Specific Design of a Piezoelectric Direct Discharge transformer

For 20 years, the piezoelectric transformers are considered as an interesting solution for plasma discharge generation. Its specific dielectric property, step-up voltage capability, safety operation and compactness lead to... [ view full abstract ]

For 20 years, the piezoelectric transformers are considered as an interesting solution for plasma discharge generation. Its specific dielectric property, step-up voltage capability, safety operation and compactness lead to investigate this seducing technological solution for this particular application. Contrary to a conventional use of piezo transformers as a two-port network, the strongly non-linear behavior of a plasma discharge brings up to reconsider the design of a such transformer. The main purpose is to increase the power of the plasma discharge by satisfying the voltage ignition condition as well as the holding voltage requirement. Several Finite Element Analysis (FEA) were performed to develop new original designs and presented in this paper.

The composition Pb((Zr_0,49Ti_0,51)_0,94Mn_0,0252Sb_0,0192W_0,0156)O₃ + 0.2 wt.% NiO was chosen because of its convenient high Curie temperature, high mechanical quality factor and high piezoelectric constants. The composition was synthetized by a conventional solid state route: oxide (PbO, ZrO₂, TiO₂, Sb₂O₃, WO₃, NiO) and carbonate (MnCO₃) powders were mixed and calcined at 825 °C, ground in an agate planetary mill, pressed into plates and sintered at 1150 °C. Relative densities up to 0.91 were obtained. The material constants used for FEA were determined according to the IEEE standard.

New designs were then manufactured by a laser cutting of the plates. After polarization (2.5 - 3.0 kV/mm at 80°C in a silicon bath for 1 hour), the electric properties of the as-obtained transformers were related to structure (XRD) and microstructure (SEM). Finally, the preliminary performances of the new designed piezoelectric direct discharge transformer are discussed.