Ripple Current (IR) Ripple current caused by the application of an alternating voltage waveform, will generate heat inside the capacitor. The power loss is given by: P=IR esr (Watts) Where: P=Power loss IR=Ripple current (Amps) The maximum power a capacitor can handle is dependent upon the style and surface area of the can, the thermal dissipation factor, and the permissible core temperature rise within the capacitor. Thus for a given capacitor a maximum continuous ripple current rating can be established. Capacitors have a maximum designed core temperature which is higher than the specified maximum ambient operating temperature for the component. At lower ambient temperatures higher ripple currents can be applied provided the maximum core temperature is not exceeded. Factors are given in the data sheets. Increased ripple currents are also possible at higher frequencies, since the e.s.r. is lower. Heat-sinking and forced air cooling will both aid heat transfer and thus allow higher ripple currents. Note, some additional heat is generated by the leakage current, but this is normally much less than that generated by the ripple current and so can be ignored. Since the ripple current raises the temperature of the capacitor, it has a significant effect on the operational life of the component. Further details are given under life-expectancy. back to top Temperature Range The maximum operating temperature or upper category temperature is the maximum temperature at which the capacitor is designed to operate continuously. Choice of foils, electrolyte and encapsulation materials ultimately determine this figure. The lower category temperature is the lowest temperature at which the capacitor is designed to operate continuously. The electrolyte resistivity and viscosity both increase at low temperatures causing loss of capacitance and increased e.s.r. back to top Climatic Category The Climatic Category, in accordance with IEC 68-1, is based upon three groups of digits which decode as follows: Where: LCT = Lower category temperature °C UCT = Upper category temperature °C DH = Damp heat test days (IEC 68) back to top