Will inrush PFET explode due to short term power peak dissipation

[treez]

Hello,

I have a PFET which is suffering the following power dissipation , but only at switch on.......

Power dissipation in TO220:
https://i45.tinypic.com/28s33gw.jpg


.....this PFET has no heatsink, will it explode?

..here is the circuit in which it is used...it is a current clamp, which limits inrush current at start up.

Current clamp
https://i50.tinypic.com/30vdwkj.jpg

PFET DATASHEET:
https://www.vishay.com/docs/91239/sihfp924.pdf

 

[FvM]

Vishay has a thermal SPICE model to calculate the dynamical junction temperature. https://www.vishay.com/docs/90137/irfp9240.pdf
AN609 is explaining the method https://www.vishay.com/docs/73554/73554.pdf

They have also a thermal simulation tool, but I didn't use it yet.

 

[emontllo]

According to the thermal impedance of the MOSFET (Fig. 11 - Maximum Effective Transient Thermal Impedance, Junction-to-Case) it will provably be damaged.
Rough fast estimation:
The thermal impedance according to Fig. 11 is 0.4 with duty of 0.2 and length of 20 ms (very rough approximate to your power figure). The steady state junction to air thermal resistance of the MOSFET may be approx 30 ºC/W. Consider initial ambient temperature of 20ºC. If the peak power is 50 W...
Tj = 20 + 30*0.4*50 = 620 ºC
While this is only an estimation and tools proposed by FvM are the best option, some kind of heatsink is needed here. Actually, since this is a unique very short pulse, you do not need a big heatsink with lots of cooling fins; a thick aluminum sheet may be enough. This may absorb peak thermal energy and dissipate it slowly afterwards.