CWEA Electrical/Instrumentation (E/I) Level 3 Practice Test 2026 – Your All-in-One Guide to Mastering the Exam!

Unlock all questions

This demo includes only 20 questions. Upgrade to access hundreds of questions, flashcards, exam simulations, and disable ads.

Full question bankExam simulationsFlashcards

From $12.50Unlock all

Session length

1 / 20

What is an energy-saving mechanism of a VFD besides reducing pump speed?

A device that increases motor speed beyond rated maximum.

A device that allows motor speed to be varied by changing supply frequency and voltage.

A device that reduces energy consumption by soft starting and speed control.

A device that controls motor speed by varying supply frequency and voltage.

A VFD saves energy primarily by adjusting how fast the motor runs through changes in the electrical supply, specifically the frequency and the corresponding voltage. By lowering the frequency, the motor slows down; by adjusting the voltage to maintain a proper V/Hz ratio, it still delivers the needed torque without wasting energy. This lets the system operate close to what the load actually requires, which can cut power use significantly because, for pumps and fans, power consumption falls rapidly as speed is reduced.

So, the mechanism described as controlling motor speed by varying supply frequency and voltage captures the essential way a VFD enables energy savings beyond simply running at full speed. (Soft starting helps reduce inrush and mechanical stress, but the ongoing energy savings come from this precise speed control through frequency and voltage.)