FAA Powerplant Written Practice Test

What is the total rated output when more than one generator is used in parallel?

1. The output of the weakest generator

2. The combined output of all generators

3. Only the first generator's output is considered

4. No output is generated

The correct answer is: The combined output of all generators

When generators are used in parallel, the total rated output is the combined output of all generators. This occurs because each generator contributes to the overall electrical load, and their outputs can be added together as long as they are synchronized correctly. Parallel operation allows for redundancy and can improve reliability, as the loss of one generator does not eliminate the entire output; the remaining generators can continue supplying power. In parallel operation, each generator should be of a compatible design and matched in voltage, frequency, and phase to ensure proper load sharing. If each generator is rated for a specific output, say 100 kW each, two generators can theoretically provide a total output of 200 kW when running together, assuming they are properly engaged with the load. The other options provide incorrect interpretations of how parallel generators function. The option that suggests limiting output to the weakest generator does not apply in the context of total rated output, as this could imply only one generator's contribution without considering the additional capacity of others involved. The option stating that only the first generator's output is considered disregards the functionality of parallel systems altogether, while claiming no output is generated misrepresents the nature of how multiple generators work together to provide power.