Industrial Automation

AUTOMATION IN ELECTRICAL

&

ELECTRONICS

A Summer Training Report

Bachelor of Technology

in

ELECTRICAL ENGINEERING

Submitted by: Supervisor:

YOGESH.R Mr. R.K. KUMAWAT

IV YEAR , EE Associate Lecture of Electrical

DEPARTMENT OF ELECTRICAL ENGINEERING

Mewar University,

NH - 79 Gangrar, Chittorgarh (Rajasthan) – 312901

1

CERTIFICATE

This is to certify that the Report titled “ Automation in Electrical & Electronics

” was prepared and presented by YOGESH.R (10MUBEE136) of Mewar

University, Chittorgarh in partial fulfilment of the requirement as a part of

curriculum under the Mewar University, Chittorgarh during the B.Tech

program in the session 2013 - 2014

Mr. S.K.Singh Project Supervisor

HOD (EE)

2

DECLARATION

I YOGESH.R, IV Year VII Semester B.Tech. (E.E.), student of Mewar

University, Chittorgarh do hereby declare that the Training report entitled

“Automation in Electrical and Electronics” is the original work carried out

by me under the supervision of Mr R. K. Kumawat towards partial

fulfillment of the requirement of B.Tech. Degree.

YOGESH.R

B. Tech Final Year

Electrical Engineering

3

ACKNOWLEDGEMENT

I am very pleased to express my deep sense of gratitude to my esteem guide

“Mr. Prabhakar” for his valuable training, encouragement and facilities

provided during the Training Work.

There were umpteen moments when I learned heavily from him. It is the fact,

without his construction and simulating criticism arduous but invaluable

advice sought time to time, masterly guidance deep personal interest and

attention, this work would not have seen the down of the day and could never

have attend the present stage. I am also heartily thanks to Mr. Ashok

Gadiya(Honorable,Chancellor), Mr. Harish Gurnani(Director, Training and

placement), Mr. S. K. Singh (HOD, Department of EE) and all faculty members

for their co-operation . I extend my sincere thanks to my friends who were there

with me directly or in directly during the Work.

YOGESH.R

B.Tech, IV year

Electrical Engineering

PLACE : Mewar University

DATE : 07-09-13

4

ABSRACT

Automation devices such as controllers and data systems and/or services.

Systems and methods are provided that receive statements or other unit of data

interaction from an automation device, provide the statements to an appropriate

system or service for processing, and optionally return a response such as a

result set. An Automation in electrical and electronics or Automatic controller is

a soft and hard computer used for automation of electromechanical processes,

such as control of machinery on factory assembly lines, amusement rides, or

lighting fixtures. Automation are used in many industries and machines. An

electrical switch is any device used to interrupt the flow of electrons in a

circuit.A sensor (also called detector) is a converter that measures a physical

quantity and converts it into a signal which can be read by an observer or by an

(today mostly electronic) instrument. Sensors is an important component in

closed loop automation system. Timer is an effective tool in each and every

industry. They keep beat of an enterprise or an industry in synchrony.A timer

provides a way to perform a delayed action or a periodic action. The timer waits

until a certain time interval has elapsed and then fires, sending a specified

message to a specified object. For example, you could create a timer that sends

a message to a controller object, telling it to update a particular value after a

certain time interval.

5

CONTENTS

S. No TITLE PAGE.NO

CERTIFICATE i

DECLARATION ii

AKNOWNLEGMENT iii

ABSTRACT iv

1 Automation 1 - 4

1.1 Introduction 1

1.2 Significance of automation 1

1.3 Application of automation 4

2 Sensor 5 - 13

2.1 Introduction 5

2.2 Criteria to choose a sensor 5

2.3 Classification of sensor 6

2.4 Temperature sensor 8

2.4.1. Thermocouple 9

2.4.2. RTD 9

2.4.3. Thermistor 10

2.5 Proximity sensor 10

2.6 Different types of proximity sensor 11

2.6.1. inductive sensor 11

6

2.6.2. capacitive sensor 11

2.6.3. ultrasonic sensor 11

2.6.4. optical sensor 12

3 Front control & Switching concepts 15 - 21

3.1 Introduction 14

3.2 Push button 14

3.3 Toggle button 16

3.4 Selector switch 18

3.5 Rocker switch 19

3.6 Switching control 21

4 Drives 22 - 28

4.1 Ac drives 22

4.2 Voltage / frequency concept 23

4.3 Dc motor 25

4.4 Speed control of dc motor by dc drive. 26

5 TIMERS 29 - 34

5.1 Introduction 29

5.2 Types of Timer 30

5.3 Operating modes of timer 31

CONCLUTION vi

BIBLIOGRAPHY vii

7

Table index

S.NO LIST OF TABLES PAGE.NO

1 Advantages And Disadvantages 28

of Dc Drive

Figure Index

S.NO LIST OF FIQURES PAGE.NO

1 Automation

1.1 Block diagram of 12

industrial automation

2 Sensors

2.1 Thermocouple 10

2.2 Resistance temperature Detectors 9

2.3 Thermistor 10

2.4 Proximity sensor 19

3 Front Control And Switching Concepts

3.1 Push Button 14

3.2 Toggle Switch 15

3.3 Indication Lamp 16

8

3.4 Selector Switch 17

3.5 Rocker switch 18

3.6 Rotary / Cam Switch 19

3.7 Buzzer & Hooter 19

4 DRIVES

4.1 Ac Drive 22

4.2 Speed-torque characteristics 23

4.3 Voltage / Frequency Curve 24

5 TIMERS

5.1 Timer 29

5.2 Timer circuit 31

5.3 Operation of Timer 34

9

CHAPTER 1

AUTOMATION

1.1 INTRODUCTION

Industrial automation or numerical control is the use of control systems such

as computers to control industrial machinery and processes, reducing the need

for human intervention. In the scope of industrialization, automation is a step

beyond mechanization. Whereas mechanization provided human operators

with machinery to assist them with the physical requirements of work,

automation greatly reduces the need for human sensory and mental

requirements as well. Processes and systems can also be automated.

Automation plays an increasingly important role in the global economy

and in daily experience. Engineers strive to combine automated devices with

mathematical and organizational tools to create complex systems for a rapidly

expanding range of applications and human activities.Many roles for humans

in industrial processes presently lie beyond the scope of automation. Human-

level pattern recognition, language recognition, and language production

ability are well beyond the capabilities of modem mechanical and computer

sys.ms. Tasks requiring subjective assessment or synthesis of complex sensory

data, such as scents and sounds, as well as high-level tasks such as strategic

planning, currently require human expertise. In many cases, the use of humans

is more cost-effective than mechanical approaches even where automation of

industrial tasks is possible.

10

1.2 SIGNIFICANCE OF AUTOMATION

For the purpose of AUTOMATION Specialized hardened computers,

referred to as programmable logic controller. (PLC), are frequently used to

synchronize the flow of inputs from (physical) sensors. and events with the

flow of outputs to actuators and even. This leads to precisely controlled actions

that permit a tight control of almost any industrial process. Human-machine

interfaces (HMI) or computer human interfaces (CHI), formerly known as

man-machine interface, are usually employed to communicate with PLCs and

other computers, such as entering and monitoring temperatures or pressures for

further automated control or emergency response. Service personnel who

monitor and control these interfaces are often referred to as stationary

engineers.

Automation has had a noble impact in a wide range of highly visible

industries beyond manufacturing. Once-ubiquitous telephone operators have

been replaced largely by automat. telephone switchboards and answering

machines. Medic. processes such as primary screening in electrocardiography

or radiography and laboratory analysis of human genes, sera, cells, and tissues

are carried out at much greater speed and accuracy by automated systems

Automated teller machines have reduced the need for bank visits to obtain cash

and carry out transactions. In general, automation has been responsible for the

shift in the world economy from agrarian to industrial in the 19th century and

from industrial to services in the 20th century.

Currently, for manufacturing companies, the purpose of automation has

shifted from increasing productivity and reducing costs, to broader issues, such

as increasing quality and flexibility in the manufacturing process.The old focus

on using automation simply to increase productivity and reduce costs was seen

to be short-sighted, because it is also necessary to provide a skilled workforce

11

who can make repairs and manage the machinery. Moreover, the initial costs of

automation were high and often could not be recommend by the time entirely

new manufacturing processes replaced the old. (Japan's 'robot junkyards" were

once world famous M the manufacturing industry )

Automation is now often applied primarily to increase quality in the

manufacturing process, where automation can increase quality substantially

For example , automobile and truck piston used to be installed into engines

manually. This is rapidly being transitioned to automated machine installation,

because the error rate for manual installment was around 1-1.5%, but has been

reduced to 0.00001%) with automation Hazardous operations, such as oil

refining, the manufacturing of industrial chemicals, and all forms of metal

working, were always early contenders for automation.

Another major shift in automation is the increased emphasis on flexibility

and convertibility in the manufacturing process Manufacturers are increasingly

demanding the ability to easily switch from manufacturing Product A to

manufacturing Product B without having to completely rebuild the production

lines. Flexibility and distributed

Fig 1.1 Block Diagram of Industrial Automation

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1.3 APPLICATION OF AUTOMATION

1) ANN - Artificial neural network

2) DCS - Distributed Control System

3) HMI - Human Machine Interface

4) SCADA - Supervisory Control and Data Acquisition

5) PLC - Programmable Logic Controller

6) Instrumentation

7) Motion control

8) Robotics

13

CHAPTER 2

SENSOR

2.1 INTRODUCTION

Sensors are sophisticated devices that are frequently used to detect and

respond to electrical or optical signals. A Sensor converts the physical

parameter (for example:- temperature, blood pressure, humidity, speed, etc.)

into a signal which can be measured electrically. Let’s explain the example of

temperature. The mercury in the glass thermometer expands and contracts the

liquid to convert the measured temperature which can be read by a viewer on

the calibrated glass tube.

2.2 CRITERIA TO CHOOSE A SENSOR

There are certain features which have to be considered when we choose a

sensor. They are as given below:

1. Accuracy

2. Environmental condition - usually has limits for temperature/

humidity

3. Range - Measurement limit of sensor

4. Calibration - Essential for most of the measuring devices as the

readings changes with time

5. Resolution - Smallest increment detected by the sensor

6. Cost

7. Repeatability - The reading that vanes is repeatedly measured

under the same environment

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2.3 CLASSIFICATION OF SENSORS:

The sensors are classified into the following antenna:

1) Property

2) Application

3) Power / energy supply requirement

4) Material and Technology

Transduction principle is the fundamental criteria which are followed for an

efficient approach. Usually, material and technology criteria are chosen lay the

development engineering group.

2.3.1 Classification based on property:-

1) Temperature - Thermistors, thermocouples, RTD's,

IC and many more.

2) Pressure - Fibre optic, vacuum, LVDT, electronic.

3) Flow - differential pressure, positional displacement, thermal

mass , etc.

4) Level Sensors - Differential pressure, radar, thermal

displacement, etc.

5) Proximity and displacement - LVDT, photoelectric,

capacitive, magnetic, ultrasonic.

6) others - moisture humidity sensor,Speed sensor

15

2.3.2 Classification based on Application

1) Industrial use - Process control, measurement and automation

2) Non-industrial use - Aircraft, Medical products, Automobiles

2.3.3 Classification based on power or energy supply requirement

1) Active Sensor - Sensors Mat require power supply are called as Active

Sensors.

Example: LiDAR (Light detection and ranging), photoconductive cell.

2) Passive Sensor - Sensors that do not require power supply are called as

Passive Sensors.

Example: Radiometers, film photography.

2.3.4 In the current and future applications, sensors can be classified

into groups as follows:-

1) Accelerometers - These are based on the Micro Electro

Mechanical sensor technology. They are used for patient

monitoring which includes pace makers and vehicle dynamic

systems.

2) Biosensors - These are based on the electrochemical technology,

They are used for food testing, medical care device, water testing,

and biological warfare agent detection.

3) Image Sensors - These are based on the CMOS technology. They

are used in consumer electronics, biometrics traffic and security

surveillance and PC imaging

16

4) Motion Detectors - These are based on the Infra Red, Ultrasonic,

Microwave/ radar . They are used in video games and simulations,

light. activation and security detection.

2.4 TEMPERATURE SENSOR

This device collects information about temperature from a source and converts

into a form that is understandable by other device or person. The best

illustration of a temperature sensor is mercury in glass thermometer. The

mercury in the glass expands and contracts depending on the alterations in

temperature. The outside temperature is the source element for the temperature

measurement. The position of the mercury is observed I, the viewer to measure

the temperature.

There are two basic types of temperature sensors:

Contact Sensors - This type of sensor requires direct physical contact with the

object or media that is being sensed. They supervise the temperature of solids,

liquids and gases over a wide range of temperatures.

Non contact Sensors - This type of sensor does not require any physical

contact With the object or media that is being sensed. They supervise non-

reflective solids and liquids but are not useful for gases due to natural

transparency. These sensors use Plank's Law to measure temperature.

This law deals with the heat radiated from the source of heat to measure the

temperature.

17

2.4.1.1 Different types of Temperature Sensors

(i) Thermocouple - They are made of two wires (each of different

homogeneous alloy or metal) Mich form a meas.., junction by joining at one

end. This measufing junction is open to the elements being measured. The

other end of the Wre is terminated to a measuring device where a reference

junction is loaned. The current flows through the circuit since the temperature

of the two junctions are different. The resulted milli-voltage is measured to

determine the temperature at the junction. The diagram of thermocouple is

shown below.

Fig 2.1 Thermocouple

(ii) Resistance Temperature Detectors (RID) — These are types of thermal

resistors that are fabricated to alter the electrical resistance with the alteration

in temperature. They are very expensive than any other temperature detection

devices. The diagram of Resistance Temperature Detectors is shown below.

Fig 2.2 Resistance Temperature Detectors

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(iii) Thermistors — They are another kind of thermal resistor where a large

change in resistance is proportional to small change in temperature.

Fig 2.3 thermistor

2.5 PROXIMITY SENSOR

A proximity sensor detects the presence of objects that are nearly placed

without any point of contact. Since there is no contact between the sensors and

sensed object and lack of mechanical parts, these sensors have long functional

life and high reliability. The different types of proximity sensors are Inductive

Proximity sensors, Capacitive Proximity sensors, Ultrasonic proximity sensors,

photoelectric sensors, Hall-effect sensors, etc.

Working Process :- A proximity sensor emits an electromagnetic or

electrostatic field or a beam of electromagnetic radiation (such as infrared),

and waits for the return signal or changes in the field. The object which is

being sensed is known as the proximity sensor's target.

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2.5.1 Inductive Proximity sensors

They have an oscillator as input to change the loss resistance by the proximity

of an electrically conductive medium. These sensors are preferred for metal

targets.

2.5.2 Capacitive Proximity sensors -

They convert the electrostatic capacitance variation flanked by the detecting

electrode and the ground electrode. This occurs by approaching nearby object

with a variation in an oscillation frequency. To detect the nearby object, the

oscillation frequency is transformed into a direct current voltage which is

compared with a predetermined threshold value These sensors are preferred for

delectric material and fluids .

2.5.3 Ultrasonic sensor

They are used to detect the presence of an object. It achieves this by emitting

ultrasonic waves from the device head and then receiving the reflected

ultrasonic signal from the concerned object. This helps in detecting the

position, presence and movement of objects.

Since ultrasonic sensors rely on sound rather than light for detection, it is

widely used to measure water-levels, medical scanning procedures and in the

automobile industry. Ultrasonic waves can detect transparent objects such as

transparent films, glass bottles, plastic bottles, and plate glass, using its

Reflective Sensors.

2.5.4 Optical sensor -

Photoelectric sensor are small and fairly simple optical switches. They are

used in place where the environment contains conductive dust and more

20

sensing range is required. They have two main components : an emitter and a

receiver . The emitter contains light source which is either LED or LASER .

The receiver contains an Opts electronics element such as photo transistor or a

photodiode that detects the light from the emitter and converts the received

light intensity is “tuned” to the pulse frequency of its emitter and ignore all of

the other ambient light , which is gathered by it's lens.

There are three types of photoelectric sensors are available,

• Thru beam

• Diffused beam

• Retro reflective type

i. THRU BEAM – these are consist of two devices , a light emitter and a

light receiver .these two devices are kept apart facing each other. Emitter

sends pulse in the range of infrared rays , which is received by a receiver

placed opposite to the emitter. On any interruption of these rays by the

target , the receiver gives a signal, which is amplified & fed into the

output section of the sensors.

Applications–

• sensing the fill level of liquid before sealing

• Counting objects

ii. DIFFUSED MODE – these are consist of emitter and receiver

together. The emitter emits infrared rays are diffused on the receiver by

the surface of object to be sensed, and switches it's output. When there is

no target , no light is reflected to the receiver .

21

Applications –

• Position sensing of objects

• Counting of objects

iii. Retro reflective mode – these are consist of emitter and receiver in one

device & a reflector.the reflector reflects the rays emitted by the emitter

to receiver.the sensing of objects occurs,when these rays are

interrupted .

Applications –

• Edge detection in paper/sheet metal

• Effective for non reflective surface

22

CHAPTER 3

FRONT CONTROL AND

SWITCHING CONCEPTS

An electrical switch is any device used to interrupt the flow of electrons in a

circuit. Switches are essentially binary devices: they are either completely on

(“close”) or completely off (“open”), There are many different types of

switches, front panel controls are nothing but different devices installed on a

machine/control panel/operation console for the operator such as

1) Push buttons

2) Selector switches

3) Rocker Switches

4) Indication Lamps

5) Rotary/Cam

6) Hooters & Buzzer

3.1 PUSH BUTTON

Push button switches are two-posit■to devices actuated with a button that is

pressed and released. Most pushbutton switches have an internal sprIng

mechanism returning the button to its out, or unpressed," position, for

momentary. Pushbutton switches will latch alternately on or off with every

push of the button. Other pushbutton switches stay in 'Brhs.d," Poet . nth the

button is pulled back out. Ohs last type of pushbutton witches usually have a

23

mushroom-shaped button for easy push-pull Mon.

Working principle & application :

It is a spring return switch. The NO NC contacts which can be connected as

accessories get activated when the push button element is passed These Ott

useful for giving momentary signal to the actuators. For example, in a motor

starter the motor by passing push button momentarily, motor contactor gets

latched.'

Ordering Information :

• colors: such as Red, green ,Yellow,White,white,blue

• illuminated/No illuminated

• structure type: Flush mounting

• Protection type

• mushroom type

• mushroom type lockable

• diameter:diameter in mm such as 8,16, 22 mm

24

• Rating:- AC(V/I): 24/4,120/3,230/2

DC(V/I): 24/0.5,110/0.2

2.2 TOGGLE SWITCH

Toggle switches are actuated by a lever angled in one of two or more numbers.

The common light switch used in household mono is an example of a toggle

munch. Most toggle switches come to rest in hon of their lever positions, while

others have an internal Wong mechanism returning the lever to a certain

normal problem, allowing for what is called 'momentary" operation

Symbol of Circuit diagram :-

Working principle & application :

These are similar in working to that of selector switches, and are generally

used. switching of low power appliances, These switches are not modular in

25

nature i.e. extra contacts can't be added.

• Contact types : Single pole double through (SPOT)

Double pole double through (DPDT)

• Ratings such as 1.5A, 3A, 5A, 10A

Indication lamp :-

Symbol of circuit diagram:-

Working principle & application:

These are used l'or visual indication of process. For example for

the indication of whether some machine is ON OFF

26

• Type :- LED type, Lamp type Lamp

• colors:- Red, Green, Yellow, WILD, and Blue

2.4 Selector Switch

Selector switches are actuated with a rotary knob or lever of some

sort to select one of two or more positions.

Symbol of circuit diagram:-

Working principle & application:

Selector switch are used to select position, mode or actuators.

These are useful in control & low power control systems.

27

Ordering Information

• Types: Spring return, Stay put (Maintained contact)

• Switching sequence, 2 or 3-way with/without OFF position.

• Illuminated/Non illuminated

• Key selector two position

• Right position

• Len position

• Right & Left position.

Rocker switch:

Working principle & application:

These are similar in working to that of selector switches, but due

to their compactness, they are useful for switching of low power appliances.

Ordering information :

Contact types: ON/OFF

Momentary ON

Momentary OFF

Both sides ON

Center OFF with both Odes ON

Single pole / Double pole

Rating: 2, 4, 6, 10

28

2.6 Rotary / Cam Switches

Working principle & application:

Rotary switches are like selector switches except it has three or

more positions used to select position, mode or actuators. These are useful in

control circuits & low power control systems

Buzzers & Hooters

they are small in size & there audible sound range is limited,

whereas hooters & sirens sound can be reachable up to 2 K.M. Buzzer are

normally used in low power application. Hooters are used in industry as an

alarm or fault generator. Hooter uses different sound These are used where

audible sound signal/ alarm is to be generated. Buzzers modes to signal various

alarm level.

29

Switching control

switching is used to have control over any electrical circuit.

Switching is nothing but maiking and breaking of an electrical circuit .

NO- Normally open configuration :

in it's deactivated condition ie, NO mode,it does not allow the power supply to

reach to load and no electrical current flows through load.In this condition ,

contact& load, both are deactivated . After the activation f contact it allows the

power supply to reach to load (it makes the contact) and the load decides the

electrical current flowing through it & contact. Activation condition of NO

contact is known as Functionally Closed , i.e , FC . In this condition contact

and load , both are activated.

NC – Normally closed configuration

in it's deactivated condition ie, NC mode,it allow the power supply to reach to

load and the electrical current flows through load. Though contact is

deactivated, load is activated . After the activation of contact it does not allows

the power supply to reach to load (it breaks the contact) and hence,nocurrent

flows through it . Activation condition of NC contact is known as Functionally

Open, i.e , FO . In this condition contact is activated and load is deactivated.

30

CHAPTER 4

DRIVES

4.1 AC DRIVE

In an induction motors, when the 3-phase stator windings, are IS by 3— phase

AC supply then, a magnetic flux of constant magnitude, but rotating at

synchronous speed, is set up. The flux passes through the air gap; sweeps past

the rotor surf., and so cuts the rotor conductors, which as yet, are stationary.

Due to the relative speed between the rotating flux and the stationary

conductors, an E.M.F. is induced in the letter according A Faraday's law of

Electro—Magnetic induction. The frequency of the induced E.M.F. is the same

as the supply frequency. Its magnitude is proportional to the relative velocity

between the flux and the conduct°. Ad Fleming's Right HAd Rule Mves It

directions.The Synchronous Speed (Ns) of an induction motor is given by,

Ns = (120.1)/ P

31

where

“ F ”= frequency

“ P ”= no's of Pole.

In an induction motor, the motor run at a speed, which is always less

than the speed of the stator field. The difference in speeds depends upon the

load on the motor. The difference between the synchronous speed Ns & the

actual speed N of the rotor is known as Slip.

Therefore, Slip (S) = (Ns - N) / Ns

Where, N is the rotor speed.

Therefore, Actual speed of shaft CY) = Ns • (I- S).

The torque equation . AC motor is given as,

32

4.2 VOLTAGE/FREQUENCY CONCEPT

The V/F concept is mainly used in AC drives. Therefore AC drives are also

known as "V/F DRIVES".

In drives it is necessary for a motor to deliver rated torque at set speed. In

order to change the speed of AC motor stator frequency is to be changed. Since

torque delivered by motor is proportional to the product of the stator current

and flux, it is essential that

motor flux be to be kept constant. This means at any speed, motor can deliver

torque (maximum up to rated torque) demanded by load and is roughly

proportional to the product of stator current and motor flux. So we have,

Torque = la * Where, la = Armature current which varies with load . = Motor

flux Wash ',mans constant

4.2.1 VOLTAGE / FREQUENCY CURVE:

The EMF generated is proportional to the raW at which conductors cut the

flux. So we have,

33

EMF = Rate of change of flux

Therefore, in order to maintain constant flux in motor, the ratio of voltage to

frequency is always maintained constant so that motor can deliver rated torque

through out the speed range.

4.2 DC MOTOR

DC MOTOR BASICS

An electrical motor is a machine, which converts electrical energy into

mechanical energy. The basic principle is that when a current carrying

conductor is placed in a magnetic field it experiences a mechanical force

whose direction is given by Fleming's VII hand rule. There is no basic

difference between the construction of a dc generator and do motor the same

machine can be used as a generator or a motor.

In case of a dc motor the field electromagnet kart armature conductors are

supplied with the current from mains supply and mechanical force is obtained

by rotation of armature. In case of dc motor, the e.m.1 (E) is less than the

applied voltage (V) and the direction of the current (Ia) is the reverse of that

when the machine is used as a generator.

E = V — laRa OR V = E IaRa

As the e.m.f. generated in the armature of a motor is in oppose on to the

applied voltage, it is also referred as 'Back emf '

34

4.3.1 WHY WE USE A DC DRIVE?

Basically, DC drive is used due to following things: -

DC drive has precise control on speed & torque. DC drive is a soft starter

means it has ramp input. It is useful in order to minimize the maintenance of

the DC motor. DC drive has good efficiency, which is around 80 % to 95 %

giving good result during running condition of DC motor. DC drive gives

speed regulation means it can sense load (From no-load to full-Imd) in proper

manner & maintain the same speed. DC drive has speed controlling range from

0% to 100%, so it can control speed from 0 mm rated rpm of the motor. DC

drive has 0.01% accuracy which means motor can run at 001% of rated rpm

speed. DC drive gives various types of protection over the motor control like

Feedback loss, Integrated Overload, Ph am sequence failure, Under Co hap,

Over Voltage, Over Current, Over Speed, Over temperature etc.

4.4 SPEED CONTROL OF DC MOTOR USING DC

DRIVES

The speed control of DC motor is given by N = (Va laRa)

From the above equation we can say that, the speed of separately excited DC

motor can be varied in two ways. I Field current is kept consMnt avhile the

armature voltage is varied from zero to rated value. 2 Armature voltage is kept

constant at the rated value and field current is varied from maximum to

minimum. These hvo speed control result in speed-torque characteristics,

which are different from each other. Armature voltage control gives constant

torque and variable power characteristics while variable field flux gives

constant power and variable torque characteristics

35

4.3.2.1 Armature Voltage Control:

This method is used for controlling speed up to base speed of the motor. Base

speed is the ,speed at which the motor deliver. the rated power and torque at

rated armature and field current. Since the field flux is kept constant, the

torque is entirely dependent on the value of armature current. Once the value

of starting, torque i.e. starting current is determined, the armature volt,e .n be

varied smoothly ,up to base speed, keeping the armature current within the

fixed limit. As the motor speeds,Eb increases and the current tends to lower

but since the voltage is also increase the current level can be mainlined. As the

current and the flux are kept constant the motor has constant torque

characteristics and power machine rises.

By abrading the armature voltage below the nominal rated voltage, motor can

be made to operate at various speeds in a wader range delivering lull torque

and reduce power output. It is not possible to operate the motor at higher than

the base speed by increasing the armature voltage above nominal rated voltage.

This method a speed control is used in crimes, rolling mills etc. Thus up to

base speed the motor can be controlled easily by controlling the armature

voltage, called as 'constant torque application'

4.3.2.2 Field current control: Up to the base speed, the motor is controlled by

armature voltage control. Now if the speed required is more than the base

speed and the armature voltage is not be increased beyond the rated voltage,

the choice is to decrease the field flux. To achieve this, the field current is to be

decreased. This is called 'constant power application' since power remains

constant. This is also termed as field weaking of the system.

36

Advantage & Disadvantages of DC Drive

37

CHAPTER 5

TIMERS

5.1 INTRODUCTION

In modern, high tech and professionally managed organization true regard of

time is a prime necessity, proper, uniform, synchronous timing means no more

production losses, less man hour’s wasted and precious resources saved.

Timer is an effective tool in each and every industry. They keep beat of an

enterprise or an industry in synchrony. Timer is a relay with an additional facility

of time. It is a frequently used automation product. It starts counting time as soon

as Auxiliary power supply or a start pulse is applied and actuates output

according to operational mode configured.

Timer coil represents an electronic circuit, it may have digital display and

potential free output contacts are essential part of Timer. These potential free

contacts are available in standalone NO/NC versions or are available in various

combination thereof.

Fig 5.1 Timer

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5.1.1 Applications

• Control circuitry of various machines & processes like…

• Molding machines

• Air-conditioning equipment & plants, chillier packages

• Pharmaceutical machinery

• Cement industries

• Mixing industries

• Photographic equipment

• Textile/Sugar/Steel/Fertilizer processes

• Power generation plants

5.1.2 Common examples -

• Traffic signal control

• Hand dryer

• Microwave oven

• Washing machine

• Television sets

• Streetlights

• Alarm clocks

• Camera

5.2 TYPES OF TIMER

• Electromechanical

• Pneumatic

• Thermal

• Electronic

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fig 5.2 Timer circuit

5.3 OPERATING MODES OF TIMER

1) on delay

2) interval

3) cyclic OFF first

4) Cyclic ON first

5) star delta timer

6) OFF delay

5.3.1 ON Delay Timer

When input auxiliary power or start instruction pulse is applied,

time measurement for ‘t’ seconds beings. Time measurement is shown on the

digital display, if it is available in the model. During time measurement, the

output relay remains in its de-activated condition. At the end of the time

measurement output relay contacts get activated. These output relay contacts

get de-activated when power is removed or reset pulse is provided thus

resetting the timer for the next cycle.

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5.3.2 INTERNAL timer

When input auxiliary power OR start instruction pulse is applied,

time measurement for ‘t’ seconds beings. Time measurement is shown on the

digital display, if it is available in the model. During time measurement, the

output relay contacts get activated and at the end of the time measurement

output relay contacts again get de-activated. One can reset the operation at any

moment by providing Reset pulse or switching OFF/ON the auxiliary power

supply.

5.3.3 Cyclic OFF FIRST Timer

When input auxiliary power OR start instruction pulse is applied,

time measurement for ‘t1’ seconds beings, which is known as OFF TIME. Time

measurement for ‘t1’ is shown on the digital display, if it is available in the

model. During this t1 time measurement, the output relay contacts remain

deactivated and after completion of t1 time measurement output contacts get

activated and timer starts time measurement for t2 duration which is known as

ON TIME. Time measurement t2 is shown on the digital display, if it is available

and after completion of t2 time measurement, output relay contacts get de-

activated again. Till the auxiliary power supply is on, this OFF/ON cycle repeat

continuously. One can reset the operation at any moment by providing Reset

pulse or switching off/on the auxiliary power supply

5.3.4 Cyclic ON FIRST Timer

When input auxiliary power OR start instruction pulse is applied,

time measurement for ‘t1’ seconds beings, which is known as ON TIME. Time

measurement for ‘t1’ is shown on the digital display, if it is available in the

model. During this t1 time measurement, the output relay contacts remain

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activated and after completion of t1 time measurement output contacts get

deactivated and timer starts time measurement for t2 duration which is known as

OFF TIME. During the Time measurement t2 is shown on the digital display, if it

is available and after completion of t2 time measurement, output relay contacts

get de-activated again. Till the auxiliary power supply is on, this ON/OFF cycle

repeat continuously. One can reset the operation at any moment by providing

Reset pulse or switching off/on the auxiliary power supply

5.3.5 OFF Delay Timer

upon application of input auxiliary power, the output relay contacts

get activated. These outputs contacts remain activated till the auxiliary power

supply is in and further remain activated even after the withdrawal of auxiliary

power supply for the pre set time “t”.Actually time measurement begins after the

withdrawal of auxiliary power supply and output contacts get deactivated only

after the preset time “t” is elapsed. These types of Timers are used where the next

process require sometime for completion of incomplete job or to come to normal

condition after power supply is off.

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Fig 5.3 Operation of timer

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CONCLUSION

This report has discussed the role that Automation in Electrical and

Electronics have in the efficient design and control of mechanical

processes.Also discussed was the understanding Automation and controlling

motor and machines involved with it. Finally, the report has discussed relay

logic and the evolution that auto control logic made from it.

1. Automation History: This section discussed the history and advancement

controls technology, with a comparison of machines logic controllers and hard-

wired relays.

2. automation components: This section defined what is automation control

and logic and described all hardware associated with it.

3. Automation in electrical and electronics: This section covered various

technique of automation machines.

4 Automation : This section contain all basic introduction of automation

system.

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BIBLIOGRAPHY

1. G.B.Gupta, Rajeev gupta, SCADA Security Strategy, Theory &

performance of ELECTRICAL MACHINES, August 8, 2001

2. www.automationnews.com

3. www.princetonindiana.com/wasetewater/Pages

4. www.ref.web.cern.ch/ref/CERN

5. www.sss-mag.com/automation.html

6. www.automation.comwww.scrib.com

7. IDEMI MUMBAI

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