Archive for January 2017
Scheme of Studies for
BS Technology (Electrical)
Semester 1
Course No.
|
Course Title
|
Credit Hrs.
|
GS-111
|
Mathematics- I
|
2 - 1
|
CS-112
|
Introduction to Computers
|
2 - 1
|
HS-113
|
Communication Skills
|
0 - 0
|
EL-114
|
Network Analysis – I
|
2 - 1
|
HS-115
|
Pakistan Studies
|
2 - 0
|
Semester 2
Course No.
|
Course Title
|
Credit Hrs.
|
MT-124
|
BASIC MECHANICAL TECHNOLOGY
|
2 - 1
|
EL-125
|
Network Analysis-II
|
3 - 1
|
GS-121
|
Mathematics-II
|
3 - 0
|
HS-112
|
Islamic Studies
|
2 - 0
|
HS-123
|
Communication Skills -II
|
0 - 0
|
Semester 3
Course No.
|
Course Title
|
Credit Hrs.
|
GS128
|
Pakistan Studies
|
2 - 0
|
EE210
|
Digital Electronics
|
3 - 1
|
ENG315
|
Business Communication
|
3 - 0
|
EE120
|
Electric Machines for Technologies
|
3 - 1
|
EE140
|
Network Analysis-I
|
2 - 1
|
Semester 4
Course No.
|
Course Title
|
Credit Hrs.
|
CS252
|
Computer Architecture
|
3 - 0
|
EE-315
|
Electromagnetic Field Theory
|
3 - 0
|
LS-450
|
Occupational Health Safety
|
3 - 0
|
EE-150
|
Network Analysis-II
|
2 - 1
|
EE310
|
Power Generation
|
3 - 0
|
Semester 5
Course No.
|
Course Title
|
Credit Hrs.
|
CS323
|
Microprocessors Architecture and Assembly Language
|
3 - 1
|
BT255
|
Switchgear
|
3 - 0
|
COM304
|
Data Communications and Computer Networks
|
3 - 0
|
EE228
|
Communication Systems -I
|
3 - 1
|
EE416
|
Power Electronics
|
2 - 1
|
Semester 6
Course No.
|
Course Title
|
Credit Hrs.
|
EE338
|
Microprocessor Interfacing Technologies
|
2 - 1
|
MGT427
|
Industrial Management
|
3 - 0
|
EE408
|
Substation Technology
|
2 - 1
|
EE254
|
Power Transmission
|
2 - 1
|
Semester 7
Course No.
|
Course Title
|
Credit Hrs.
|
EE334
|
Industrial Electronics
|
3 - 0
|
EE-463
|
High Voltage Technology
|
2 - 1
|
MGT410
|
Project Management
|
3 - 0
|
RES-491
|
Project-I
|
0 - 3
|
Semester 8
Course No.
|
Course Title
|
Credit Hrs.
|
EE221
|
Instrumentation
|
3 - 1
|
EE-321
|
Control System
|
3 - 1
|
MGT-450
|
Total Quality Management
|
3 - 0
|
RES492
|
Project Phase II
|
0 - 3
|
Presentation.
Few differences between C.T. and P.T. are listed below –
Definition of Transformer Electrical power transformer is a static device which transforms electrical energy from one circuit to another without any direct electrical connection and with the help of mutual induction between two windings. It transforms power from one circuit to another without changing its frequency but may be in different voltage level. This is a very short and simple definition of transformer, as we will go through this portion of tutorial related to electrical power transformer, we will understand more clearly and deeply "what is transformer ?" and basic theory of transformer. Working Principle of Transformer The working principle of transformer is very simple. It depends upon Faraday's law of electromagnetic induction. Actually, mutual induction between two or more winding is responsible for transformation action in an electrical transformer.
Few differences between C.T. and P.T. are listed below –
| Sl. No. | Current Transformer (C.T.) | Potential Transformer (P.T.) |
| 1 | Connected in series with power circuit. | Connected in Parallel with Power circuit. |
| 2 | Secondary is connected to Ammeter. | Secondary is connected to Voltmeter. |
| 3 | Secondary works almost in short circuited condition. | Secondary works almost in open circuited condition. |
| 4 | Primary current depends on power circuit current. | Primary current depends on secondary burden. |
| 5 | Primary current and excitation vary over wide range with change of power circuit current | Primary current and excitation variation are restricted to a small range. |
| 6 | One terminal of secondary is earthed to avoid the insulation break down. | One terminal of secondary can be earthed for Safety. |
| 7 | Secondary is never be open circuited. | Secondary can be used in open circuit condition. |
Ammeter Working Principle and Types of Ammeter
Introduction of Ammeter
As we know a word "meter"
associated with the measurement. Meter is an instrument which can measure a
particular quantity. we know, the unit of current is Ampere. Ammeter means
Ampere-meter which measures ampere value. Ampere is the unit of current so an
ammeter is a meter or an instrument which measures current.
Working Principle of Ammeter
The main principle of ammeter is that
it must have a very low resistance and also inductive reactance. Now, why do we
need this? can't we connect an ammeter in parallel? The answer to this question
is it has very low impedance because it must have very low amount of voltage
drop across it and must be connected in series connection because current is
same in the series circuit. Also due to very low impedence the power loss will
be low and if it is connected in parallel it becomes almost a short circuited
path and all the current will flow through ammeter as a result of high current
the instrument may burn. So due to this reason it must be connected in series.
For an ideal ammeter, it must have zero impedance so that it has zero voltage
drop across it so the power loss in the instrument is zero. But the ideal is
not achievable practically.
ammeter
Classification or Types of Ammeter
Depending on the constructing
principle, there are many types of ammeter we get, they are mainly –
· Permanent Magnet Moving Coil(PMMC) ammeter.
· Moving Iron(MI) Ammeter.
· Electrodynamometer type Ammeter.
· Rectifier type Ammeter.
Depending on this types of measurement
we do, we have-
DC Ammeter.
AC Ammeter.
DC Ammeter are mainly PMMC
instruments, MI can measure both AC and DC currents, also Electrodynamometer
type thermal instrument can measure DC and AC, induction meters are not
generally used for ammeter construction due to their higher cost, inaccuracy in
measurement.
Description of Different Types of
Ammeters
PMMC Ammeter
Principle PMMC Ammeter: When current
carrying conductor placed in a magnetic field, a mechanical force acts on the
conductor, if it is attached to a moving system, with the coil movement, the
pointer moves over the scale.
Explanation: As the name suggests it
has permanent magnets which are employed in this kind of measuring instruments.
It is particularly suited for DC measurement because here deflection is
proportional to the current and hence if current direction is reversed,
deflection of the pointer will also be reversed so it is used only for DC
measurement. This type of instrument is called D Arnsonval type instrument. It
has major advantage of having linear scale, low power consumption, high
accuracy. Major disadvantage of being measured only DC quantity, higher cost
etc.
Deflecting torque,
Where,
B = Flux density in Wb/m².
i = Current flowing through the
coil in Amp.
l = Length of the coil in m.
b = Breadth of the coil in m.
N = No of turns in the coil.
Extension of Range in a PMMC Ammeter:
Now it looks quite extraordinary that we can extend the range of measurement in
this type of instrument. Many of us will think that we must buy a new ammeter
to measure higher amount of current and also many of us may think we have to
change the constructional feature so that we can measure higher currents, but
there is nothing like that, we just have to connect a shunt resistance in
parallel and the range of that instrument can be extended, this is a simple
solution provided by the instrument.
pmmcIn the figure I = total
current flowing in the circuit in Amp.
Ish is the current through the shunt
resistor in Amp.
Rm is the ammeter resistance in Ohm.
MI Ammeter
It is a moving iron instrument, used
for both AC and DC, It can be used for both because the deflection θ
propotional square of the current so what ever is the direction of current, it
shows directional deflection, further they are classified in two more ways-
Attraction type.
Repulsion type.
Its torque equation is:
where I is the total current flowing
in the circuit in Amp.
L is the self inductance of the
coil in Henry.
θ is the deflection in Radian.
Attraction Type MI Instrument
Principle: When an unmagnetised soft iron is placed in the magnetic field, it
is attracted towards the coil, if a moving system attached and current is
passed through a coil, it creates a magnetic field which attracts iron piece
and creates deflecting torque as a result of which pointer moves over the
scale.
Repulsion Type MI Instrument
Principle: When two iron pieces are magnetized with same polarity by passing a
current than repulsion between them occurs and that repulsion produces a
deflecting torque due to which the pointer moves.
The advantages of MI instruments are
they can measure both AC and DC, cheap, low friction errors, robustness etc. It
is mainly used in AC measurement because in DC measurement error will be more due
to hysteresis.
Electrodynamometer Type Ammeter
This can be used to measure both i.e.
AC and DC currents. Now we see that we have PMMC and MI instrument for the
measurement of AC and DC currents , a question may arise - "why do we need
Electrodynamometer Ammeter? if we can measure current accurately by other instrument also?". The answer
is Electrodynamometer instruments have the same calibration for both AC and DC
i.e. if it is calibrated with DC , then also without calibrating we can measure
AC.
Principle Electrodynamometer Type
Ammeter: There we have two coils, namely fixed and moving coils. If a current
is passed through two coils it will stay in the zero position due to the
development of equal and opposite torque. If somehow, the direction of one torque
is reversed as the current in the coil reverses, an unidirectional torque is
produced.
For ammeter, the connection is a
series one and φ = 0
Where, φ is the phase angle.
Where, I is the amount of current
flowing in the circuit in Amp.
M = Mutual inductance of the coil.
They have no hysteresis error, used
for both AC and DC measurement, the main disadvantages are they have low
torque/weight ratio, high friction loss, expensive than other measuring
instruments etc.
Rectifier Ammeter
rectifier ammeter
Principle of Rectifier Ammeter: They
are used for AC measurement which is connected to secondary of a current
transformer, the secondary current is much less than primary and connected with
a bridge rectifier to moving coil ammeter.
Advantages:
It can be used in high frequency also.
Uniform scale for most of the ranges.
Disadvantages
being error due to
temperature decrease in sensitivity in AC operation.
Galvanometer
is the historical name given to a moving coil electric current detector. When a
current is passed through a coil in a magnetic field, the coil experiences a
torque proportional to the current. If the coil's movement is opposed by a coil
spring, then the amount of deflection of a needle attached to the coil may be
proportional to the current passing through the coil. Such "meter
movements" were at the heart of the moving coil meters such as voltmeters
and ammeters until they were largely replaced with solid state meters.
The accuracy
of moving coil meters is dependent upon having a uniform and constant magnetic
field. The illustration shows one configuration of permanent magnet which was
widely used in such meters.
Binary
to Decimal and Decimal to Binary Conversion
The number system that we are mostly familiar with
is a decimal number system. The decimal number system has a base of ten which
implies that there are ten numbers by the help of which we can represent any
number of the decimal family. The numbers are from 0 to 9. Representation is
such as (15)10 the base 10 is written as suffix or radix. If it is not written
then by default we must understand that it is a decimal number by default. On
the other hand, binary number invented by Gottfried Leibniz in 1679 has a base
of two. “Bi” means two so from there we can say that the base of the binary
system is 2. That is, only two numbers are sufficient to represent a number in
binary format. The numbers which are used in binary number system are 0 and 1.
Binary number can be represented by putting 2 in the prefix which denotes the
base. If the base is not given, then it is by default assumed to be a decimal
number .We have to be very careful in writing a binary number, a slight mistake
may result in a very serious error. For example, a binary number is written as
follows-
(00110)2.
Now a question may arise, why do we need binary
number? We have decimal number system which is familiar to all of us and most
of the persons do not understand binary. The answer is that any programmable
device or a processor can work in two modes either high or low. Here, high
denotes the supply is connected to that point and low denotes that the point is
grounded or is at a state of zero volts. This is called positive logic and in other
logic system the reverse is taken which is known as negative logic system.
Also, we can say that a high means that it performs
some function or work and low indicates that it has not performed any work. The
reverse may also be true if we take negative logic system. So, from the above
description we can say that it is much easier and convenient to use binary
number system in the computer instead of decimal and also conversion will be
required in order that the output result which is given in binary form should
be converted to decimal for the sake of the user.
Conversion from Binary to Decimal
Conversion of Integer Numbers
Expand the number given in binary form in the power
of 2 and sum the values, the result which we will get will be in the decimal
form. For example-
Convert Binary Number to Decimal Number
Conversion of Decimal Point Number to Decimal
This can also be done in the same way, however after
the decimal point the number should be multiplied with 2-1, 2-2 etc.
For example,
Conversion from Decimal to Binary
Integer Numbers
Divide the number by 2 and take only the remainder,
if division is completed than take only the remainder which gives the binary
number.
Example
integer numbers
So, the binary equivalent of (14)10 is (1110)2
After the dash (-) remainder is written.
Suppose we are converting the decimal number (87)10.
Now the conversion is shown below
∴ (87)10 = (1110101)2
For Fractional Numbers
In this case, the successive multiplication is done.
The number which is to be converted is multiplied with base or radix of binary
number which is 2. The integer part or the carry of the product is taken out
and the same process is repeated until we get an integer. For example-
The binary equivalent of (.95)10 is evaluated as
follows-
Since, we are not getting the integer value after
successive multiplication, we can approximate the value to be (.111110….)2.
Conversion of Negative Number
In case of a negative number we can go for 2’s
complement representation of a signed number.
Example- 9 = 0000 1001
1’s complement = 1111 0110.
Adding 1 we get = 11110111 which is the 2’s
complement representation of (-9).
