INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
Sakarya Üniversitesi
Teknoloji Fakültesi
Elektrik Elektronik Mühendisliği Bölümü
T4 Blok
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Introducing the department
Introducing the EEE
Engineering ethic
Unit systems
Direct and alternative current
Resistor, capacitor, and coil
Voltage and current supplies
Ohm’s law, Kirchoff’s Laws
Electrical and Electronics Engineering
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Circuit concept, Serial, Parallel and Mixed
circuits
Semiconductor technology
General Occupational Health and Safety
Occupational Health and Safety in Electrical
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
The term DC is used to refer to power systems that use only one polarity of voltage
or current, and to refer to the constant, zero-frequency, or slowly varying local
mean value of a voltage or current. That is the direction and quantity according to
the time is constant in DC. The generation and transmission of DC, which are
difficult don’t preferred much.
Batteries, cells, DC generators and DC power supplies can be given as example.
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
The current which its direction and quantity changes according to the time is called
Alternative Current (AC). The basic structure of AC is a sinusoidal waveform.
Electrical energy is produced as AC and DC. Today, more than 90% of electrical
energy, consumed is produced as an alternative current. There are many reasons
for that.
First of all, to be able to economically carry the electrical energy too far there is a
need for higher voltages. Otherwise, because of too much energy loss, the
transmitted energy can not be sufficient for users.
Also, DC generators can not be designed for high voltages.
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
DC generators, just produce up to 1500 V have been designed due to the
difficulties of commutation (switching). On the contrary, such alternators can
produce higher voltages such as 230, 6300, 10500 and 20000 V, it is also possible
to increase these voltages up to 60 kV, 100 kV, and more by using a static machine,
called transformator. Carrying the electrical energy is done by higher AC voltages.
At the end of the transmission line, higher AC voltages are reduced to user voltage
by transformators.
It is possible to converting higher AC voltage to higher DC voltage with some
rectifiers first, and then carrying the energy, and finally converting it to lower AC
voltage with some inverters at the end of the line but these procedures can not be
preferred. Powerful and high-speed generators can not be made because of the
difficulties in commutation. Alternators can be made as powerful and high-speed.
Thus, the energy cost per kilowatt hour and operating costs are lower.
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
Alternators can be made for 200000 kVA, 400000 kVA in power. At a constant
speed in the industry, AC motor (induction motor) works more efficient than DC
motor. Induction motor is more robust, and cheaper than DC motor, and its
maintenance is also easy. The only advantage of the DC motor is that the speed
can be set properly.
The use of direct current is preferred, or where there is an obligation. DC can be
used in electrical vehicles, metal plating, metal treatment, all electronic systems,
and communications systems. In such these applications, DC can usually be
obtained by converting from AC.
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
Production of AC
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
Wire moving in a magnetic field
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
Alternance
Cycle and Period
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
The values of alternative current and voltage
Maximum Value
It is the biggest one of instantaneous
values. Notice that, at the angle of 90
and 270 degrees, current reaches the
maximum value.
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
The values of alternative current and voltage
Average Value
The average value is the average of
instantaneous values in a cycle.
Because of the number of positive
instantaneous value in one cycle of
alternating current is equal to the
number of negative instantaneous
value, the mean value in the alternating
current is zero. For this reason,
calculation of the average value is done
by in one alternance only. If the
maximum value is known, then the
average value can be calculated as
below:
Iort= 0.636.Im
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
Effective Value (Root mean square)
In physics it is a characteristic of a continuously varying quantity, such as a cyclically
alternating electric current, obtained by taking the mean of the squares of the
instantaneous values during a cycle. It is equal to the value of the direct current that would
produce the same power dissipation in a resistive load.
The RMS value of a continuous function or signal can be approximated by taking the RMS of
a series of equally spaced samples. Additionally, the RMS value of various waveforms can
also be determined without calculus.
In the case of set of n values
, the RMS
The corresponding formula for a continuous function (or waveform) f(t) defined over the
interval
is,
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
Period
The period is the duration of time of one cycle in a repeating event, so the period is
the reciprocal of the frequency. The period, usually denoted by T. The SI unit for
period is the second.
T = 1/f
Frequency
Frequency is the number of occurrences of a repeating event per unit time.
For cyclical processes, such as rotation, oscillation, or waves, frequency is defined as a
number of cycles per unit time. It is usually denoted by a Latin letter f. The SI unit of
frequency is the hertz (Hz); one hertz means that an event repeats once per second.
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
MULTIMETRE
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING
DIRECT AND ALTERNATIVE CURRENT
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