Comparison of NEMA and ultra-high slip motors on cyclic loads

Cyclic loads, such as eccentric pumping units, cause a varying torque on the driver. Determination of the most efficient induction motor for such a load is discussed. Ultra-high-slip motors as well as NEMA design motors are evaluated. Operating costs and investment are compared. The study indicates that: (1) any type of motor will work on a pumping unit; (2) the motor must be carefully sized to provide minimum operating cost; (3) the least expensive operating cost and the smallest investment are for the motors with the least slip; (4) the lower slip motors cause an increase in peak torque on the unit; and (5) an accurate computer model with an easy-to-use program that allows `what if´ options is highly desirable