Which of the following scenarios would most likely necessitate the use of a variable frequency drive?

The situation that requires a variable frequency drive (VFD) is when there is a need to control motor speed for process requirements. A VFD allows for precise control over the frequency and voltage supplied to an electric motor, enabling it to operate at different speeds efficiently. This is particularly important in applications where the speed of the motor needs to be adjusted to match varying load conditions or operational demands, such as in conveyor systems, pumps, or fans.

Using a VFD not only improves efficiency but also enhances process control, allowing for smoother operation and increased reliability. In contrast, operating a motor at constant speed or using a single-phase motor does not utilize the capabilities of a VFD since these scenarios do not require frequency adjustments or speed modulation. Additionally, controlling motor wear during starting can often be accomplished through soft starters or other means that do not necessitate a variable frequency drive. Thus, the need for variable speed adjustment clearly highlights the importance of VFDs in modern motor control applications.