Certified Energy Manager Practice Exam 2025 - Free Energy Manager Practice Questions and Study Guide

The primary advantage of using variable frequency drives (VFDs) in motors is their capability to control motor speed, which directly leads to energy savings. By adjusting the frequency and voltage supplied to the motor, VFDs can match the motor's output more closely to the process demand, rather than running at full speed and wasting energy. This dynamic control is essential in applications where motor loads fluctuate, such as in fans, pumps, and compressors. Operating at lower speeds when full speed is not necessary can significantly reduce energy consumption, translating to lower operational costs.

While the other options mention benefits that could be associated with VFDs, they do not encapsulate the core advantage. For instance, while reducing motor noise might occur with smoother speed variations, it is not the primary reason for VFD implementation. Likewise, improvements in motor lifespan or installation cost comparisons do not highlight the fundamental energy efficiency and operational adaptability that VFDs bring to motor systems. Thus, the emphasis on controlled speed and energy savings positions option B as the most compelling reason for utilizing variable frequency drives in motor applications.