Hi, what about relative humidity of air ? I believe breakdown voltage depends also on humidity content of air. One thing anybody can experience is the much higher frequency of ESD jolts one gets in dry weather vs. humid weather. Anyone knows a quantitative relation or formula ?
my penny's worth... Regards Paolo Roncone -----Messaggio originale----- Da: bogdan matoga [SMTP:[email protected]] Inviato: sabato 8 luglio 2000 22.57 A: Rich Nute Cc: [email protected]; [email protected] Oggetto: Re: Voltage Breakdown Gentlemen: Let me add my penny's worth to Rich's information. a. Parallel plates provide a homogenous field only in their center, the field fringes at the edges. (One could configure the plates according to Rogowski form). b. The breakdown voltage is not a linear function, even for spherical electrodes. What applies is Paschen's law, which gives the voltage as a function of distance x atmospheric pressure. Have fun! Regards, Bogdan. Rich Nute wrote: > Hi Allen: > > The voltage breakdown of air is presented in > IEC 664. > > There is no fixed number (i.e., mm/kV) that > describes or predicts voltage breakdown of air. > > The principle factor that affects voltage > breakdown is the shape of the electrodes > (degree of homogeneousness of the electric > field between the two electrodes). The more > homogeneous the field, the higher the breakdown > voltage, and vice versa. > > For example, at 2 mm, the breakdown of an > inhomogeneous field is about 2.5 kV, while the > breakdown of an homogeneous field is almost 8 > kv! > > An homogeneous field is created by two parallel > planes. An inhomogeneous field is created by > a needle-point and a plane. > > The second factor that affects voltage > breakdown of air is the voltage waveshape. The > more impulse-type waveshape, the higher the > breakdown voltage; the more sinusoidal-type > waveshape, the lower the breakdown voltage. > > The third factor that affects voltage breakdown > of air is the air pressure. The higher the air > pressure, the higher the breakdown voltage, and > vice-versa (Paschen's Law). > > There are still other factors such as temperature, > but these are minor effects compared to the first > three. > > If you are interested, I can send a Powerpoint > 4.0 file of the voltage-distance curves of the > homogeneousness effect. It covers the distance > range from 0 to 2 mm for both homogeneous and > inhomogeneous fields for sinsoidal waveforms. > The data is taken from IEC 664. > > Best regards, > Rich > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
