Just to add DC commutator ripple can be reduced by a capacitor shunted across a say reduce interference on a radio receiver.
Very simply if the aircraft we are talking is large then the main alternator would be a generator providing an Alternating Current 115volts or 200volts (depending on wiring) at a constant frequency of 400Hz.
The provider of the D.C current is either the battery or the AC mentioned above converted to DC through a Transformer Rectifier Unit (TRU) this provides 28vdc to many of the control circuits amongst other devices.
The main feeder cables run into the main bus bars and through various relays to the consumers. These relays are usually pulled down by switches or solenoids etc by the control DC volts.
The Consumer of either the AC or DC supply will be earthed to a location on the airframe. They are usually grouped together in various locations in bars or terminal blocks, hopefully in a place where they do not corrode. Invariably they are not and do corrode and reap havoc lol..
Don't know if this helps but good luck.