Step down power transformers are extremely popular with American expatriates who continue using American appliances, such as microwaves or vacuums, after moving to Europe or other foreign countries. However, step down transformers are most widely used in power transmission applications at power-generating stations to raise voltages with a corresponding decrease in current.
Very high voltages and low currents are used for long-distance transmission lines in order to reduce power losses; as a result, at the receiving end step-down transformers reduce the voltage and increase the current to the lower residential or industrial voltage levels. Materials used to construct the coil windings include copper, special steel alloys, chromium, nickel and aluminum, of which copper windings are the most efficient as well as being a little more costly.
Sizes of step down transformers range from large devices intended for use in electrical power systems, such as power plants, to much smaller units that are used in electronic equipment such as loudspeakers in radios, high fidelity equipment and television sets.
A step down transformer is comprised of two sets of coils or windings linked by a magnetic field. The core can be a ferrite compound or a laminated core wound with bare copper or enameled coils. The coils are primary and secondary and function as conductors. Although there is no connection between the two circuits, the coil windings are inductively linked.
The principal function of a step down transformer is to convert high voltage, low current power into low voltage, high current power. The conversion begins when the primary coil receives alternating current, or AC, voltage; this produces a varying magnetic field of voltage surrounding the conductor, and the magnetic field activates the secondary conductor coil. Once the voltage conversion is made, the energy is transferred to the load center and the electrical process continues from there.
The ratio of turns (also known as windings) in the primary coil to the number of turns in the secondary coil determines the magnitude of the voltage; in a step down transformer there will be fewer turns in its secondary coil than the primary. Even though there are fewer turns, the turns in the secondary coil are of a larger gauge wire than used in the primary coil in order to handle the increased current power that has been transferred to the secondary coil.
The voltage ratio between the windings of the primary and the secondary circuit mirrors the ratio of the number of windings. Correctly used, step down transformers can protect against safety hazards such as short-circuiting, blowing equipment or starting fires.