This tool calculates the heat dissipated in a capacitor. Every capacitor has a finite amount of series resistance associated with it. This results in heat dissipation.
The resulting temperature rise can be calculated by entering:
- Power dissipated Pd (mW)
- Heat Conductivity G (mW/oC)
G, the heat conductivity is the inverse of ϴ, the thermal resistance with units oC/W (or oC/mW).
Pd can be calculated using the capacitor power dissipation calculator.
If the power dissipated is 1500 mW and the conductivity is 90 mW/oC, then the rise in temperature is calculated to be 16.7 oC.
ΔT is added to the ambient temperature to calculate the operating temperature of the capacitor. This number can be used to determine if the input voltage exceeds the voltage rating of the cap.
Do Capacitors Get Hot?
Yes, depending on the power dissipated (which in turn depends on the Equivalent Series Resistance ESR and the current through it) the capacitor can get hot. In the example above the temperature rise is 16.7 oC. The temperature of cap is given by
TC = TAmb + ΔT
Where TAmb is the ambient temperature.
For TAmb = 25oC, the capacitor’s temperature TC = 25 + 16.7 = 41.7 oC which can feel quite warm to the touch. As the cap’s ESR increases, the dissipated power and therefore the temperature increase.
- Capacitor Dissipation Factor. Calculates the Dissipation Factor – a measure of a capacitor’s dielectric losses
- Capacitor Q Factor. Where Q stands for Quality Factor
 Thermal Resistance on Wikipedia