Contributions to Elimination of Excitation Field Harmonics in Turbogenerators

Abstract

Turbogenerators driven by high-speed turbines are frequently used in electrical power generation. Power quality of a synchronous generator is directly associated with its excitation field harmonics. Conventional method to eliminate the most prominent harmonics is to distribute the slots to 2/3 of the rotor perimeter with equal slot pitches and identical slots while keeping 1/3 of the rotor perimeter without slots. All slots placed on the rotor have equal dimensions and numbers of turns that carry the same excitation current. In this study, new slot positions and new numbers of conductors in slots for a turbogenerator were calculated by using Newton-Raphson algorithm to eliminate the most prominent harmonics. The physically applicable optimum solution was determined and implemented to a rotor of a conventional generator. Only necessary quantities like numbers of turns and slot dimensions were altered while no changes to the stator and other rotor dimensions were applied. Operational performance of the novel design was then compared with that of the conventional one. It was traced that the total harmonic distortion, material consumption, and total losses were decreased while the power quality and power factor were improved with a slight increase in efficiency.

Keywords

• harmonic analysis
• iterative algorithms
• power quality
• total harmonic distortion
• turbogenerators