Which statement describes the function of a VFD?

Which statement describes the function of a VFD?

• A. It Uses Only DC Input
• B. It Varies the Frequency and Voltage Supplied to the Motor
• C. It Converts AC to DC Only
• D. It Cannot Regulate Voltage

Answer: (B)

A Variable Frequency Drive controls motor speed by changing both the frequency of the output and the voltage delivered to the motor. By adjusting the output frequency, the motor speed varies; by shaping the voltage in step with that frequency (keeping a roughly constant V/Hz ratio), the drive preserves motor torque as speed changes. In operation, the VFD typically takes AC power, converts it to DC, then inverts it back to AC at a controllable frequency and voltage. This combination is what lets the motor run at different speeds smoothly and efficiently. Other statements are incomplete or misleading because VFDs don’t rely solely on DC input, don’t simply convert AC to DC without converting back to variable-frequency AC, and do regulate voltage to maintain proper torque at different speeds.

A Variable Frequency Drive controls motor speed by changing both the frequency of the output and the voltage delivered to the motor. By adjusting the output frequency, the motor speed varies; by shaping the voltage in step with that frequency (keeping a roughly constant V/Hz ratio), the drive preserves motor torque as speed changes. In operation, the VFD typically takes AC power, converts it to DC, then inverts it back to AC at a controllable frequency and voltage. This combination is what lets the motor run at different speeds smoothly and efficiently. Other statements are incomplete or misleading because VFDs don’t rely solely on DC input, don’t simply convert AC to DC without converting back to variable-frequency AC, and do regulate voltage to maintain proper torque at different speeds.