Electromagnetic Radiation Generated by Electric Breakdown of Polypropylene Films
- PDF / 564,928 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 54 Downloads / 207 Views
omagnetic Radiation Generated by Electric Breakdown of Polypropylene Films V. A. Pakhotina* and N. T. Sudar’b a
Ioffe Physical Technical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia b Peter the Great St. Petersburg Polytechnic University, St. Petersburg, 195251 Russia *e-mail: [email protected] Received June 19, 2020; revised August 3, 2020; accepted August 5, 2020
Abstract—Electric breakdown of a thin film of polypropylene is accompanied by emission of the electromagnetic radiation pulse of about 400 ns duration with a spectrum consisting of three main frequencies. A relationship between the electric resistance of the breakdown channel and observed radiation spectrum is explained. Keywords: electric breakdown, radiofrequency emission, polypropylene. DOI: 10.1134/S1063785020110255
A final stage of the electrical fracture of polymeric dielectric films is their electric breakdown. During this period, a conducting channel capable of passing highdensity currents appears in a local region of the film. Previously, it was established that a short-time front of the true breakdown current pulse initiates damping electric oscillations in a measuring electric circuit [1, 2]. It was shown that data on the frequency of these oscillations and their damping time can be used for determining the resistance of the conducting channel and estimating the rate of its variation [2]. The electric breakdown current pulse in polymer films and related current oscillations in the measuring circuit must generate electromagnetic radiation in the radiofrequency (RF) range, the parameters of which can also be used for studying the phenomenon of polymer film breakdown. It should be noted that the phenomenon of broadband RF wave emission from electric discharges [3–6], including partial discharges in dielectrics, is well-known and actively discussed. However, no studies devoted to RF wave emission induced by breakdown in polymeric dielectrics have been reported so far. The present work was aimed at establishing the fact of RF pulse generation during electric breakdown in a polymer film and estimating the parameters of this radiation. Figure 1a shows a scheme of the measuring circuit. The object of study was a 4-μm-thick film of polypropylene (PP) with a 10- to 20-nm-thick aluminum layer deposited on one side by thermal evaporation in vacuum. The film was fixed between two brass rings with a 30-mm inner diameter so as to fill the entire area inside the ring. An electric contact covered with an Al
layer could be pressed to the rings from beneath to serve a bottom electrode. The second (top) electrode was a steel ball of 4-mm diameter rolled up into a copper tube. The ball electrode had a negative potential and was positioned approximately at the center of the brass ring holding the polymer. The electrodes and a film sample (measuring cell) constituted a part of the experimental setup comprising a square frame with arm length lo = 40 mm. The frame was made of a copper wire with diameter 2a = 5 mm and connected to the
Data Loading...
