Power Resistor -need document that describes the calcultion

[ballimo]

resistor rth

Hello,

I want to dissipate power using Power Resistors. I found that the maximum power dissipated depend on the thermal resistance of the heat sink used.
did any one have a detailed application note or any document that describe the calcultion?

Thanks in advance,

Ballimo

 

[IanP]

Re: Power Resistor

**broken link removed**

rgds,
ianp

 

[eem2am]

Power Resistor

you just get the thermal resistance of the resistor Rth(Res).
Then you get the thermal resisrtance of the heetsink Rth(HS)

You then get the power dissipated in the resistor
P(res)

And....

Get the ambient temp T(amb)

[T(res) - T(Amb) / P(res) ] = Rth(Res) + Rth(HS)

 

[brumi]

Re: Power Resistor

You could use liquid cooling for the resisitors for large power disipation.
Be carefull if you are working with radio frequency.
Working frequency ?
Power to disipate ? Voltage - Intensity

 

[ballimo]

Re: Power Resistor

Thank you for you Help,

I'am not working with radio frequency, but My problem is that I have a huge power to disipate, I found a 50 w resistor(nominal) from Bournus, but with a TO 220 heetsink the Max power disipated in a resistro is small. liquid cooling is expensive, for this reason it is better to use a Fan; did anyone have a document or any information about using Fan for large power disipation?

 

[FvM]

Power Resistor

If you're referring to heatsinks, the manufacturers usually specify the thermal resistance as a function of air velocity, so you are basically able to perform a calculation. Considering various geometry options, an empirical test is possibly easier.