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7/31/2019 Power Main

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Presented by:- priyatam kr. priyadarsiECE (3rd) yr


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contentsWhat is power electronicsHistory of power electronicsWhy power electronicsPower electronics devices

Power electronics equipment Application of power electronicsFuture of power electronics


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What is power electronicsPower electronics is a technology associated with efficient conversion or control of electrical power by power semiconductor devices

P.E


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History of power electronics 1783 : Concept of semiconductor (VOLTA) 1876: Selenium rectifier (SIEMENS)

1896 : Rectifier bridge circuit (POLLAK) 1948 : Invention of transistor 1953 : Silicon power diode

1957 : Thyristor (SCR) blocking voltagecapablityup to 2012: developed power electronicsdevices are IGBT ,GTO ,IGCT ;


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ThermalLife=200yr use=87%

nuclearLife=150yr

6%Othersuse 7%


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Power electronics devices

Power diode

Power transistor Silicon control rectifier

GtoIgct


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I d

V d V f

V r

A (Anode)

K (Cathode)

+V d _

I d

Diode: SymbolWhen diode is forward biased, it conducts current with asmall forward voltage (V f ) across it (0.2-3V)

When reversed (or blocking state), a negligibly small leakagecurrent (uA to mA) flows until the reverse breakdown occurs.

Diode should not be operated at reverse voltage greater thanV r

v-i characteristics


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Power transistorsCan be turned ONand OFF by relatively very small control signals.Operated in SATURATION and CUT-OFF modes only.

No linear region operation is allowed due to excessive power loss.In general, power transistors do not operate in latched mode.

Traditional devices: (BJT), ( MOSFET), (IGBT),


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Silicon control rectifier I a

V ak

V r I g=0 I g>0 I h I bo

V bo

v-i characteristicsIf the forward breakover voltage (V bo ) is exceeded, the SCR self -triggers into the conducting state.

The presence of gate current will reduce V bo .

Normal conditions for thyristors to turn on: the device is in forward blockingstate (i.e V ak is positive), a positive gate current (I g ) is applied at the gate

Once conducting, the anode current is latched. V ak collapses to normal forward volt-drop, typically 1.5-3V.

In reverse -biased mode, the SCR behaves like a diode.


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Gate turn off thyristor

Behave like normal thyristor, but can be turned off using gate signal

However turning off is difficult. Need very large reversegate current (normally 1/5 of anode current).Gate drive design is very difficult due to very largereverse gate current at turn off.Ratings: Highest power ratings switch: Voltage: V ak


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Integrated gate commutated thyristor

K (Cathode)

+V ak _

I a

I g

IGCT

Among the latest Power Switches. Conducts like normal thyristor (latching), but can be turned

off using gate signal, similar to IGBT turn off; 20V is

sufficent. Power switch is integrated with the gate-drive unit. Ratings:

Voltage: V ak


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Power Switches: Power Ratings

10Hz 1kHz 1MHz100kHz 10MHz

1kW

100kW

10kW

10MW

1MW

10MW

1GW

100W

MOSFET

IGBT

GTO/IGCT

Thyristor


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Circuit and equipments AC input DC output

DC input DC output

DC input AC output

Rectifier

chopper

inverter

Phase controler


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ApplicationUnintrruptable power supply (ups) forcomputerLighting (for low i/p voltage) like CFLLighting using electronic ballast boostefficiency of fluorescent lamp by 20% Active filter (if harmonics in power supply we need to filter them)

Variable speed compressor air-conditioningsystem: 30% savings compared tothermostat-controlled system.Telecommunication industry (SMPS)

HVDC transmission system

regulator

21


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Future of power electronics

Distributed power electronics


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Priyatam kumar priyadarsi

electronics & communication

3rd yr


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are always welcome

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