In 1885 the ZBD model alternating-current transformer was invented by three Hungarian engineers: Ottó Bláthy, Miksa Déri and Károly Zipernowsky. (ZBD comes from the initials of their names). – Source Wikipedia
In the basement I have a shelf loaded with all sizes of transformers. These are electrical devices not the action toys. They are used to step voltage up or down as needed for electronic circuits. They are an essential part of our everyday life, mounted on telephone poles and the key part of the “wall warts” that charge our smart phones.
This is a fairly typical configuration of a full wave rectifier. The transformer on the left steps down the line voltage. That output which is alternating current is fed to the bridge rectifier in the middle of the photo. Normally that would be bolted to a heat sink since it gets quite warm. The blue can is an electrolytic capacitor which smooths out direct current from the rectifier.
I have kept this transformer for over 50 years because it is somewhat unusual. Transformers were used in tube amplifiers and radios to provide vacuum tube filament and plate voltages. Most of the time the filament voltage was 6.3 volts but this transformer is rated at 2.5 volts. Note that this was made in the Chicago. Note to the Brits (vacuum tube = valve)
The shape of the case gives away the construction of a transformer. The bulge surrounds the copper winding around the laminated steel. I’ve taken one apart to get the wire, a tedious task.
Each tap has a different voltage. You don’t get something for nothing, if you step up the voltage the current is less. Transformers are highly efficient for power transfer.
A isolation transformer is used in laboratory environments. It outputs line voltages but electrically it is unattached to the grid. It is very “quiet”.
A Jones Strip is attached to the transformer
This is one hefty unit