Using DFT to Obtain the Equivalent Circuit of Aluminum Electrolytic Capacitors

This paper presents an economic and automatic experimental technique that allows the determination of the equivalent circuit of aluminum electrolytic capacitors. To implement the proposed technique it is necessary to arrange experimentally the capacitor under test in series with a resistor and connected to a sinusoidal voltage. The relationship between gain and phase of the sinusoidal voltage waveform applied to both capacitor and resistor, and the gain and phase of capacitor voltage give enough information to compute the capacitors equivalent circuit. To obtain both gain and phase of both waveforms with high accuracy, the discrete Fourier transform algorithm is used.