Power Electronics

Chapter 1 Sayan Das

Assistant Professor
Dept. Of Electrical
Engineering
  Concept
 History
 Converter System
• Application

Overview • Advantages & Disadvantages

• Power Electronics System

• Power Semiconductor Devices

• Classification of devices

• Types of converters
Books to be  Power Electronics by Dr. P.S. Bimbhra – Khaana publication.

followed  Power Electronics by Singh, Khanchandani – Tata Mcgraw Hill.

1.1 Concept

Power Electronics

Electronics
Power Engineering
Engineering
High Efficiency

Efficiency not
considered
Generation. Distortion less Production,
Transmission. Transmission,
Distribution. reception of data & signals of very low power level (watt /
Utilization. miliwatts).
 Deal with the apparatus and equipment based mainly on
electromagnetic principle working on the principle of
Electronics but rated at Power Level rather than Signal
Level.
1.1
Concept Electronic devices based upon physical phenomena in
vacuum, gases/ vapours, semiconductors, are used working
on the principle of electronics but have the name Power
attached to them only as description of their power ratings.
 Era of modern power electronic began with the invention of
Silicon Controlled Rectifier (SCR) by Bell Laboratories in
1956.
Prototype was introduced by GEC in 1957 and subsequently
commercialization of SCR based systems comes in 1958.
1.2
History Conventional Power Controllers based Replaced by
 Thyratrons Power Electronic Controllers using
 Mercury-Arc Rectifiers Semiconductor Devices.
 Magnetic Amplifiers
 Rheostatic Controllers
  AC to DC
 Diode rectifier
 Phase controlled rectifier
 DC to AC
1.3  Inverter

Converter  DC to DC
 DC Chopper
System  AC to AC
 AC voltage regulators
 Cycloconverters
 1.3 Enhanced control
Power Semiconductor Devices

Power strategies and

Synthesizing
Electronics capabilities of
Power Electronic
Converter Converters
Microprocessor/ Microcontrollers
 a. Aerospace
b. Commercial
c. Industrial
1.4 d. Residential
Application e. Telecommunication
f. Transportation
g. Utility
 1.4 Aerospace
Application Power supplies in aircraft, satellites, space shuttles,
advance control in missiles, unmanned vehicles and
other defence equipment.
 1.4
Application Commercial
If we look around ourselves, we can find a whole lot of power
electronics applications such as a fan regulator, light dimmer, air-
conditioning, induction cooking, emergency lights, personal
computers, vacuum cleaners, UPS (uninterrupted power system),
battery charges, etc.
 1.4
Application Industrial
Almost all the motors employed in the industries are controlled
by power electronic drives, for eg. Rolling mills, textile mills,
cement mills, compressors, pumps, fans, blowers, elevators,
rotary kilns etc. Other applications include welding, arc furnace,
cranes, heating applications, emergency power systems,
construction machinery, excavators etc.
 1.4
Transportation
Application
Subways, hybrid electric vehicles, trolley, fork-lifts, and many
more. A modern car itself has so many components where power
electronic is used such as ignition switch, windshield wiper
control, adaptive front lighting, interior lighting, electric power
steering and so on. Besides power electronics are extensively
used in modern traction systems and ships.
 1.4
Utility
Application
HVDC (High Voltage DC) transmission, VAR compensation (SVC),
static circuit breakers, generator excitation systems, FACTS,
smart grids, etc.
 I. High Efficiency due to low loss in Power Semiconductor Devices.
II. High Reliability of power electronic converter systems.
1.5 III. Long life and low maintenance due to the absence of any moving parts.
Advantages IV. Fast dynamic response compared to electromechanical converter
systems.
V. Small size, less weight result in less floor space and therefore lower
installation cost.
VI. Mass production has resulted in lower cost.
 a. Tendency to generate Harmonics in the supply systems as well as in the
load circuit.
Load Circuit
Performance of the load is influenced.
1.5 High harmonic content in load circuit causes
Disadvantages Commutation problems in DC machines,
increases motor heating,
more acoustical noise in both DC and AC machines.

Remedy: Use of filter to filter this out from output side of converter.
 a. Tendency to generate Harmonics in the supply systems as well as in
the load circuit.
Supply Systems
1.5 Distorts the voltage waveform and seriously influence the
Disadvantages performance of the other equipment connected to the same supply
line.
Cause interference with the communication lines.

Remedy: Use of filter on the input side of converter.

 b. For both AC to DC and AC to AC conversion
1.5 Operate at low input power factor under certain operating conditions.
Disadvantages Power Factor - the ratio of the actual electrical power dissipated
by an AC circuit to the product of the r.m.s.
values of current and voltage.
Remedy: Some special measures have to be adopted.
 c. Low overload capacity.

1.5 Must be rated for taking momentary overloads.

Cost may increase.
Disadvantages
d. Regeneration of power is difficult.
 1.6
Power
Electronics
System
 Output should be
Variable DC or AC voltage
1.6 Variable Voltage and Frequency
Power
Electronics If the load is a DC motor then the converter output must be
adjustable direct voltage.
System
If the load is 3-phase induction motor, converter may have
adjustable voltage and frequency at its output terminal.
1.7 Power Semiconductor Devices
Rating
Device Image
V A F (kHz)
Power Diode 3000 3500 1

Thyristor 6000 3500 1

Static Induction Thyristor SITH 4000 2200 20

1.7 Power Semiconductor Devices
Rating
Device Image
V A F (kHz)
Gate-turn off Thyristor (GTO) 4000 3000 10

MOS controlled Thyristor (MCT) 600 60 20

TRIAC 1200 300 400

1.7 Power Semiconductor Devices
Rating
Device Image
V A F (kHz)
BJT 1200 400 10

Power MOSFET 1000 50 100

Static Inductor Transistor 1200 300 100

1.7 Power Semiconductor Devices

Rating
Device Image
V A F (kHz)
Insulated Gate Bi-polar transistor 1200 400 20
 Classification
1.8
Classification
of devices
Turn on and Turn off Gate signal
characteristics requirements
 A. Diodes – Uncontrolled rectifying device. Power supply
controls on and off states.
1.8 B. Thyristors – Controlled turn on by gate signal. After turned
Classification on, they remain latched in on-state due to internal
regenerative action.
of devices
C. Controllable switches – Turned on and off by the application
of control signals.
1.8 Classification of devices
Controllable
Switches for Require continuous signal for keeping them in turn-on
turning on state
• BJT
• MOSFET
• GTO
• SITH
• IGBT
• SIT
• MCT

Pulse gate Signal

Once the devices are on gate pulse is removed
• SCR
• GTO
• SITH
• MCT
1.8 Classification of devices
 1. Diode Rectifier

1.9 Types of AC input Voltage Fixed DC

converters (Single/3 phase) Voltage
 AC input Voltage Fixed DC
(Single/3 phase) Voltage

1. Diode Rectifier
1.9 Types of Uses: Electric Traction, battery charging, electroplating,
electromechanical processing, power supplies, welding, UPS.
converters
 2. Ac to Dc Converter (Phase controlled rectifier)

1.9 Types of
converters Constant Ac Variable
Voltage Dc voltage
 Constant Ac Variable
Voltage Dc voltage

2. Ac to Dc Converter (Phase controlled rectifier)

1.9 Types of Uses: DC drives, Metallurgical and Chemical industries, Excitation

systems for synchronous machines.
converters
 3. Dc to DC Converter (DC chopper)

1.9 Types of
converters
Fixed Dc Voltage Controllable
Dc voltage
 Fixed Dc Voltage Controllable
Dc voltage

3. Dc to DC Converter (DC chopper)

1.9 Types of Uses: Dc drives, subway cars, trolley trucks, battery driven
converters vehicles.
 4. Dc to Ac Converter (Inverter)

Variable Ac
1.9 Types of voltage
converters Fixed Dc Voltage (variable
voltage &
frequency)
 Variable Ac
voltage
Fixed Dc Voltage (variable
voltage &
frequency)

4. Dc to Ac Converter (Inverter)
1.9 Types of Uses: Induction motor, synchronous motor drives, induction heating,
UPS, HVDC transmission.
converters
 5. Ac to Ac Converter
a) Ac voltage regulator

1.9 Types of
converters Variable Ac
voltage (same
Fixed Ac Voltage frequency)
By varying firing
angle delay
 Variable Ac
voltage (same
Fixed Ac Voltage frequency)
By varying firing
angle delay

5. Ac to Ac Converter
1.9 Types of a) Ac voltage regulator

converters Uses: Lighting control, speed control of fans, pumps.

 5. Ac to Ac Converter
a) Cyclo-converters

1.9 Types of
converters Output
Input power at power at
one frequency different
frequency
 Output
Input power at power at
one frequency different
frequency

5. Ac to Ac Converter (Inverter)

1.9 Types of a) Cyclo-converters

Uses: Slow speed large ac drives like rotary kiln (A rotary kiln is a
converters pyro processing device used to raise materials to a high
temperature (calcination) in a continuous process. Materials
produced using rotary kilns include: Cement. Lime.).
1.9 Types of 6. Static Switches
Power semiconductor devices acts as static switches or contactors.
converters Have advantages over mechanical and electromechanical circuit breakers.
 Power
Electronics
Application
Video