Lession 1 Introduction
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Transcript of Lession 1 Introduction
Book
Power Electronics
By Muhammad H Rashid.
•It combines Power, Electronics and Control.•POWER deals with the static and rotating power equipment.•CONTROL deals with the steady-state and dynamic characteristics of the system.•ELECTRONICS deals with the solid state devices and circuits.
What is POWER ELECTRONICS
Example:Suppose a DC motor is to be operated at a variable speed to meet the industry requirement. A variable
DC power supply is required for it, which can be meet as follows.
DC SUPPLY
Variable speed
DC motor
Power transist
or
Base of the transistor can be fed with different
signals.
t
VbCase 1 : Constant dc voltage
t
VbCase 2 : Ton >Toff
Vb
t
Case 3 : Ton <Toff
Highest speed
Medium
speed
Lowest speed
These can be implemented by
simple electronics
Question
Q.1.1 What is ‘Power Electronics’? Explain with an example.
Can handle much more
power
Modern Power Semiconductor
Devices has two aspects :
High switching
speed
Power semiconductor
devices that can be regarded as the
muscle
Modern Power Electronics uses two things :
Microcontrollers / microelectronics
that can be regarded as the
brain
Power semiconductor
DevicesDifferent types of devices:
• Power Diode
• Thyristors
• Power bipolar transistors, BJT
• Power MOSFET
• Insulated gate bipolar transistors IGBT
• Static Induction Transistors SITDifferent types of Diodes:
• General purpose
• High speed (fast recovery)
• Schottky
Different types of Thyristors:
• Forced commutated
• Line commutated
• Phase controlled Thyristors (Silicon controlled rectifier) SCR
• Bidirectional Triode thyristors TRIAC
• Gate Turn Off GTO
• Reverse conducting thyristors RCT
• Static Induction Thyristor SITH
• Gate assisted Turn Off Thyristor GATT
• Light Activated Silicon Controlled Rectifier LASCR
• MOS controlled Thyristor MCT
• More…..
Symbols & Characteristics
A K
VAK
VAK
ID
ID
Diode
Symbols & Characteristics
A K
VAK
VAK
IA
IA
ThyristorG
Symbols & Characteristics
VAK
ID
IAA KSITH
G
A KGTO
G
MCTA
G
K
Symbols & Characteristics
IAA KTRIAC
GVAK
ID
Symbols & Characteristics
VAK
IALASCR
A KIA
G
Question
Q.1.2. Draw and explain (i) the symbols and (ii) I-V characteristics of the following.
• Power diode
• Thyristor
• Static Induction Thyristor, SITH
• Gate Turn Off Thyristor, GTO
• MOS-controlled Thyristor, MCT
• TRIAC
• Light Activated Silicon Controlled Rectifier, LASCR
Symbols & Characteristics
VCE
ICBJT (npn)
IB1
IBn
IBn > IB1
B
C
E
Symbols & Characteristics
VCE
IC VGn > VG1
IG
IC VGn
VT
VG1
IGBT
G
C
E
Symbols & Characteristics
VDS
ID VGn > VG1
ID VGSn
VGS0
VGS1
MOSFET
G
D
S
VDS
ID VGS1 < VGSn
VGSn
VGS1
VGS= 0V
SIT
G
D
S
Symbols & Characteristics
Question
Q.1.3. Draw and explain (i) the symbols and (ii) I-V characteristics of the following.
• Power BJT
• Insulated Gate Bipolar Transistor, IGBT
• Metal Oxide Semiconductor Field Effect Transistor, MOSFET
• Static Induction Transistor, SIT
Control Characteristics of
Power DevicesA K
-
VS
+
-
VO
+
R
VO
t
VS
Current will start flowing immediately
after the supply voltage is applied and we do not have any control
over it.
Power diode is a uncontrolled device
Uncontrolled turn on and off
Control Characteristics of
Power Devices
-
VS
+
-
VO
+
R
VO
t
VS
A K
G
Vgk
t
+
-
Vgk
Thyristor does not conduct unless the gate is fired /
triggered.
Once fired, it will continue conduction till the anode voltage
is higher than the cathode voltage.
Controlled turn on and Uncontrolled turn off
-
VS
+
-
VO
+
R
VO
t
VS
Vgk
t
+
-
Vgk
A KGTO
G
MCTA
G
K
A KSITH
GDo not conduct unless the gate is fired / triggered.Conduction starts and
continues once gate is fired.Conduction stops if gate is fired
by negative pulse.Conduction may again start if gate is fired by positive pulse.
Controlled turn on and turn off
-
VS
+
-
VO
+
RVO
t
VS
VBE
t+
-
VBE
B
C E
Controlled turn on and turn off
-
VS
+
-
VO
+
R
VO
t
VS
VGE
t
+
-
VgE
IGBT
G
C E
MOSFET
G
D S
Question
Q.1.4. Explain the control mechanism of the following Power Devices by drawing (i) circuit diagram and (ii) voltage vs time characteristics.
• Thyristor
• GTO
• Power Transistor
• IGBT
• MOSFET
Turn-on Turn-off Trigger Example
Uncontrolled Uncontrolled - Power Diode
Controlled Uncontrolled Pulse SCR, Thyristor
Controlled Controlled Pulse SITH, GTO, MCT
Controlled Controlled Continuous BJT, IGBT, SIT
Classification of Power Semiconductor Switching Devices:
Based on Triggering technique.
Turn-on Turn-off Trigger
Uncontrolled Uncontrolled -
Controlled Uncontrolled Pulse
Controlled Controlled Pulse
Controlled Controlled Continuous
Q.1.5. Draw proper circuit diagram and V-t characteristics to explain the following switching operation.
Unipolar Voltage BJT, MOSFET, IGBT, GTO
Classification of Power Semiconductor Switching Devices:
Based on Operating Voltage & Current
Bipolar Voltage SCR, GTO, Thyristor
Unidirectional Current
SCR, GTO, BJT, IGBT
Bidirectional Current TRIAC, RCT
Types of Power Electronics Circuits :
• Diode rectifiers (Uncontrolled rectifier )
• ac-dc converters ( Controlled rectifiers)
• ac-ac converters ( ac voltage controllers )
• dc-dc converters ( dc choppers )
• dc-ac converters ( Inverters )
• Static Switches.
About the Instructor• Professor Dr. Muhammad Abdul Goffar Khan• SSC from Bogra Zilla School in 1975.• HSC from Bogra A H Govt college in 1977, 12th place.• BSc Engg from Rajshahi Engineering College in 1981,
3rd place.• MSc Engg from BUET in 1987.• PhD from Indian Institute Of Technology, Kanpur, India
in1997, with specialization in HV engineering.• Have 25 years of teaching experience in both UG and
PG level.• Have 35 publications including two books.• Field of interests are HV, Optoelectronics, Optical fiber
design, PC based Instrumentation, Microcontroller, Power Electronics, Control Systems and many more.