The transformers

A transformer is a device made of two or more inductors, one of which is powered by AC,
inducing an AC voltage across the second inductor. If the second inductor is connected to a
load, power will be electromagnetically coupled from the first inductor's power source to that
load.

The powered inductor in a transformer is called the primary winding. The unpowered inductor
in a transformer is called the secondary winding.

Total primary current in an unloaded transformer is called the exciting current, and is comprised of magnetizing current plus any additional current necessary to overcome core losses. It
is never perfectly sinusoidal in a real transformer, but may be made more so if the transformer
is designed and operated so that magnetic flux density is kept to a minimum.

Core flux induces a voltage in any coil wrapped around the core. The induces voltage(s) are
ideally in phase with the primary winding source voltage and share the same wave-shape.


Any current drawn through the secondary winding by a load will be "reflected" to the primary
winding and drawn from the voltage source, as if the source were directly powering a similar
load.