I have a sealed metal enclosure of size 20inches x 13 inches x12 inches.


A 500W isolated transformer with about half the load producing constant 51 Celsius will be put inside.


How do you compute for the temperature increase inside the enclosure? Ambient temperature outside is 36 Celsius.

Can the transformer survive it?

  • 1
    Need some more info on the transformer. The 51.6C surface temperature of the transformer isn't really what you need, what you need is the energy consumed by the transformer - not the load, the transformer itself. You'd also need to provide the transformer's operating temperature range. – batsplatsterson Oct 26 '18 at 11:10
  • Operating range of the transformer is -40C to +40C. How do you know or compute the energy consumed by the transformer? – Samzun Oct 26 '18 at 11:55
  • You'd go by the efficiency of the transformer, say the efficiency is 93%, with a 500w load, that comes to 537w consumed, 37w will go to heat. With an ambient temp of 36*C, there's no way. – batsplatsterson Oct 26 '18 at 12:02
  • What is the formula that relates 37w with 36*C or how do you convert 37w to heat? Also I'd like to know the temperature of air inside the enclosure.. 36*C is the temperature outside the enclosure. – Samzun Oct 26 '18 at 12:17
  • Here is the spec sheet of it. farnell.com/datasheets/… the efficiency is 96%. With a 250w load, it's 260w consumed. Can mere 10w produce consant heat of 51 Celsius at the surface? If not, where does the heat come from? I'd like to know what will be the temperature of the air inside the sealed enclosure mentioned above if it will release the heat by convection to the air and wall, etc. given an outside ambient temperature of say 33 Celsius. – Samzun Oct 26 '18 at 12:58

Even with what seems like a small amount of heat generated in the enclosure by the transformer, with no ventilation, and an ambient temperature not far below the operating temperature of the transformer, it will overheat pretty quick.

You can ventilate the cabinet with a cooling fan, you can even do calculations to figure out how much air the fan must move. Alternately, you could mount the transformer on the outside of the cabinet, where the heat can dissipate. However, these may be an issue in a corrosive environment or other conditions where the components must be kept sealed up.

If the cabinet must be sealed from the environment (due to presence of corrosive agents, etc.) there are cooling systems that cool the interior of the enclosure without exchanging outside air, but these are expensive and elaborate.

  • I will no longer put the transformer inside sealed enclosure.. but put it outside exposed to natural air. However in my country, the temperature can reach over 40 Celsius during summer. And indoor it can reach up to 45 C. Let's say the transformer has operating temperature of between -40 C to 40 C. Do you think the surface of the transformer can increase in temperature from 51 C to maybe 55 C? I know one must know the energy consumed by the transformer.. but the surface temperature is one indicator of the temperature inside the core of the transformer. – Samzun Oct 27 '18 at 22:13
  • If the ambient temperature exceeds the operating temperature range the manufacturer specifies, unfortunately you may expect problems. It might break down quickly, it might just take some time of the normal service life of the device. It may turn out that the manufacturer's recommendation is conservative and it functions fine. – batsplatsterson Oct 28 '18 at 1:47
  • If there is no load, and the efficiency of the transformer is 96% and it is 500w capacity.. what wattage would be the heat loss from the iron core resistance and primary winding resistance? Is it really 4w? If not. What is your estimate? Any formula to compute it. The transformer heats even with zero load. – Samzun Oct 28 '18 at 3:09
  • By the way.. I made a new post out of it see: electronics.stackexchange.com/questions/403815/… – Samzun Oct 29 '18 at 7:51

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