Why does a separately excited generator maintain constant voltage delivery?

A separately excited generator maintains constant voltage delivery primarily because its design allows for the field current to be kept constant, regardless of variations in output load. In a separately excited generator, the field winding is powered by an independent source, which ensures that, under normal operating conditions, the excitation remains stable even if the load on the generator varies.

This stable excitation directly contributes to maintaining a consistent terminal voltage. When the field current is constant, the magnetic field strength remains stable, which enables the generator to produce a predictable and steady output voltage. Variations in load do not significantly impact the output voltage because the excitation system is not dependent on the generator's output current, unlike self-excited generators where changes in load can lead to corresponding fluctuations in voltage output.

While other factors such as the ability to adjust excitation dynamically for load variations can be aspects of generator operation, the fundamental design feature that promotes voltage stability in a separately excited generator is its capacity to maintain a constant field current. This ensures a steady voltage delivery irrespective of changes in generator demand.