Dynamics of a PT Driven Atmospheric Pressure Plasma Discharge*

Several approaches have been pursued to study piezoelectric transformer (PT) generated discharge that works on piezoelectric principles, yet there is a gap in information about the discharge characteristics. The objective of this study is to characterize an atmospheric pressure plasma discharge driven by a PT which is composed of Lead Zirconate Titanate (PZT). The PT is driven with 120V (peak to peak) with an input frequency of 60.8 KHz. The amplification of the voltage in the driven section results in plasma discharge at the secondary side corners of the PT. The discharge with a PZT-Cu having a separation distance of approx. 500 um is monitored with two different monitoring circuits (a combination of resistor (R) and capacitor (C)) connected to the Cu electrode. Experiments show, even for the same impedance, a series versus parallel RC monitoring circuit significantly changes the discharge characteristics. In a series circuit, a spike in the current (i.e. breakdown) is observed ~5.5 us after the tip voltage reaches its maximum. On the other hand, for the parallel circuit the breakdown is synced with the tip voltage of the driven side reaching its maximum and no temporal lag is present. High speed image analysis reveals surface discharge behavior; formation of multiple plasma spots on the PT surface which progressively merge and dissipates. A multi-physics mathematical model is proposed that considers both the material physics of the PT and gas phase plasma dynamics. Preliminary predictions show qualitative agreement of the breakdown phenomena with experimental observations.