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POWER ELECTRONICS LAB. EED

4. Draw the equivalent Circuit of IGBT.

5.    What arc on stałe conduction losses? How is it Iow in IGBT?

A high current Ls required to break the junctions in BJT. Tlus resulLs in On State conduction losses. 'Ute conduction losses in IGB T are proportional To duty cycle of the applied voltąge. By reducing Ute duty cycle conduction losses can be reduced.

6.    What is second breakdown phenonienon?

As Ute collector voltage drops in BJT there is an increase in collector Current and this substantially increase the power dissipation. This Dissipation Ls not uniformly spread over the entire volume of Ute device but is concenuated in highly localized regions where the local temperaturę may grow and forms tlte black spots. This causes tlte destruction of BJT. This is second breakdown.

7.    What is switching speed?

The time taken to tum on or tum off a power device is called switching Speed.

8.    Can we ohserve the transfer and collector characteristics of IGBT on CRO?

No. Because tlte waveform which is to be ohsenred on Ute CRO should vary witli respect to time otherwLse we can see only a straight linę on the CRO.

9.    What are merrts of IGBT?

'♦The drive Ls simple.

•Onstage losses are reduced.

•No commutation circuits are required.

•Gate has fuli controi.

•Switching frequencies are higher.

*lt has fiat temperaturę coefficient.

10.    What are demerits of ICiBT?

•They have static charge problems.

•They are very costly.

11.    What aretheapplkations of IGBT^łs?

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