transform

To transform is to use a transformer to alter the voltage and current characteristics of an alternating electrical signal. A transformer does this through electromagnetic induction: a changing magnetic field in one coil induces a voltage in a second coil. The ratio of turns between the primary and secondary coils determines the output voltage. A step-up transformer increases voltage and decreases current; a step-down transformer does the opposite. The power (measured in watts or kilovoltamps) remains nearly constant between coils, accounting for losses.

Industrial transformers range from small control transformers handling a few hundred watts to large power transformers rated in the hundreds of megavoltamperes. A 3-phase power transformer at a substation might transform 138 kV to 13.8 kV for distribution to a factory. A single-phase control transformer might reduce 480 V to 120 V for logic circuits and indicator lights. Core materials vary: laminated steel sheet for low-frequency work, ferrite for higher frequencies, and air cores for specialized applications.

Efficiency and failure modes

Ideal transformers have no losses, but real units experience core loss (hysteresis and eddy current loss in the magnetic material) and copper loss (resistive heating in the windings). Efficiency typically ranges from 95 percent in small units to 99 percent in large, well-designed power transformers. Transformers fail when insulation breaks down from age, overheating, or overvoltage; when windings short due to mechanical damage or moisture; or when the core saturates from DC bias or extreme overcurrent.

The verb transform is also used more broadly in electrical work to describe any conversion of voltage or current characteristics, even when the underlying device is not strictly a transformer. In power electronics, rectifiers and inverters also transform AC to DC or vice versa, though the mechanism differs. Within transformer-specific contexts, the term is precise and unambiguous.