Committee Chair

Eltom, Ahmed H.

Committee Member

Parten, Cliff; Owino, Joseph


Dept. of Electrical Engineering


College of Engineering and Computer Science


University of Tennessee at Chattanooga

Place of Publication

Chattanooga (Tenn.)


This study investigates the impact of harmonics on the performance, efficiency, and the economics of energy efficient motors (EEMs) and standard motors (STMs). In this research, the skin effect impedance model that incorporates the skin effect in the rotor bars is used to study the motor’s behavior under harmonics. The characteristic behavior of the motors are simulated using a computer program which compares the performance, efficiency, and the economics of these motors and identifies the harmonic level at which these behavior are most prominent. The following motor sizes 25, 50, 100, 150, 200, 250, and 300 hp are used in the execution of this study. Verification of the skin effect impedance model is done by comparing the calculated current and efficiency at full load, with manufacturers supplied data under normal conditions. The efficiency of the standard motor and the energy efficient motor decreases as the order of harmonics increases. It is found that the 5th and 7th harmonics contributed over 45% and 25% respectively of the total rotor loss of both the EEM and STM. The rate of drop of the EEM efficiencies is greater than the rate of drop of efficiencies for the STM at the same load condition this implies that although the EEM is a much better design, it is more susceptible to harmonic due to the skin effect in the rotor bars. The payback analysis shows that the EEMs are more cost effective even when subjected to harmonic. However, the losses due to harmonics need to be minimized and further research need to be devote d to the losses at the 5th and 7th harmonics.


M. S.; A thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Master of Science.




Harmonics (Electric waves)


Electrical and Computer Engineering

Document Type

Masters theses


ix, 89 leaves




Under copyright.