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Gabster 11th April 2002 01:01 AM

Real "cool" R-Theta heatsink simulation
Hi folks,

I'm experimenting R-theta's heatsink simulator. It looks very poweful, but I would like to have the seal of approval on my simulation from forum's elders.

- My chassis design (see it here) provides a 4"x5" heatsink (R-Theta extrusion# 66414...this is actually what I'm planing to buy) for each IRFP244 FET (Aleph2). Therefore, I've set up 25W of heat to dissipate per heatsink (300W overall...12 FETs).
- From IR's datasheets I've found out that the max. junction thermal resistance is 0.83 for the IRFP244
- I've use generic grease for the simluation, Rimp = 0.1 as suggested by the simulator

You can see the output below. Temperature elevation seems not too bad...this is in fact why I'm doubting and asking your advice.

best regards,

Gabster 11th April 2002 01:02 AM

2 Attachment(s)
Here's the result:

Gabster 12th April 2002 12:17 AM

I forgot to mention that the ambient temperature is 20C

AudioFreak 12th April 2002 12:39 AM

it doesn't look like you've accounted for the electrical insulator ....

Gabster 12th April 2002 12:49 AM

How do I do that?

AudioFreak 12th April 2002 02:41 AM

You could just increase Rimp to about 0.75degrees/W

Edwin Dorre 12th April 2002 11:28 AM


I am building a Aleph 4 myself. How can you reach the r-theta simulator. I tried something, but I cannot find anything on their website!

I am going to use 5 times a 80mm x 80mm x 150mm heatsink of 0.5 C/W which gives me about 3 * 21 = 63 * 0.50 = 31 C/W ...


Edwin Dorre 12th April 2002 11:29 AM

Did any one look at the Fischer Elektronik SKE 6 400 19" case?



Gabster 12th April 2002 02:20 PM

Edwin, website is You can find the simulator in R-tools section. The simulator only works with netscape and some older IE version.

AudioFreak, having the Rimp increased at 0.75 doesn't change the temperature range. The only error I would see is a unit error. There're talking about "Cin^2/W" for Rimp and you're saying "/W". What is a "Cin^2/W"?


AudioFreak 12th April 2002 02:31 PM

it should increase the die temp....

Cin^2/W i think is C x area in square inches / Watts

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