AC drives can vary the speed of a motor using which configuration?

AC drives can vary the speed of a motor using which configuration?

• A. Single-phase
• B. Three-phase
• C. None
• D. Either

Answer: (D)

Speed control with AC drives works by changing the output frequency (and adjusting voltage to keep a constant V/Hz ratio), so the motor speed follows the commanded frequency. A variable frequency drive can be powered from either a single-phase supply or a three-phase supply, depending on the model and rating. Even if the input is single-phase, many drives convert that to DC and then invert to a three-phase output for the motor. This versatility means the same drive concept applies whether you’re using a single-phase or a three-phase configuration, so “Either” is the best choice.

Speed control with AC drives works by changing the output frequency (and adjusting voltage to keep a constant V/Hz ratio), so the motor speed follows the commanded frequency. A variable frequency drive can be powered from either a single-phase supply or a three-phase supply, depending on the model and rating. Even if the input is single-phase, many drives convert that to DC and then invert to a three-phase output for the motor. This versatility means the same drive concept applies whether you’re using a single-phase or a three-phase configuration, so “Either” is the best choice.