Alifás

Alifás, in electrical terminology, refers to a single-phase electrical power system. It describes a distribution or supply that uses a single alternating current waveform, typically carried by two conductors (live and neutral) with an optional protective earth. In some regions the supply is derived from a center-tapped transformer, delivering two live conductors that are 180 degrees apart, providing the equivalent of a split-phase system. The standard voltage and frequency vary by country, commonly around 230 V at 50 Hz or 120/240 V at 60 Hz.

The key characteristic of alifás is its sinusoidal voltage that changes over time, causing the instantaneous voltage and current to rise and fall together. This results in power that fluctuates with the cycle of the waveform. While single-phase power is adequate for many household and light commercial loads, the current must be higher to deliver the same power as a three-phase system, making long-distance transmission and large loads less efficient.

Common applications include residential lighting, household outlets, and small appliances. For motors and other heavy loads, single-phase motors often require starting mechanisms such as capacitors or shaded-pole designs to achieve rotation, and they typically have lower starting torque and efficiency compared with three-phase motors.

Advantages of alifás include simplicity and lower upfront wiring for small-scale use, while disadvantages cover limited ability to supply large powers, greater conductor losses for the same load, and potential voltage flicker on large or non-linear loads. It remains common for domestic power where three-phase distribution is not necessary. Standards and practices are governed by national electrical codes and international standards.