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SMPS temperature operating range consideration

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dark

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Hi All,

I have a big SMPS (Output 48V at 80Amps) which is rated for 50C ambient operating and 65C storage. I need this to operate at 65C or little above ,at the moment I am planing to increase the rating of sink and apply fan over it as it is openframe and fanless .It has capacitors rated 85C ,what other components will you suggest to look for and replace in order to increase its operating range
 
What temperature is the air that the fan will be blowing into the SMPS?

If it has no fan, blowing cool air through it will increase its heat dissipation rating by a factor of two or three. I would put a thermocouple inside the enclosure and load it to its rating. Then begin blowing air through it while watching the temp. You might be able to put a thermostat to turn on the fan only when needed...
 
The fan would blow ambient air about 2degC to 50degC (climatic changes) .

Thanks
 
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So what is the meaning of this statement: "I need this to operate at 65C or little above"?
 
So what is the meaning of this statement: "I need this to operate at 65C or little above"?

It means Ambient temperature of 65C . There are chances where the Ambient operating temp might rise to 65C or above due to closed locations.
 
So then the fan could be blowing ambient air as hot as 65C, not 50C as you previously stated?

But as MikeMl noted, a fan would likely keep the module temperature acceptable, even at an ambient of 65C.
 
Thanks for the replies, I will make a thermal fan actuator circuit now, should I mount thermistor on the sink or just on the PCB ?. What amount of air flow rate is required for such high dissipation? (I know that would require emperical data but what is a starting guess). The modules dimensions are L=280mm x B=220mm , with sink in the center running 160mm length wise ,height 70mm and mounting MOSFETS on either side .
 
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