170 and a pulse width modulation (PWM) signal for controlling the output unit to output a variable voltage and a variable frequency power using a DC power source made by the input unit. The pulse width modulation generator 180 outputs a signal and detects whether a sudden change occurs in the DC voltage through the DC voltage detector, and turns the electronic contactor OFF through the excitation signal of the electromagnetic contactor from the detection signal. The control part 40 comprised and the control power supply part 160 which supplies power to the control part 40 are comprised.

The input unit 20 includes a rectifier 60 consisting of a three-phase rectifier diode bridge, a charging resistor 90 for preventing excessive inrush current from flowing during initial charging, and when initial charging is completed and becomes a normal energized state. And a capacitor 100 and 110 for smoothing the power rectified by the rectifier 60 and the electromagnetic contactor 80 for short-circuit preventing loss due to charging resistance. In the case of 400V class inverters, two capacitors are connected in series due to the breakdown voltage, and Vdc represents the magnitude of the voltage across the smoothing capacitor.

The output unit 30 is composed of six power switches, and the power switch turns on / off the DC voltage stored in the capacitor to change the DC voltage into an AC voltage and an output current. It consists of a current detector 150 for detection.

Referring to Fig. 2, the operation of the present invention is as follows.

As shown in FIG. 2, the three-phase AC power supply 10 is rectified through the rectifier 60 and then input to the capacitor bank through an initial charging section consisting of a charge resistor 90 and an electromagnetic contactor 80.

In the initial stage when the three-phase power is turned on, the magnetic contactor 80 is turned off, and the rectified DC power supplied through the charging resistor 90 is input to the capacitors 100 and 110. In addition, since there is no means for limiting excessive inrush current without the charging resistor 90 at the beginning, it is used for current limiting to prevent excessive current from flowing in.

As the capacitor, an electrolytic capacitor having a polarity and a very small charge / discharge is used for smoothing, and maintains a constant voltage during normal operation, and loads the induction motor 50 connected to the output of the inverter. This output also plays a role in making the DC voltage change small.

The control power supply unit 160 supplies the control power required to the control unit 40 by inputting the DC voltage stored in the capacitors 100 and 110. The control power supply unit 160 consumes a certain amount of power because the control power supply unit 160 operates even when the inverter is stopped.

The control operation unit 170 of the control unit 40 receives a DC voltage and an output current from the DC voltage detector 130 of the input unit 20 and the output current detector 150 of the output unit 30, respectively. A frequency is generated, and the generated voltage and frequency are outputted through the pulse width modulation generator 180 to the output module 70 to output a gate signal of the pulse width modulation. In addition, when the initial charging is completed when the inverter is powered on, the electronic contactor 80 is turned on to immediately flow the rectified power smoothly into the capacitors 100 and 110.

The capacitor short detection unit 190 detects whether a sudden change in the DC voltage occurs through the DC voltage detector 130, and if the detected value is more than a reference value, the magnetic contactor 80 is turned off through an excitation signal of the electromagnetic contactor. Generates a signal.

The output unit 30 converts the DC power into three-phase AC power by inputting a gate signal to the output module to supply the three-phase variable voltage and variable frequency power to the induction motor 50. The output current signal of the induction motor 50 is transmitted to the control unit 40.

3 is an explanatory diagram for explaining the operation of the present invention. Referring to Figure 3 describes the operation of the present invention.

As shown in ① of Fig. 3, when t = T1, for example, a short circuit occurs at both ends of the capacitor 110, the capacitor 110 discharges in an instant, so that the power supplied through the rectifier 60 limits the current. All will flow into the condenser 100 without.

Therefore, the DC voltage drops rapidly to a voltage close to half of normal time, as shown by 2 in FIG. At this time, the falling slope of the voltage (that is, the falling voltage (dv / dt) with respect to the predetermined time) falls very rapidly than the changing slope of the voltage when the inverter is loaded.

Next, as shown in 3 in FIG. 3, the capacitor short circuit detection unit 190 detects the slope of the DC voltage and when this value is equal to or greater than a certain reference value (e.g., a value larger than the slope that changes when the inverter is loaded). (I.e., if t = T2), the signal to be turned off is transmitted to the magnetic contactor 80 through the excitation signal of the magnetic contactor 8.

Then, the magnetic contactor 80 is turned off (i.e., t = T3) as shown in ④ of FIG. 3, and the current flowing through the rectifier 60 flows through the charging resistor 90.

Through the above process, it is possible to prevent excessive voltage from being applied to one capacitor due to a short circuit.

Here, if the inverter is not in operation and is in the stopped state, only the control power supply unit 160 operates. If the inverter is in operation, the output voltage is larger than the input power input through the resistor, so the DC voltage keeps falling and the inverter cannot operate. The voltage reaches up to this level, which causes the output of the inverter to be blocked so that the inverter is stopped and only the control power supply unit 160 operates.

The control power supply unit 160 continues to consume power of the DC unit because the inverter continues to operate even in the stopped state. Therefore, the current of this power consumption causes a voltage drop of the charging resistor 90, thereby lowering the voltage of the capacitor so that the capacitor does not explode.

In addition, a capacitor that does not have a short circuit is subjected to a high voltage above the rated voltage, and an overcurrent flows between the electrodes inside the capacitor. However, because of the presence of the charging resistor, the current is limited, and this current causes a voltage drop in the charging resistor. The voltage applied will also decrease. In other words, the capacitor which has been overvoltage is lowered again so as not to become overvoltage.

On the other hand, the embodiment is only for illustrating the present invention, the scope of protection of the present invention is not limited by the embodiment, it can be applied to the range that those skilled in the art can easily use the present invention for other external devices. Affirm that there is.

As described above, according to the present invention, even if a short circuit occurs in one of the DC capacitors connected in series in the inverter control device, the input current input to the capacitor can be restricted through the capacitor short circuit detection unit, and the capacitor voltage is also reduced to explode the capacitor. It is effective to avoid.                     

Other effects of the present invention, as well as those described in the above-described embodiments and claims of the present invention, as well as the effects that can occur within a range that can be easily estimated from them and the potential of the potential advantages that contribute to industrial development Add that they will be covered by a wider scope.

Claims (3)

An output unit including an input unit receiving electric power from a three-phase power source to form a DC power source, an output module for outputting an AC voltage for driving an electric motor by turning on and off a DC voltage stored in a capacitor, and pulse width modulation on the output module A control unit including a pulse width modulation generator for outputting a gate signal of the control unit; a control operation unit for receiving a DC voltage and an output current from a DC voltage detector of the input unit and an output current detector of the output unit; In the inverter control device consisting of a control power supply for supplying power to the control unit, The control unit detects the falling voltage for a predetermined time of the DC voltage through the DC voltage detector as the falling slope (dv / dt), and if the detected falling slope is greater than the falling slope value which is changed when the inverter is loaded, the magnetic contactor Inverter short circuit detection unit for outputting a signal for turning off the excitation signal of the inverter control device comprising a. delete The method of claim 1, The capacitor short circuit detecting unit detects a DC voltage value through an AD converter.

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