kolmivaihejärjestelmis

Kolmivaihejärjestelmä, often translated as three-phase system, refers to an alternating current (AC) electrical power system that uses three conductors, each carrying a sinusoidal current. These currents are identical in frequency and amplitude but are out of phase with each other by 120 degrees. This phase difference is crucial for the efficient generation, transmission, and utilization of electrical power.

The primary advantage of a three-phase system is its ability to deliver a constant amount of power, unlike a single-phase system where the power fluctuates. This smoother power delivery makes it ideal for industrial applications and for powering large motors. Three-phase motors are generally simpler, more efficient, and more robust than their single-phase counterparts, requiring no special starting mechanisms.

In power generation, three-phase alternators are used. The rotating magnetic field within the alternator induces voltages in three sets of stationary windings, each offset by 120 degrees. This naturally produces the three-phase currents. For transmission, three-phase power allows for more efficient use of conductors. For the same amount of power transmitted, a three-phase system requires less copper than three separate single-phase systems.

At the distribution level, three-phase power is commonly used for industrial facilities and larger commercial buildings. Residential areas are typically supplied with single-phase power, which is derived from the three-phase grid. This is achieved by using one phase and a neutral conductor from the three-phase supply. The three-phase system is the standard for high-power electricity grids worldwide due to its inherent efficiency and versatility.