Harmonics generated by variable frequency drives (VFD) can have a considerable impact on the performance of the entire electrical distribution system. Typically, these harmonics are accounted for and controlled to meet the requirements set by the standards. But, when the system is complex and a large number of VFDs are present, the harmonics generated could exceed those limits resulting in undesirable effects. In this thesis, we discuss the effects of harmonics generated by AC variable frequency drives on transformers under various operating conditions. We developed a simulation model using MATLAB/SIMULINK. This model, consisting of feeders, VFDs, motors, and a transformer, is capable of simulating the harmonics generated by VFDs under balanced and unbalanced loading conditions. We conclude that the two most influencing factors on a transformer feeding a variable frequency drive are the load unbalance and the transformer leakage impedance. We also show that excessive harmonic currents may lead to transformer overloading and eventually to its failure.
|Commitee:||Mozumdar, Mohammad, Talebi, Mohammad|
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 51/05M(E), Masters Abstracts International|
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