A power offer is applied to cut back mains or three phase electric power, normally at 240 Vac or 440 Vac right down to a voltage that is usable, like 12 Vdc. The PSU also converts The existing ranking, in the form of AMPS, to the degree that is Safe https://simonqdpzk.blogminds.com/helping-the-others-realize-the-advantages-of-power-supplies-repair-27746667