6.1. Separately Excited Generators:
(i) The separately excited generators are usually more expensive than self-excited generators as they require a separate source of supply. Consequently they are generally used where self-excited arc relatively unsatisfactory. These are used in Ward Leonard systems of speed control, because self-excitation would be unsuitable at lower voltages.
(ii) These generators are also used where quick and requisite response to control is important (since separate excitation gives a quicker and more precise response to the changes in the resistance of the field circuit).