Mehrphasenströme

Mehrphasenströme, also known as polyphase currents, are electrical currents in which multiple alternating currents with time-shifted phase relationships are generated and transmitted. The most common form is the three-phase system, which utilizes three alternating currents that are offset from each other by 120 degrees. This phase difference is crucial for efficient power generation, transmission, and utilization.

The generation of mehrphasenströme typically occurs in alternators, where multiple windings are arranged around a stator, and a rotating magnetic field induces voltages in each winding. The spatial arrangement of these windings dictates the phase shift between the generated currents. In a three-phase system, three such voltages are produced, each with the same frequency and amplitude but differing in their instantaneous phase.

Mehrphasenströme offer significant advantages over single-phase systems. Their primary benefit lies in their efficiency for power transmission. Three-phase transmission lines can carry more power for the same amount of conductor material compared to single-phase lines. Furthermore, the constant power delivery of a balanced three-phase system leads to smoother operation of machinery and a reduced tendency for vibrations.

In industry, three-phase power is the standard for driving electric motors, as these motors are inherently more efficient and simpler in construction when designed for three-phase operation. They can achieve self-starting without the need for auxiliary starting mechanisms often required in single-phase motors. The ability to easily change the direction of rotation of a three-phase motor by simply interchanging any two of the phase connections is another practical advantage. While three-phase systems are predominant in industrial and commercial applications, single-phase power is generally sufficient for most residential power needs.