MEM402: Power Electronics

Mechatronics Engineering
Ahram Canadian University

Dr. Sayed Ahmed Zaki

Assistant Prof. in Electrical Engineering
Faculty of Engineering
Cairo University
 What is Power Electronics ?

The term power electronics refers to solid-state electronic devices used

for the conversion and control of electric power.

Power
Source Load

Solid-state
Electronic

Control Signals

Control

Power Electronics is a field which combines Electric Power, Electronics and Control
What does Power Electronics do ?

Efficient, flexible control and conversion of electrical energy

Rectification
AC sources: single AC DC DC loads : heater, lamp, DC motor
phase or three phase AC DC sources : batteries, solar panel,
DC to DC
Conversion power supply

AC to AC
Conversion
AC loads: machines, power DC loads : electronic circuits,
transmission and distribution AC DC machines
systems Inversion
Power Electronic Switching Devices

1. Uncontrolled turn on and off (Power Diode)

2. Controlled turn on uncontrolled turn off (Thyristors)
3. Controlled turn on and off characteristic (Power Transistor, BJT,
MOSFET, GTO, IGBT)
4. Continuous gate signal requirement (BJT, MOSFET, IGBT)
5. Pulse gate requirement (SCR(Silicon-Controlled Rectifier), GTO)
6. Bidirectional current capability (TRIAC)
7. Undirectional current capability (SCR, GTO, BJT, MOSFET,
IGBT)
 Power Electronic Applications

 Commercial/Industrial Applications
Heating Systems Ventilating, Air Conditioners, Central Refrigeration, Lighting, Computers and
Office equipment, Uninterruptible Power Supplies (UPS), Elevators, and Emergency Lamps.

 Domestic Applications
Cooking Equipment, Lighting, Heating, Air Conditioners, Refrigerators & Freezers, Personal
Computers, Entertainment Equipment, UPS
 Power Electronic Applications
 Aerospace Applications
Space shuttle power supply systems, satellite power systems, aircraft power systems.

 Telecommunications
Battery chargers, power supplies (DC and UPS), mobile cell phone battery chargers.

 Transportation
Traction control of electric vehicles, battery chargers for electric vehicles, electric locomotives,
street cars, trolley buses, automobile electronics including engine controls.
An Overview of Module Content
(Sem 1)

 Power Semiconductor Devices

 Power Transistors
 Thyristors
 Losses and efficiency
 DC to DC Converters
 Controlled and Uncontrolled AC to DC Converters
 Inverters (DC to AC Converters)
 An Overview of Module Content
(Sem 1)
 Reading list
Main Text Book: Power Electronics, M. Rashid
Optional Text Book: Fundamentals of Power Electronics, R. Erickson
Why Power Electronics?

Coal Fuel Turbine Generator Transmission Load

-65% ME EE
100% 35% 16.5%

- Fossil fuel (Oil, natural gas and coal) still the most used energy source, >85%.
- In best scenarios, the fossil fuel energy sources will last for +150 years
- What will happen after 150 years ? We don’t know ……

But we can extend this period or even replace the traditional resources by:
1. Using it efficiently  Global warning still a problem
2. Improve the energy conversion efficiency
3. Promote more integrated renewable energy sources Role of Power Electronic circuits
Why Power Electronics?

Coal Fuel Turbine Generator Transmission Load

-65% ME EE
100% 35% 16.5%

6:1
Why do we spend
effort on the load
100kW 16.5kW side (i.e. Motor
efficiency) when
saving most of losses are
6kW 1kW
at front end ?
So it is necessary to have (6%)
higher efficiency drives,
chargers and circuits for the
loads …. Done by PE.
 Switches
Diodes, transistors, thyristors
Silicon, Silicon Carbide, GaN
Higher Efficiency

Topologies
Interleaving, switched capacitors, etc
Hard and soft switching
 POWER SEMICONDUCTOR DEVICES
The power semiconductor devices are used as on/off switches in power
control circuit. These devices are classified as follows.

Power Devices

Diodes Transistors Thyristors

General purpose BJT SCR

High speed MOSFET GTO

Schottky IGBT Triac

SITH
POWER SEMICONDUCTOR TOPOLOGIES
POWER SEMICONDUCTOR DEVICES
 transistor

1k ohm

P = (100m)2 * 1k = 10 W
PP==(100m)
(1)2 * 100
2 * 100
= 100
= 1WW
 Linear operation

Vs Vs

RL RL

ibQ
ibQ + +
VCE VCE
- Vb -
Vb
 100V
Vs Linear operation
+
100V VCE
RL VL
-
ibQ +
VCE
-
Vb
ib
 100V
Vs Linear operation
+ VL
100V VCE
RL VL
-
ibQ + 50V
VCE
-
Vb
ibQ ib
 𝟓𝟎
𝑰𝑪 = = 𝟏𝟎𝑨
𝟓

𝒕 𝑪𝑬 𝑪 100V
Vs Linear operation
𝒕

+ VL
100V
RL VL
-
ibQ + 50V
VCE
VCE
-
Vb
ibQ ib
What is the PWM ?
Voltage
Pulse Width Modulation ?

Average (mean) value

What is the PWM ?
V Pulse Width Modulation
Average (mean) value

50%
50% 50%

10%
90% 10%

80%
20% 80%
What is the PWM ?
V
Average (mean) value

50%
50% 50%

Duty Cycle
10%
90% 10%
It is the ON time
over the total
80%
duration time

20% 80%
 Vs Vs

RL RL

Vb Vb
 𝟓𝟎
𝑰𝑪 = = 𝟏𝟎𝑨
𝟓

𝒕 𝑪𝑬 𝑪 100V
Vs Linear operation
𝒕

+ VL
100V
RL VL
-
ibQ + 50V
VCE
VCE
-
Vb
ibQ ib
 100V
Vs Switched operation
+ VL
100V VCE
Average = 50V RL VL VL

-
t

+ 50V ib

VCE
t
-
Vb
ib
Dissipated power in transistor

Linear operation Switched operation

Vsw OFF ON

Isw

t
𝟓𝟎
𝑰𝑪 = = 𝟏𝟎𝑨 𝒕 𝑪𝑬 𝑪
𝟓

𝒕 𝑪𝑬 𝑪
ON state 𝒕

OFF state 𝒕
𝒕
𝒕
𝑻
𝒕 𝑪𝑬 𝑪
𝟎