Inverter & PLC service and maintenance support by System Engineering Ltd

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“Inverter & PLC service and maintenance support by System Engineering Ltd.”


An inverter is an electrical device that converts direct current (DC) to alternating current (AC); the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits. An inverter is essentially the opposite of a rectifier.

Static inverters have no moving parts and are used in a wide range of applications, from small switching power supplies in computers, to large electric utility high-voltage direct current applications that transport bulk power. Inverters are commonly used to supply AC power from DC sources such as solar panels or batteries.

The electrical inverter is a high-power electronic oscillator. It is so named because early mechanical AC to DC converters was made to work in reverse, and thus was “inverted”, to convert DC to AC.


1.1 DC power source utilization

1.2 Uninterruptible power supplies

1.3 Induction heating

1.4 HVDC power transmission

1.5 Variable-frequency drives

1.6 Electric vehicle drives

1.7 Air conditioning

1.8 The general case

1.9 Warnings

In this report contains only the variable frequency inverter or drive. A variable-frequency drive controls the operating speed of an AC motor by controlling the frequency and voltage of the power supplied to the motor. An inverter provides the controlled power. In most cases, the variable-frequency drive includes a rectifier so that DC power for the inverter can be provided from main AC power. Since an inverter is the key component, variable-frequency drives are sometimes called inverter drives or just inverters.

A PLC (Programmable Logic Controller) is a device that was invented to replace the necessary sequential relay circuits for machine control. The PLC works by looking at its inputs and depending upon their state, turning on/off its outputs. The user enters a program, usually via software, that gives the desired results. A programmable logic controller is currently defined by National Electrical Manufacturers Association of America as a digital electronic device that uses a programmable memory to store instruction to implement specific functions such as logic, sequence, timing, counting and arithmetic to control machines and processes. At beginning of its invention and application (during 1980’s) it was the replacement of conventional sequence system such as electromechanical relays, timers, counters and so on. But now a day it is using for automation of equipment as well as for automation of industrial plant as a whole, monitoring and control of all process variables, data acquisition and analysis, production monitoring and forecasting, trouble shooting of equipment and so on.

Broad Objective:

The broad objectives of this report are mainly understood the servicing and maintenance of Variable frequency inverter and PLC.

Specific Objectives:

In order to the broad objectives I have to find out the following objectives. They are as follows:

1. Study on Variable frequency inverter and PLC.

2. Identifying different types of Variable frequency inverter and PLC.

3. Suggest probable solution of the identified problem.


· Both primary and secondary data are being collected for the purpose of this report. The report is concentrated of the technical support service and maintenance of variable frequency inverter and PLC.

· Primary Data are collected from the maintenance Chart, the User Manual handbooks and Text books.

· Secondary data are being collected from the printed Journals, brochures and websites.


Sometimes operator trying to repair it but they are not efficient. So machine breakdown time increasing. Though the workers are experienced and efficient, there is lack of monitoring personnel. It would be better to appoint few more personnel of respective fields. Discipline among the workers is not well established. In the marketing section semi finished products and finished products should be minimized. I found few people are applied to tear down excess outer carton during packing a batch. So care should be taken or there should be an option of immediate delivery of packing materials when needed.

1.1 Background:

System Engineering Ltd is one of the most reputed organizations in Bangladesh kind of for different Industrial Automation works, Electro-Mechanical & Electrical Engineering works, Plant Election & maintenance, Man-Machine Customization etc. Its objective is to help to make maximum return from the system. It has self-supported expertise technical teams with modern tools & technology.

System Engineering Ltd is authorized sole-agent of some world-class manufacturers in Bangladesh. SEL has selected these companies for their high quality products with justified price for Bangladesh. SEL thinks, high quality products & services are the most important factors to our industrial sector for developing our country.

Our outlook is totally different. We were born differently. We are growing with a different view. We are stuffed with courteous, responsive, dependable professionals, who are able to provide a variety of services.

The company enjoys good reputation due to its quality product sales and after sales services, innovation, productivity and customer support. The company is looking forward to providing with efficient customer service, support and better technology to the local market.

1.2 List of Services:

· Plant Erection & Maintenance

· Trouble Shooting & Up gradation of Industrial Machinery

· Man-Machine Customization

· Electrical LT Panel, MCC Panel, PFI Panel Fabrication

· Pipe-Line and Cable Work

· Duct Fabrication

List of products:

PLC LS Korea ABB Finland
Touch Screen & XGT Panel LS– Korea ABB–Finland
Electric Motor ABB – India
Name of Organization System Engineering Ltd Hyundai – Korea
Year of Establishment 2000
Earlier/Old Name System Automation (Till 2007)
Type of Business Plant Erection on turnkey basic

Selling of Automation Products

Selling of Low & Medium Voltage Products

Partnerships Distributor of LS, Korea (Old name of LG) for automation products

Channel Partner of ABB, Finland for Inverter, PLC, Electric Motor and Instruments

Sole-Agent of Autonics, Korea for Sensor and Controllers

Exclusive distributor of Hyundai, Korea for low and medium volt electric products

Employees 63 employees
Address House # 53, Road # 03, Sector # 3, Uttara, Dhaka – 1230

House # 15, Road # 18, Sector # 3, Uttara, Dhaka – 1230


1.4 History

Year Activities
2000 Three dynamic engineers formed a company named System Automation for Plant Erection, Maintenance & Trouble Shooting.
2001 Joined with LG as Local Distributor in Bangladesh at Sep’2001 for their industrial automation products.
2003 Successfully completed our first plant erection project on Battery Manufacturing Plant of Rahimafrooz, Zirani Bazar, Savar, Dhaka which they started at 2001 and capacity was 1,50,000 battery/month.
2004 Joined with Autonics Corporation as their Sole-Agent in Bangladesh.
2006 Successfully completed plant erection of Global Dyeing & Spinning Mills Ltd at Rupgonj, Narayangonj.
2007 Became a Limited company and changed its name to “System Engineering Ltd”.
2007 Joined with Hyundai as their Exclusive Distributor in Bangladesh for their LV & MV products.
2008 Joined with ABB as their Channel Partner in Bangladesh for their Inverter, PLC, Electric Motor and Instruments.
2008 Started Battery Manufacturing Plant erection project of Rahimafrooz (10,00,000 battery/month) at Iswordi EPZ (running).
2008 Started erection project of Battery Accumulator Plant of Rahimafrooz at Saver (running).

1.6 Vision

The vision of system Engineering Ltd is to become the country leader for industrial solutions and establish ourselves as the largest and most lucrative service provides in our country.

1.7 Mission

System Engineering Ltd. has acknowledged the responsibility to eradicate the deficit in country’s industrial automation equipment service and to improve the quality of the lives of their employees and the communities they serve. The company aims to achieve this mission not only through best quality products but also through excellence in service.

1.7 Theme

System Engineering Ltd. Always said as their theme “Best service way of progress”. They also use this theme beside their logo.

1.8 Quality Commitment

System Engineering Ltd .has acknowledged the responsibility to eradicate the deficit in country’s Industrial automation equipment Industrial automation equipment and to improve the quality of the lives of their employees and the communities they serve. The company aims to achieve this mission not only through best quality products but also through excellence in its service.

The goal of System Engineering Ltd. is to become best electro-mechanical firm in Asia by achieving excellence in all facets of its activities. System Engineering Ltd. believe that with strong dedication, their continued research on quality control and their commitment to ‘Just in Time’ delivery and quality after sales support will certainly lead them to our goal.

Their various quality policies involve employing fully qualified experienced engineers some are foreign trained, carrying on regular inspection of their equipments by both local and foreign renowned experts, providing full time training to their newly recruited employees and sharing their ideas. System Engineering Ltd. emphasize greatly on after sales care. With a 12-member team of experienced teams and graduate engineers in charge of support and service department are available even during non working hours, System Engineering Ltd. believe that they serve the customers with the best quality commitment System Engineering Ltd. is proud to declare that their quality management system is better then others company.

1.9 Uncompromising Integrity

Reputation of System Engineering Ltd. is based upon their ability to fulfill promises to shareholders, customers and employees. They do so by being honest in their dealings, taking responsibility and being accountable for their actions. System Engineering treats everyone the way they would like to be treated. They are proactive in identifying issues and coming up with solutions. They ensure that the highest ethical standards guide in making decisions. System Engineering is true to our word.

1.10 Respect & Care for Others

By working as one team with shared goals System Engineering Ltd. achieve great things. They value ideas and contributions from everyone. System Engineering recognize, respect and value diversity in the team. They develop strong bonds by communicating and sharing knowledge. They encourage open discussion and commit to an agreed position.

System Engineering Ltd. has implemented a Quality Management System that is continuously maintained for effectiveness and process improvements in accordance with the requirements of clients.

2.1 The Process Approach

In accordance with the requirements of the standard, EEL has adopted a process approach in design of quality management system.

The processes as applicable and relevant to EEL has been identified and defined. Output of every process is input to one or more processes. In case the output is not flowing to any internal of the processes, it flows to customers and other interested parties. Thus input to every process is outcome of one or more processes. In case input is not being derived from any internal process, the same flows from customers and other interested parties or from external sources.

Methods have been defined to ensure that operation and control of these processes are effective and efficient. Resource requirements for each of the processes are assessed by management to ensure that operation and monitoring of the process can be done as planned.

Strong monitoring, measurement and analysis of the process has been defined as a support process to ensure process performance and is measured and communicated at regular intervals within the organization. Based on the results, action plans are developed for implementing actions necessary for improvement of the processes.

2.2 Product Realization Processes:

1. Order Bagging (Institutional)

2. Forecasting

3. Planning

4. Product Development

5. Procurement

6. Manufacturing

7. Dispatch & Installation

8. Maintenance

9. Customer Complaint Handling

2.3 Measurement, Analysis and Improvement Processes:

· Measurement and Monitoring

· Customer Satisfaction Measurement

2.4 Top Management Process:


Management Review

General Manager

Figure: Organization overview

2.5 Sequence and Interaction Process

Product Realization Processes:

Past Years Performance ResultsFrom other External Sources


Planning Process
Dispatch and Installation

Manufacturing Process

Chapter One


1.2 Block diagram of PLC :

Reference LG Manual book.

Fig-2: Bolck diagram of PLC

Fig-3: Input and Output of PLC

Fig-4: Structure of PLC

Fig-5: PLC Processor

Fig-6: PLC I/O Port

1.3 PLC I/O Configuration

1.4 PLC I/O Configuration

Figure of PLC module

1.5 Programming Device

1.6 Advantage of a PLC Control System

Fig-7:Ladder diagram

Fig-9: Electro magnetic relay

Fig-9: PLC Communication system

Fig-10: PLC machine control system

1.7 Difference from a pc

Fig-11: PLC

1.8 PLC Programming

1.9 Symbol of ladder logic

1.10 Process of programming

1.11 <href=”#1.2>Control panel with a PLC controller

with invention of programmable controllers, much has changed in how an process control system is designed. Many advantages appeared. Typical example of control panel with a PLC controller is given in the following picture.

Fig-12: PLC Control System Panel Board.

1.12 Advantages of control panel that is based on a PLC controller can be presented in few basic points:

Compared to a conventional process control system, number of wires needed for connections is reduced by 80%

Consumption is greatly reduced because a PLC consumes less than a bunch of relays

Diagnostic functions of a PLC controller allow for fast and easy error detection.

Change in operating sequence or application of a PLC controller to a different operating process can easily be accomplished by replacing a program through a console or using a PC software (not requiring changes in wiring, unless addition of some input or output device is required).

Needs fewer spare parts

It is much cheaper compared to a conventional system, especially in cases where a large number of I/O instruments are needed and when operational functions are complex.

Reliability of a PLC is greater than that of an electro-mechanical relay or a timer.

PLC Communication

A: It depends on the two devices being connected, whether they are DTE or DCE devices, how they are connected together before adding a RS-232/RS-422 Converter, how many signal lines are required. This information is for devices requiring only Receive (Rx) and Transmit (Tx) signal only, other devices require more connection pairs.

A1: CASE #1: The Device connects directly to the serial port on the Computer. The computer serial port is configured as a DTE port, the device cabling is configured as DCE to connect directly. With this connection, the first RS-422 converter connects with a Standard serial cable wired pin #1 to #1, #2 to #2, etc. The second converter requires a null modem connection between it and the device, since our converter is configured as DCE on the RS-232 side, and the device cabling is also DCE. See the connection diagram for CASE #1.

Fig-13: PLC Communication

A2: CASE #2: The Device connects through a Null Modem (Crossover) Cable to the serial port on the Computer. This original connection requires a Null Modem cable because both Computer and Device are configured as DTE. In this case, the first RS-422 Converter connects to the Computer with a Standard serial cable wired pin #1 to #1, #2 to #2, etc. The original Null Modem Cable is set aside, not used. A new Standard serial Cable is connected to the device and the second converter. See the connection diagram for CASE #2.

A3: CASE #3: In the third case, we want to extend a set of RS-232 connections between two devices, but we don’t know how either port is configured. Both devices use DB9F (female) connectors. We have a voltmeter. We know the converters are DCE devices. When powered, the RS-232 output will have a negative DC voltage compared to GND. So, we connect a Standard cable to the device, power it up, measure between Pin #5 of the cable to Pin #3. If it has a minus voltage (usually between -3VDC to -11VDC), connect it to the DB9 connector of the converter. This connection should be okay. If almost no voltage on Pin #3, check Pin #2. If it has the minus voltage, use a Null Modem Connection between the device and converter to swap the pin connections. If neither has a voltage, you need pinouts for the connector/cable. Make a similar test for the RS-232 connections at the other end. The voltage should be on the cable pin connecting to Pin #3. No Connection diagram for CASE #3, it will either match CASE #1 or CASE #2, but could instead require connections with Null Modem Connections on both converters if the original cable is not used.

The pin numbers for the RS-422 connections are not shown, they may vary according to the model, but the signal name will be shown on the data sheet.

In the case of DB25 RS-232 connections, Pin #2 is TD, Pin #3 is RD, and Pin #7 is GND.

Note: These connection figures do not show power supplies or handshaking lines needed to power “port powered” converters. The port powered devices usually need the RTS line and DTR line high (signal level +11 VDC), a power supply may be required for both ends if the RS-422 transmitter voltage is less than 4.4 volts TD(B) to TD(A). For pin outs of RS-232, refer to the FAQ on RS-232 Connections that WORK!

RS-232 Facts

RS-232 is a point-to-point serial communications standard that defines the electrical and mechanical details of the interface between Data Terminal Equipment (DTE) and Data Communications Equipment (DCE). Compared with newer standards RS-232 is limited in terms of data rate, maximum distance and noise immunity. The standard defines 25 electrical connections including data lines, control (hardware handshake) lines, timing lines and special secondary function lines. In typical applications many of these lines are not used.

Cables: When connecting a DTE to a DCE all connections are straight through. When connecting a DTE to a DTE a special ‘null modem’ or crossover cable is required.

Connectors: The original RS-232 connector was a DB-25, which supported all RS-232 lines. Often, DB-9 connectors are used, which support the most common data and hardware handshake lines.

Speed/Distance: The standard suggests RS-232 can operate at about 20 kbps over distances of 50 feet, a conservative estimate depending on grounding and noise considerations. Over short distances RS-232 is sometimes operated at rates as high as 115.2 kbps. Several hundred feet is possible at data rates of 9600 bps or lower.

Tech Tip: For longer distances, higher speeds and more noise immunity, convert to RS-422 for point-to-point, or RS-485 for multi-drop applications.



DB9-Female To DB9-Male or Terminal



DB9-Female to DB9-Male or Terminal

RS232 serial cable layout

Almost nothing in computer interfacing is more confusing than selecting the right RS232 serial cable. These pages are intended to provide information about the most common serial RS232 cables in normal computer use, or in more common language “How do I connect devices and computers using RS232?”

RS232 serial connector pin assignment

The RS232 connector was originally developed to use 25 pins. In this DB25 connector pin out provisions were made for a secondary serial RS232 communication channel. In practice, only one serial communication channel with accompanying handshaking is present. Only very few computers have been manufactured where both serial RS232 channels are implemented. Examples of this are the Sun SPARCstation 10 and 20 models and the Dec Alpha Multia. Also on a number of Telebit modem models the secondary channel is present. It can be used to query the modem status while the modem is on-line and busy communicating. On personal computers, the smaller DB9 version is more commonly used today. The diagrams show the signals common to both connector types in black.

The defined pins only present on the larger connector are shown in red. Note, that the protective ground is assigned to a pin at the large connector where the connector outside is used for that purpose with the DB9 connector version.

The pin out is also shown for the DEC modified modular jack. This type of connector has been used on systems built by Digital Equipment Corporation; in the early day’s one of the leaders in the mainframe world. Although this serial interface is differential (the receive and transmit have their own floating ground level which is not the case with regular RS232) it is possible to connect RS232 compatible devices with this interface because the voltage levels of the bit streams are in the same range. Where the definition of RS232 focused on the connection of DTE, data terminal equipment (computers, printers, etc.) with DCE, data communication equipment (modems), MMJ was primarily defined for the connection of two DTE’s directly.

RS232 DB9 pinout

DEC MMJ pinout

RS232 DB25 pinout

RS232 DB25 to DB9 converter

The original pinout for RS232 was developed for a 25 pins sub D connector. Since the introduction of the smaller serial port on the IBM-AT, 9 pins RS232 connectors are commonly used. In mixed applications, a 9 to 25 pins converter can be used to connect connectors of different sizes. As most of the computers are equipped with the DB9 serial port version, all wiring examples on this website will use that connector as a default. If you want to use the example with a DB25, simply replace the pin numbers of the connector according to the conversion table below.

RS232 DB9 to DB25 converter

DB9 – DB25 conversion
DB9 DB25 Function
1 8 Data carrier detect
2 3 Receive data
3 2 Transmit data
4 20 Data terminal ready
5 7 Signal ground
6 6 Data set ready
7 4 Request to send
8 5 Clear to send
9 22 Ring indicator

RS232 serial loopback test plugs

The following RS232 connectors can be used to test a serial port on your computer. The data and handshake lines have been linked. In this way all data will be sent back immediately. The PC controls its own handshaking. The first test plug can be used to check the function of the RS232 serial port with standard terminal software. The second version can be used to test the full functionality of the RS232 serial port with Norton Diagnostics or CheckIt.

DB9 DB25 Function
1 + 4 + 6 6 + 8 + 20 DTR CD + DSR
2 + 3 2 + 3 Tx Rx
7 + 8 4 + 5 RTS CTS

Testing occurs in a few steps. Data is sent on the Tx line and the received information on the Rx input is then compared with the original data. The signal level on the DTR and RTS lines is also controlled by the test software and the attached inputs are read back in the software to see if these signal levels are properly returned. The second RS232 test plug has the advantage that the ring-indicator RI input line can also be tested. This input is used by modems to signal an incoming call to the attached computer.

RS232 null modem cables

The easiest way to connect two PC’s is using an RS232 null modem cable. The only problem is the large variety of RS232 null modem cables available. For simple connections, a three line RS232 cable connecting the signal ground and receive and transmit lines is sufficient. Depending of the software used, some sort of handshaking may however be necessary. Use the RS232 null modem selection table to find the right null modem cable for each purpose. For a Windows 95/98/ME Direct Cable Connection, the RS232 null modem cable with loop back handshaking is a good choice.

RS232 null modem cables with handshaking can be defined in numerous ways, with loopback handshaking to each PC, or complete handshaking between the two systems. The most common null modem cable types are shown here.

Simple RS232 null modem without handshaking (Null modem explanation)


Connector 1 Connector 2 Function
2 3 Rx Tx
3 2 Tx Rx
5 5 Signal ground

RS232 null modem with loop back handshaking (Null modem explanation)


Connector 1 Connector 2 Function
2 3 Rx Tx
3 2 Tx Rx
5 5 Signal ground
1 + 4 + 6 DTR CD + DSR
1 + 4 + 6 DTR CD + DSR
7 + 8 RTS CTS
7 + 8 RTS CTS

RS232 null modem with partial handshaking (Null modem explanation)

Connector 1 Connector 2 Function
1 7 + 8 RTS2 CTS2 + CD1
2 3 Rx Tx
3 2 Tx Rx
5 5 Signal ground
7 + 8 1 RTS1 CTS1 + CD2

RS232 null modem with full handshaking (Null modem explanation)


Connector 1 Connector 2 Function
2 3 Rx Tx
3 2 Tx Rx
5 5 Signal ground

1.12 PC to RS485 Interface


Figure 1: Circuit Diagram of Isolated RS485 Interface

Figure 1 shows the circuit diagram of RS485 interface. Connector K1 is linked to the serial port of the PC, power to the PC side of the circuit is derived from the signal lines DTR and RTS. Positive supply is derived from RTS and negative supply from the DTR line. The RTS line is also used to control the data direction of RS485 driver IC U4.

Optical isolation is achieved by optocouplers U1, U2 and U3. Opto U1 is used to control the data direction of U4 opto U2 provide RXD line isolation while opto U3 provide TXD line isolation.

The other side of the isolator carries TTL levels. This side is powered by an unregulated dc supply between 9V and 18V dc. IC U5 provide 5V regulated output and IC U4 provide the RS485 bus interface. The TXD and RXD lines status are provided by data indicating LEDs. The interface has been tested at the baud rate of 19.2k baud.

For Data Reception RTS = 1 (at +ve level)

For Data Transmition RTS = 0 (at -ve level)

DTR line is always set to 0 (at -ve level)

Figure 2 & 3 shows the component layout of the isolator pcb and the track patterns respectively.

Fig-15: Component layout of the Isolator PCB

Figure 16: Track patterns of the Isolator PCB

Component details of the project.

1 4 C1,C2,C3,C6 100nF

2 1 C4 10uF 16V

3 1 C5 470uF 25V

4 3 D1,D2,D3 1N4148

5 2 D4,D5 LED RED 3mm

6 2 D7,D6 TRANSIL 6.8V

7 1 D8 1N4003



10 3 R1,R2,R3 1K8

11 2 R7,R4 4K7

12 2 R5,R8 1K

13 3 R9,R12 150R

14 1 R6 680R

15 2 R11,R10 10R

16 1 R13 120R



19 1 U4 MAX487, SN75176B

20 1 U5 LM7805

PLC programming cables for several brands

Most PLC’s can be programmed from a PC via a serial cable. Unfortunately, many of these cables have a non standard layout. De cables shown here can be bought from the regular sales channels, but it is often much cheaper to solder them yourself.

Mitsubishi PLC cable layouts

Melsec PLC’s from Mitsubishi can be connected to PC’s running Medoc programming software using various cables. Each different I/O module uses a different pin assignment.

Not all Mitsubishi PLCs can be connected directly to a programming PC. The signal levels of the A series CPU units are not RS232 compatible and must be converted with a SC-02N or SC-05 converter. The serial cable layout to connect this converter to a PC is shown in this diagram.

PC to Mitsubishi SC-02N/SC-05 adapter cable

If more than one serial port is necessary on an A series melsec PLC, the AJ71C24 or AJ71C21 serial communication modules can be plugged into the system. These modules provide RS232 compatible serial ports, so no signal conversion is necessary to connect these modules with a PC. Both modules are equipped with a DB25 connector. The cable layout for these two modules is shown below.

PC to Mitsubishi AJ71C24 serial programming cable

PC to Mitsubishi AJ71C21 serial programming cable

The A1SJ71C24-R2 can also be used to connect computers and devices to a melsec series A PLC. This plug-in module contains two serial ports, each with a DB9 connector. The wiring layout is in fact identical to the

PC to Mitsubishi A1SJ71C24-R2 serial programming cable

Omron PLC cable layouts

The PLC’s from Omron can be connected to various peripheral equipment. Each device requires its own cable layout. Only the more common cables are shown here.

DB9 RS232 programming cable

DB25 RS232 programming cable

CV500-CIF01 tool bus programming cable

Siemens PLC’s

Most programming of Siemens S5 PLC’s is done using a special RS232 to TTY converter. The S7 series are programmed using a RS232 to MPI bus converter. The easiest thing to do is buy these special cables from your local Siemens supplier. The operator terminals however can be programmed using a normal serial cable. The following cable can be used to program the OP series of operator displays.

Programming cable for OPxx display series

<href=”#1.3>Systematic approach to designing a process control system

first, we need to select an instrument or a system that you wish to control. Automated system can be a machine or a process and can also be called a process control system. Function of a process control system is constantly watched by input devices (sensors) that give signals to a PLC controller. In response to this, PLC controller sends a signal to external output devices (operative instruments) that actually control how system functions in an assigned manner (for simplification it is recommended that we draw a block diagram of operations’ flow).

Secondly, we need to specify all input and output instruments that will be connected to a PLC controller. Input devices are various switches, sensors and such. Output devices can be solenoids, electromagnetic valves, motors, relays, magnetic starters as well as instruments for sound and light signalization.

Following an identification of all input and output instruments, corresponding designations are assigned to input and output lines of a PLC controller. Allotment of these designations is in fact an allocation of inputs and outputs on a PLC controller which correspond to inputs and outputs of a system being designed.

Thirdly, should make a ladder diagram for a program by following the sequence of operations that was determined in the first step.

Finally, program is entered into the PLC controller memory. When finished with programming, checkup is done for any existing errors in a program code (using functions for diagnostics) and, if possible, an entire operation is simulated. Before this system is started, we need to check once again whether all input and output instruments are connected to correct inputs or outputs.

Maintenance Part

Fig-17: Font view of plc

Fig-18: Power Circuit of PLC

Fig-19: Control circuit of PLC


Power Failure


Power section of PLC fault occurred.

Replace capacitor

Economical Benefit Using a PLC Control Panel Board

Increased production

Improved quality

Greater product uniformity

Saving in raw materials

Saving in energy

Saving in manpower

Increase safety

Chapter Two

2.1 Introduction

An inverter is an electrical device that converts direct current (DC) to alternating current (AC); the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits. An inverter is essentially the opposite of a rectifier.

Static inverters have no moving parts and are used in a wide range of applications, from small switching power supplies in computers, to large electric utility high-voltage direct current applications that transport bulk power. Inverters are commonly used to supply AC power from DC sources such as solar panels or batteries.

Inverter designed to provide 115 VAC from the 12 VDC source provided in an automobile. The unit shown provides up to 1.2 amperes of alternating current, or just enough to power two sixty watt light bulbs.

An inverter converts the DC electricity from sources such as batteries, solar panels, or fuel cells to AC electricity. The electricity can be at any required voltage; in particular it can operate AC equipment designed for mains operation, or rectified to produce DC at any desired voltage.

Grid tie inverters can feed energy back into the distribution network because they produce alternating current with the same wave shape and frequency as supplied by the distribution system. They can also switch off automatically in the event of a blackout.

Micro-inverters convert direct current from individual solar panels into alternating current for the electric grid

A variable-frequency drive controls the operating speed of an AC motor by controlling the frequency and voltage of the power supplied to the motor. An inverter provides the controlled power. In most cases, the variable-frequency drive includes a rectifier so that DC power for the inverter can be provided from main AC power. Since an inverter is the key component, variable-frequency drives are sometimes called inverter drives or just inverters.

2.2 Main part of inverter

Input Section

Control Section

Power Section

Output Section

Input section

There are many parts of input section


Breaking resistor

Health relay

Control Section

There are three types of control

Key pad



Power Section

Main parts of power Section

SMPS card


Output Section

DC Converter

Chopper transformer

Operation mode

Frequency reference mode

Keypad mode

Terminal mode

Communication mode

Input function



Analog input

Variable pot, Terminal RS232

ACC-Accelerations time

DEC-De acceleration time

Base frequency

Maximum frequency

Digital input




Multifunction 1

Multifunction 2

Multifunction 3

2.3 Inverter Specification


kW/Voltage Ratings:

o 0.75 ~ 55kW, 3 phase, 200 ~ 230VAC

o 0.75 ~ 75kW, 3 phase, 380 ~ 480VAC

– Selectable V/f, Sensor less vector, Sensor vector control (Optional)

– Built-in process PID control

– Optimum acceleration & deceleration for a maximum torque

– APP parameter group for special operations;

Traverse, Multi Motor Control, DRAW

– Multi-function I/O terminal:

Input: 27 functions / Output: 21 functions

– Multi Motor Control (Up to 4 motors: Optional)

– Motor parameter Auto-tuning

– Parameter Read/Write function using a detachable LCD Keypad

Fig-20: Inverter iG5A-4

– Power terminal configuration
Symbols Functions
R AC Line input (3 Phase 200-230 VAC or 380-460 VAC)
G Earth Ground
U 3 Phase power output terminal to motor (3 Phase 200-230 VAC or 380-460 VAC)
G Earth Ground
P1 Positive DC bus terminal

External DC Reactor connection terminal and DB Unit connection terminal

LS Starvert iG5A is very competitive in its price and its functional strength compared to iG5. User-friendly interface, extended inverter ranges up to 7.5kW, superb torque competence and small size of iG5A provides an optimized user environment.

Selectable V/f, sensor less vector control

– Motor parameter Auto-tuning

– Powerful torque at overall speed range

– 0.1 ~ 400Hz frequency output

– -15% ~ +10% input voltage margin

– Fault history: Last 5 faults

– 0~10Vdc / -10 ~ +10Vdc analog input

– IP20 enclosure, UL Type 1 (Option)

– Selectable manual/automatic torque boost

– Selectable PNP/NPN input signal

– 2nd motor control and parameter setting

– Built-in Dynamic braking transistor as standard

– Enhanced process PID control

– Built-in RS485 (LS Bus / Modbus RTU) communication

– Cooling fan On/Off control & Easy change

– Remote control using external keypad * RJ45 cable(Optional)

– Upgraded functions: Sleep & Wake-up (Energy savings)

KEBKinetic Energy Buffering) protection

Low l (eakage PWM algorism

– Monitoring & commissioning PC based software tool


Starvert iP5A series adopt various functions as standard for operation of Fan and Pump. iP5A’s optimum performance for Fan & Pump, you can optimize system stability in user-environment and reduce system construction cost.

– Dual PID
When additional PID control or Cascade PID control is required, Dual PID provides users various uses of the system with only iP5A.
– Multi Motor Control
The built-in algebra control function enables an inverter to control many motors without a controller so that user can take advantage of energy-saving and cost-down.
– Sleep and Wake-Up
The built-in energy saving function makes inverter stop automatically when the capacity is very low.
– Pre Heater
The pre heater function is built-in to prevent motor damage and inverter break-down caused from humidity.
– Flying Start
When the inverter drives many ventilators or when the fan in a big load system turns due to a natural convection, iP5A operates the motor by searching the motor speed automatically.
– Auto energy saving
iP5A provides the auto energy saving function by the optimal flux control which minimizes an energy loss caused by a change of the load.
– Improved Management from Instant Power-off and Power Dip Generation
During the power Dip or instant power-off, which is generated by lightening, ground fault and power-failure, loads still keep the mechanical energy and this energy flows back to inverter by regeneration. The power-failure guarantee time is extended by using this electrical character of inverter.
– Constant and Stable Performance (24 hours 365 days)
Regardless of outside alteration such as input voltage variation by load change or weather effect, iP5A can handle moter and load with best performance.
– Safety Stop
When unexpected power-failure blocks power supply, inverter stops motor by using inertia energy of load that prevents unexpected second accident (Parameter setting is required).
– 200V Class
SV ¡ iP5A – 2 055 075 110 150 185 220 300
Motor Rating1) [HP] 7.5 10 15 20 25 30 40
[kW] 5.5 7.5 11 15 18.5 22 30
Output ratings Capacity[kVA]2) 9.1 12.2 17.5 22.9 28.2 33.5 43.8
Rated current[A] 24 32 46 60 74 88 115
Output frequency 0.01 ~ 120 [Hz]
Output voltage(V) 200 ~ 230V