| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 92 === In this work, we develop a 3-D finite element method (FEM) solver, NTUPZE, for piezoelectric transformer (PT) analyses. Although commercial FEM packages, such as ANSYS and ABAQUS, have the capability of performing piezoelectric analyses, they are not capable of taking electric loading effects into consideration. Therefore, the solver we developed is based on a new finite-element piezoelectric formulation that can account for various types of electric loading conditions. The solver employs the 8-node brick element, and applies the harmonic analysis to study voltage gains and phase difference at different frequencies. Using the NTUPZE, we analyze three different types of piezoelectric transformers: the Rosen-type, the modal-type, and the unipoled-disk-type. In order to discuss the influences of loadings, we adapt two different damping models, the Rayleigh model and the loss tangent model, to simulate a Rosen-type transformer. The simulated results show that the second longitudinal mode has a higher voltage gain than that of the first mode. The resonant frequency changes significantly when the loading is between and ; the voltage gain changes significantly when the loading is between and . Finally, the simulated results of the voltage gains and the phase difference for the modal-type transformers are also verified with the measured results. Also, the simulated frequency responses of the unipoled-disk-type transformers also agree with the measured results published in previous works.
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