- Author
- Tanaka, T. J. | Baynes, E., Jr. | Nowlen, S. P. | Brockmann, J. | Gritzo, L. | Shaddix, C.
- Title
- LDRD Report: Some Effects on Electrical Equipment.
- Coporate
- Sandia National Labs., Albuquerque, NM
- Sponsor
- Department of Energy, Washington, DC
- Report
- SAND2000-0599, March 2000, 44 p.
- Distribution
- AVAILABLE FROM National Technical Information Service (NTIS), Technology Administration, U.S. Department of Commerce, Springfield, VA 22161. Telephone: 1-800-553-6847 or 703-605-6000; Fax: 703-605-6900. Website: http://www.ntis.gov
- Contract
- DE-AC04-94AL85000
- Keywords
- electrical equipment | electronics | smoke | smoke production | smoke measurement | optical density | humidity | conductance
- Abstract
- The immediate effects of smoke on electronics are different from the long-term effects of metal loss by corrosion, which has been studied by insurance companies to reduce losses of equipment. This report concentrates on the immediate effects, in particular the increase of conductance through the presence of smoke, because this change has been found to be the most harmful to electrical circuits. When smoke is present, the conductivity between air-insulated conductors will increase, and this can lead to shorts or arcs. For static electric fields as in the case of direct current (dc) circuits, the electric field attracts smoke, which deposits on contacts to form a bridge. Typical values of conductivity for smoke-bridged circuits are as low as 1 M omega. For a high voltage alternating current circuit, ionized particles of soot provide a path for arcing. Smoke effects on capacitance and inductance were studied in earlier papers and found to be low. The goal of this project was to quantify how much smoke would be needed to cause a circuit or component to fail so that a model for the risk from smoke could be formulated. Finding a failure threshold for a particular circuit requires three types of information: how much smoke will cause a given loss of resistance, how much resistance loss can be tolerated by a circuit, and how does the electric field from the circuit modify smoke deposition. Failure thresholds are important in determining the reliability of equipment. In addition to the amount of smoke present, conductivity changes also depended on the amount of humidity present. Humidity levels above 60% have been found by others to contribute significantly to the conductivity of soot on surfaces. These effects were also observed here. Modeling conductivity through empirical equations, however, can be difficult, because of the random nature of the smoke and soot produced. Smoke particle sizes vary, and some single particles can be large enough to short a small-featured component. Humidity increases the conductivity of the soot once the soot has formed on a solid surface. Hence all the variables needed to model the conductivity that would result from burning a given amount of fuel are not easily known and incorporated. This project has laid some groundwork for estimates of failure rates, but has not measured all of the parameters required to predict the conductivity that results from the presence of smoke. Experiments included in this report on how smoke deposits for different electric fields and the resulting conductivity have shown that deposition is highly dependent on the electric fields. The experiments using the parallel plates and mass vs. conductivity boards especially show how the electric field determines smoke distribution. Even relatively low voltages, such as 50 V, will affect the distribution of the smoke. The distribution of smoke on surfaces then affects the conductivity of the smoke layer.