Short Notes: Introduction to Basic Electrical Technology | Basic Electrical Technology - Electrical Engineering (EE) PDF Download

 Page 1


1 Short Notes: In tro duction to Basic Electrical T ec hnology
1.1 In tro duction
Basic Electrical T ec hnology la ys the groundw ork for understanding electrical circuits,
p o w er systems, and energy con v ersion. It is crucial for GA TE Electrical Engineering,
co v ering concepts lik e circuit analysis, A C/DC systems, and electromec hanical principles,
whic h are foundational for adv anced topics lik e mac hines and p o w er systems.
1.2 Basic Circuit Elemen ts
• Resistor : Resists the flo w of curren t, con v erting electrical energy in to heat. Ohm’s
La w relate s v oltage, curren t, and resistance:
V =IR
where V is v oltage (V), I is curren t (A), and R is resistance (? ).
• Capacitor : Stores c harge in an electric field, used in filtering and timing circuits.
The curren t t hrough a capacitor dep ends on the rate of v oltage c hange:
I =C
dV
dt
, E =
1
2
CV
2
where C is capacitance (F) and E is stored energy (J).
• Inductor : Stores energy in a magnetic field, opp osing c hanges in curren t. V oltage
across an i nductor is prop ortional to the rate of curren t c hange:
V =L
dI
dt
, E =
1
2
LI
2
where L is inductance (H).
1.3 Kirc hhoff ’s La ws
• Kirc hhoff ’s Curren t La w (K CL) : Based on c harge conserv ation, the total cur-
ren t en tering a no de equals the total curren t lea ving it. This is critical for analyzing
complex cir cuits:
?
I
in
=
?
I
out
• Kirc hhoff ’s V oltage La w (KVL) : Based on energy conserv ation, the sum of
v oltage drops around a closed lo op is zero. It ensures consisten t v oltage analysis:
?
V = 0
1.4 A C and DC Circuits
• DC Circuits : F eature constan t v oltage and curren t, analyzed using Ohm’s La w
and Kirc hhoff ’s La ws. They are simpler but limited in p o w er transmission e?iciency .
1
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1 Short Notes: In tro duction to Basic Electrical T ec hnology
1.1 In tro duction
Basic Electrical T ec hnology la ys the groundw ork for understanding electrical circuits,
p o w er systems, and energy con v ersion. It is crucial for GA TE Electrical Engineering,
co v ering concepts lik e circuit analysis, A C/DC systems, and electromec hanical principles,
whic h are foundational for adv anced topics lik e mac hines and p o w er systems.
1.2 Basic Circuit Elemen ts
• Resistor : Resists the flo w of curren t, con v erting electrical energy in to heat. Ohm’s
La w relate s v oltage, curren t, and resistance:
V =IR
where V is v oltage (V), I is curren t (A), and R is resistance (? ).
• Capacitor : Stores c harge in an electric field, used in filtering and timing circuits.
The curren t t hrough a capacitor dep ends on the rate of v oltage c hange:
I =C
dV
dt
, E =
1
2
CV
2
where C is capacitance (F) and E is stored energy (J).
• Inductor : Stores energy in a magnetic field, opp osing c hanges in curren t. V oltage
across an i nductor is prop ortional to the rate of curren t c hange:
V =L
dI
dt
, E =
1
2
LI
2
where L is inductance (H).
1.3 Kirc hhoff ’s La ws
• Kirc hhoff ’s Curren t La w (K CL) : Based on c harge conserv ation, the total cur-
ren t en tering a no de equals the total curren t lea ving it. This is critical for analyzing
complex cir cuits:
?
I
in
=
?
I
out
• Kirc hhoff ’s V oltage La w (KVL) : Based on energy conserv ation, the sum of
v oltage drops around a closed lo op is zero. It ensures consisten t v oltage analysis:
?
V = 0
1.4 A C and DC Circuits
• DC Circuits : F eature constan t v oltage and curren t, analyzed using Ohm’s La w
and Kirc hhoff ’s La ws. They are simpler but limited in p o w er transmission e?iciency .
1
• A C Circuits : Use sin usoidal signals, enabling e?icien t p o w er transmission. Key
parameters include RMS v alues and imp edance:
V
rms
=
V
p eak
v
2
Z =R+j(X
L
-X
C
)
where X
L
=?L , X
C
=
1
?C
, and ? = 2pf (angular frequency , rad/s).
1.5 P o w er and Energy
• P o w er in DC Circuits : P o w er is the pro duct of v oltage and curren t, represen ting
energy tra nsfer rate:
P =VI =I
2
R =
V
2
R
• P o w er in A C Circuits : Only the real p o w er con tributes to useful w ork, adjusted
b y the p o w e r factor:
P =V
rms
I
rms
cos?
where cos? is the p o w er factor, indicating e?iciency .
• Energy : Energy is p o w er in tegrated o v er time, measured in joules:
W =P ·t
1.6 Three-Phase Systems
• Line and Phase Quan tities : Three-phase systems are used in p o w er distribution
for e?iciency . Star and Delta connections differ in v oltage and curren t relationships:
– Star:
V
L
=
v
3V
ph
, I
L
=I
ph
– Delta:
V
L
=V
ph
, I
L
=
v
3I
ph
• P o w er in Three-Phas e : T otal p o w er accoun ts for all phases:
P =
v
3V
L
I
L
cos?
1.7 Magnetic Circuits
• Magnetomotiv e F orce (MMF) : Driv es magnetic flux, analogous to v oltage in
electrical circuits:
F =NI
where N is the n um b er of coil turns, I is curren t (A).
• Magnetic Flux : Flux dep ends on MMF and reluctance, similar to curren t in
electrical circuits:
? =
F
R
whereR is reluctance (A/Wb) .
2
Page 3


1 Short Notes: In tro duction to Basic Electrical T ec hnology
1.1 In tro duction
Basic Electrical T ec hnology la ys the groundw ork for understanding electrical circuits,
p o w er systems, and energy con v ersion. It is crucial for GA TE Electrical Engineering,
co v ering concepts lik e circuit analysis, A C/DC systems, and electromec hanical principles,
whic h are foundational for adv anced topics lik e mac hines and p o w er systems.
1.2 Basic Circuit Elemen ts
• Resistor : Resists the flo w of curren t, con v erting electrical energy in to heat. Ohm’s
La w relate s v oltage, curren t, and resistance:
V =IR
where V is v oltage (V), I is curren t (A), and R is resistance (? ).
• Capacitor : Stores c harge in an electric field, used in filtering and timing circuits.
The curren t t hrough a capacitor dep ends on the rate of v oltage c hange:
I =C
dV
dt
, E =
1
2
CV
2
where C is capacitance (F) and E is stored energy (J).
• Inductor : Stores energy in a magnetic field, opp osing c hanges in curren t. V oltage
across an i nductor is prop ortional to the rate of curren t c hange:
V =L
dI
dt
, E =
1
2
LI
2
where L is inductance (H).
1.3 Kirc hhoff ’s La ws
• Kirc hhoff ’s Curren t La w (K CL) : Based on c harge conserv ation, the total cur-
ren t en tering a no de equals the total curren t lea ving it. This is critical for analyzing
complex cir cuits:
?
I
in
=
?
I
out
• Kirc hhoff ’s V oltage La w (KVL) : Based on energy conserv ation, the sum of
v oltage drops around a closed lo op is zero. It ensures consisten t v oltage analysis:
?
V = 0
1.4 A C and DC Circuits
• DC Circuits : F eature constan t v oltage and curren t, analyzed using Ohm’s La w
and Kirc hhoff ’s La ws. They are simpler but limited in p o w er transmission e?iciency .
1
• A C Circuits : Use sin usoidal signals, enabling e?icien t p o w er transmission. Key
parameters include RMS v alues and imp edance:
V
rms
=
V
p eak
v
2
Z =R+j(X
L
-X
C
)
where X
L
=?L , X
C
=
1
?C
, and ? = 2pf (angular frequency , rad/s).
1.5 P o w er and Energy
• P o w er in DC Circuits : P o w er is the pro duct of v oltage and curren t, represen ting
energy tra nsfer rate:
P =VI =I
2
R =
V
2
R
• P o w er in A C Circuits : Only the real p o w er con tributes to useful w ork, adjusted
b y the p o w e r factor:
P =V
rms
I
rms
cos?
where cos? is the p o w er factor, indicating e?iciency .
• Energy : Energy is p o w er in tegrated o v er time, measured in joules:
W =P ·t
1.6 Three-Phase Systems
• Line and Phase Quan tities : Three-phase systems are used in p o w er distribution
for e?iciency . Star and Delta connections differ in v oltage and curren t relationships:
– Star:
V
L
=
v
3V
ph
, I
L
=I
ph
– Delta:
V
L
=V
ph
, I
L
=
v
3I
ph
• P o w er in Three-Phas e : T otal p o w er accoun ts for all phases:
P =
v
3V
L
I
L
cos?
1.7 Magnetic Circuits
• Magnetomotiv e F orce (MMF) : Driv es magnetic flux, analogous to v oltage in
electrical circuits:
F =NI
where N is the n um b er of coil turns, I is curren t (A).
• Magnetic Flux : Flux dep ends on MMF and reluctance, similar to curren t in
electrical circuits:
? =
F
R
whereR is reluctance (A/Wb) .
2
• Reluctance : Opp oses flux, dep ending on material and geometry:
R =
l
µA
where l is length (m), µ is p ermeabili t y (H/m), A is cross-sectional area (m²).
1.8 Electromec hanical Energy Con v ersion
• Con v erts electrical energy to mec hanical (motors) or mec hanical to electrical (gen-
erators) via a magnetic field, whic h acts as a coupling medium.
• Motoring A ction : Curren t in a magnetic field pro duces a force, causing rotation:
F =I(L×B)
where B is magnetic flux densit y (T), L is conductor length (m).
• Generating A ction : Motion in a magnetic field induces EMF, p er F arada y’s La w:
E =-N
d?
dt
• Energy Balance : Energy is conserv ed, distributed among losses, stored energy ,
and useful o utput:
Electrical Input = Losses+ Stored Energy+ Mec hanical Output
1.9 Key Notes for GA TE
• Master K CL and KVL for circuit analysis, fo cusing on n u merical applications.
• Understand A C vs. DC differences, esp ecially RMS calculations and p o w er factor.
• Practice three-phase p o w er problems and magnetic cir cuit calculations.
• F amiliarize with energy con v ersion principles, as they link t o electrical mac hines.
3