To limit voltage and prevent damage when the rotor DC excitation current is removed in an alternator, what component can be included in the circuit?

The inclusion of a field discharge resistor in the circuit serves to limit the voltage and protect the alternator when the rotor DC excitation current is removed. When the excitation is lost, the magnetic field collapses, which can lead to high voltage spikes or overvoltage conditions due to the stored energy in the rotor inductance.

The field discharge resistor effectively provides a path for the induced current from the collapsing magnetic field, dissipating this energy as heat, thereby preventing damage to the alternator's windings and other connected components. This is crucial for maintaining the integrity of the alternator and ensuring safe operation.

While other components like a current transformer, voltage regulator, or load resistor play important roles in different aspects of alternator functioning and protection, they do not specifically address the issue of voltage control in the scenario of removing rotor DC excitation. A current transformer is useful for monitoring current levels, a voltage regulator maintains steady output voltage under varying loads, and a load resistor can help manage load conditions but does not directly protect against voltage spikes from excitation loss.