here you can see in a glance what we study in power electronics field

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“IN THE NAME OF ALLAH
THE MOST MERCIFULAND
THE MOST BENEFICIAL”

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POWER ELECTRONICS
Presented By:
Engr.Tafseer Ahmed
BS in Electrical (Electronics) Engineering
CIIT, Abbottabad
a.tafseer@gmail.com

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What is Power Electronics
Power electronics deals with the
applications of power semiconductor
devices such as Thyristor and transistors
for the conversion and control of electrical
energy at high power levels.

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Relationship of Power Electronics

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Elements of Power Electronics
• Analogue circuits
• Control Systems
• Power Systems
• Electronics Devices
• Electric Machines
• Numerical Simulation

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POWER ELECTRONICS MAIN AREAS
• As the technology for the power semiconductor devices and integrated
circuit develops, the potential for applications of power electronics become
wider. The power semiconductor devices or power electronic converter fall
generally into four categories :
• Thyristor Devices
• AC to DC Converter (Controlled Rectifier)
• DC to DC Converter (DC Chopper)
• AC to AC Converter (AC voltage regulator)
• DC to AC Converter (Inverter)

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Diagram Block of Converters

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• AC to DC Converters: An AC to DC converter circuit can convert AC
voltage into a DC voltage. The DC output voltage can be controlled by varying
the firing angle of the thyristors. The AC input voltage could be a single phase or
three phase.
• AC to AC Converters: This converters can convert from a fixed ac input voltage
into variable AC output voltage. The output voltage is controlled by varying firing
angle of TRIAC. These type converters are known as AC voltage regulators.
• DC to DC Converters : These converters can converte a fixed DC input voltage
into variable DC voltage or vice versa. The DC output voltage is controlled by
varying of duty cycle.
• DC to AC Converters: These converters can convert a constant DC input voltage
into a variable AC voltage with variable frequency.

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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.Undirectionalcurrent capability (SCR, GTO, BJT, MOSFET,
IGBT)
POWER ELECTRONIC SWITCHING
DEVICES

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COMMONLY USED DEVICES
• Power Diodes
• Power Transistors
• Thyristor Family
• SCR( Silicon Controlled Rectifier)
• SCS( Silicon controlled Switch)
• GTO( Gate Turnoff Thyristor )
• The DIAC
• The TRIAC
• MCT( The MOS-Controlled Thyristor)

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Devices Along with Symbols &
Characteristics

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Power Ratings of Devices

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Ratings of Power Devices

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Applications of Power Devices

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Control Characteristics of Devices

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Control Characteristics of Devices

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Uncontrolled Rectifiers (AC to DC)
( )
2 m
o average
V
V
π
=

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Controlled Rectifier( AC to DC)
• AC to DC Converters
-Single phase, half wave AC to DC converter
Input voltage
Output average voltage :
rms value of Output voltage :
Waveform of single-phase, half wave AC to DC converter α

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AC-DC Rectifier( Full Wave)

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( ) (1 cos )m
o
V
V average α
π
= +
1 sin 2
(( ) )
22
m
rms
V
V
α
π α
π
= − +

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AC-AC (Voltage Regulator)
1/2
( )
1 sin 2
22
m
o rms
V
V
α
π α
π
  
= − + ÷ 
  

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AC to DC Converters
Single phase, Full wave AC to DC converter
The average output voltage can be found from :

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AC to DC Converters
Three-phase, Half wave AC to DC converter
If the phase voltage is : van= Vm Sin(wt). The
average output voltage for a continuous load current is :

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AC to DC Converters
Three-phase, Full Wave AC to DC converter

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DC-DC CONVERTER (DC Chopper)
• In many industrial application , DC-DC converter is required to
convert a fixed-voltage DC source into a variable-voltage DC source.
Like a transformer, DC-DC converter can be used to step down or
step up a DC voltage source.
• Application :
Traction motor control in electric automobiles, trolley cars, marine
hoists, forklift trucks, mine haulers, etc
• Advantages :
High Efficiency and fast dynamic response

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DC-DC CONVERTER (DC Chopper)
Principle Of Step-Down Operation
When the switch SW is closed for a time t1, the input voltage Vs appears across
the load Vo = Vs. If the switch remains off a time t2, the voltage across the load is
zero, Vo= 0.
The converter switch SW can be implemented by using Transistor, MOSFET,
GTO, IGBT, BJT, etc.

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The average output voltage is given by :
The average output current is given by :
The rms output voltage is given by :
=
Where : T is the chopping period
k = t1/T is the duty cycle
f = 1/T is chopping frequency

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STEP UP DC to DC CONVERTER
When switch SW is closed for t1, the inductor current rises and energy is
stored in the inductor L. If the switch SW is opened for time t2, the energy
stored in the inductor is transferred to load through diode D1and the
inductor current falls.

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When this DC to DC converter is turned on “switch SW is closed, the
voltage across the inductor L is :
And this gives the peak-to-peak ripple current in inductor as
The average output voltage is :

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Buck – Boost Regulators
• Abuck–boostRegulatorprovidesanoutputvoltagethatmaybelessthanorgreaterthantheinputvoltage-hencethename"buck-boost";the
outputvoltagepolarityisoppositetothatoftheinputvoltage.thisregulatorisalsoknownasan invertingregulator.
• Thecircuitoperationcanbedividedintotwomodes.duringmode1,transistorQ1isturnedonanddiodeDmisreversedbiased.theinputcurrent,
whichrisesflowsthroughinductorLandtransistorQ1.Duringmode2,transistorQ1isswitchedoffandthecurrent,whichwasflowingthrough
inductorL,wouldflow throughL,C,Dm,andtheload.TheenergystoredininductorLwouldbetransferredtotheloadandtheinductorcurrent
wouldfalluntiltransistorQ1isswitchedonagaininthenextcycle.Theequivalentcircuitforthemodesareshowninthenextslide.

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DC-AC Converter (Inverter)
1( )
4
0.90
2
s
o rms fundamental S
V
V V
π
− = =

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Examples of
Some
Applications

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