Affiliation:
1. College of Electric and Information Engineering, Zhengzhou University of Light Industry, Zhengzhou, Henan, China
Abstract
Background:
The safe and stable operation of large-capacity hydro-generators is of great
significance to the power grid. However, due to the armature reaction and the stator slots of the
hydroelectric generator, the torque ripple of the generator is usually large. Long time running under
the condition of large torque ripple will cause damage to the generator components and even threaten
the safety of the power grid.
Objective:
To study the factors affecting the torque ripple of the hydro-generator and reduce the
torque ripple.
Methods:
A 24 MW bulb tubular hydro generator is taken as an example, a two-dimensional transient
electromagnetic field model was established, and the correctness of the model was verified by
experiments. The causes of armature reaction and cogging effect on motor torque are analyzed. The
effects of these two factors on torque ripple are studied respectively. The torque ripple under different
working conditions is calculated, and the main factors causing and increasing torque ripple
during normal operation of hydro generator are determined.
Results:
The torque ripple increases approximately linearly with the increase of the 7th and 11th
harmonic contents, while it increases nonlinearly with the increase of the 5th harmonic contents.
When the excitation current increases from 720 A to 960 A, the torque ripple is increased by
11.4kN•m. In addition, when the excitation current increases from 720A to 840A (Rated excitation
current of the generator is 840A), the torque ripple increases greatly, the torque ripple increases by
6.6kN•m. When the excitation current exceeds the rated excitation current, due to the influence of
magnetic saturation, the increasing extent of torque ripple gradually decreases. When the excitation
current increases from 840A to 960A, the torque ripple increases only by 4.8kN•m.
Conclusion:
Due to the armature reaction, the harmonic magnetic potential will be generated in the
generator, which will affect its torque ripple. The torque ripple of the generator will increase obviously
with the increase of harmonic content. When the generator is in no-load operation, the slot
effect is the main cause of the torque ripple. In the actual operation of the generator, it usually
needs to adjust the excitation current to make the generator meet the requirements of various working
conditions.
Funder
National Natural Science Foundation of China
Foundation for Key Teachers of Henan Province
University Science and Technology Innovation Talent Support Program of Henan province
Publisher
Bentham Science Publishers Ltd.