Corona discharge phenomenon and behavior of water droplets on the surface of polymer in the AC electric field

This paper describes the results of experiments made to examine behavior of water droplets on the polymer surface in an increasing ac electric field and corona discharge phenomenon during this process. Tests were done by placing water droplets with different conductivities and volumes on the silicone rubber surface with a micropipette. The factors that affect the corona discharge from water droplets were analyzed by means of electric field calculation and some experiments. It is demonstrated that water droplets on the polymer surface locally enhance the electric field and may cause corona discharge. Behavior of water droplet, corona discharge current pulses and the light emission images were investigated with a digital oscilloscope and a high-speed camera. It can be observed that the droplet vibrates and elongates with being pulled towards the positive electrode in a wave synchronism with the frequency of the power source. The volume and conductivity of water droplet are shown to have a marked effect on the mode of corona discharge development.