THE ALUMINUM ELECTROLYTIC CONDENSER 



59 



It will be noted that the capacities of the condensers decrease with 

 increasing frequency. While there is a slight decrease in the unit- 

 area capacity of films that accompanies a rise of frequency ^ this 

 drooping characteristic is due principally to the corrugated shape of 

 the plates on which the film is formed. The resistance through the 

 electrolyte from the negative electrode to the film at the mouth of a 

 "U" shaped corrugation, is less than that to the portion of the film 

 at the bottom of the "U." 



Thus, as the frequency increases, the alternating-current density 

 at the mouth of the corrugations increases, while that in the trough 

 decreases, resulting in a decrease of the effective capacity of the 

 unit. The change in capacity due to frequency is greater in con- 



20 



30 40 10 20 



TEMPERATURE-DEGREES CENTIGRADE 



Fig. 14- 



-Effect^of temperature upon capacity and equivalent series resistance of 

 24- volt and 48-volt condensers at 1,000 cycles 



densers with high-resistance electrolytes, and is more pronounced in 

 the case of low-voltage films. The series resistance of the condensers 

 is also observed to fall quite rapidly as the frequency is increased. 

 This is due to the inverse proportionality between frequency and the 

 component of the total condenser resistance, representing dielectric 

 loss. 



Since the change in capacity with frequency is caused by the 

 difference at the crest and in the trough of the corrugations of the 

 ratios of unit-area capacity to associated electrolyte resistance, changes 

 in electrolyte resistance, caused by variations in temperatures, also 

 influence the effective capacity of the cells. 



The temperature effect is particularly noticeable at high frequencies, 

 ^ De Bruyne and Sanderson, Trans. Faraday Soc, 23, 42 (1927). 



