The main disadvantage of a separately excited generator is that it requires a separate power source to excite the field winding. This means that the generator cannot produce any electrical power until the field winding is excited, which can be a time-consuming and costly process. Additionally, if the excitation power source fails, the generator will not be able to produce any electrical power. This makes the separately excited generator less reliable than other types of generators that do not require a separate power source for excitation.
