Mitsubishi Electric PSSxxMC1Fx, Руководство пользователя

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< Dual-In-Line Package Intelligent Power Module >
Series Application note
Publication Date: September 2016
41
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
2
1
2
1 D D
+ −
～
(%/100), (D: modulation depth).
(4) Output current various with Icp · sinx and it does not include ripple.
(5) Power factor of load output current is cos
θ
, ideal inductive load is used for switching.
● Expressions Derivation
PWM signal duty is a function of phase angle x as
2
x sin D 1
× +
which is equivalent to the output voltage
variation. From the power factor cos
θ
, the output current and its corresponding PWM duty at any phase angle
x can be obtained as below:
2
) sin( 1
sin
θ
+ × +
=
× =
x D
Duty PWM
x Icp current Output
Then, V
CE(sat)
and V
EC
at the phase
x
can be calculated by using a linear approximation:
) sin )(@ ( ) ( x Icp sat Vce sat Vce
× =
) sin ) ( (@ ) 1 ( x Icp Iecp Vec Vec
× = × − =
Thus, the static loss of IGBT is given by:
dx
x D
x Icp sat Vce x Icp
•
+ +
× × × ×
∫
2
) sin( 1
) sin )(@ ( ) sin (
2
1
0
θ
π
π
Similarly, the static loss of free-wheeling diode is given by:
∫
•
+ +
× × × − × × −
π
π
θ
π
2
2
) sin( 1
) sin (@ ) 1 )(( sin ) 1 ((
2
1
dx
x D
x Icp Vec x Icp
On the other hand, the dynamic loss of IGBT, which does not depend on PWM duty, is given by:
dx fc x Icp off Psw x Icp on Psw
• × × + ×
∫
π
π
0
)) sin )(@ ( ) sin )(@ ( (
2
1