A turbine that operates at variable speeds uses ___________.

• A. An Synchronous Generator
• B. An Asynchronous Generator
• C. A DC Generator
• D. A Wound-Rotor Generator

Answer: (B)

Variable-speed operation needs a generator that can work effectively even as rotor speed changes. An asynchronous generator fits this need because it operates with slip between the rotor and stator and does not require a fixed, synchronous speed to produce power. When the turbine speed varies, the rotor speed shifts relative to the stator, yet power continues to be generated, with frequency managed by the grid connection or power electronics in configurations like doubly-fed induction generators. This makes asynchronous generators the practical choice for variable-speed turbines. Synchronous generators, by contrast, are tied to a constant speed to keep the output frequency steady, a DC generator isn’t used for large wind-turbine scale, and a wound-rotor generator is a type of induction machine but the broader, standard solution for variable speed is the asynchronous generator.