(electricity) The voltage measured at a specified current in the electrical breakdown region of a semiconductor diode. Also known as Zener voltage. The voltage at which an electrical breakdown occurs in a dielectric. The voltage at which an electrical breakdown occurs in a gas. Also known as breakdown potential; sparking potential; sparking voltage.
Breakdown voltage
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(′brāk′dau̇n ′völ·tij)
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The potential difference at which an electrically stressed gas is transformed from an insulator to a conductor. In an electrically stressed gas, as the voltage is increased, the free electrons present in the gas gain energy from the electric field. When the applied voltage is increased to such a level that an appreciable number of these electrons are energetically capable of ionizing the gas, the gas makes the transition from an insulator to a conductor; that is, it breaks down. The potential difference at which this transition occurs is known as the breakdown potential for the particular gaseous medium.
The breakdown potential depends on the nature, number density, and temperature of the gas; on the material, state, and geometry of the electrodes; on the type of voltage applied (steady, alternating, impulsive); and on the degree of preexisting ionization. Areas of surface roughness at the electrodes (especially the cathode) or the presence of conducting particles in the gas greatly reduces the breakdown potential because at such points the electric field is significantly enhanced, increasing the electron energies and thus gas ionization. The breakdown voltage varies considerably from one gaseous medium to another; it is very low for the rare gases, and very high for polyatomic, especially electronegative, gases such as sulfur hexafluoride (SF6).
The transition of a gas from an insulator to a conductor under an imposed electrical potential occurs in times ranging from milliseconds to nanoseconds, depending on the form of the applied field and the gas density. This transition depends on the behavior of electrons, ions, and photons in the gas, especially the processes which produce or deplete free electrons. Knowledge of these processes often allows prediction of the breakdown voltage of gases and the tailoring of gas mixtures which can withstand high electrical potentials for practical uses. See also Electrical breakdown; Electrical conduction in gases.
The systematic development of gaseous dielectrics with high dielectric strength (that is, high breakdown potential) is most significant for high-voltage technology, which has a multiplicity of gas insulation needs. Dielectric gases are widely used as insulating media in high-voltage transmission lines, circuit breakers, transformers, substations, high-voltage research apparatus, and other electrical equipment. See also Circuit breaker; Dielectric materials; Transmission lines.
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The voltage at which an electrical insulation ruptures, thereby destroying its insulating value and permitting current flow.
| Electronics Dictionary: breakdown voltage |
Voltage at which the breakdown of a dialectric or insulator occurs.
| Wikipedia: Breakdown voltage |
The breakdown voltage of an Insulator is the minimum voltage that causes a portion of an insulator to become electrically conductive.
The breakdown voltage of a diode is the minimum reverse voltage to make the diode conduct in reverse. Some devices (such as TRIACs) also have a forward breakdown voltage.[1]
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In Detail
Insulators
Breakdown voltage is a characteristic of an insulator that defines the maximum voltage difference that can be applied across the material before the insulator collapses and conducts. In solid insulating materials, this usually creates a weakened path within the material by creating permanent molecular or physical changes by the sudden current. Within rarefied gases found in certain types of lamps, breakdown voltage is also sometimes called the "striking voltage".[2]
The breakdown voltage of a material is not a definite value because it is a form of failure and there is a statistical probability whether the material will fail at a given voltage. When a value is given it is usually the mean breakdown voltage of a large sample. Another term is also 'withstand voltage' where the probability of failure at a given voltage is so low it is considered, when designing insulation, that the material will not fail at this voltage.[3]
Two different breakdown voltage measurements of a material are the AC and impulse breakdown voltages. The AC voltage is the line frequency of the mains (either 50 or 60 Hz depending on where you live). The impulse breakdown voltage is simulating lightning strikes, and usually uses a 1.2 microsecond rise for the wave to reach 90% amplitude then drops back down to 50% amplitude after 50 microseconds.[4]
Two technical standards governing performing these tests are ASTM D1816 and ASTM D3300 published by ASTM.[5]
Breakdown in vacuum
Main article: Electrical Breakdown in Vacuum
In standard conditions at atmospheric pressure, gas serves as an excellent insulator, requiring the application of a significant voltage before breaking down (e.g. lightning). In vacuum, this breakdown potential may decrease to an extent that two uninsulated surfaces with different potentials might induce the electrical breakdown of the surrounding gas. This has some useful applications in industry (e.g. the production of microprocessors) but in other situations may damage an apparatus, as breakdown is analogous to a short circuit.[6]
The breakdown voltage in a partial vacuum is represented as[7][8] [9]:
![V_\mathrm{b} = \frac {Bpd}{\ln Apd - \ln[\ln(1 + \frac {1}{\gamma_\mathrm{se} })]}](http://wpcontent.answers.com/math/e/8/f/e8f7e9b0c9625e94f7ed174e35697d16.png)
where Vb is the breakdown potential in volts DC, A and B are
Diodes
Breakdown voltage is a parameter of a diode that defines the largest reverse voltage that can be applied without causing an exponential increase in the current in the diode. As long as the current is limited, exceeding the breakdown voltage of a diode does no harm to the diode. In fact, Zener diodes are essentially just heavily doped normal diodes that exploit the breakdown voltage of a diode to provide regulation of voltage levels.
References
- ^ Emelyanov, A.A. and Emelyanova, E.A., Abstracts of Papers, Proc. XXII ISDEIV, Matsue, 2006, vol. 1, p. 37.
- ^ J. M. Meek and J. D. Craggs, Electrical Breakdown of Gases, John Wiley & Sons, Chichester, 1978.
- ^ Relationship between Electrode Surface Roughness and Impulse Breakdown Voltage in Vacuum Gap of Cu and Cu-Cr Electrodes, Shinji Sato and Kenichi Koyama, Mitsubishi Electric Corporation, Advanced Technology R & D Center, 8-1-1 Tsukaguchi-Honmachi, Amagasaki-City, Hyogo 661-8661, Japan
- ^ Emelyanov, A.A., Izv. Vyssh. Uchebn. Zaved., Fiz., 1989, no. 4, p. 103.
- ^ Kalyatskii, I.I., Kassirov, G.M., and Smirnov, G.V., Prib. Tekh. Eksp., 1974, no. 4, p. 84.
- ^ Stefanov, L.S., Tekhnika vysokikh napryazhenii (High-Voltage Engineering), Leningrad: Energiya, 1967.
- ^ G. Cuttone, C. Marchetta, L. Torrisi, G. Della Mea, A. Quaranta, V. Rigato and S. Zandolin, Surface Treatment of HV Electrodes for Superconducting Cyclotron Beam Extraction, IEEE. Trans. DEI, Vol. 4, pp. 218<223, 1997.
- ^ H. Moscicka-Grzesiak, H. Gruszka and M. Stroinski, ‘‘Influence of Electrode Curvature on Predischarge Phenomena and Electric Strength at 50 Hz of a Vacuum
- ^ R. V. Latham, High Voltage Vacuum Insulation: Basic concepts and technological practice, Academic Press, London, 1995.
- ^ Yemelyanov, A.A., Kalyatskiy, I.I., Kassirov, G.M., and Smirnov, G.V., Abstracts of Papers, Proc. VII ISDEIV, Novosibirsk, 1976, p. 130.
See also
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