Dielectric strength table

Dielectric breakdown strength is a function of microporosity but not molecular weight or crystallinity. The number and size of the microvoids affect the dielectric strength. Table 10.11 shows the relationship of dielectric breakdown strength to microporosity. 

It is evident from this discussion that the power loss and heat dissipation in a dielectric will be aided by a high dielectric constant, high dissipation factor, and high frequency Therefore, for satisfactory performance electrical insulating materials should have a low dielectric constant and a low dissipation factor but a high dielectric strength (Table 3.6) and a high insulation resistance. 

Dielectric strength (Table 11.3) is analogous to tensile strength. The voltage on a thin slab of material held between two electrodes is increased until catastrophic failure occurs, usually burning a hole completely through the slab. The shape of the... 

Sheet Miea. Good quahty sheet mica is widely used for many iadustrial appHcations, particularly ia the electrical and electronic iadustries, because of its high dielectric strength, uniform dielectric constant, low power loss (high power factor), high electrical resistivity, and low temperature coefficient (Table 6). Mica also resists temperatures of 600—900°C, and can be easily machined iato strong parts of different si2es and shapes (1). 

Referring to the data available from experiments, as shi)wn in Table 23.1, it hits been estimated that a Vp, of I. Hj should be sufficient to account for the harmonic effects. For this dielectric strength is designed a capacitor unit and selected a switching or protective device. 

These values are considered for an altitude of up to 2000 m for LT and 1000 m for HT systems. For higher altitudes to achieve the same level of dielectric strength, the values of clearances and creepage distances, as given in Tables 28.4 and 28.5, may be increased by at least 1 % for every 100 m rise in altitude. 

The Johnsonfigure of merit, based on saturated carrier velocity and dielectric strength (product of power x frequency squared x impedance), predicts the suitability of a material for high power applications. It is normalized with the value of one given to silicon. As shown in Table 13.2 below, diamond is clearly the preferred material on this basis. 

These postulated mechanisms3 are consistent with the observed temperature dependence of the insulator dielectric properties. Arrhenius relations characterizing activated processes often govern the temperature dependence of resistivity. This behavior is clearly distinct from that of conductors, whose resistivity increases with temperature. In short, polymer response to an external field comprises both dipolar and ionic contributions. Table 18.2 gives values of dielectric strength for selected materials. Polymers are considered to possess... 

Table 18.2. Intrinsic Dielectric Strength (Breakdown Voltage)... 

The electronic insulation of these electrodeposited polymer layers must hold to a two-terminal voltage of 4 V if lithium (or lithium ion) anodes are to be used in the 3-D nanobattery. Because the polymers must also be thin, high dielectric strengths are critical. As seen in Table 2, diminishing the thickness of the dielectric to the nanoscale exacts a higher standard in terms of the quality of the dielectric. For example. 

Table 2. Required Dielectric Strengths for Nanometer-Thick Dielectrics...

PVF films exhibit high dielectric constant and a high dielectric strength.96 Typical electrical properties for standard polyvinyl fluoride films are shown along with its physical properties in Table 3.11. 

Electrical properties — dielectric constant (e), representing polarization dissipation factor (tan 8), representing relaxation phenomena dielectric strength (EB), representing breakdown phenomena and resistivity (pv), an inverse of conductivity — are compared with other polymers in Table 5.14.74 The low dielectric loss and high electrical resistivity coupled with low water absorption and retention of these properties in harsh environments are major advantages of fluorosilicone elastomers over other polymeric materials.74... 

It also has superior electrical properties, for example extremely high dielectric strength and very high resistivity. For this work, parylene C was used because of its excellent combination of physical and electrical properties. Table 15.1 lists its important properties. 

Table III lists some of the physical properties of polymers which contain ethylenebis [tris (2-cyanoethyl) phosphonium bromide]. This additive caused an increase in the dissipation factor and dielectric constant and lowered the dielectric strengths of polyethylene and poly (methyl methacrylate). The effects on mechanical properties were mixed. Obviously, lower concentrations of phosphonium halides would have less effect on mechanical and electrical properties. At levels of 1-3% very little change in properties would be expected. It was surprising that the phosphonium salts were compatible with such a range of polymers. We did not observe any tendency for the phosphonium salts to plate out of or exude from the polymer. In all cases homogeneous blends were obtained.

Constant, dissipation factor dielectric strength. A literature search indicated that little work of this nature has been done with expl materials. Further, such electrical measurements can be used as supplementary criteria for evaluating the purity, homogeneity and, with the exception of the dielectric strength determination, as possible nondestructive tests of expls. Hence the data listed in the following table were deed at Pic Arsn (Ref 2) for the common readily avail expls which are believed to be of interest in research... 

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