Functions of Transformers
1. Voltage Transformation
This is the primary function of a transformer. By using coils with different numbers of turns, it either increases (step-up transformer) or decreases (step-down transformer) the input AC voltage:
Step-up: For instance, electricity generated by power plants (around 10 kV) is stepped up to high voltages (e.g., 110 kV, 220 kV) via step-up transformers, reducing power loss during long-distance transmission (high-voltage transmission reduces current, with loss following the formula P=I2R).
Step-down: After high-voltage electricity is transmitted near users, it is gradually reduced to voltages suitable for domestic and industrial use (e.g., 220 V, 380 V) through step-down transformers.
2. Current Transformation
According to the electromagnetic induction principle that "voltage is proportional to the number of turns, and current is inversely proportional to the number of turns," when voltage increases, current decreases, and vice versa. For example, step-up transformers reduce transmission current to minimize losses, while industrial equipment (such as welding machines) may utilize transformers to obtain high currents.
3. Impedance Matching
In electronic circuits (e.g., audio systems, communication devices), transformers can adjust the load impedance to match the signal source impedance, maximizing energy transfer efficiency (e.g., small transformers in headphones).
4. Electrical Isolation
In some transformers (such as isolation transformers), the primary and secondary coils are not directly electrically connected; energy is transferred solely through the magnetic field. This isolates the electrical potentials of different circuits, ensuring safety in applications like medical equipment and laboratory power supplies.