A generator works by converting mechanical energy into electrical energy. It is typically driven by a steam turbine, water turbine, or internal combustion engine. Generators are broadly classified into DC generators and AC generators, with AC generators further divided into synchronous generators and asynchronous generators.
The most commonly used generator in modern power plants is the synchronous generator. Excited by direct current, it can provide both active and reactive power to meet the needs of various loads. The asynchronous generator, on the other hand, does not have an independent excitation winding; its structure is simple and easy to operate, but it cannot provide reactive power to the load.
For this reason, asynchronous AC generators must be connected in parallel with other synchronous generators or with a considerable number of capacitors during operation. DC generators have commutators, are complex in structure, more expensive, prone to failure, difficult to maintain, and less efficient than AC generators. Therefore, since the 1950s, AC generators have gradually been replaced by DC generators that obtain AC power through power semiconductor rectification.
