A power supply rated at 12V 30A means it provides a constant output voltage of 12 volts and a maximum current of 30 amperes. Here's what this specification implies:
Voltage (V): The power supply provides a constant output voltage of 12 volts. Voltage is the electrical force that drives current (amperes) through a circuit. In this case, the voltage is 12 volts.
Current (A): The power supply can deliver a maximum current of 30 amperes. Amperes, often referred to as amps, measure the rate of flow of electric current. A current of 30A means it can deliver a significant amount of power to devices that require 12V input.