KR101884388B1 - System for detecting voltage unbalance of three phase motor control center - Google Patents

System for detecting voltage unbalance of three phase motor control center Download PDF

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KR101884388B1
KR101884388B1 KR1020160138463A KR20160138463A KR101884388B1 KR 101884388 B1 KR101884388 B1 KR 101884388B1 KR 1020160138463 A KR1020160138463 A KR 1020160138463A KR 20160138463 A KR20160138463 A KR 20160138463A KR 101884388 B1 KR101884388 B1 KR 101884388B1
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voltage
diode
phase
capacitor
anode
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KR1020160138463A
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KR20180044665A (en
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곽동걸
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강원대학교 산학협력단
대우강건(주)
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
    • G01R29/18—Indicating phase sequence; Indicating synchronism
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks

Abstract

The voltage unbalance detection system of the present invention comprises a three-phase capacitor connected to each line of the three-phase power sources R, S and T and having the same capacitance, a first diode whose anode is connected to the three-phase capacitor, A second diode whose cathode is connected to the anode of the first diode, a third diode whose anode is connected to ground, a fourth diode whose cathode is connected to the ground, one side of which is connected to the cathode of the first diode and the third diode And the other side of which is connected to the anode of the second diode and the fourth diode, and an electrolytic capacitor connected to both sides of the electrolytic capacitor. When a direct current voltage is generated in the electrolytic capacitor, And a voltage unbalance detection circuit section.
According to the present invention, a three-phase motor control panel voltage imbalance detection system is proposed to prevent an electric fire accident due to a voltage unbalance accident and an image accident, and to prevent various accidents related to voltage unbalance.

Description

[0001] The present invention relates to a three-phase motor control panel, a voltage unbalance detection system,

The present invention relates to a three-phase power system using a three-phase motor, and more particularly, to a system for detecting a voltage imbalance in a three-phase motor control panel.

In the field, short-circuit faults, insulation deterioration and overcurrent accidents occupy more than 20% of all electric accidents in the field using three-phase motors. The main causes of accidents are accidents caused by voltage imbalance of 3-phase motor control panel used in industrial field , Overload, and insulation aging. This is because, when voltage unbalance, phase short circuit or phase one is formed in a 3-phase power system using a 3-phase motor, unbalance current flows in the system or single phase power is supplied to cause a fire due to overcurrent of the motor coils, .

According to the statistics released by the Korea Electric Association, the cause of the motor failure in the industrial field and the cause of the motor-based fire are the relays installed in the motor control panel, that is, the aging of the electromagnetic contactor (EMC) or the electromagnetic switch Chattering due to contact failure due to contact aging, chattering tracking, current generation, phase loss, overload, aging of surrounding insulation, abrasion of contacts, etc., and mechanical wear such as wear of motor shaft and aging of surrounding insulation The cause is predicted to some extent, and it is possible to prevent breakdown or power failure due to deterioration in advance. However, it can not be predicted because of overcharging due to chattering phenomenon such as insulation aging, connection contact failure, And are classified as main factors of electric fire.

When voltage unbalance or phase failure occurs in such a three-phase motor, a current of about 1.5 times the rated current flows in the motor, and a fire caused by the deterioration of the motor internal winding is attracting attention. In addition, when the motor is started or turned on in a voltage unfavorable state or in an image-forming state, a starting current of 6 to 8 times the rated current flows, resulting in a serious disaster as well as burnout of the motor.

The protection against the voltage imbalance of the three-phase motor is not required, so it is almost defenseless in the actual field, and most of the cases are installed depending on the recognition of the field manager and the necessity.

Also, since the motor control system is composed of a plurality of relays (electromagnetic contactors and electromagnetic switches) in the motor control panel, it is very important to provide separate protection measures for the safety management of the electromagnetic contactors and the electromagnetic switches.

In a three-phase power system using a three-phase electric motor in an industrial field, the prevention of electric accidents depends entirely on the protective relays of thermal breaker (THR: Thermal Relay) of the circuit breaker in the panel board and the motor control panel.

First, a wiring breaker is a mechanism that can open and close a converter in a normal state manually or electrically, and automatically shut off the converter when an accident such as an overload or a short circuit occurs. In recent years, the circuit breaker has been manufactured for both electric leakage and overload. However, such a circuit breaker is analyzed to have no chattering phenomenon, voltage imbalance, and detection of image formation due to poor contact between the electronic contactor and the electromagnetic switch.

The thermal overcurrent relay (THR) or the electronic motor protection relay (EMPR), which is used as a protective relay for the motor control panel, can detect only when overcurrent or overheating occurs, and the voltage unbalance rate is 70% The system is designed to trip within 3 seconds, and the response speed is slow, and frequent malfunctions and precision in the field are lowered. In addition, the electronic motor protection relay is sold at a high price, making it difficult for general users to easily purchase.

For this reason, electrical fires in industrial sites are increasing every year, and damage to property as well as property damage is a problem in our society.

In order to solve this problem, in the present invention, when voltage unbalance or phase failure due to defects, aging, contact failure, etc. of relays such as electromagnetic contactors and electromagnetic switches used in a motor control panel occurs, There is a need to develop a new motor control panel voltage imbalance detection system that prevents electrical fires from overloading the load.

Korean Patent Publication No. 10-2015-0133383

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above-mentioned problems, and it is an object of the present invention to provide a motor control apparatus and a motor control apparatus capable of promptly interrupting a voltage unbalance or an imaging error caused by defects, aging, The present invention provides a three-phase motor control panel voltage unbalance detection system that protects a power system and prevents electric fires due to an overcurrent of a motor load.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, a voltage unbalance detection system according to the present invention is a voltage unbalance detection system in which one side is connected to each line of three-phase power sources R, S and T, and a three-phase capacitor having the same capacitance value, A second diode having a cathode connected to the anode of the first diode, a third diode having an anode connected to ground and a cathode connected to the cathode of the first diode, A fourth diode having a cathode connected to the ground and an anode connected to the anode of the second diode, one end connected to the cathode of the first diode and the third diode, the other end connected to the anode of the second diode and the fourth diode, And an electrolytic capacitor connected to both sides of the electrolytic capacitor. When a DC voltage is generated in the electrolytic capacitor, Unbalanced voltage detection circuit for detecting an equilibrium and a trip (trip) a circuit connected to the unbalanced voltage detecting circuit.
The voltage unbalance detection circuit unit includes a terminal for connecting one terminal of the electrolytic capacitor, the other terminal of the electrolytic capacitor, and a terminal for dividing a DC voltage applied to the electrolytic capacitor, A first resistor having one side connected to the variable terminal of the variable resistor and a fifth capacitor having one side connected to the other side of the first resistor and the other side connected to the other terminal of the variable resistor, A Zener diode whose cathode is connected to the other side of the first resistor and one side of the fifth capacitor, a gate connected to the anode of the Zener diode, and a cathode connected to the other side of the fifth capacitor A silicon controlled rectifier (SCR) and one side thereof are connected to one terminal of the variable resistor, And a relay connected to the anode of the SCR.
Phase voltage is 0 V, a stable state is maintained without detection of an abnormal voltage, and when a neutral-point voltage appears in the three-phase capacitor, a DC voltage is generated in the electrolytic capacitor, When the magnitude of the divided voltage becomes larger than the Zener voltage of the Zener diode, the Zener diode conducts and triggers the gate of the SCR so that the SCR is turned on, so that the trip circuit is operated by the contact operation of the relay.
The voltage unbalance detection circuit may further include an LED connected between one side of the variable resistor and one side of the relay.

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According to the present invention, a three-phase motor control panel voltage imbalance detection system is proposed to prevent an electric fire accident due to a voltage unbalance accident and an image accident, and to prevent various accidents related to voltage unbalance.

Further, according to the present invention, it is possible to prevent electrical fire due to relay chattering phenomenon and voltage unbalance accident which can not be prevented by conventional circuit breaker, wiring breaker, thermal overcurrent relay, electronic motor protection relay, etc., Safety and life protection as well as economic loss is effective.

In addition, it is expected that it will contribute to improvement of domestic competitiveness and prevention of national economic loss by lowering dependence on foreign countries and import dependence due to lack of technology of domestic electric fire companies, and inducing related technology development and technology diffusion.

In addition, since the three-phase motor control panel voltage imbalance detection system of the present invention can be implemented in a small size and lightweight, it is expected to prevent large-scale human injury and property damage caused by electric fire, do.

Further, the three-phase motor control panel voltage imbalance detection system of the present invention can be easily mounted in an electric motor control panel, so that the stability and handling of the product can be facilitated.

Further, according to the present invention, it is expected that the safety frustration of the field workers to the disaster of various unexpected motor control panels and the well-working working conditions and environment due to the emotional stability can be settled.

1 is a diagram illustrating a basic principle of voltage unbalance detection according to an embodiment of the present invention.
2 is a circuit diagram of a voltage imbalance detection system according to an embodiment of the present invention.
3 is an exemplary diagram illustrating a connection between a three-phase motor control panel and a voltage unbalance detection system according to an embodiment of the present invention.
4 is a circuit diagram illustrating a voltage unbalance detection system for operating an RCD according to an exemplary embodiment of the present invention.
5 is a diagram illustrating circuit constant values of main circuit elements of a voltage unbalance detection system according to an exemplary embodiment of the present invention.
6 is a graph showing an operation waveform of the voltage unbalance detection system according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted in an ideal or overly formal sense unless expressly defined in the present application Do not.

In the following description of the present invention with reference to the accompanying drawings, the same components are denoted by the same reference numerals regardless of the reference numerals, and redundant explanations thereof will be omitted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The present invention relates to a system for detecting voltage imbalance in a three-phase motor control panel.

FIG. 1 is a diagram illustrating a basic principle of voltage unbalance sensing according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a voltage unbalance sensing system according to an embodiment of the present invention.

FIG. 1 shows a basic principle diagram of a control algorithm using a neutral voltage to detect voltage unbalance, phase loss, and chattering tracking electric accidents in a motor control panel or a three-phase power system. The detection algorithm proposed in the present invention uses a composite potential of a three-phase power supply, that is, a neutral voltage. In the case of a balanced three-phase power supply, the composite potential is 0 V, but when an unbalanced three- The neutral point voltage V n appears as shown in Equation (1).

Figure 112016103176458-pat00001

Here, V a , V b , and V c are magnitudes of respective phase voltages for R, S, and T phases.

The circuit proposed in the present invention has a principle in which a trip circuit according to the adjusted voltage unbalance ratio operates as well as an image using the magnitude of the neutral point voltage.

Referring to FIGS. 1 and 2, a voltage unbalance detection system according to an exemplary embodiment of the present invention includes a voltage unbalance detection circuit unit 100 and a trip circuit unit 200.

The three-phase capacitors C 1 , C 2 , and C 3 are connected to the respective lines of the three-phase power sources R, S, and T, respectively, and have the same capacitance value.

The first diode D a has an anode connected to the three-phase capacitors C 1 , C 2 and C 3 .

The second diode D b has a cathode connected to the anode of the first diode D a .

The third diode (D c ) has its anode connected to ground (G).

The cathode of the fourth diode (D d ) is connected to the ground (G).

The electrolytic capacitor C 4 has one side connected to the cathodes of the first diode D a and the third diode D c and the other side connected to the anode of the second diode D b and the fourth diode D d It is connected.

Unbalanced voltage sensing circuit 100 is coupled to both sides of the electrolytic capacitor (C 4), when the direct current voltage generated in the electrolytic capacitor (C 4), detects it and detects the unbalance in the three-phase voltage.

The voltage unbalance detection circuit unit 100 includes a voltage unbalance rate adjuster 110, an RC integrator 120, a zener diode D z , a silicon controlled rectifier (SCR), and a relay RL.

In one embodiment of the present invention, the voltage unbalance rate adjuster 110 is implemented with a variable resistor (VR).

One end of the variable resistor VR is connected to one side of the electrolytic capacitor C 4 and the other side is connected to the other side of the electrolytic capacitor C 4 and a terminal for dividing the DC voltage applied to the electrolytic capacitor C 4 And serves to adjust the voltage unbalance rate.

The Zener diode (D z ) has its cathode connected to the terminal of the variable resistor (VR).

The SCR has a gate connected to the anode of the Zener diode (D z ), and a cathode connected to the other side of the variable resistor (VR).

The relay RL has one side connected to one side of the variable resistor VR and the other side connected to the anode of the SCR.

The trip circuit 200 is operated by the relay RL. That is, when the relay RL is excited by the turn-on of the SCR, the trip circuit 200 is operated by the contact operation of the relay RL.

The RC integrator 120 includes a first resistor R 1 connected between the terminal of the variable resistor VR and the cathode of the Zener diode D z and a second resistor R 1 connected on one side to the cathode of the Zener diode D z , And a fifth capacitor C 5 connected to the other side of the variable resistor VR.

The LED is connected between one side of the variable resistor (VR) and one side of the relay (RL).

The circuit structure of the voltage unbalance detection system proposed in the present invention can be realized by forming a capacitor of the same capacity in each line of three-phase power sources R, S and T to form a voltage unbalance or an image And constitutes a trip circuit using high-speed semiconductor elements.

The operation principle of the voltage unbalance detection system of the present invention is as follows. In a steady state, since the neutral voltage of the three-phase capacitor connected is 0 V, the stable state is maintained without abnormal voltage detection.

However, when the three-phase voltage imbalance or a phase loss accident is displayed a neutral point voltage of the three-phase star-connected capacitor (C 1 ~C 3), full-wave rectifier diode (D a ~D d) to deliver direct current to the capacitor C 4 by When a voltage is being generated, a DC voltage is divided by a variable resistor (VR), the size of the divided output voltage larger than the Zener voltage of the Zener diode (D z) a Zener diode (D z) is conductive, and the switching element Trigger the gate of SCR. Then, the relay RL is excited by the turn-on of the SCR, and a series of operations for operating the trip circuit 200 by the relay contact operation is performed. In addition, an LED for indicating the operation of the detection system is turned on at the time of an accident.

Then, the voltage unbalance ratio is adjusted in consideration of the conditions of the field and the use environment by using the variable resistor (VR) used as the voltage unbalance rate regulator.

In the present invention, in order to prevent a sensitive tripping operation of the voltage unbalance detection system for a minute three-phase unbalance voltage such as a momentary voltage change such as a temporary opening / closing of an industrial site, RL) Synchronization By using the RC integrator (R 1 , C 5 ) at the gate of the switching element SCR, the time delay circuit using the RC time constant is designed to prevent the sensitive trigger operation of the SCR. It is appropriate to design the RC time constant from 30 ms to 50 ms in consideration of the operation of the phase lag protecting unit in two to three cycles in the case of normal phase lag.

The voltage unbalance detection system proposed in the present invention is advantageous in that it is manufactured in a small size and light weight and is easy to install because of its simple circuit configuration, and also has a simple technical control principle and is designed in a structure using high- And the reliability is high because of high accuracy.

3 is an exemplary diagram illustrating a connection between a three-phase motor control panel and a voltage unbalance detection system according to an embodiment of the present invention. Fig. 3 shows an example in which a voltage unbalance detection system is built in a motor control panel in the field.

Referring to FIG. 3, electrical disturbances such as insulation aging of contacts due to aging and frequent use of relays installed in the motor control panel, that is, electromagnetic contactors or electromagnetic switches, chattering tracking accidents due to contact failure, voltage unbalance, The voltage unbalance detection system proposed in the present invention operates to operate the control circuit and trip the main contact point MC of the motor control panel to protect the power system.

4 is a circuit diagram illustrating a voltage unbalance detection system for operating an RCD according to an exemplary embodiment of the present invention. FIG. 4 is a diagram illustrating a voltage unbalance detection system according to an embodiment of the present invention that generates a leakage current forcibly by a ground line when an electric accident is detected, thereby causing an overdriving residual current device (RCD) used in an electric motor control panel or an electric distribution panel Fig.

Referring to FIG. 4, a leakage current forcibly flows through a ground line by operation of a relay contact at the time of voltage unbalance or phase failure by using a three-phase diode (D 1 to D 3 ) The system is protected by blocking the RCD installed in the system. Here, the PTC thermistor serves to prevent the element from being burned out due to an increase in the leakage current and to overheat to the ground line.

In order to test the operation characteristics of the voltage unbalance detection system of the present invention, an example of a circuit constant value of main device components used in the fabrication of the voltage unbalance detection system is illustrated in FIG.

5 is a diagram illustrating circuit constant values of main circuit elements of a voltage unbalance detection system according to an exemplary embodiment of the present invention.

6 is a graph showing an operation waveform of the voltage unbalance detection system according to an embodiment of the present invention.

In order to analyze the operation performance of the proposed voltage unbalance detection system, FIG. 6 shows a three-phase winding induction motor / generator (M / G set) of 380 V, 1.5 kW class having the circuit constants shown in the table of FIG. And shows the motion waveform measured by inducing an artificial phase-1 phase-loss and a phase-2 phase-loss.

6 (a) and (b) of FIG. 6, the voltage of each phase of R, S, and T is supplied to a power supply of a balanced power having a phase difference of 120 °, Phase system (S phase, T phase) occurs, the voltage unbalance detection system proposed in the present invention operates and the three-phase system is shut off.

In the case of the single-phase image-forming accident in FIG. 6 (a), about 48 ms was required from the image-forming point to the interruption of the three-phase power source, and in the case of the two- .

As a result of analyzing the operation characteristics several times, it was found that the detection system proposed in the present invention has a good blocking operation time of 32 to 50 ms for one-phase image formation, and for the various two-phase image formation, 45 ms.

While the present invention has been described with reference to several preferred embodiments, these embodiments are illustrative and not restrictive. It will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims.

100 voltage unbalance detection circuit part 200 trip circuit part
110 Voltage unbalance rate regulator 120 RC integrator

Claims (5)

A three-phase capacitor having one side connected to each line of the three-phase power source R, S, and T and having the same capacitance value;
A first diode having an anode connected to the other side of the three-phase capacitor;
A second diode having a cathode connected to an anode of the first diode;
A third diode having an anode connected to ground and a cathode connected to the cathode of the first diode;
A fourth diode having a cathode connected to ground and an anode connected to the anode of the second diode;
An electrolytic capacitor having one side connected to the cathodes of the first diode and the third diode and the other side connected to the anodes of the second diode and the fourth diode;
A voltage unbalance detection circuit unit connected to both sides of the electrolytic capacitor and detecting a DC voltage generated in the electrolytic capacitor to detect an unbalance of the three-phase voltage; And
And a trip circuit coupled to the voltage unbalance detection circuitry,
The voltage unbalance detection circuit unit includes:
A variable resistor connected to one side of the electrolytic capacitor, the other terminal connected to the other side of the electrolytic capacitor, and a terminal for dividing a DC voltage applied to the electrolytic capacitor, the variable resistor for adjusting a voltage unbalance rate;
An RC integrator including a first resistor having one side connected to a variable terminal of the variable resistor and a fifth capacitor having one side connected to the other side of the first resistor and the other side connected to the other terminal of the variable resistor;
A zener diode having a cathode connected to the other side of the first resistor and one side of the fifth capacitor;
A SCR (Silicon Controlled Rectifier) having a gate connected to the anode of the Zener diode and a cathode connected to the other side of the fifth capacitor; And
And a relay having one side connected to one terminal of the variable resistor and the other side connected to an anode of the SCR,
If the neutral point voltage of the three-phase capacitor is 0 V, the stable state is maintained without detection of abnormal voltage,
When a neutral voltage appears in the three-phase capacitor, a direct-current voltage is generated in the electrolytic capacitor, the direct-current voltage is divided by the variable resistor, and when the magnitude of the divided voltage is greater than the zener voltage of the zener diode, The zener diode is turned on to trigger the gate of the SCR so that the SCR is turned on so that the relay is excited so that the trip circuit is operated by the contact operation of the relay Voltage imbalance detection system.
delete delete delete The method according to claim 1,
Wherein the voltage unbalance detection circuit part further comprises an LED connected between one side of the variable resistor and one side of the relay.
KR1020160138463A 2016-10-24 2016-10-24 System for detecting voltage unbalance of three phase motor control center KR101884388B1 (en)

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KR20230016736A (en) 2021-07-26 2023-02-03 한국기술교육대학교 산학협력단 Open phase fault protection device and method in grid-connected transformer for ess

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CN112070396B (en) * 2020-09-08 2024-04-09 国网河北省电力有限公司石家庄供电分公司 Regional power supply risk assessment system and method based on visualization

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KR20230016736A (en) 2021-07-26 2023-02-03 한국기술교육대학교 산학협력단 Open phase fault protection device and method in grid-connected transformer for ess

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