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Computer Clothing

There is a major movement going on in the electronics and computer industries to develop wearable devices for what’s being called Post-PC era. We are now at the dawn of that era and some of these devices are already making their way to the consumer market .Computerized clothes will be the next step in making computers and devices portable without having to strap electronics into our body. These digital clothes will able to perform some of the PC functions. These devices are small in size and portable. This apparel can be used to read our heart rate and breathing. The LED monitors could even be integrated into this apparel to display text and images.

CT scanning

CT scanning – computed tomography is a mechanism of getting the internal details of a section. It is a diagonostic imaging procedure in which anatomical information is digitally reconstructed from X-ray transmission data obtained by scanning an area from many directions in the same plane to visualize information in that plane. CT is a fast patient friendly and has the unique ability to image a combination of soft tissue, bone, lungs and blood vessels.

Data Compression Techniques

Data compression is the technique of converting an input data stream or the original data into another data stream which is shorter in length. There are many known methods for data compression. They are based on different ideas and are suitable for different types of data. But they all have the same principle that they compress data by removing the redundancy in the original data. Otherwise data compression can be looked up on as a change in representation from inefficient to efficient form.

Electromagnetic bombs

 Electromagnetic bombs are Weapons of Electrical Mass Destruction with applications across a broad spectrum of targets, spanning both the strategic and tactical. As such their use offers a very high payoff in attacking the fundamental information processing and communication facilities of a target system. The massed application of these weapons will produce substantial paralysis in any target system, thus providing a decisive advantage in the conduct of Electronic Combat, Offensive Counter Air and Strategic Air Attack. Generators would be useless, cars wouldn’t run, and there would be no chance of making a phone call. In a matter of seconds, a big enough e-bomb could thrust an entire city back 200 years or cripple a military unit. The basic principle used in an e-bomb is electromagnetic pulse effectEMP effect can result in irreversible damage to a wide range of electrical and electronic equipment, particularly computers and radio or radar etc. having military importance. Commercial computer equipment is particularly vulnerable to EMP effects.The technology base which may be applied to the design of electromagnetic bombs is both diverse, and in many areas quite mature. Key technologies which are extant in the area are explosively pumped Flux Compression Generators (FCG), explosive or propellant driven Magneto-Hydrodynamic (MHD) generators and a range of HPM devices, the foremost of which is the Virtual Cathode Oscillator or Vircator.

Electrical and chemical diagnostics of transformer insulation

This paper describes the application of two relatively new diagnostic techniques for the determination of insulation condition in aged transformers. The techniques are (a) measurements of interfacial polarization spectra by a DC method and (b) measurements of molecular weight and its distribution by gel permeation chromatography. Several other electrical properties of the cellulose polymer were also investigated. Samples were obtained from a retired power transformer and they were analysed by the developed techniques. Six distribution transformers were also tested with the interfacial polarization spectra measurement technique, and the molecular weight of paper/pressboard samples from these transformers were also measured by the gel permeation chromatography. The variation of the results through different locations in a power transformer is discussed in this paper. The possible correlation between different measured properties was investigated and discussed in this paper.

AUDIO SPOTLIGHTING

ABSTRACT

Audio spot lighting is a very recent technology that creates focused beams of sound similar to light beams coming out of a flashlight. By ‘shining’ sound to one location, specific listeners can be targeted with sound without others nearby hearing it. It uses a combination of non-linear acoustics and some fancy mathematics. But it is real and is fine to knock the socks of any conventional loud speaker. This acoustic device comprises a speaker that fires inaudible ultrasound pulses with very small wavelength which act in a manner very similar to that of a narrow column. The ultra sound beam acts as an airborne speaker and as the beam moves through the air gradual distortion takes place in a predictable way due to the property of non-linearity of air. This gives rise to audible components that can be accurately predicted and precisely controlled. Joseph Pompei’s Holosonic Research Labs invented the Audio Spotlight that is made of a sound processor, an amplifier and the transducer. The American Technology Corporation developed the Hyper Sonic Sound-based Directed Audio Sound System. Both use ultrasound based solutions to beam sound into a focused beam. Audio spotlight can be either directed at a particular listener or to a point where it is reflected.
The targeted or directed audio technology is going to a huge commercial market in entertainment and consumer electronics and technology developers are scrambling to tap in to the market. Being the most recent and dramatic change in the way we perceive sound since the invention of coil loud speaker, audio spot light technology can do many miracles in various fields like Private messaging system, Home theatre audio system, Navy and military applications, museum displays, ventriloquist systems etc. Thus audio spotlighting helps us to control where sound comes from and where it goes!

ASSYMETRIC DIGITAL SUBSCRIBER LINE (ADSL)

ABSTRACT
Digital Subscriber Lines (DSL) are used to deliver high-rate digital data over existing ordinary phone-lines. A new modulation technology called Discrete Multitone (DMT) allows the transmission of high speed data. DSL facilitates the simultaneous use of normal telephone services, ISDN, and high speed data transmission, e.g., video. DMT-based DSL can be seen as the transition from existing copper-lines to the future fiber-cables. This makes DSL economically interesting for the local telephone companies. They can offer customers high speed data services even before switching to fiber-optics.
DSL is a newly standardized transmission technology facilitating simultaneous use of normal telephone services, data transmission of 6 M bit/s in the downstream and Basic- rate Access (BRA). DSL can be seen as a FDM system in which the available bandwidth of a single copper-loop is divided into three parts. The base band occupied by POTS is split from the data channels by using a method which guarantees POTS services in the case of ADSL-system failure (e.g. passive filters).

EUVL

ABSTRACT

This paper discusses the basic concepts and current state of development of EUV lithography (EUVL), a relatively new form of lithography that uses extreme ultraviolet (EUV) radiation with a wavelength in the range of 10 to 14 nanometers (nm) to carry out projection imaging. Currently, and for the last several decades, optical projection lithography has been the lithographic technique used in the high-volume manufacture of integrated circuits. It is widely anticipated that improvements in this technology will allow it to remain the semiconductor industry’s workhorse through the 100 nm generation of devices. However, some time around the year 2005, so-called Next-Generation Lithographies will be required. EUVL is one such technology vying to become the successor to optical lithography. This paper provides an overview of the capabilities of EUVL, and explains how EUVL might be implemented. The challenges that must be overcome in order for EUVL to qualify for high-volume manufacture are also discussed.

Energy transmission system for an artificial heart- leakage inductance compensation

A power supply system using a transcutaneous transformer to power an artificial heart through intact skin has been designed. In order to realize both high-voltage gain and minimum circulating current, compensation of leakage inductances on both sides of a transcutaneous transformer is proposed. A frequency region which realizes the robustness against coupling coefficient and load variation is identified. In this region, the converter has inherent advantages such as zerovoltage switching (ZVS) or zero-current switching (ZCS) of the switches, high-voltage gain, minimum circulating current, and high efficiency. Artificial heart, energy transmission system, high efficiency, high-frequency converter, high-power density, high-voltage gain, inductance compensation, soft-switched converter, transcutaneous transformer, zero-current switching (ZCS), zero-voltage switching

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BiCMOS Technology

The need for high-performance, low-power, and low-cost systems for network transport and wireless communications is driving silicon technology toward higher speed, higher integration, and more functionality. Further more, this integration of RF and analog mixed-signal circuits into high-performance digital signal-processing (DSP) systems must be done with minimum cost overhead to be commercially viable. While some analog and RF designs have been attempted in mainstream digital-only complimentary metal-oxide semiconductor (CMOS) technologies, almost all designs that require stringent RF performance use bipolar or semiconductor technology. Silicon integrated circuit (IC) products that, at present, require modern bipolar or BiCMOS silicon technology in wired application space include the essential optical network (SONET) and synchronous digital hierarchy (SDH) operating at 10 Gb/s and higher. The viability of a mixed digital/analog. RF chip depends on the cost of making the silicon with the required elements; in practice, it must approximate the cost of the CMOS wafer, Cycle times for processing the wafer should not significantly exceed cycle times for a digital CMOS wafer. Yields of the SOC chip must be similar to those of a multi-chip implementation. Much of this article will examine process techniques that achieve the objectives of low cost, rapid cycle time, and solid yield

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Grid Network

ABSTRACT

Grid is as an emerging technology for enabling resource sharing and coordinated problem solving in dynamic multi-institutional virtual organizations. In the grid environment, resources may belong to different institutions, have different usage policies and pose different requirements on acceptable requests.
one of the fundamental operations needed to support location independent computing is resource discovery .It is the process of locating relevant resources based on application requirements of a user.
The description of a resource is essential for automated resource discovery and search, selection, matching, composition and interoperation, invocation and execution monitoring; different middle-ware specifies different rules for describing a resource. Hence, the information gathered from these diverse sources tends to be semantically heterogeneous and needs to be correlated.
Efficient resource discovery needs uniform unambiguous resource description. To date there is no universal resource description language common to all state of art grid middleware. Different grid middleware systems have different methods of resource description and it is not yet known how well these can interoperate. Hence, there is a need to utilize semantic matching of these resource descriptions.

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IEEE 802.11n –Next Generation Wireless Standard

ABSTRACT

The newest standard in Wireless LAN is called 802.11n. 802.11 is an industry standard for high-speed networking. 802.11n is designed to replace the 802.11a, 802.11b and 802.11g standards. 802.11n equipment is backward compatible with older 802.11gab and it supports much faster wireless connections over longer distances. So-called “Wireless N” or “Draft N” routers available today are based on a preliminary version of the 802.11n. The beta version of this standard is used now in laptops and routers. 802.11n will work by utilizing multiple input multiple output (MIMO) antennas and channel bounding in tandem to transmit and receive data. It contains at least 2 antennas for transmitting data’s. 802.11n will support bandwidth greater than 100 Mbps and in theory it can have a speed of 600 Mbps.It can be used in high speed internets, VOIP, Network Attach Storage (NAS), gaming. The full version will be implemented in the laptops and in the LANs in upcoming years

Adaptive Piezoelectric energy harvesting circuit

This paper describes an approach to harvesting electrical energy from a mechanically excited piezoelectric element. A vibrating piezoelectric device differs from a typical electrical power source in that it has a capacitive rather than inductive source impedance, and may be driven by mechanical vibrations of varying amplitude. An analytical expression for the optimal power flow from a rectified piezoelectric device is derived, and an “energy harvesting “ circuit is proposed which can achieve this optimal power flow. The harvesting circuit consists of an ac-dc rectifier with an output capacitor, an electrochemical battery, and a switch-mode dc-dc converter that controls the energy flow into the battery. An adaptive control technique for the dc-dc converter is used to continuously implement the optimal power transfer theory and maximize the power stored by the battery. Experimental result reveal that the use of the adaptive dc-dc converter increases power transfer by over 400% as compared to when the dc-dc converter is not used.

ANN Based Power System Restoration

Power System Restoration (PSR) has been a subject of study for many years. In recent years many techniques were proposed to solve the limitations of predetermined restoration guidelines and procedures used by a majority of system operators to restore a system following the occurrence of a wide area disturbance. This paper discusses limitations encountered in some currently used PSR techniques and a proposed improvement based on Artificial Neural Networks (ANNs). This proposed scheme has been tested on a 162-bus transmission system and compared with a breadth search transmission system. The results indicate that, this is a feasible option that should be considered for real time applications.
Artificial Neural Networks (ANNs) are computational techniques that try to obtain a performance similar to that of human’s performance when solving problems. The building block of ANN is Artificial Neuron, which has got structural & functional similarities with biological neurons. ANN is also an efficient alternative for problem solutions where it is possible to obtain data describing the problem behavior, but a mathematical description of the process is impossible. The proposed restoration scheme is composed of several Island Restoration Schemes (IRS). Each IRS is responsible for the development of an Island Restoration Plan when the power system is recovering from a wide area disturbance.

INTERVIEW QUESTIONS FOR EEE

DESIGN OF ELECTRICAL APPARATUS
For Electrical and Electronics
Important QA
1. What are the main dimensions of a rotating machine?
The main dimensions of a rotating machine are armature diameter and stator core
length.
2. Define specific magnetic loading.
It is defined as the average flux density over the air gap of a machine.
Specific magnetic loading=total flux around the air gap/area of flux path at the
air gap
3. Define specific electric loading.
It is defined as the number of armature conductors per meter of armature periphery at the
air gap.
Specific electric loading=total number ampere conductors/armature periphery at air gap.
4. What is output equation?
The equation describing the relation between the output and main dimensions, specific
loadings and speed of a machine is known as output equation.
5. Write the expressions for output coefficients
For dc machine, output coefficient.C0= 2Bav acx10-3, in KW/m3-rps
For ac machine, output coefficient.C0= 2Bav ac Kwsx10-3, in KVA/m3-rps
6. List the factors that influence the separation of D and L of a dc machine.
1. Pole proportions 2.moment of inertia 3. Peripheral speed 4. Voltage between adjacent
segments.
7. What is square pole criterion?
The square pole criterion states that for a given flux and cross section area of pole, the
length of mean turn of field winding is minimum, when the periphery forms a square.
This implies that the length must be approximately equal to pole arc.
8. In a dc machine what are the limiting values of armature peripheral speed and
voltage between adjacent commutator segments
Maximum armature peripheral speed=Vamax=30m/sec
Maximum voltage between commutator segments Ecm=30Volts
9.List the various L/ used for separation of D and L in induction motor.
For minimum cost, 1.5 to 2
For good power factor, 1.0 to 1.25
For good efficiency, 1.5
For overall length, 1.0
10. What are the factors that affect the size of rotating machines?
The factors affecting the size of the rotating machines are speed, specific electric and
magnetic loadings.
11. What are the factors that decide the choice of specific magnetic loading?
Maximum flux density in iron parts of machine
Magnetizing current
Core losses
12. .What is the factors that decide the choice of specific electric loading.
Permissible temperature rise
Voltage rating of machine
Size of machine
Current density.
13. What is magnetic circuit.
It is the path of magnetic flux. The mmf of the circuit creates flux in the path by
overcoming the reluctance of the path.
The equation which relates flux, mmf and reluctance are given by
Flux=mmf/reluctance
14. What are the constituents of magnetic circuit in rotating machines.
The magnetic circuit of rotating machine consists of airgap,stator and rotor cores, stator
and rotor teeth.
15. What is magnetization curve?
It is a graph showing the relation between the magnetic field intensity and the flux
density, B of a magnetic material ,it is used to estimate the mmf required for flux path in
the magnetic material and it is supplied by the manufacturers of stampings of
laminations.
16. What is leakage flux?
The leakage flux is the flux passing through unwanted path. The leakage flux will not
help either for transfer or conversion of energy.
17. What is leakage coefficient?
It is defined as the ratio of total flux to useful flux.
Leakage coefficient,Cl=total flux/useful flux
18. What is fringing flux.
The bulging of magnetic path at the air gap is called fringing. The fluxes in the bulged
portion are called fringing effect.
19. What are the differences between leakage flux and fringing flux?
The leakage flux is not useful for energy transfer. But the fringing flux is useful flux.
The leakage flux flows in unwanted path but fringing flux flows in magnetic path.
20. what are the factors that modify the reluctance of air gap
It is modified by slots, radial ventilating ducts and non uniform air gaps.
21. Define gap contraction factor for slots.
It is defined as the ratio of reluctance of air gap of slotted armature to reluctance of air
gap of smooth armature.
Kgs=reluctance of air gap with slotted armature/ reluctance of air gap with smooth
armature
22. Define gap contraction factor for ducts.
It is defined as the ratio of reluctance of air gap of with ducts to reluctance of air gap
without ducts.
Kgs=reluctance of air gap with ducts / reluctance of air gap without ducts.
23. Define total gap contraction factor.
It is defined as the ratio of reluctance of slotted armature with ducts and the reluctance of
smooth armature without ducts.
24. Define field form factor.
It is defined as the ratio of average gap density over the pole pitch to maximum flux
density in the air gap.
25. What are the problems encountered in estimating the mmf for teeth.
The flux density in different section of a tooth is non uniform.
The slot provides another parallel path for the flux, shunting the tooth.
26. List the methods used for estimating the mmf for teeth.
Graphical method
Three ordinate method
Bt1/3 method.
27. What is real and apparent flux density?
The real flux density is due to the actual flux through a tooth. The apparent flux density is
due to total flux that has to be pass through the tooth. Since some of the fluxes passes
through slot the real flux density is always less than the apparent flux density.
28. Define specific permeance.
It is defined as the permeance per unit length of field.
29. What is unbalanced magnetic pull.
It is the radial force acting on the rotor doe to non uniform air gap around armature
periphery.
30. List the various techniques employed to over come unbalanced magnetic pull.
The length of the rotor is small and diameter is made higher.
Ball bearings are employed and rotor is dynamically balanced.
The combinations of rotor and stator slots which produce vibrations are avoided.
31. What factor decides the number of turns in a winding?
The number of turns in a winding is decided by the emf/turn and flux density. The
emf/turn depends on the type of insulation employed.
32. How the area of cross-section of a conductor is estimated.
The area of cross-section of a conductor is estimated based on temperature rise,resistivity
and cooling methods. Assume a current density based on the above factors. For copper
conductors the normal range of current density is 2.5to5A/mm2.
Area of cross-section of a conductor=current per conductor/current density.
33. What is the range of specific magnetic loading in dc machine?
The range of specific magnetic loading in dc machine is 0.4 to 0.8wb/m2.
34. What is the range of specific electric loading in dc machine?
The range of specific electric loading in dc machine is 15000to50000amp.cond/m.
35. What are the factors to be considered for the selection of number of poles in a dc
machine?
The factors to be considered for the selection of number of poles in a dc machine
are frequency of flux reversals, current/brush arm and armature mmf per pole.
36. What are the parameters that are affected by the number of poles?
Weight of iron and copper, length of commutator and dimension of brushes are the
parameters affected by number of poles.
37. List the advantages and disadvantages of large number of poles.
Advantages.
Weight of armature core and yoke.
Cost of armature and field conductors.
Overall length and diameter of machine.
Length of commutator.
Distortion of field form under load condition.
Disadvantages:
Frequency of flux reversals.
Labour charges.
Possibility of flash over between brush arms.
38. Why square pole is preferred.
If the cross section of the pole body is square then the length of the mean turn of
field winding is minimum. Hence to reduce the copper requirement a square cross section
is preferred for the poles of dc machine.
39.What factors decides the minimum number of armature coils.
The maximum voltage between adjacent commutator segments decides the minimum
number of coils.
40. State the difference between the armature winding of dc machine and the stator
winding of ac machine.
The armature winding of dc machine has closed coils but the stator winding of ac
machine has open coils
41. Define winding pitch.
It is defined as the distance between the starts of two consecutive coils measured in
terms of coil sides.
42. What is back pitch?
The distance between top and bottom coil sides of a measured around back of the
armature is called back pitch.
43. What is front pitch?
It is the distance between two coil sides connected to the same commutator segment.
44. Define commutator pitch.
It is defined as the distance between the two commutator segments to which the two
ends of a coil are connected.
45. What is equalizer connection?
The equalizer connections are low resistance copper conductors employed in lap
winding to equalize the induced emfs in parallel paths. The difference in induced emf in
parallel paths is due to slight unsymmetrical in flux per pole in dc machines.
46. What are the factors to be considered for estimating the length of air gap in dc
machines?
The factors to be considered for estimating the length of air gap are armature reaction,
cooling, iron losses, distortion of field form and noise.
47. What are the effects of armature reaction?
The various effects of armature reaction are reduction in induced emf, increase in iron
losses, delayed commutation, sparking and ring firing.
48. How the polarities of inter pole are decided.
The polarity of the interpole must be that of the main pole just ahead for the generator
and just behind for a motor.
49. What is the effect of interpole on main pole?
In case of generator the interpole will magnetize the leading edge and demagnetizing the
trailing edge of main pole. In case of motor the interpoles will demagnetize the leading
edge and magnetize the trailing edge main pole.
50.What are standard periods for short time rating of a machine.
The standard periods for short time ratings are 10, 30,60 and 90mts.
51. Why silicon content in electrical sheet steel is limited to 4-5%.
Silicon content in sheet steel exceeds 5%acts brittle and creates difficulty in punching.
52. What is the fundamental requirement of a good insulating material?
High dielectric strength, high insulating resistance with low dielectric loss, good
mechanical strength, good thermal conductivity, high degree of thermal stability.
53. What is the importance of temperature as a factor in the life of insulating
materials?
The life of an insulating material is closely related with the maximum temperature rise to
which it is subjected. The life is halved or doubled for each 8oC rise or fall in temperature
from its specified permissible temperature.
54. Why mineral insulating oils are the most widely used liquid insulation.
Because of its easy availability, cheap and good electrical properties as well as heat
transfer capability.
55. Why large size machines have large rating time constant.
As the size of the machine increases the volume and hence weight increases in
proportion to third power of linear dimensions and surface area in proportion to second
power giving large heating time constant for large size machines.
56. Why the real flux density is always less than the apparent flux density with
reference to armature teeth of a dc machine.
It is because the actual flux passing through the tooth is always less than the total or
apparent flux making the real flux density less than apparent flux density.
57. Why are ac armature winding is always made short-pitched.
It helps in reducing the effect of harmonics in the voltage wave and also gives a saving
in the amount of copper in the overhang.
58. Why equalizer connections are necessary for the armature winding of a dc
machine with lap winding.
The emfs developed in the various parallel paths of lap winding are not equal giving rise
to circulating current and increased heating. the equalizer connections help in by passing
the circulating current through the winding and avoid over heating.
58. Why the voltage wave form of an ac armature winding contains harmonics.
It is because of the field flux and variation in the reluctance of air gap due to slotting in
the stator and rotor core.
59. Why the conductor eddy current loss increases of embedded deeper in the slot.
The conductor faces increased amount of leakage flux if embedded deeper in the slot,
thereby increasing the conductor eddy loss.
60. Why short time rating of an electrical machine is much higher than the
continuous rating.
To reach the maximum permissible temperature rise in a short duration, the machine can
be loaded to higher than the continuous rating.
61. What is the cause of noise in transformer?
The cause of noise in the transformer is mainly because of magneto-striction effect and
also loosening of stampings and mechanical forces produced during working.
62. Why is the area of yoke of a transformer usually kept 15-20% more than that of
core.
By keeping yoke area 15-20% higher the flux density in the yoke is reduced, resulting
into reduction in iron losses for yoke.
higher
63. Why does induction motor designed with specific electric loadings have smaller
over load capacity.
A machine having higher value of specific electric loading results in large number of
turns/phase , hence high leakage reactance resulting in to a circle diagram of small
diameter, hence lesser over load capacity.
64.Why is the harmonic leakage flux in squirrel cage induction ,rotor is not present.
In squirrel cage induction motor, the current in the rotor balances the stator current at
every point; hence there is no harmonic leakage flux.
65. Why the length of air gap in induction motor is kept minimum possible.
The air gap of a poly phase motor is kept small to reduce the possibility of crawling,
reduce the noise, reduce the magnetizing current, to obtain high starting torque.
66. Why do die cast rotors is extensively used in making 3 phase cage induction
motor.
Because it gives quiet operation it is economical and ease in mass production, it improves
the starting torque, it avoids the problem of harmonics.
67. Why do 3 phase squirrel cage induction motor finds wide application in
industry.
Because the robust construction and vary little maintenance, its high starting torque, its
high power factor, its wide range of speed control.
68.What is hot spot temperature.
Hot spot temperature is the temperature of that part in which heat generated is having
highest value.
69. Mention the magnetic material used for the magnetic frames.
Hot rolled silicon steel, cold rolled grain oriented silicon steel
70. What are the important properties of transformer steel.
High permeability, high resistivity, low coercive force.
71.Why stepped core are generally used for transformer.
LV and HV coils are circular ,for better utilization of apace, for reducing the mean
length of LV and HV turns, resulting in saving of copper material.
72. What are the advantages of using higher flux density in the core?
Reduction in core and yoke section for same output. reduction in mean length of LV and
HV turns, resulting in saving of copper material, reduced over all size and weight of
transformer.
73. List various disadvantages of using higher flux density in design of core.
Increased magnetizing current and iron losses, saturation of magnetic material, lower
efficiency, because of higher no load losses, higher temperature rise of transformer.
74. Why the cross section of yoke is taken greater than core section.
In order to reduce flux density in the yoke, there by reducing iron losses and no load
current in the yoke section.
75. What are the types of windings, commonly used for lv winding.
Cylindrical winding with rectangular conductors and helical winding.
76. What are the draw backs of sand width winding?
Requires more lab our in its maintenance, more difficult to insulate different coils from
each other and from yoke.
77. Name a few insulating materials that are used in transformers.
Press board, cable paper, varnished silk, transformer oil, porcelain, insulating varnish.
78. How iron losses occurring in transformers are minimized.
By laminating the magnetic cores and yokes, by using lamination of low thickness,
0.35mm, by using good quality steal like cold rolled grain oriented silicon steel.
79. Mention clearly the condition for maximum efficiency.
Efficiency is maximum at a load, at which copper losses are equal to iron losses.
80. Why the efficiency of a transformer is so high.
I. Mechanical losses are zero, which forms great part of total losses.
ii. Iron losses are comparatively less, because of better magnetic material used for
magnetic frame.
81. Mention the main function of cooling medium used in transformers.
i. To transfer the heat by convection from the heated surface to the tank surface.
ii. To create good level of insulation between various conducting parts.
82. How much heat is dissipated by radiation and convection.
6w/m2/oC by radiation and 6.5w/m2/oC by convection.
83. Why salient pole construction is rejected for high speed alternators.
i. The rotating part are subjected to very high mechanical stress.
ii. Excessive wind age loss
iii. The machine would be very noisy.
84. What material user for the construction of turbo alternator.
Chromium nickel steel is generally used for the rotor of turbo alternator.
85. What is run away speed, in case of hydraulic turbine used as prime movers for
hydro generators.
The speed attained by the hydraulic turbine under suddenly unloaded conditions is called
run away speed.
86. What is approximately the run away speed of Kaplan turbine.
The run away speed of Kaplan turbine is around 2.4 to 2.7 times the rated speed.
87. Write the expression for the output coefficient of synchrouns machine.
Output coefficient,K=11Bavqkw10-3.
Where Bav=average flux density in the air gap,Tesla
q= specific electric loading, amp-cond/m
kw=stator winding factor.
88. What are the advantages of designing the alternators with higher flux density?
I. Reduced size of the machine
ii. Higher stability limit.
iii. Satisfactory parallel operation.
iv. Reduced cost of machine.
89. What are the disadvantages of designing the alternators with higher gap flux
density?
i. Higher iron losses.
ii. Increased transient short circuit current.
iii. decreased efficiency.
iv. Higher temperature rise.
90. What are the various types of 3phase induction motor.
i. squirrel cage induction motor.
ii. Slip ring induction motor.
91. Why semi- closed slots are generally preferred for the stator of induction
motors.
Use, of semi-closed slots reduces the magnetizing current drawn by the motor; as a result
power factor is improved. Moreover, noise is also reduced by using semi closed slots.
92. What is the effect of specific magnetic loading on the size of the machine?
Size of the machines is reduced with increase in specific magnetic loading.
93. What is the effect of specific electric loading on the copper losses.
Copper losses increases with increase in specific electric loading.
94. Write down the main consideration in the selection of specific loadings for the
design of induction motor.
Main considerations are,i.size of the machine .ii.cost of the machine.iii.power factor.
iv.efficiency. v. temperature rise. vi. Noise and over load capacity.
95. What is critical speed of alternator?
A rotor is a structure with mass and velocity, and so has a natural frequency of vibration.
The speed at which this takes place is known as critical speed of turbo-alternator.
96. What are the functions of damper winding.
Damper windings are provided to damp out the oscillations. These also help in starting
as they form a cage winding.
97. Why SCR is one of the most important parameters in synchronous machine
design.
SCR value affects the machine performance like stability, voltage regulation etc. Hence it
is important.
98. What is the effect of SCR on synchronous machine performance?
SCR affects the vital performance like stability, voltage regulation, short circuit current
and parallel operation.
99. Why copper is the most widely used conducting material in making an electrical
machine?
Copper offers excellent electrical and mechanical properties so most widely used
conducting material.
100. Why it is necessary to cool an electrical machine.
The energy losses in the machine generate heat and temperature rise has to keep within
permissible limit to avoid insulation deterioration. Thus it is necessary to cool an
electrical machine.
16 MARKS QUESTIONS
1. Explain how to select the number of poles for a DC machine.
2. Discuss the requirements of high conductivity materials.
3. Write notes on temperature gradient in conductors placed in slots, with help of
equations.
4. Explain the heat flow in two dimensions.
5. Writes notes on classification of insulating materials.
6. Derive the voltage per turn equation for a single phase transformer.
7. Derive an expression to find the specific slot permeance of s fully opened rectangular
slot.
8. What are the various types of synchronous machines based on rotor construction?
Bring out the constructional differences between them.
9. Discuss the effects of short circuit ratio on the performance of a synchronous machine.
10. Explain the concept of determining the temperature gradients in conductors placed in
slots.
11. What are the limitations of design of electrical apparatus? Explain them.
12. Explain the various factors that affected by the selection of number of poles in DC
machines.
13. Explain the design of rotor bars and slots.
14. Explain the choice of specific magnetic and electric loadings of synchronous
machines.
15. Explain the design of induction motors using circle diagram.
16.i Discuss the factors that influence the choice of number of poles of a dc machine
ii.Design a shunt field coil of a dc motor from the following data.
Field ampere turns/pole=9000
Mean length of turn=1.4m
Depth of coil=35*10-3m
Voltage across field coil=40V
Receptivity of wire=0.021 ohm/m and mm2.
Thickness of insulating varnish=0.2mm
Power dissipation from total surface of the coil <700w/m2
Check your design for power dissipation
17. i.. How do you estimate the ampere turns required for an interpole with
compensating winding
ii.A 4 poles 25hp, 500V, 600rpm series motor have an efficiency of 82%. The pole
faces are square and ratio of pole arc to pole pitch is 0.67. Take Bav=0.55wb/m2 and
ampere conductors are 17000 amp.cond/m. obtain the main dimensions of the core and
particulars of a suitable armature winding.
18.i.. Derive the relation ship between real and apparent flux densities
ii. Determine the mmf required for the air gap of a dc machine having open slots,
given the following particulars.
Slot pitch=4.3cm; gross core length=48cm; air gap length=0.6cm; slot
opening=2.1cm; pole arc=18cm; flux per pole=0.056wb. There are 8 ventilating ducts
each 1.2cm wide.
The data given below is applicable for slots and ducts.
Ratio slot
opening/gap
length
1 2 3 3.5 4.0
Carter’s
coefficient
0.15 0.28 0.37 0.41 0.43
19..i.. Derive the expression for temperature rise –time curve for an electrical machine
ii. A single phase transformer is on full load for 1 ½ hrs, no load for 1 hour and 25%
over load for 1 hour. Calculate the temperature rise at the end of the period if the
temperature rise s of 20oC and 35oC occur at 1 hour and 2 hours respectively on full
load. The temperature starts from cold in both the cases. Take full load copper loss as 2.5
times the core loss.
20.i... For a transformer show that the emf per turn Et=K KVA.
Where KVA= rating of transformer
What are the factors on which the value of K depends on
ii. Determine the dimensions of the core, the number of turns and the core sectional area
of conductors in the primary and secondary windings of a 100 KVA, 2200/480V, single
phase core type transformer to operate a frequency of 50 Hz, approximate voltage per
turn=7.5V, maximum flux density=1.2wb/m2,ratio of effective cross-sectional area of
core is square of diameter of circumscribing circle=0.6, ratio of height to width of
window=2, window space factor 0.28, current density 2.5A/mm2
21.i.. Obtain the expression for leakage reactance of a single phase core type
transformer
ii. Calculate the no load current of a 400V,50Hz single phase core type transformer ,
the of which are follow as;
Length of mean magnetic path =200cm
Gross core section=100cm2, joints equivalent to 0.1mmair gap. Maximum flux density
0.7 tesla, specific core loss at 50 Hz and 0.7 tesla, stacking factor 0.9, density of core
material 7.5*103Kg/m3
22i.What are the factors to be considered in the selection of magnetic and electric loading
in a 3 ph induction motor.
ii.Estimate the main dimensions, air gap length, No. of stator slots, stator turns/phase and
cross sectional area of stator conductors for a 3 phase 20 hp, 400V,6 pole, 50 Hz,970 rpm
induction motor suitable for a star delta starting. Assume magnetic and electric loading as
0.45 wb/m2and 23000 ac/m respectively, ratio of core length to pole pitch 0.85, full load
efficiency 0.88 and power factor 0.89.
23. i.Explain the dispersion coefficient and how does it affect the performance of
induction motor.
ii. Calculate the equivalent resistance of rotor per phase referred to stator for the
following data of a 400V,3 phase, 4 pole, 50 Hz cage motor. Stator slots 48, conductors
per slot 30, rotor slots 53, one bar per rotor slot, length of each bar 12 cm, area of bar 0.6
cm2, mean diameter of end rings 18cm, area of ring 1.5cm2. full pitch winding with 600
phase spread for stator. Specific resistance is 0.021 /m length per mm2 area.
24. i.Prove that with usual notations, that the KVA rating of a synchronous generator is
given by the following relation.
KVA=1.11 Kw Bav ac L Va2*10-3.
Where Va= peripheral speed in m/sec
ii. Design suitable values of diameter and length of a 75 MVA, 11KV, 50 Hz,3000
rpm 3 phase star connected alternator. Also determine the value of flux, conductor/slot,
number of turns/phase and size of alternator conductor.
Given: Average gap density=0.6 Tesla
Ampere cond/m=50000
Peripheral speed=180m/sec
Winding factor=0.95
Current density=6A/
25.i. How do you estimate the length of air gap in a salient pole alternator? What are the
advantages of having large air gap
OR
ii. A 1250 KVA, 3 phase, 6600V salient pole alternator has the following data.
Air gap diameter= 1.6m, length of core=0.45m, number of poles=20, armature
ampere conductors per meter=28000, ratio of pole pitch=28mm, current density in
damper bars 3 A/mm2. Design a suitable damper winding for the machine

Finger Print Based Voting System for Rigging Free Governance

Finger Print Based Voting System for Rigging Free

Governance

Title of the project: Finger Print Based Voting System for Rigging free governing System

Domain: Biometrics & Embedded Design

Software: Embedded C, Keil, Proload

Microcontroller: AT89S52

Power Supply: +5V, 500mA Regulated Power Supply

Display: LED 5mm, 16 X 2 LCD

Crystal: 11.0592MHz

Biometric Sensor: FIM3030N

Storage Capacity: Up to 100 finger print images

Image Registration: Through Serial Communication

Applications: Industries, Banks, Office, Library, colleges

ABSTRACT

According ancient Greek scripts BIOMETRICS means study of life.Biometrics studies commonly include fingerprint, face, iris, voice, signature, and hand geometry recognition and verification. Many other modalities are in various stages of development and assessment. Among these available biometric traits Finger Print proves to be one of the best traits providing good mismatch ratio and also reliable. Registering the attendances of students has become a hectic work as sometimes their attendance may be registered or missed. To overcome this problem i.e. to get the attendances registered perfectly we are taking the help of two different technologies viz. EMBEDDED SYSTEMS and BIOMETRICS.

Firstly discussing about Biometrics we are concentrating on Fingerprint scanning. For this we are using FIM 3030N high voltage module as a scanner.

This module has in-built ROM, DSP and RAM. In this we can store up to 100 user’s fingerprints. This module can operate in 2 modes they are Master mode and User mode. We will be using Master mode to register the fingerprints which will be stored in the ROM present on the scanner with a unique id.

When this module is interfaced to the microcontroller, we will be using it in user mode. In this mode we will be verifying the scanned images with the stored images. When coming to our application the images of the citizens will be stored in the module with a unique id. To poll their vote the citizens have to scan their image which is then verified with the image present in fingerprint module and their vote will be updated.

This scanner is interfaced to 8051 microcontroller through max232 enabling serial communication. By using this controller we will be controlling the scanning process. After the scanning has been completed the result is stored in the microcontroller. By simply pressing a switch we can get the details of the polling.

This project uses regulated 5V, 500mA power supply. 7805 three terminal voltage regulator is used for voltage regulation. Bridge type full wave rectifier is used to rectify the ac out put of secondary of 230/12V step down transformer

 

Advantages:

No manual errors

No false Voting

Need not remember any password

Need not to carry any card

Scopes for Advancements:

 GSM modem can be connected to this unit to communicate to remote reporting office

 RTC can be interfaced to record login and logout time.

Applications

 Government Elections

 Company / Corporate internal elections

 Union Elections

microprocessor µcontroller projects of eee,ece

89C51 Based PC Based Industrial Automation with auto/manual modes of Operation

Title of the project: 89C51 Based PC Based Industrial Automation

Domain: PC Based Projects and Embedded

Software: Assembly Language

Relay: 5V, 100Ω SPDT

Power Supply: +5V, 500mA Regulated Power Supply

Display: LED, PC Screen

LED: 5mm White-in-Red, 5mm White-in-Blue

Input: Computer Key Board

Tool: Hyper Terminal

ABSTRACT

One of the 8051s many powerful features is its integrated UART, otherwise known as a serial port. The fact that the 8051 has an integrated serial port means that you may very easily read and write values to the serial port. If it were not for the integrated serial port, writing a byte to a serial line would be a rather tedious process requiring turning on and off one of the I/O lines in rapid succession to properly "clock out" each individual bit, including start bits, stop bits, and parity bits.

However, we do not have to do this. Instead, we simply need to configure the serial ports operation mode and baud rate. Once configured, all we have to do is write to an SFR to write a value to the serial port or read the same SFR to read a value from the serial port. The 8051 will automatically let us know when it has finished sending the character we wrote and will let us know whenever it has received a byte so that we can process it. We do not have to worry about transmission at the bit level--which saves us quite a bit of coding and processing time.

By using this project one can control his various electrical appliances by means of PC using PC’s hyper terminal window. The speed of a fan also can be varied depending on the user’s requirement. LED Indication is provided on the Kit for on/off condition of appliances and fan speed indication.

This project is best suitable for homes, hotels and showrooms to control all the electrical appliances and fan speed from a centralized point. This project uses regulated 5V power supply.