INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

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INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

Sakarya Üniversitesi

Teknoloji Fakültesi

Elektrik Elektronik Mühendisliği Bölümü

T4 Blok

Introducing the department Introducing the EEEEngineering ethic Unit systems Direct and alternative current Resistor, capacitor, and coil Voltage and current supplies Ohm’s law, Kirchoff’s Laws

Circuit concept, Serial, Parallel and Mixed circuits Semiconductor technology General Occupational Health and Safety Occupational Health and Safety in Electrical

1

Electrical

and

Electronics

Engineering

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

2

Electrical

and Electronics Engineering

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

d

irection

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

.

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

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

.

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

DC

generators

,

just

produce

up

to

1500 V

have

been

designed

d

ue

to the

difficult

ies

of

commutation

(

switching

). On

the

contrary

,

such

alternator

s

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

. P

owerful

and high-speed

generator

s

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.

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

Alternators

can be

made

for

200000

kVA

, 400000

kVA

in

power

. A

t

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.

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

Production

of AC

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

W

ire

moving in a magnetic field

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

Cycle

and Period

Alternance

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and

Electronics Engineering

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.

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

The

values of alternative current and voltage

Average ValueThe 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

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

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,

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

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

.

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

MULTIMETRE

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering

INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING

DIRECT AND ALTERNATIVE CURRENT

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Electrical

and Electronics Engineering