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