Elevator Mechanic Practice Exam

The correct answer is that the exciter voltage comes from an alternator. In many electrical systems, particularly in generators and synchronous machines, an alternator is used to provide the necessary excitation voltage to control the magnetic field of the machine. This excitation is critical for maintaining the stability and output of the generator or motor.

Typically, the alternator converts mechanical energy into electrical energy, and part of this electrical output is used to supply the excitation current required for the rotor winding. This ensures the machine operates efficiently and effectively, enabling it to produce the required power output.

Other sources listed, such as a battery, generator, or transformer, do play important roles in electrical systems but are not primarily responsible for supplying the exciter voltage. For instance, while a battery can supply DC voltage and is sometimes used in smaller or specific applications, it is not the standard source for excitation in larger, alternating current machines. Generators can produce power, but in the context of exciter voltage, an alternator is the usual source that provides the necessary AC voltage for this purpose. Transformers, on the other hand, are used to adjust voltage levels for transmission and do not generate the excitation voltage needed for machine operation.