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
12

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
14

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
18

(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.
19

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 CONTROLAND
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:-
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:
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
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
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
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
41

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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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-
wiredrelays.
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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Industrial Automation

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