1. DC exciter excitation system is mostly used for small and medium-sized units before the 1970s.
2. The AC exciter-stationary rectifier excitation system with the coaxial co-exciter of the generator ("three-machine" excitation system) is mostly used for large thermal power units of more than 100MW after the 1960s.
3. AC Exciter-Rotary Rectifier Excitation System with Coaxial Exciter with Generator ("Brushless" Excitation System) For large, medium and small units (less usage) after the 1980s.
4. Static thyristor self-excited magnetic system ("self-excited" excitation system) is mostly used in hydropower units after the 1970s, and large and medium-sized thermal power units after the 1990s. It is a high-quality excitation system.