A transformer is a basic device that converts electrical energy from one voltage level to another, thus enabling the transmission of energy. Consisting of two or more windings, the transformer is wound around a magnetic core. When AC voltage is applied to the primary winding, a magnetic field is created and this field induces energy into the secondary winding, thus voltage conversion takes place.

Working Principle
It is based on the principle of transferring electrical energy through magnetic induction. The AC voltage applied to the primary winding creates a flux in the magnetic field and this flux is induced into the secondary winding and voltage transformation is achieved.

Different Transformer Types and Usage Areas
1) Power Transformer:
- Transforms energy from high voltage to low voltage or vice versa.
- Used in electricity transmission lines and distribution systems.
2) Current Transformer (CT):
- Used for current measurement.
- Important in protection and measurement applications.
3) Voltage Transformer (PT):
- Used for voltage measurement and protection.
- Commonly found in high voltage systems.

Importance and Application Areas
Transformers provide safe and efficient transmission of electrical energy. They have important functions such as power factor correction, isolation and reduction of energy loss in energy systems. They are the cornerstone of modern electricity networks and play a critical role in delivering electrical power to users.