of all other eligibility criteria
pop
infolinks
of all other eligibility criteria
RECRUITMENT OF SPECIALIST CADRE OFFICERS IN STATE BANK GROUP
of all other eligibility criteria
Chennai petroleum corp. job 2015
How Transformer work??
Transformers are capable of receiving AC power at one voltage and delivering it at another voltage. In this article, we will go through the working and construction of a 3 phase transformer by starting from its simplest form. We will also understand what is power transformer and how it is constructed.
Why Transformers are used ?
Transformers are ubiquitous devices. They are used to either step-up the A.C voltage or to step-down it. But, why should we do this voltage transformation ?. It is a science fact that a stepped-up voltage is associated with a reduced current. A reduced current leads to low eddy current energy loss. In this way, transformers help achieve better transmission efficiency while transferring the power over longer distances.Transformers help in step-up or step-down the voltage; this in turn increases the transmission efficiency After the electrical power has transmitted to the desired spot, the voltage can be reduced to the desired level, using a step-down transformer.
The Basic Working Principle
The basic working principle of a transformer is simple, electromagnetic induction. According to this principle, a varying magnetic flux associated with a loop will induce an electromotive force across it. Such a fluctuating magnetic field can easily be produced by a coil and an alternating E.M.F (EP) system. A current carrying conductor produces a magnetic field around it. The magnetic field produced by a coil. With the fluctuating nature of the alternating current, the magnetic field associated with the coil will also fluctuate.This magnetic flux can be effectively linked to a secondary winding with the help of a core. This fluctuating magnetic field will induce an E.M.F in the secondary coils due to electromagnetic induction. The induced E.M.F is denoted by ES.AC current in a coil produces a fluctuating magnetic field; this magnetic field can effectively linked to a secondary coil with the help of a coreSince the turns are arranged in a series, the net E.M.F induced across the winding will be sum of the individual E.M.Fs (eS) induced in each turn. Nsrepresents, number of turns at the secondary winding.Since the same magnetic flux is passing through the primary and secondary coils, the EMF per turn for both the primary and secondary coils will be the same.The E.M.F per turn for the primary coil is related to the applied input voltage as shown.By rearraging the above equations, it can be established that, the induced E.M.F at the secondary coil is expressed as follows.This simply means that with fewer turns in the secondary than in primary, one can lower the voltage. Such transformers are known as step-down transformers. For the reverse case, one can increase the voltage (step-up transformer).But since energy is conserved, the primary and secondary currents have to obey the following relationship.
3 Phase Transformer
Three phase transformers use 3 such single-phase transformers.
Power Transformer - Construction Features
The transformers which are used in high voltage applications are referred as 'Power Transformers'. They handle voltage in the range of 33 to 400 kV. The winding of a power transformer is quite different from that of a low voltage transformer (Distribution Transformer). We will explore the construction and connection details of the power transformer .
Winding Connection
The low-voltage windings of a power transformer are connected in a delta configuration and the high-voltage windings are connected in a star configuration.The low voltage winding is connected in a Delta configurationThe delta connection in low voltage windings result in 3 terminals to connect the electrical power. This is marked as 'R','Y' and 'B' . The high voltage windings are connected in a Star configurationOn the contrary, the star connection in high voltage transformer results in 4 terminals to connect the electric power.This is marked as 'r','y','b' and 'n' .. Thus, if you tap the electrical power between any pair of the phase wires the voltage further rises to root 3 times. This voltage is known as 'line voltage'. This also means that, from a 3 phase step-up transformer we can draw 4 output wires; 3 phase power wires and one neutral. If you draw power between a neutral and phase wire, that is know as 'phase voltage'.High voltage insulated bushings are required to bring out the electrical energy. It is clear that, the bushings at the high voltage side are quite bigger compared to the low voltage bushings. Insulated bushings are required for smooth transfer of electrical power
The Core Construction
The core of the transformer is made of thin, insulted, steel laminations. Such steel laminations are stacked together to form 3 phase limbs. The purpose of thin laminations is to reduce energy loss due to eddy current formation. The separated out layer blocks in the first part is a stacked layer of much thinner steel laminations. The thickness of each steel laminations varies from 0.25 - 0.5 mm. The core is made of thin insulated steel laminations; Such laminations are stacked together to form 3 phase limbs. The low voltage windings usually sit near the core. If HV windings were placed near to the cored, due to the winding's high voltage, a huge amount of insulation material would be required between the winding and core. Thus by placing the LV winding near to the core, we can save a good amount of insulation material.The output voltage of a transformer will undergo minor fluctuations due to the reasons like load variation and change in power input supply. A tapping mechanism in the secondary coil helps in regulating the output voltage to the specified limit. The tapping mechanism simply changes the number of active coils in the transformer action, thus controls the output voltage. Since more number of turns are there in the HV windings, voltage fine tuning can be more accurately controlled by providing the tapping on the HV side. This is another reason why HV windings are not placed near to the core. If they were placed near to the core, movement of tapping mechanism would have been more difficult, causing the tapping design more complex.
We are here too
An online forum for Final Year Project
Networking Questions
System ?
2. Give examples of NOS (Network
Operating System) and SOS (Server
Operating System)
3. Difference between FAT and NTFS
4. Enhancements in Windows 2003 from
Windows 2000
5. Enhancements in Windows 2003 from
Windows NT
6. What is Active Directory ?
7. Types of Firewall
8. Difference between Hardware and
Software Firewall
9. Name the seven layers of OSI model
10. How to enable Firewall in Windows XP?
11. How to Disable Firewall in Windows XP?
12. Minimum System requirement of
Windows XP, Vista, 2003 and 2008
13. Explain ping command
14. Explain Cookies
15. How to boot the computer in Safe mode
16. Types of printer
17. Explain Last Known Good Configuration
18. What is Disk clean up, Disk
Defragmentation, Device manager and
System Restore
19. USB port Vs Firewire port
20. How to install a printer in Windows XP?
21. What is a Browser and name any 5
browsers ?
22. Serial port Vs Parallel port
23. What is a port number ?
24. Where is the HOSTS file located
25. Explain different RAID levels
26. Explain APIPA, IP address and Subnet
mask
27. Difference between IP v4 and IP v6
28. How to remove virus from a computer
29. How to make a computer run faster?
30. What is attrib command ?
31. What is edit command ?
32. How to copy a file or folder using copy
command?
33. How to format the hard disk using
command line utilities?
34. Explain mkdir, rmdir and chdir
commands
35. Types of hard disk
36. Difference between primary and
secondary partition
37. Types of backups in Window OS
38. Differential Backup Vs Incremental
Backup Vs Copy backup
39. What is remote desktop.
40. Recovery Console Vs Automated System
Recovery
41. What is NTLDR file?
42. How to tackle "missing NTLDR file"
error?
43. How many bytes are there in MAC
address
44. Range of Class A IP address
45. Range of Class B IP address
46. Range of Class C IP address
47. Default subnet mask of Class A, Class B
and Class C IP address
48. What is BSOD (Blue Screen of Death)
and how to overcome it
49. Difference between Preferred DNS and
Alternate DNS server
50. Transmission speed of T1 carrier
TOP 50 INTERVIEW QUESTIONS
1. What are your strengths?
2. What are your weaknesses?
3. Why are you interested in working for
[ insert company name here]?
4. Where do you see yourself in 5 years?
10 years?
5. Why do you want to leave your current
company?
6. Why was there a gap in your
employment between [insert date] and
[insert date] ?
7. What can you offer us that someone else
can not?
8. What are three things your former
manager would like you to improve on?
9. Are you willing to relocate?
10. Are you willing to travel?
11. Tell me about an accomplishment you
are most proud of.
12. Tell me about a time you made a
mistake.
13. What is your dream job?
14. How did you hear about this position?
15. What would you look to accomplish in
the first 30 days/60 days/90 days on
the job?
16. Discuss your resume.
17. Discuss your educational background.
18. Describe yourself.
19. Tell me how you handled a difficult
situation.
20. Why should we hire you?
21. Why are you looking for a new job?
22. Would you work holidays/weekends?
23. How would you deal with an angry or
irate customer?
24. What are your salary requirements?
25. Give a time when you went above and
beyond the requirements for a project.
26. Who are our competitors?
27. What was your biggest failure?
28. What motivates you?
29. What’s your availability?
30. Who’s your mentor?
31. Tell me about a time when you
disagreed with your boss.
32. How do you handle pressure?
33. What is the name of our CEO?
34. What are your career goals?
35. What gets you up in the morning?
36. What would your direct reports say
about you?
37. What were your bosses’ strengths/
weaknesses?
38. If I called your boss right now and
asked him what is an area that you
could improve on, what would he say?
39. Are you a leader or a follower?
40. What was the last book you’ve read for
fun?
41. What are your co-worker pet peeves?
42. What are your hobbies?
43. What is your favorite website?
44. What makes you uncomfortable?
45. What are some of your leadership
experiences?
46. How would you fire someone?
47. What do you like the most and least
about working in this industry?
48. Would you work 40+ hours a week?
49. What questions haven’t I asked you?
50. What questions do you have for me?
Try to answer
Top 10 Interview Puzzles
Puzzles, riddles, logical questions, and lateral
thinking questions are important part of any
selection process for a job interview.
You can check how good you are by
answering these top 10 interview puzzles.
1. Ant and Triangle Problem
Three ants are sitting at the three corners of
an equilateral triangle. Each ant starts
randomly picks a direction and starts to move
along the edge of the triangle. What is the
probability that none of the ants collide?
2. Crossing the Bridge Problem
Four people need to cross a rickety bridge at
night. Unfortunately, they have only one torch
and the bridge is too dangerous to cross
without one. The bridge is only strong enough
to support two people at a time. Not all
people take the same time to cross the bridge.
Times for each person: 1 min, 2 mins, 7 mins
and 10 mins. What is the shortest time needed
for all four of them to cross the bridge?
3. Burning Rope Problem
A man has two ropes of varying thickness
(Those two ropes are not identical, they aren’t
the same density nor the same length nor the
same width). Each rope burns in 60 minutes.
He actually wants to measure 45 mins. How
can he measure 45 mins using only these two
ropes.
He can’t cut the one rope in half because the
ropes are non-homogeneous and he can’t be
sure how long it will burn.
4. Heaven’s Gate Probelm
You are standing before two doors. One of the
path leads to heaven and the other one leads
to hell. There are two guardians, one by each
door. You know one of them always tells the
truth and the other always lies, but you don’t
know who is the honest one and who is the
liar. You can only ask one question to one of
them in order to find the way to heaven. What
is the question?
5. 10 Coins Problem
You are blindfolded and 10 coins are place in
front of you on table. You are allowed to
touch the coins, but can’t tell which way up
they are by feel. You are told that there are 5
coins head up, and 5 coins tails up but not
which ones are which. How do you make two
piles of coins each with the same number of
heads up? You can flip the coins any number
of times.
6. King and Wind Bottles Problem
A bad king has a cellar of 1000 bottles of
delightful and very expensive wine. A
neighboring queen plots to kill the bad king
and sends a servant to poison the wine.
Fortunately (or say unfortunately) the bad
king’s guards catch the servant after he has
only poisoned one bottle. Alas, the guards
don’t know which bottle but know that the
poison is so strong that even if diluted
100,000 times it would still kill the king.
Furthermore, it takes one month to have an
effect. The bad king decides he will get some
of the prisoners in his vast dungeons to drink
the wine. Being a clever bad king he knows he
needs to murder no more than 10 prisoners –
believing he can fob off such a low death rate
– and will still be able to drink the rest of the
wine (999 bottles) at his anniversary party in
5 weeks time. Explain what is in mind of the
king, how will he be able to do so ?
7. Mislabeled Jar Puzzle
You have 3 jars that are all mislabeled. One
jar contains Apple, another contains Oranges
and the third jar contains a mixture of both
Apple and Oranges.
You are allowed to pick as many fruits as you
want from each jar to fix the labels on the
jars. What is the minimum number of fruits
that you have to pick and from which jars to
correctly label them?
8. Red and Blue marbles Puzzle
You have two jars, 50 red marbles and 50 blue
marbles. You need to place all the marbles
into the jars such that when you blindly pick
one marble out of one jar, you maximize the
chances that it will be red. When picking,
you’ll first randomly pick a jar, and then
randomly pick a marble out of that jar. You
can arrange the marbles however you like, but
each marble must be in a jar.
9. Gold Bar Problem
You’ve got someone working for you for seven
days and a gold bar to pay him. The gold bar
is segmented into seven connected pieces.
You must give them a piece of gold at the end
of every day. What and where are the fewest
number of cuts to the bar of gold that will
allow you to pay him 1/7th each day?
10. 100 Doors Puzzle
You have 100 doors in a row that are all
initially closed. you make 100 passes by the
doors starting with the first door every time.
the first time through you visit every door and
toggle the door (if the door is closed, you
open it, if its open, you close it). the second
time you only visit every 2nd door (door #2, #
4, #6). the third time, every 3rd door (door #
3, #6, #9), ec, until you only visit the 100th
door. What state are the doors in after the
last pass? Which are open which are closed?