Transformer
A transformer is a passive electrical device that transfers electrical energy from one alternating current (AC) circuit to one or more other circuits, either increasing (step-up) or decreasing (step-down) the voltage. It operates on the principle of electromagnetic induction.
Key Points About Transformers
Basic Operation:
- Primary Coil: When an alternating current flows through the primary coil (the winding connected to the power source), it creates an alternating magnetic field around the transformer's core.
- Core: The core, typically made of laminated soft iron, concentrates and guides this magnetic field.
- Secondary Coil: The alternating magnetic field passing through the core induces an alternating voltage in the secondary coil (the winding connected to the load).
- Voltage Transformation: The ratio between the number of turns in the primary coil (N₁) and the secondary coil (N₂) determines the voltage change:
- Step-up transformer: If the secondary coil has more turns than the primary, the output voltage is higher than the input voltage.
- Step-down transformer: If the secondary coil has fewer turns than the primary, the output voltage is lower than the input voltage.
Key Characteristics:
✔ Works only with AC: A varying magnetic field is required for induction. Direct current (DC) produces a constant magnetic field and thus cannot induce voltage in the secondary coil.
✔ Passive device: It does not generate electrical energy but transfers and transforms it.
✔ No direct electrical contact: Energy is transferred via the magnetic field, providing galvanic isolation between primary and secondary circuits.
✔ Power conservation (ideally): Input power (voltage × current) equals output power (neglecting losses). Thus, if voltage increases, current decreases, and vice versa.
Common Applications:
- Electric power distribution: Essential for transmitting electricity over long distances at high voltages (to minimize losses) and stepping it down to safe levels for household and industrial use.
- Powering electronic devices: Many electronics use transformers to reduce mains voltage (e.g., 230V or 120V) to the required internal circuit voltage (e.g., 12V, 5V).
- Galvanic isolation: Used to electrically separate two circuits, preventing electric shocks or ground loops.
- Impedance matching: In audio and communication circuits, transformers match impedance between stages to maximize signal transfer.
Transformer Types
| Type | Function | Example Use |
|---|
| Step-up | Increases voltage | Power plants → High-voltage transmission |
| Step-down | Decreases voltage | Substations → Household (230V/120V) |
| Isolation | Provides electrical separation | Medical equipment, lab instruments |
| Autotransformer | Single winding with taps | Voltage adjustment in industrial equipment |
Efficiency & Losses
Transformers are highly efficient (typically 95–99%), but losses occur due to:
- Copper losses (I²R heating in windings)
- Iron losses (eddy currents & hysteresis in the core)
- Leakage flux (magnetic field not linking both coils)
See other components: