Wechselstroms
Wechselstroms, in English usually called alternating current (AC), describes an electric current whose magnitude and direction reverse periodically. In most power systems the voltage also alternates in a near-sinusoidal waveform. The frequency, measured in hertz (Hz), defines the rate of reversal: 50 Hz is standard in much of Europe, Africa, and Asia; 60 Hz is common in the Americas and parts of Oceania. The waveform is typically sinusoidal, though real systems include harmonics from nonlinear loads.
AC is advantageous for long-distance transmission because voltage can be transformed with transformers, reducing current and
Key elements of AC systems include transformers, transmission lines, and rotating electrical machines such as induction
Historically, polyphase AC development in the late 19th century, notably by Nikola Tesla and George Westinghouse,