derating curve การใช้

Derating curves are included in data sheets for such capacitors.
Some manufacturers may have quite different derating curves for their capacitors compared with the generic curves given in the picture at the right.
With an " infinite " heatsink, that is : when the case temperature is certain to be 25 degrees, the power rating is about 115W ( some manufacturers specify 117W ), but most applications ( and certainly when the ambient temperature is high ) a significantly lower power rating would be expected, as per the manufacturer's power derating curve.
As can be seen from the derating curve image for a hypothetical bipolar junction transistor, the device ( rated for 100 W at ) cannot be expected to dissipate anything more than about 40 W if the ambient temperature is such that the temperature at which the device's case will stabilise ( after thermal resistance between the device's case and the heat-sink; and the heat-sink and the ambient ( this includes the heat-sink's temp / watt rating-with lower values implying better cooling characteristics ).