Electrical transformers are used to transform voltage from one level to another, usually from a higher voltage to a lower voltage. Electrical transformer is a passive device, which transforms alternating current from one circuit into another through electromagnetic induction. An electrical transformer normally consists of a ferromagnetic core and two or more coils called windings. A changing current in the primary winding creates an alternating magnetic field in the core. In turn, the core multiplies this field and couples the most of the flux through the secondary transformer windings. This in turn induces alternating voltage in each of the secondary coils. Electrical transformers can be configured as either a single-phase or a three-phase configuration. An electrical transformer may provide more than one secondary voltage value. The rated power is the sum of the VA (volts x amps) for all of the secondary windings. Output choices include AC or DC.