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


A K

VAK

VAK

IA

IA

ThyristorG


VAK

ID

IAA KSITH

G

A KGTO

G

MCTA

G

K


IAA KTRIAC

GVAK

ID


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


VCE

ICBJT (npn)

IB1

IBn

IBn > IB1

B

C

E


VCE

IC VGn > VG1

IG

IC VGn

VT

VG1

IGBT

G

C

E


VDS

ID VGn > VG1

ID VGSn

VGS0

VGS1

MOSFET

G

D

S

VDS

ID VGS1 < VGSn

VGSn

VGS1

VGS= 0V

SIT

G

D

S


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.

lession 1 introduction

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