A power source is utilised to lower mains or three stage electrical energy, typically at 240 Vac or 440 Vac down to a voltage which is usable, like 12 Vdc. The PSU also converts the current ranking, in the shape of AMPS, to some level that's Harmless with the system https://power-supplies-repair01099.bleepblogs.com/30599709/helping-the-others-realize-the-advantages-of-power-supplies-repair