Hitachi IGBT Module Application Manual
5.5
Calculation of Power Dissipation
When an IGBT is used in a Variable-Voltage Variable-Frequency (VVVF) inverter circuit, a general
calculation of power dissipation can be estimated as shown below.
Note:All calculations are based on a premise that the output is a sine wave.
5.5.1 Power Losses Occurring in Dual-Pack IGBT Modules
Total power dissipation = 2
!
{Power dissipation in IGBT + Power dissipation in FWD}
IGBT power dissipation = Steady-state power dissipation ( P
on
)
+ Turn-ON power dissipation ( P
ton
)
+ Turn-OFF power dissipation ( P
toff
)
FWD power dissipation = Forward power dissipation ( P
f
) + Recovery power dissipation ( P
rr
)
5.5.1.1
5.5.1.1.1
IGBT Power Dissipation
Steady-state Power Dissipation
π
Equation 16:
P
on
= 1/2
π
∫
i
v
0
D dt;
( D: On-duty )
Equation 17:
D = (1 + sin
Θ
)/2
A real control value
D =
κ
(1 + sin
Θ
)/2
can be obtained by multiplying by the coefficient
of on-duty. In this case,
κ
= 1 is supposed.
The steady-state power dissipation can be obtained using Equation 18:
Equation 18:
P
on
={
2
I
0
/ ( 2
π
)}
!
{ a + (
π
/4 ) b
!
2
I
0
2
I
0
]
}
+ (
π
/4)
!
cos
φ
!
[ a +(8 b/(3
π
))
!
Definitions:
i
v
I
0
a, b
cos
φ
:
Collector current flowing to IGBT (instantaneous value)
Saturation voltage (instantaneous value)
Inverter phase output current rms value (equal to the IGBT current)
Linear approximate curve value represented by
V
CE
(sat)= a + bi
(Obtain it from the I
C
- V
CE
characteristics shown in Figure 33)
Load power factor
Figure 33.
I
C
vs. V
CE
Characteristic
32