 Hitachi IGBT Module Application Manual
5.5.1.1.2
Turn-ON Power Dissipation and Turn-OFF Power Dissipation
Supposing that the inverter phase output current rms value is I
0
, the output current peak value becomes
2 I
0
.
The average value of IGBT module turn-ON current and turn-OFF current is, according to Equation 19:
Equation 19:
I
ave
= (2/
Ï€
)
!
2I
0
Obtain the turn-OFF power dissipation and the turn-ON power dissipation for the above I
ave
(per pulse)
and specify them as E
ton
and E
toff
(Figure 34), respectively.
Figure 34. Switching Loss vs. Collector Current
Equations 20 and 21 can be used to calculate turn-ON power dissipation P
ton
and turn-OFF power
dissipation P
toff
as a function of carrier frequency
f
c
.
Equation 20:
Equation 21:
5.5.1.2
5.5.1.2.1
P
ton
= E
ton
!
f
c
/2
P
toff
= E
toff
!
f
c
/2
Power Dissipation in a Free-Wheeling Diode
Forward Power Dissipation
Equation 22 provides a means for calculating forward power dissipation in a free-wheeling
diode.
Ï€
Equation 22: P
f
= (1/2
Ï€
)
âˆ«
2 I
0
sin
Î¸
!
(a + b
0
2 I
0
sin
Î¸
)
!
[ (1- sin (
Î¸
-
Ï†
)) / 2 ] d
Î¸
2 I
0
- (
Ï€
/ 4 )
!
cos
Î¸
= {
2 I
0
/ ( 2
Ï€
)}
!
{ a + (
Ï€
/4 ) b
!
!
[ a + (8b/(3
Ï€
)
!
2 I
0
]}
Definitions:
I
0
a, b
cos
Ï†
Inverter phase output current rms value
Linear approximate curve value represented by
V
f
=a + bi
(refer to Figure 35)