Which VFD Control Method is Most Efficient?

How to Choose the Right Control Method for VFD

Machine Design, October 23, 2014

Motors account for at least half of the energy consumed in the U.S. Selecting the right control method for an application lets the motor run most efficiently while maximizing torque and overall performance. Efficiently run motors also use less energy and experience less downtime for greater overall savings.

For motors controlled by a variable frequency drive (VFD), the control method used in large part determines a motor’s efficiency and performance in an application. Once engineers and designers understand the advantages, disadvantages, and particular specifications for each control method, choosing the right one for any application becomes simple.

Many people in the industry think control methods are the sequencing methods that control VFDs, as in 2- and 3-wire setups. Such 2- and 3-wire setups determine whether a VFD’s input-control terminals interface with maintained contacts or momentary push buttons to start and stop the drive. The control methods this article focuses on are perhaps more accurately called motor-control methods. They determine how VFDs control motors.

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