Download criteria for the selection of power cables

AN INDUSTRIAL TRAINNING REPORT
AT
“Universal Cables Limited, Satna (M.P.)”
Submitted in Partial Fulfillment for the award of
Bachelor of Engineering in Electronics &Communication
Engineering (2014-2015)
Submitted to
RAJIV GANDHI PROUDYOGIKI VISHWAVIDYALAYA
BHOPAL (M.P.)
Submitted By:
Neeraj Kumar Singh
(0302EC111081)
Approved By
Under the Guidance of
Mr. A.P. Singh
Mr. R.K. Mishra
(Head of the Department
Electronics & Communication
(H.O.D. OF INSTRUMENT
DEPARTMENT)
DEPARTMENT OF Electronics & Communication ENGINEERING
VINDHYA INSTITUTE OF TECHNOLOGY AND SCIENCE SATNA (M.P.)
1
Rajiv Gandhi Proudyogiki Vishwavidyalaya,Bhopal(M.P)
Vindhya Institute of Technology & Science
Satna (M.P)
CERTIFICATE
This is to certify that the Industrial Training at “Universal
Cables Limited” which has been completed & submitted by Neeraj
Kumar Singh in partial fulfillment of the requirement for the award
of the degree of Bachelor of Engineering in Electronics&
Communication Engineering for the session 2011-2015 is a bonafied
work by them and has been completed under my guidance and
supervision.
H.O.D
Mr.A.P.Singh
Guided By
Mr. R.K. Mishra
(Head of the E&C Department)
(H.O.D. of Instrument Department)
Principal
Mr.R.C.Shrivastava
2
Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal (M.P)
Vindhya Institute of Technology & Science
Santa (M.P)
CERTIFICATE
This is to certify that the Industrial Training at “Universal
Cables Limited ”which has been completed & submitted by
Neeraj Kumar Singh in partial fulfillment of the
requirement for the award of the degree of Bachelor of
Engineering in Electronics & Communication Engineering
for the session 2011-2015.
(External Examiner)
(Internal Examiner)
3
ACKNOWLEDGEMENT
Though words are seldom sufficient to express gratitude and feelings, I
would like to fulfill a fraction of my moral obligation by expressing a
word of gratitude to all those who have profoundly contributed to this
project.
First of all I would like to thank Mr. Sudhir jain, (Asst. Vice
President, Administration), Universal CablesLimited , Universal
Cables Limited for accepting me as a trainee and giving me opportunity
to visit in the company.
I would also like to take this opportunity to convey my respect and
special gratitude towards Mr. R.K Mishra(HOD of Instrument
department ) and Mr. Akhil Pratap Singh (HOD of E&C
Department VITS) who consider me worthy of doing project in their
esteemed establishment and never failed to satisfy my over-zealous thirst
to obtain information.
I also want to say thanks to my whole faculty, whole UCL, friends and
family.
Under the guidance of Mr. R.K. Mishra (Head of department of
Instrument department) at universal cables It was their knowledge, skills
and professionalism which helped me. Their suggestions,
encouragement has been instrumental in the study.
Working on this project has been a great experience. I am thankful to all
concerned people who have played active role in the successful
completion of this project.
DECLARATION
4
I hereby Declare that this project report has successfully done
the training, in industry at Universal Cables Private Limited
Satna (M.P.) , during the period June 09, 2014 to July 08,
2014.The project is based on the original study conducted and
has not formed a basis for the award of any Degree/Diploma by
any other University or Institution.
The project is done for partial fulfillment of the B.E. from the
aforesaid institute.
Signature
Name of student : Neeraj Kumar Singh
B.E (VI-SEM)
VITS (Satna)
5
PREFACE
The following report is the outcome of my research project
during the month of June and July.
Provides an opportunity to demonstrate application of
knowledge skill and competence required during the technical
sessions. Research also helps to analyze the problem and suggest
alternative solutions, to evaluate them and to provide feasibility
recommendation on the provided data.
Instrument plays an important role in every production unit. To
improve it at every step is very important. The use of
Instrument in many highly innovative companies in
Scandinavian countries has been proven.
This tool is suitable for all levels of employee within an
organization. However, it will only succeed if it has genuine
management involvement and full understanding throughout all
levels of management and the organization concerning the
multifaceted purposes served by the Instrument.
INDEX
6
SECTION
SECTION NAME
PAGE
NO.
1.
COMPANY PROFILE
6-10
2.
FACTORS INFLUENCING THE CHOICE
OF CABLES
11-14
3.
15-21
4.
MANUFACTURING PROCESS OF
CABLES
EHV & XLPE CABLES
5.
TELECOMMUNICATION CABLES
28-29
6.
ELECTRICAL&MACHANICAL
MAINTENANCE
30
7.
CONTROLLERS, AC DRIVES, UPS
31-37
8.
INVERTERS
38-40
9.
AC&DC MOTORS, CRO, FUNCTION
41-54
22-27
GENERATORS , AUTOMATION
10.
PROFIBUS INTERACE
57
11.
SOLID STATE RELAY
58
12.
TELECOMMUNICATION - EPABX
59-60
13.
NETWORK COMMUNICATION
61
14.
CCTV ON LAN
62
15.
IGBT
63-64
7
COMPANY PROFILE
8
Universal Cables Limited (UCL) was established in the year 1962 as a modern
mass production unit to manufacture paper insulated power cables in technical
collaboration with world's largest cable producer BICC, UK. Late Shri M.P. Birla,
who had adorned the chair of the Company for over 25 years since its inception,
enabled the Company to flourish in a highly competitive world, while
distinguishing itself by the latest technological tie-ups with the foremost leaders in
the world of this industry and the most up-to date technology.
Universal Cables Limited entered into a collaboration agreement with ABB high
Voltage Cables, Sweden in 1977 to manufacture cross-linked Polythene Power
Cable for the first time in the country. The Company is the foremost manufacturer
of XLPE Cables with modern dry cured dry cooled process for voltage range
extending from 1.1 to Extra High Voltage up to 132 KV grade.
Under the collaboration Agreement with ABB high Voltage Cables, Sweden, UCL
brought in complete know how of compounding of Polymer and produced
complete range of dielectrics presently used in all special cables.
In 1983, UCL embarked on a joint venture with MPAVN to manufacture Jelly
Filled Telephone Cable in technical collaboration with one of the world's leading
manufacturers of Telephone Cable, Ericsson Cable AB, Sweden. This plant was
incorporated as Vindhya Telelinks Limited (VTL) and is situated at Rewa, only 50
Kms away from its Power Cable Plant at Satna.
9
Since 1985, ABB High Voltage Cables, Sweden, is further assisting UCL to
manufacture Fluroplastic Cables, specifically for very high temperature operation
and high frequency signaling circuitry.
In 1993, UCL & VTL jointly entered into the field of optical communication by
way of manufacturing Optical Fibre Cables in technical and financial collaboration
with Ericsson Cables AB, Sweden. This marked the birth of Birla Ericssion Optical
Limited (BEOL).
QUALITY CONSCIOUSNESS
Whether conventional or specially designed to any Indian or International
specification, UCL's products are put to the grill of rigorous in-process quality
cheeks by stage inspection and testing Its quality is taken as standard in the world
market.
MEANS ARE AS IMPORTANT AS THE END
UCL proudly claims to have the most sophisticated plant, equipment, laboratory
and testing facilities available in the country. The entire plant is housed in dustproof pressurized building to ensure consistency in the product quality.
CERTIFICATION
The above claim is certified by various test authorities of the country like NTH,
Calcutta and CPRI Bhopal & Bangalore and all consultants like Ell, DCPL, M.N.
Dastur, Lloyds register of Shipping, MECON, Crown Agents and others. This
confirms the dependability and reliability of UCL products.
ISI MARKING
10
All standard UNISTAR cables are ISI marked.
IS/ISO QUALITY CERTIFICATION
UCL is accredited with IS/ISO 9001/2000 Quality Systems Certification in
recognition of the High Quality Standard of its cables. The company is also
accredited for its well-established environmental friendly activities and
atmosphere.
TECHNICAL SERVICES
The Company welcomes enquiries on cable engineering problems and provides
solutions through its design and development team. It also assists customers in
cable design to suit their specific requirement. A team of experts is always ready to
assist cable engineers for installation, laying and jointing cable systems through
out the India. When requested the technical dept. of the company provides help to
customers for fault location and other related problem.
RESEARCH & DEVELOPMENT
UCL emphasizes on in-house Research and Development. The R & D programme
is mainly directed to applied research for product development, process
development and technological up gradation. The R & D laboratory of UCL is a
recognized unit of Department of Scientific and Industrial Research of Govt. of
India. This laboratory has developed many new Cables for special applications
such as FRLS Cables, Ship wiring, Air craft wiring, Radars, Submarine, Medical
Equipments etc.
CAPACITORS
UCL set up its Capacitor Division in the year 1967, in technical collaboration with
world renowned TOSHIBA, to manufacture Paper & Power Capacitors. In 1977
this division entered into a technical collaboration with General Electric Company
of USA, to manufacture Mixed Dielectric Capacitors. Subsequently the
collaboration was extended to include All Polypro- propylene (All-PP) Dielectric
Capacitors impregnated with Non PCB oil. Today the Capacitor Division is rated
11
to be the foremost manufacturer of All-PP Power Capacitors in LT & HT range in
the country.
This division offers complete schemes for power factor improvement and can
supply capacitors along with associated equipments on turnkey basis. It can also
carry out harmonic analysis of Power System on request and design & supply
Filter Banks. EXPORTS UCL also exports its products to various countries of the
world and has earned due recognition for its export efforts. Universal Cables
limited is a vibrant progressive company, a leader in its field of activities, serving
the aspiration of the nation in the field of Power Development.
.
CRITERIA FOR THE SELECTION OF POWER CABLES
The electrical current in a conductor causes a voltage drop and power losses. The
temperature rise in the cable caused by the losses must be kept within certain limits
in order not to shorten the service life of the cable. The temperature limit varies
with the type of cable, or more precisely the type of insulation. The best way to
keep the temperature within limits specified for the type of cable, is to choose the
conductor cross-section so that the cable and its surroundings with the actual
continuous load, achieve thermal balance at a temperature below or equal to the
temperature limit recommended. Cable type and size should be selected keeping in
view the following:(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
2.
Application.
Working voltage; earthed or unearthed neutral system.
Load current, load factor, starting duty and frequency.
Installation method.
The environment in which the cable has to operate.
Short circuit current and system protection.
Acceptable voltage drop
Economies.
How the above factors influence on the choice of cable?
12
1) The application of the cable determines the basic factors for the choice of
cable type and the rules according to which it must be manufactured. Following
are the major factors for choice of cable type.
(a) Conductor materials: No doubt copper is better conductor material
owing to its high electrical conductivity and other electrical/mechanical properties
but due to its high cost and scarcity, researches are being carried out to find other
cheaper and abundant metals which may be a close substitute to copper in
electrical application. Aluminium conductors are being used in place of copper
conductors for the past many years and have proved to be quite satisfactory.
The lower conductivity of a Aluminium (61 % of the annealed copper) results
in increased dimensions of the cable and ultimately of conduits and fittings for
the same current carrying capacity as that of a copper conductor cable.
Aluminium conductor cables although bigger and somewhat stiffer when lower
number of wires is used for the conductor than the equivalent copper conductor
cables, are still flexible enough to be installed where a copper conductor cable
was formerly used. The advantages of the lighter weight offset the
disadvantages of larger sizes for a given capacity. The use of Aluminium
conductor cables should be preferred as far as possible. The use of flexible
copper conductor is recommended where very high degree of flexibility is
required as in the case of mines etc.
(b) Insulating materials: The right type of insulation material for a
particular usage depends upon the voltage grade, operating temperature
required, degree of flexibility, current capacity requirement and restrictions on
size etc. and other climatic conditions.
(C) Metallic Sheathing: Either pure lead or different lead alloys are used
for Sheathing of PILC cables and each has it’s own advantages.The most common
andmpopular alloy is lead Alloy 'E'.
13
(d) Bedding and Serving materials: In case of PVC cables the normal
bedding and serving materials are PVC compound. The normal bedding and
serving in case of PILC cables consist of a combination of an impregnated paper,
cotton and Hessian tapes and bituminous compound. These materials provide
protection against corrosion of armour and lead and are suitable in great majority
of installations. However, in special cases where severe chemical corrosion is to
be encountered, the use of PVC bedding and PVC serving is recommended.
(D)Armouring: The purpose of armour is to provide mechanical protection
to the cable and to facilitate earthling for safety requirements. This also carries
phase to ground fault currents of the system safely.
Double steel tape provides good mechanical protection but when in addition
longitudinal stresses are encountered during the installation or in service, steel
wire/strip armouring is recommended for vertical armouring should be preferred.
Double wire runs, strip armouring is recommended for vertical armouring should
be preferred. Double wire runs, river crossing, cables laid on bridges and mine
shafts etc. where longitudinal stresses are expected.
2. The system voltage determines the voltage class of the cables.
3. The current rating is, in general, the decisive factors for fixing conductor crosssection. But in certain applications where intermittent load is required, it is more
relevant to use the squared average r.m.s. current with a reduced cross section.
4. The power cables must be capable of carrying, the required normal full load
current continuously under the site conditions throughout the year. Therefore, the
current ratings specified must be corrected to site conditions by applying suitable
derating/uprating factors depending upon -
(a)
(b)
(c)
Ground or ambient air temperature (max.).
Thermal resistivity of soil during dry season.
Depth of laying.
14
(d)
Total number of cables/circuits in groups.
5. (A) Chemical substances in the environment might cause special stringent
requirements on the outer covering.
(B) If it is necessary to reduce the propagation of fire along cable route combined
with low corrosivity, toxicity and smoke generation characteristics for cables,
"FRLS' cables (Flame Retardant low Smoke) with thermoplastic or
thermosetting material or fire survival cables with elastomeric material should be
used. These types of cables are designed with special composition of protective
sheath materials, and by using beat barrier tapes etc. for use in such critical fire
risk installations.
6) Short circuit current together with duration of short circuit determines the short
circuit energy the cable insulation has to with stand thermally.ln certain cases a
larger size of cable then the cable required for normal full load current may be
needed to match system short circuit current levels.
Voltage drop is also a major factor in deciding the conductor size of the cable.
The cross section of the cable should be chosen such that voltage drop of the
cable for the given route length does not exceed the statutory requirement.
7) Naturally, the most economical construction and the size of the cable
consistent with required current carrying capacity and laying condition has to be
selected. Thus the selection of particular type of cable i.e. PVC, XLPE, PILC or
rubber and the particular material for screening, sheathing, bedding, armouring
or serving etc. out of many choices available depends upon the usages, laying
and climatic conditions. The design of the cable for a particular application
must be optimized taking into account all the above-mentioned factors. In case
expert guidance in this respect is desired, please contact UCI Technical Service
Division. UCL SATNA
15
MANUFACTURING PROCESS
OF CABLES
16
The over all stages of manufacturing consists of the following different types of
processes :-
Wire Drawing - Annealing
Tinning
Bunching
Stranding
Insulation
Paper/PVC/Rubber/XLPE/Fluroplastic/Polythelene
Laying Impregnation
Lead Sheathing
Bedding – Extruded/wrapped/fibrous lapping
Armoring
Round wire/Flat strip/Steel tape
Sheathing/ Serving
Extruded/Fibrous lapping
17
The details of above manufacturing processes are as given here
under :CONDUCTOR:
Wires of different sizes are drawn from Aluminium/Copper rods on wire-drawing
machines. The size(diameter) of wire depends upon the over all cross sectional
area of the ultimate cable under manufacture as well as the flexibility requirement.
Annealed copper Wires for flexible rubber cables are then tinned before they are
released for next process. The tinning is done by passing the cleaned cu. wires
seated with the flux through molten tin both. The excess of tin adhering to wire
surface is wiped out by means of wipers
Stranding - The Al or Cu. wires or tinned copper wires as the case may be are
bunched/stranded together. The direction of stranding of alternate layers is always
kept in opposite direction in order to have tight and balanced configuration of
wires. The standard Conductor may be compact circular or shaped as per the cable
construction.
18
INSULATION
(1) PVC:- Different type of PVC compounds are used for required
Physical & electrical properties and continuous operating temperature
of cables. PVC compound extruded over conductor by extrusion
process on differe.
(2) The sizes of extruders as per the size of conductor. In line to extrusion
process H.V. testing (Spark testing) is being done to check the quality
of extruded core.
2. Rubber - Natural or synthetic rubber based compounds are prepared to meet
the physical & Elec. properties and continues operating temp. of cable. Various
types of rubber compounds are then extruded over the conductor as per the
requirement of the customer.
3. Paper insulation - In this case insulated paper tapes are lapped on conductor.
The thickness of insulation is built up by required number of paper tapes according
to voltage grade of cables. The top layer of paper tapes is suitably numbered for
core identification.
4. XLPE – XlPE cables have become very much popular now a day. These cables
are replacing paper-insulated cables right from low voltage grade to extra high
voltage grade. In these cables two types of constructions are used ie screened and
unscreened. 11 KV and above grade cables are all screened. Conductor screen,
insulation and insulation screen are generally applied in one operation called dualtandem process. M/s Universal Cables Ltd is one of the pioneer cable
manufacturers of XLPE cable up to 132 KV grade cables in INDIA.
Vulcanization/Cross-linking: Rubber and XLPE cables are vulcanized after
extrusion. This process is done just after extrusion on CV/CCV/PLCV lines. This
process is done to improve the electrical and physico-mechanical properties of
rubber and polyethylene compounds. In some cases batch vulcanization is carried
out for rubber cables and low voltage XLPE cables.
19
Laying up of cables.
The insulated cores are laid up along with filling material and twisted to get
approximate circular Cable. A binding tape is also provided to hold the fillers and
maintain the circularity of laid up cables. In case of paper-insulated cables if the
cables are belted type, belt insulation is done along with laying up process by
providing required no. of paper tapes and in screened type cables copper woven
fabric tape is provided over laid up cores.
Impregnation Process :Paper insulated cables need a special process known as impregnation. The function
of this process is to extract moisture out of paper insulation and impregnate the
insulation with moisture resistant insulating compound.
Heating the Cable under vacuum for some period and then filling the insulating
compound over cable within the impregnating vessel do this process. The cycle of
drying flooding and cooling etc. depends on size and voltage grade of cables. By
impregnation the electrical properties of paper insulation are enhanced. Procedure
adopted for drying and impregnation of paper-insulated cables comprises the
following stages :Rewinding the cables in impregnation trays
Loading the trays in the impregnation tanks
Heating the cables under vacuum
Impregnating of cables with impregnation compound for required period
Unloading the cable-trays from the tanks after impregnation.
The compound used for impregnation is a petroleum product and has excellent
electrical and mechanical properties.
20
Lead sheathing
After impregnation, lead sheath is applied over the paper-insulated cables. This
process is done by sleeve extrusion (pipe extrusion). The object of Lead sheathing
is to prevent the entry of moisture in the impregnated cable while maintaining
the flexibility of cable.
Inner Sheathing/Bedding
PVC and Rubber insulated cables are provided with inner sheathing over laid up
cores as bedding for armoring. In case on PVC cables inner sheathing may be done
by lapping PVC/PE tapes or by PVC extrusion but in case of rubber insulated
cables rubber extrusion is done for this purpose.
Armoring
The armoring is provided to provide mechanical protection of cables during
handling and installation. This is done by providing galv. round steel wires or
galvanized steel strips or double steel tapes over the bedded cables. Though the
main function of armoring is to protect the cable from outside mechanical
damages to the cable but it also serves the purpose of carrying the short circuit
current produced during system failure or any type of short circuit in the system.
21
Sheathing/Serving:After armoring or in case of un-armored cables, the laid and bedded cables are
provided with a protective sheathing of extruded PVC or PE sheath. Paper
insulated cables are generally provided with a fibrous lapped serving but PVC or
any other type of extruded sheath can also be given if required.
22
Power and control cables
23
Introduction:Universal cables Ltd manufactures PVC cables up to 11 KV grade to Indian as
well as international standards. Both utilities and domestic users find them
suitable for power distribution, control system, utility network, railway signaling
installations, switching stations, textile mills, chemical plants, and machine
shops etc. Normal PVC insulated cables are suitable for an operating conductor
of 700C and HR PVC insulated cables are suitable for an operating conductor
temperature of 850C.
PVC CABLES
24
VCV PLANT
EXTRA HIGH VOLTAGE CABLES
VCV PLANT
25
Introduction:UNIVERSAL CABLES LTD, the pioneer of XLPE cables in India, manufactures
Extra High Voltage (EHV) XLPE cables in the range of 66-220 kV using ‘Vertical
Continuous Vulcanizing (VCV) technology in technical collaboration with World
Leader in Cable manufacturing, FURUKAWA ELECTRIC CO. LTD. (In
association with VISCAS Corporation, Japan). This technology for EHV XLPE
Cable manufacturing process is the only of its kind in the Country.
EHV Underground Power Transmission is the solution for meeting today’s growing
power demand of the power starved Metro Cities. Underground Power Transmission
System requires highest reliability to ensure uninterrupted power supply.
Unistar EHV cable, manufactured using VCV technology with proven know-how
from FURUKAWA ELECTRIC CO. LTD and also having in-house engineering
expertise for system designing, cable jointing and installation, can guarantee this
requirement.
The main cutting edge features of this technology as True simultaneous triple
extrusion with single (common) cross-head, Dry cure dry cooled process,
26
Dimensional accuracy for perfect geometry with Zero eccentricity/ ovality of the
insulation, Class 1000 cleanliness level with completely closed material handling
system, Online X-Ray monitoring system, Direct gravitational feeding of XLPE
compound, Control and Monitoring in production process using SCADA, all add
up to unmatched quality standard to ensure reliable and efficient performance of
the cable throughout its service life.
The main cutting edge features of this technology are:-
1.
True simultaneous triple extrusion with single (common) cross head - conductor
screen,
insulation and insulation shield applied in single process. This provides perfect
bonding of
insulation and semicon layers with smooth boundary and free of protrusions.
Insulation extruder operates with tight screen of 400 mesh for filtering.
2. Dry cure dry cooled process - Prevents formation of micro voids and
eliminates moisture
contents in the XLPE insulation - Prevents electro-chemical tree formation in the
insulation and
capable to withstand higher stress voltage.
3. Dimensional accuracy - perfect geometry with Zero eccentricity/ovality of the
insulation. This enables uniform stress distribution over the insulation.
4. Class 1000 cleanliness level in manufacturing with completely closed material
handling system - prevents insulation contamination which is an imperative for
Extra High Voltage Cables enabling high impulse and breakdown voltage levels.
5. Cables of longer lengths and larger sizes can be offered to economize the
system cost.
Other special features include:• Online X-Ray monitoring system with a fully computerized control system
including Programmable Logic Control.
27
Cross link polyethelene(XLPE OR PEX) Plant:-
SPECIFICATIONS:The extrusion of cross linked polyethylene shall be carried out on a dual tandes
continuous catenary vulcanization(ccv) line using nitrogen gas curing system.
The insulations of 1.1kv-3.3kv range cables shall extruded in a single layer in
natural colour, using only insulation extruation.
The insulation of 6.6kv-132 kv range cables shall be coextruded in natural colour
together with semiconducting layer using three extruders.
28
Telecommunication Cables
29
Apart from power and control cables, telephone cables are also manufactured.
These cables are generally called PIJF cables meaning Polyehylene Insulated Jelly
Filled cables. In these cables copper wire of suitable size is insulated with
Polyethylene. Two insulated wires are twisted together to form a pair. Required
numbers of such pairs are grouped together and filled with special moisture
resistant jelly. The filled cable is than screened with polythene laminated
aluminum foil and sheathed with LDPE compound. The cable is finally armoured
with galvanized double steel tapes and jacketed with LDPE compound.
Final testing:All cables are rewound in proper size wooden/steel reels and sent to testing section
where all the cables are subjected to rigorous electrical and physical tests. Both the
ends of cables after testing are sealed and given a unique identification number.
These are then handed over to marketing department for onward dispatch to
relevant customer
Quality control
In universal cables quality is maintained by following a in built quality system
which is based on international specification IS/ISO 9001.
A property organized system of control of quality of product and process is
followed for the efficient production of product acceptable in all respects to the
customer. Products are tested and processes are controlled at all stages of
manufactures from raw material to the finished stage. In addition certain standards
procedures are adopted in order to ensure that product successfully fulfils the
customer requirement.
30
ELECTRICAL & MECHANICAL
MAINTENANCE
Electrical and mechanical departments are responsible for the periodic
maintenance of all machines and equipments. A comprehensive schedule of PPM
is followed to avoid breakdowns and thereby loss of machine and men hours. Both
these departments are also looking after break down maintenance and installation
&commissioning of new machines and instruments. These departments also carry
out calibration of various electrical and mechanical instruments.
TEMPERATURE CONTROLLER:Temperature Controller: What is a Temperature Controller? As the name implies
a temperature controller is an instrument used to control temperature. The
temperature controller takes an input from a temperature sensor and has an
output that is connected to a control element such as a heater or fan.
31
Introduction to Temperature Controllers:How do Temperature Controllers work?
To accurately control process temperature without extensive operator involvement,
a temperature control system relies upon a controller, which accepts a temperature
sensor such as a thermocouple or RTD as input. It compares the actual temperature
to the desired control temperature, or setpoint, and provides an output to a control
element. The controller is one part of the entire control system, and the whole
system should be analyzed in selecting the proper controller. The following items
should be considered when selecting a controller:
Type of input sensor (thermocouple, RTD) and temperature range
Type of output required (electromechanical relay, SSR, analog output)
Control algorithm needed (on/off, proportional, PID)
Number and type of outputs (heat, cool, alarm, limit)
What Are the Different Types of Controllers, and How Do They
Work?
There are three basic types of controllers: on-off, proportional and PID. Depending
upon the system to be controlled, the operator will be able to use one type or
another to control the process.
On/Off Control:An on-off controller is the simplest form of temperature control device. The output
from the device is either on or off, with no middle state. An on-off controller will
switch the output only when the temperature crosses the setpoint. For heating
control, the output is on when the temperature is below the setpoint, and off above
setpoint. Since the temperature crosses the setpoint to change the output state, the
process temperature will be cycling continually, going from below setpoint to
above, and back below. In cases where this cycling occurs rapidly, and to prevent
damage to contactors and valves, an on-off differential, or “hysteresis,” is added to
the controller operations. This differential requires that the temperature exceed
setpoint by a certain amount before the output will turn off or on again. On-off
differential prevents the output from “chattering” or making fast, continual
32
switches if the cycling above and below the setpoint occurs very rapidly. On-off
control is usually used where a precise control is not necessary, in systems which
cannot handle having the energy turned on and off frequently, where the mass of
the system is so great that temperatures change extremely slowly, or for a
temperature alarm. One special type of on-off control used for alarm is a limit
controller. This controller uses a latching relay, which must be manually reset, and
is used to shut down a process when a certain temperature is reached.
Proportional Control:Proportional controls are designed to eliminate the cycling associated with on-off
control. A proportional controller decreases the average power supplied to the
heater as the temperature approaches set point. This has the effect of slowing down
the heater so that it will not overshoot the set point, but will approach the set point
and maintain a stable temperature. This proportioning action can be accomplished
by turning the output on and off for short time intervals. This "time proportioning"
varies the ratio of “on” time to "off" time to control the temperature. The
proportioning action occurs within a “proportional band” around the set point
temperature. Outside this band, the controller functions as an on-off unit, with the
output either fully on (below the band) or fully off (above the band). However,
within the band, the output is turned on and off in the ratio of the measurement
difference from the set point. At the set point (the midpoint of the proportional
band), the output on:off ratio is 1:1; that is, the on-time and off-time are equal. if
the temperature is further from the set point, the on- and off-times vary in
proportion to the temperature difference. If the temperature is below set point, the
output will be on longer; if the temperature is too high, the output will be off
longer.
PID Control:The third controller type provides proportional with integral and derivative control,
or PID. This controller combines proportional control with two additional
adjustments, which helps the unit automatically compensate for changes in the
system. These adjustments, integral and derivative, are expressed in time-based
units; they are also referred to by their reciprocals, RESET and RATE,
respectively. The proportional, integral and derivative terms must be individually
adjusted or “tuned” to a particular system using trial and error. It provides the most
accurate and stable control of the three controller types, and is best used in systems
33
which have a relatively small mass, those which react quickly to changes in the
energy added to the process. It is recommended in systems where the load changes
often and the controller is expected to compensate automatically due to frequent
changes in set point, the amount of energy available, or the mass to be controlled.
OMEGA offers a number of controllers that automatically tune themselves. These
are known as autotune controllers.
Standard Sizes:
Since temperature controllers are generally mounted inside an instrument panel,
the panel must be cut to accommodate the temperature controller. In order to
provide interchangeability between temperature controllers, most temperature
controllers are designed to standard DIN sizes. The most common DIN sizes are
shown below.
34
AC DRIVES
AC drives are AC motor speed control systems.
Slip controlled drives control the speed of an induction motor by increasing a
motor's slip. This is accomplished by reducing the voltage applied to the motor or
increasing the resistance of the rotor windings. Because they are generally less
efficient than other types of drives, slip controlled drives have lost popularity and
have recently been used only in special situations.
Adjustable-frequency drives (AFD) control the speed of either an induction
motor or a synchronous motor by adjusting the frequency of the power supplied to
the motor. Adjustable frequency drives are also known as variable-frequency
drives (VFD).
When changing the frequency of the power supplied to an AC motor, the ratio of
the applied voltage to the applied frequency (V/Hz) is generally maintained at a
constant value between the minimum and maximum operating frequencies.
Operation at a constant voltage (reduced V/Hz) above a given frequency provides
reduced torque capability and constant power capability above that frequency. The
frequency or speed at which constant-voltage operation begins is called the base
frequency or speed. Whether to applied voltage is regulated directly or indirectly,
the V/Hz tends to follow the general pattern described for the performance
described. The variable-frequency drive article provides additional information on
electronic speed controls used with various types of AC motors.
35
Operating principle
Variable frequency drives operate under the principle that the synchronous speed
of an AC motor is determined by the frequency of the AC supply and the number
of poles in the stator winding, according to the relation:
where
RPM = Revolutions per minute
f = AC power frequency (hertz)
p = Number of poles (an even number)
Synchronous motors operate at the synchronous speed determined by the above
equation. The speed of an induction motor is slightly less than the synchronous
speed.
36
UNINTERRUPTIBLE
POWER SUPPLY (UPS) SYSTEMS
Principles of static UPS systems
The basic static UPS system consists of a rectifier-charger, inverter, static switch,
and battery as Shown in figure. The rectifier receives the normal alternating current
(ac) power supply, provides direct current (dc) power to the inverter, and charges
the battery. The inverter converts the dc power to ac power to supply the intended
loads. The dc power will normally be provided from the rectifier, and from the
battery upon failure of the primary ac power source or the rectifier. The inverter
will supply the loads under normal conditions. In the event of the failure of the
inverter, the static switch transfers the load to an alternate ac source.
Single phase & 3 phase UPS:3 phase in refers to a 440/480 voltage supply. It's generally used to power heavy
industrial equipment that runs 3 phase electrical motors more efficiently.
Single phase is like household wall outlet voltage. Unless you're running
equipment that requires a 3 phase voltage, you're going to need to stick with
single phase
Normal operation.
During normal operation, the rectifier converts the ac input power to dc power
with regulated voltage. The rectifier output is normally set at the battery float
voltage to charge the battery while supplying dc power to the inverter. The rectifier
output voltage is periodically set at the battery equalize voltage to maintain the
battery capacity. The dc filter (inductor) is provided for smoothing out the rectifier
output current to reduce the current ripple content. The battery acts as a capacitor
and in conjunction with the filter, smoothes out the output voltage and reduces the
dc voltage ripple content. The inverter converts the dc power to ac power with
regulated voltage and frequency. An internal oscillator maintains the inverter
37
frequency by controlling the timing of the silicon controlled rectifier (SCR) firing
signals and matches the ac input frequency. The filters at the output transformer
secondary are provided to filter out the harmonics in the inverter output. Tuned LC filters are used - when required - to filter out the 5th
and 7th harmonics while a capacitor is adequate for filtering out the higher order
harmonics.
38
INVERTERS
39
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.
Inverter designed to provide 115 VAC from the 12 VDC source provided in an
automobile. The unit shown provides up to 1.2 Amps of alternating current, or just
enough to power two sixty watt light bulbs.
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.
Early inverters
From the late nineteenth century through the middle of the twentieth century, DCto-AC power conversion was accomplished using rotary converters or motorgenerator sets (M-G sets). In the early twentieth century, vacuum tubes and gas
filled tubes began to be used as switches in inverter circuits. The most widely used
type of tube was the thyratron.
Induction heating
Inverters convert low frequency main AC power to a higher frequency for use in
induction heating. To do this, AC power is first rectified to provide DC power. The
inverter then changes the DC power to high frequency AC power.
40
Basic designs
In one simple inverter circuit, DC power is connected to a transformer through the
centre tap of the primary winding. A switch is rapidly switched back and forth to
allow current to flow back to the DC source following two alternate paths through
one end of the primary winding and then the other. The alternation of the direction
of current in the primary winding of the transformer produces alternating current
(AC) in the secondary circuit.
The electromechanical version of the switching device includes two stationary
contacts and a spring supported moving contact. The spring holds the movable
contact against one of the stationary contacts and an electromagnet pulls the
movable contact to the opposite stationary contact. The current in the
electromagnet is interrupted by the action of the switch so that the switch
continually switches rapidly back and forth. This type of electromechanical
inverter switch, called a vibrator or buzzer, was once used in vacuum tube
automobile radios. A similar mechanism has been used in door bells, buzzers and
tattoo guns.
Three phase inverters
3-phase inverter with wye connected load
Three-phase inverters are used for variable-frequency drive applications and for
high power applications such as HVDC power transmission. A basic three-phase
inverter consists of three single-phase inverter switches each connected to one of
the three load terminals. For the most basic control scheme, the operation of the
three switches is coordinated so that one switch operates at each 60 degree point of
the fundamental output waveform. This creates a line-to-line output waveform that
has six steps. The six-step waveform has a zero-voltage step between the positive
and negative sections of the square-wave such that the harmonics that are multiples
of three are eliminated as described above. When carrier-based PWM techniques
are applied to six-step waveforms, the basic overall shape, or envelope, of the
waveform is retained so that the 3rd harmonic and its multiples are cancelled.
41
AC and DC Motors
A motor creates a rotational force when a current is circulated through a magnetic
field. In a DC motor, the magnetic field, also called the magnetic flux or just flux,
is generated by a separate magnetic circuit called the motor field.
The magnetic flux is dependent on the core material, the number of windings, and
the amps circulated through these windings.
An AC induction motor has only one circuit for both flux- and torque-producing
current. The vector summation of flux current and torque current represents total
current. A DC motor runs when DC voltage is supplied to the armature. As it spins,
it also generates voltage inside itself like a generator. This internal voltage is called
the counter electromotive force or CEMF. CEMF is dependent on the
field current (flux) and the motor speed.
The speed of an AC motor depends on its construction. The higher the input
frequency, the faster it spins. This is because the input frequency determines
the speed of the rotating field inside the motor that is generated by the stator
windings. The speed is determined as:
When an AC motor has a mechanical load, it is no longer synchronized with the
input frequency. The speed difference between no-load speed and full load
speed is called slip. It is expressed as a percentage.
42
Cathode-Ray Oscilloscope(CRO):-
electronic-display device containing a cathode-ray tube (CRT) that generates
an electron beam that is used to produce visible patterns, or graphs, on a
phosphorescent screen. The graphs plot the relationships between two or more
variables, with the horizontal axis normally being a function of time and the
vertical axis usually a function of the voltage generated by the input signal to the
oscilloscope. Because almost any physical phenomenon can be converted into a
corresponding electric voltage through the use of a transducer, the oscilloscope is a
versatile tool in all forms of physical investigation. The German
physicist Ferdinand Braun developed the first cathode-ray oscilloscope in 1897.
Speed of response is the cathode-ray oscilloscope’s chief advantage over other
plotting devices. General-purpose oscilloscopes have plotting frequencies of up to
100 megahertz (MHz), or 100 million cycles per second. Response times as rapid
as 2,000 MHz are achievable with special-purpose high-speed oscilloscopes.
The central component in this device, the cathode-ray tube, consists of an
evacuated glass container with a phosphorescent coating at one end (similar to that
of a television screen) and an electron gun and a system for focusing and deflecting
the beam of electrons at the other.
The electron beam emerging from the electron gun passes between pairs of metal
plates mounted in such a way that they deflect the beam horizontally and vertically
to control the production of a luminous pattern on the screen. The screen image is a
visual representation of the voltages applied to the deflection plates. Alternatively,
the beam may be deflected magnetically by varying the currents through externally
43
mounted deflection coils. Thus, almost any graph can be plotted on the screen by
generating horizontal and vertical deflection voltages or currents proportional to
the lengths, velocities, or other quantities being observed.
It is sometimes necessary or desirable to plot more than one waveform at the same
time on the screen of an oscilloscope. With the use of a variety of techniques, four
or more plots can be simultaneously shown. With a dual-trace amplifier and a
single electron gun, two signals may be shown at what appears to be the same time.
Actually, the amplifier electronically switches rapidly between the two observed
signals. In a split-beam CRT the electron beam from a single gun is split, with the
two parts receiving different vertical deflections. A dual-gun CRT uses two
separate electron guns, each having its own focus and brightness controls. By
combining two dual-trace amplifiers with a dual-gun CRT, four individual plots
can be obtained.
The cathode-ray oscilloscope is one of the most widely used test instruments; its
commercial, engineering, and scientific applications include acoustic research,
television-production engineering, and electronics design.
44
An oscilloscope is a test instrument which allows you to look at the 'shape' of
electrical signals by displaying a graph of voltage against time on its screen. It is
like a voltmeter with the valuable extra function of showing how the voltage varies
with time. A graticule with a 1cm grid enables you to take measurements of
voltage and time from the screen.
The graph, usually called the trace, is drawn by a beam of electrons striking the
phosphor coating of the screen making it emit light, usually green or blue. This is
similar to the way a television picture is produced.
Oscilloscopes contain a vacuum tube with a cathode (negative electrode) at one
end to emit electrons and an anode (positive electrode) to accelerate them so they
move rapidly down the tube to the screen. This arrangement is called an electron
gun. The tube also contains electrodes to deflect the electron beam up/down and
left/right.
The electrons are called cathode rays because they are emitted by the cathode and
this gives the oscilloscope its full name of cathode ray oscilloscope or CRO.
A dual trace oscilloscope can display two traces on the screen, allowing you to
easily compare the input and output of an amplifier for example. It is well worth
paying the modest extra cost to have this facility.
Function generator:-
A function generator is usually a piece of electronic test
equipment or software used to generate different types of electrical waveforms over
a wide range of frequencies. Some of the most common waveforms produced by
the function generator are the sine, square, triangular and sawtooth shapes. These
waveforms can be either repetitive or single-shot (which requires an internal or
45
external trigger source). Integrated circuits used to generate waveforms may also
be described as function generator ICs.
Specifications:Typical specifications for a general-purpose function generator are:
Produces sine, square, triangular, sawtooth (ramp), and pulse output. Arbitrary
waveform . generators can produce waves of any shape.
It can generate a wide range of frequencies. For example, the Tektronix FG 502 (ca
1974) covers 0.1 Hz to 11 MHz.
Frequency stability of 0.1 percent per hour for analog generators or 500ppm for a
digital generator.
Maximum sine wave distortion of about 1% (accuracy of diode shaping network)
for analog generators. Arbitrary waveform generators may have distortion less than
-55dB below 50 kHz and less than -40dB above 50 kHz.
Some function generators can be phase locked to an external signal source, which
may be a frequency reference or another function generator.
AM or FM modulation may be supported.
Output amplitude up to 10V peak-to-peak.
Amplitude can be modified, usually by a calibrated attenuator with decade steps
and continuous adjustment within each decade.
Some generators provide a DC offset voltage, e.g. adjustable between -5V to +5V.
An output impedance of 50 ohms.
46
AUTOMATION
WHAT IS AUTOMATION??
Automation refers to a process of optimization of energy consumption
(Heat, Light, Fuels, water etc.), and optimization of operation and
maintenance cost through a closed loop direct digital and analog
control.
Supervision and regulation of the various service equipments, using
computer network with field interface units (I/O Modules) and signal
conditioners (Sensors and signal converters).
It facilitates in remote operation of equipments.
It replaces hardware wired annunciaters, mimic panels, and local
control desks.
IMPORTANCE OF AUTOMATION
The manufacturing process which considered to be highly dynamic as
variances occur at each stage of input. An expert operator is, however,
required to run the plant in a stable condition at all times. Moreover,
each operator response to given situation may be different.
Hence, a software solution consisting of fuzzy logic, regression
analysis, neural networks are required to capture the expert knowledge
to take action well in advance to achieve optimization on a continuous
basis.
Components in Automation
Components in Automating a System.
PLC
NETWORK
SCADA
DCS
CONTROLLERS
47
Introduction to PLC
A PLC is a device that was invented to replace the necessary sequential relay
circuits for machine control. A PLC can be considered as a versatile version of
such a controller. It is a device, which can accept multiple inputs, of different
kinds, of different voltage levels, from various different devices and different parts
of a process or a machine. Based upon the state of these inputs the PLC acts
further. It controls various devices by turning on/off the outputs that these devices
are connected. The logic on which the inputs are related to the outputs or the Logic
by which the devices connected to PLC are controlled can be programmed, thus
the name Programmable Logic Controller.
The programming of a PLC is generally done through
programming software or a dedicated programming terminal. Because of this
flexibility of programming that a PLC offers a PLC finds many different, almost
endless applications in the industry. A PLC can be programmed and reprogrammed
to suit to just about any application that one can think of.
PLC's have a wide area of applicability, in Machining,
Material Handling, Automation etc.
PLC ARCHITECTURE
Memory Section
Stores user logic, state RAM, system overhead in battery
backed CMOS RAM & system’s executive firmware in nonvolatile ROM.
CPU Section
Solves the user logic program based on the current input values in
state RAM, then updates the output values in state RAM.
I/O processing Section
Directs the flow of signals from input modules to state RAM
and provides a path over which output signals from CPU’s logic solve are sent to
output module.
48
Communication Section
Allows PLC to communicate with programming
panels, host computers, hand-held diagnostic tools, and other peripheral (master)
devices as well as with other PLCs and nodes on a communication network.
Block Diagram of PLC
Basic Block Diagram of PLC
49
Basic PLC operation
PLCs consist of input modules or points, a Central Processing Unit (CPU), and
output modules or points. An input accepts a variety of digital or analog signals
from various field devices (sensors) and converts them into a logic signal that can
be used by the CPU. The CPU makes decisions and executes control instructions
based on program instructions in memory. Output modules convert control
instructions from the CPU into a digital or analog signal that can be used to
control various field devices (actuators). A programming device is used to input
the desired instructions. These instructions determine what the PLC will do for a
specific input. An operator interface device allows process information to be
displayed and new control parameters to be entered.
50
Introducing the S7-200 Micro PLC
The S7-200 series is a line of micro-programmable logic controllers (Micro PLCs)
that can control a variety of automation applications. Figure 1-1 shows an S7-200
Micro PLC. The compact design, expandability, low cost, and powerful instruction
set of the S7-200 Micro PLC make a perfect solution for controlling small
applications. In addition, the wide variety of CPU sizes and voltages provides you
with the flexibility you need to solve your automation problems. Figure 1-1 S7200 Micro PLC.
51
ADVANTAGES
Smaller physical size than hard-wire solutions.
Easier and faster to make changes.
PLCs have integrated diagnostics and override functions.
Diagnostics are centrally available.
Applications can be immediately documented.
Applications can be duplicated faster and less expensively.
Ladder Logic
Elements
Symbols
Meaning
-| |-
Normally open contact
-| \ |-
Normally closed contact
-|P|-
Positive Transition contact
-|N|-
Negative Transition contact
-( )-
Normal Coil
-(L)-
Latched Coil
EXAMPLE OF LADDER LOGIC
52
Circuit Diagram
SW1
SW2
COIL
BATTERY
Coil will activate when both switches are ON
Ladder Diagram
53
WHAT IS A NETWORK ?
A Network is a working arrangement between independent systems created to
share resources themselves so as to generate a overall system which is more
powerful than the combined power of all the systems put together.
HMI
A human–machine interface or HMI is the apparatus or device which presents
process data to a human operator, and through this, the human operator monitors
and controls the process.
Human–machine interface:-
54
SCADA
SCADA - Supervisory Control And Data Acquisition System
It is a Human Machine Interface which links between Operator and Machine
through PLC.
It provides the User with mimic resembles real Plan for the easy control of
operation.
Plant control by driving out values to the control Equipment.
Overview of the current values of all real time data.
Alarm display and acknowledgement
Maintenance logging of plant equipment
Historical data analysis for reviewing stored historical Data.
Distributed Control System
Earlier days PLC were primarily used for control of Discrete signal (
ON/OFF).
Analog signals were Processed Separately by individual analog controllers.
With the Advancement in the field of PLC’s processing analog signals but
do not have an embedded HMI.
To Integrate the HMI & I/O systems in one single Package, DCS evolved.
55
Disadvantages of PLC :
PLC were Designed for Relay Logic Ladder and have Difficulty with some
Smart Devices.
To maximize PLC performance and Flexibility, a number of Optional
Modules must be added
56
Profibus
PROFIBUS, developed by Siemens, is a powerful communications system for lowcost applications. It provides all the known advantages of a bus system and meets
all the requirements for flexible, cost-effective networking of programmable logic
controllers and computers in an industrial environment.
PROFIBUS is based on the ISO/OSI reference model, but does not implement all
seven layers. For reasons of performance and to reduce costs, only layers 1
(Physical Layer / RS485) and 2 (Data Link Layer / FDL) for the physical bus
characteristics and access techniques and layer 7 (Application Layer) as the user
interface are implemented. The attachment of layer 7 to layer 2 is controlled by the
lower layer interface (LLI). This provides all the required layer 3 to 6 functions.
Profibus interface
57
Solid-state relay:A solid-state relay (SSR) is an electronic switching device in which a small control
signal controls a larger load current or voltage. It consists of a sensor which
responds to an appropriate input (control signal), a solid-state electronic
switching device which switches power to the load circuitry, and some coupling
mechanism to enable the control signal to activate this switch without mechanical
parts. The relay may be designed to switch either AC or DC to the load. It serves
the same function as an electromechanical relay, but has no moving parts.
Solid state relays
D
L
58
,Advantages over mechanical relays:Most of the relative advantages of solid state and electromechanical relays are
common to all solid-state as against electromechanical devices.
SSRs are faster than electromechanical relays; their switching time is
dependent on the time needed to power the LED on and off, of the order of
microseconds to milliseconds.
Lower (if any) minimum output current (latching current) required
Increased lifetime, particularly if activated many times, as there are no
moving parts to wear .
Output resistance remains constant regardless of amount of use
Clean, bounceless operation
Decreased electrical noise when switching
No sparking, allowing use in explosive environments where it is critical that
no spark is generated during switching
Totally silent operation
Inherently smaller than a mechanical relay of similar specification (if
desired may have the same "casing" form factor for interchangeability).
Much less sensitive to storage and operating environment factors such as
mechanical shock, vibration, humidity, and external magnetic fields
Disadvantages:Voltage/current characteristic of semiconductor rather than
mechanical contacts:
 When closed, higher resistance (generating heat), and
increased electrical noise
 When open, lower resistance, and reverse leakage current
(typically µA range)
 Voltage/current characteristic is not linear (not purely
resistive), distorting switched waveforms to some extent. An
electromechanical relay has the low ohmic (linear) resistance
of the associated mechanical switch when activated, and the
exceedingly high resistance of the air gap and insulating
materials when open.
59
 DC load must observe polarity (− and + not interchangeable) to
avoid an undesirable "always conducting" state that does not
depend on switching input. Electromechanical relays do not
depend on polarity.
Possibility of spurious switching due to voltage transients (due to
much faster switching than mechanical relay)
Isolated bias supply required for gate charge circuit
Higher transient reverse recovery time (Trr) due to the presence of
Body diode
More likely to fail in the "closed" state compared to
electromechanical relays which are more likely to fail in the "open"
state.
60
TELECOMMUNICATION
EPABX
61
Telecommunication is the transmission of information over significant distances
to communicate.
In earlier times, telecommunications involved the use of visual signals, such
as beacons, smoke signals, semaphore telegraphs, signal flags, and optical
heliographs, or audio messages such as coded drumbeats, lung-blown horns, and
loud whistles.
In modern times, telecommunications involves the use of electrical devices such
as the telegraph, telephone, and teleprinter, as well as the use of radio
and microwave communications, as well as fiber optics and their associated
electronics, plus the use of the orbiting satellites and the Internet.
The world's effective capacity to exchange information through two-way
telecommunication networks grew from 281 petabytes of (optimally compressed)
information in 1986, to 471 petabytes in 1993, to 2.2 (optimally
compressed) exabytes in 2000, and to 65 (optimally compressed) exabytes in
2007.[1]This is the informational equivalent of 2 newspaper pages per person per
day in 1986, and 6 entire newspapers per person per day by 2007.[2] Given this
growth, telecommunications play an increasingly important role in the world
economy and the worldwide telecommunication industry's revenue was
estimated to be $3.85 trillion in 2008.[3] The service revenue of the global
telecommunications industry was estimated to be $1.7 trillion in 2008, and is
expected to touch $2.7 trillion by 2013.[
EPABX
EPABX (electronic private automatic branch exchange): These are solid state
digital systems. Our EPABX mainly have the following features:
Establishing connections (circuits) between the telephone sets of two
users (e.g. mapping a dialed number to a physical phone, ensuring
the phone isn't already busy)
62
Maintaining such connections as long as the users require them (i.e.
channeling voice signals between the users)
Disconnecting those connections as per the user's requirement
Providing information for accounting purposes (e.g. metering calls)
Time and attendance or Workforce Management clocks: we have
many varieties of clocks that suit every customer like electronic tags,
barcode badges, magnetic stripe cards, (hand, fingerprint, or facial),
and touch screens. We also have electrical time recorders, digital
keyboard time recorders and industrial time recorders.
Online/Offline UPS: We have different UPS units either to protect a
single computer or to large units powering entire data centers,
buildings etc. Offline UPS offers surge protection and battery backup.
Typical protection time is 20 minutes and the switchover time is just
25 milliseconds. The Online UPS units provide 5–30 minutes of
protection time and the capacity expansion is for several hours. We
have units ranging from 500 watts or less to 10 kW.
Mobiles
Air conditioners
Computers
Laptops
Printers
CCTVs
Telephones, Cordless etc
63
Wireless CCTV
The use of CCTV to protect our environment and assets has seen a massive
increase in demand. Wireless Networks are at the forefront of delivering high
quality communications infrastructure suitable for these bandwidth hungry
application.
CCTV is undergoing a rebirth from the old analogue and video cassette recorder
systems of the past, with many users upgrading or installing digital CCTV systems.
The advantages to digital systems are endless, with images being encoded for
transportation across IP networks, and storage on modern computer systems. IP
networks similar to other digital services such as the Internet and email allow the
user to view and retrieve images from any network connected computer. The
ability to quickly retrieve archived of these systems.
Wireless LAN MAN has a vast experience of installing, managing and maintaining
wireless CCTV systems for UK Local Authorities. The systems installed have been
proven to be reliable, and far more cost effective that traditional analogue
alternatives. Typical installation time for full CCTV network is a matter of weeks
as opposed to the months of planning, and heavy civil works required to install
cabled systems.
Wireless LAN MAN seeks to allay security risks or concerns raised through the
use of wireless transportation techniques by only deploying CESG approved radio
apparatus for CCTV Networks.
Wireless LAN MAN has sought to demonstrate itself as a serious IPCCTV
networks installer & consultant, and is now a Platinum Partner for open sourced
IPCCTV networks giant Milestone Systems.
Freedom and Mobility
As everyone knows CCTV cameras tend to act as a deterrent for crime, pushing
offenders away from areas where they know CCTV coverage exists. Wireless LAN
MAN has designed a range of mobile cameras and supporting radio networks that
allow CCTV cameras to be easily moved, relocated and connected within hours. This
new mobile policy has allowed Local Authorities to deploy the CCTV deterrent to far
wider areas than could normally be considered, and has kept offenders on the move.
64
Insulated gate bipolar transistor(IGBT):-
Cross section of a typical IGBT cell.
65
Equivalent circuit for IGBT
The insulated gate bipolar transistor or IGBT is a three-terminal power
semiconductor device primarily used as an electronic switch and in newer devices
is noted for combining high efficiency and fast switching. It switches electric
power in many modern appliances: electric cars, trains, variable speed
refrigerators, air-conditioners and even stereo systems with switching amplifiers.
Since it is designed to turn on and off rapidly, amplifiers that use it often synthesize
complex waveforms with pulse width modulation and low-pass filters.
In switching applications modern devices boast pulse repetition rates well into the
ultrasonic range— frequencies which are at least ten times the highest audio
frequency handled by the device when used as an analog audio amplifier.
The IGBT combines the simple gate-drive characteristics of the MOSFETs with the
high-current and low–saturation-voltage capability of bipolar transistors by
combining an isolated gate FET for the control input, and a bipolar
power transistor as a switch, in a single device.
The IGBT is used in medium- to high-power applications such asswitched-mode
power supplies, traction motor control and induction heating. Large IGBT modules
typically consist of many devices in parallel and can have very high current
handling capabilities in the order of hundreds of amperes with blocking voltages
of 6000 V, equating to hundreds of kilowatts.
66