123

Timeperiod todetermine the turn-onenergy

Turn-off energyE

off

•

Energy generated inside the IGBT during the turn-off of a single collector

current pulse. The time span t

Eoff

to determine E

off

starts at that moment where

U

CE

has risen to 10% of its nominal value and ends where I

C

has dropped to

2% of its nominal value. E

off

isdefined as:

dt )t(i)t(u

E

c

t

0

ce

off

Eoff

⋅

=

∫

In practiceE

off

is determinedwith adigital oscilloscope.With this u

CE

(t) and i

C

(t)

are traced. Subsequently themaths function is used to build the time integer of

the product of both traces. The maximum value of the integer then represents

the value of E

off

. Alternatively the mathematical analysis may be done on a

computer after exporting themeasured data.

Reverse recovery energyE

rec

•

Energy generated inside the diode during the diode turn-off. E

rec

is determined

by the time span beginningwhenU

R

has risen to 10% of its nominal value and

endingwhen I

RM

has dropped to 2%of its nominal value. E

rec

is definedas:

dt )t(i)t(u

E

F

t

0

R

rec

Erec

⋅

=

∫

In practice E

rec

is determinedwith a digital oscilloscope.With this u

R

(t) and i

F

(t)

are traced. Subsequently themaths function is used to build the time integer of

the product of both traces. The maximum value of the integer then represents

the value of E

rec

. Alternatively the mathematical analysis may be done on a

computer after exporting themeasured data.

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