Power Losses in Electrolytic Condensers

Electrolytic condensers on a-c. circuits have higher power losses than would be expected from the leakage currents and electrolyte resistances. Likewise, losses change with the applied voltage, with temperature of the cell, with the frequency of the applied voltage, and with external circuit conditions governing current wave shape in such ways that it is almost impossible to predict results in advance. The current wave usually contains large harmonics when a sine wave of voltage is impressed, indicating a non-linear function in the impedance of electrolytic condensers. Increases in voltage, frequency, electrolyte temperature, and concentration of the electrolyte cause increases in the harmonics in the current wave. Dielectric losses in an oxide film or a gas-oxide film are too low to account for the total losses in electrolytic condensers; and in general the losses in a polarization cell are higher than those found in electrolytic condensers. Polarized cells show some characteristics which are similar to the peculiarities of electrolytic condensers; a number of low-voltage condensers very closely approach the action of polarization cells. Electrolyte potentials of symmetrical condensers on a-c. circuits are lower than the theoretical values. These discrepancies can be accounted for only by a voltage distribution in the electrolyte. Controlling the potential from outside sources has small influence on power losses except for extreme values of potential. An equivalent circuit can be drawn for a condenser from the losses, the applied voltage, and the electrolyte potential.