Power Loss And Thermal Dissipation Calculation; Power Loss Calculation - Mitsubishi Electric PSSxxMC1Fx Manual

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DIPIPM+ Series Application note

3.2 Power loss and thermal dissipation calculation

3.2.1 Power loss calculation

Simple expressions for calculating average power loss are given as follows;
● Scope
The power loss calculation intends to provide users a way of selecting a matched power device for their
VVVF inverter application. However, it is not expected to use for limit thermal dissipation design.
● Assumptions
(1) PWM controlled VVVF inverter with sinusoidal output;
(2) PWM signals are generated by the comparison of sine waveform and triangular waveform.
(3) Duty amplitude of PWM signals varies between
(4) Output current various with Icp·sinx and it does not include ripple.
(5) Power factor of load output current is cosθ, ideal inductive load is used for switching.
● Expressions Derivation
PWM signal duty is a function of phase angle x as
variation. From the power factor cosθ, the output current and its corresponding PWM duty at any phase angle
x can be obtained as below:
Then, V and V
CE(sat)
Thus, the static loss of IGBT is given by:
Similarly, the static loss of free-wheeling diode is given by:
On the other hand, the dynamic loss of IGBT, which does not depend on PWM duty, is given by:
Publication Date: September 2016
= ×
Output current Icp
+ ×
1 D
=
PWM Duty
at the phase x can be calculated by using a linear approximation:
EC
=
Vce ( sat ) Vce ( sat )(@
= − ×
Vec ( ) 1 Vec (@ Iecp
π
1
∫
× ×
( Icp sin x ) Vce ( sat
π
2
0
π
1
∫ 2
− × ×
(( ) 1 Icp sin x )((
π
π
2
π
1
∫
×
( Psw ( on )(@ Icp sin
π
2
0
− +
1 D 1 D
～
2 2
+ ×
1 D sin x
2
sin x
θ
+
sin( x )
2
×
Icp sin x )
= ×
( Icp ) sin x )
+
1 D sin(
× ×
)(@ Icp sin x )
− × ×
) 1 Vec (@ Icp sin x
+ ×
x ) Psw ( off )(@ Icp
41
(%/100), (D: modulation depth).
which is equivalent to the output voltage
θ
+
x )
•
dx
2
θ
+ +
1 D sin( x )
× •
) dx
2
× •
sin x )) fc dx