Designing More Efficient Large Industrial Induction Motors by Utilizing the Advantages of Adjustable-Speed Drives

The rotor of an induction motor is designed to provide adequate starting torque and limit starting current when the load is being accelerated by the motor. These starting requirements on the rotor force design engineers to employ special shape rotor bars or high-resistance bars and thereby reduce motor efficiency and increase motor temperature rise. In addition to the benefits provided by an adjustable-speed drive (ASD) in controlling operating speed, this paper evaluates the benefits of ASD in allowing engineers to design higher efficiency motors and, in turn, smaller size motors.