Conductor dielectric voltage

Table 15.3 The analogy between conductor dielectric voltage...

Conductor dielectric voltage Water channel pipe wall pressure... 

Capacitance k3- pa-s9-t9n(t)s [capacity] (1893) (C, electric capacity) n. The property of a system of two conducting surfaces (plates or foils, typically) separated by a non-conductor (dielectric) that permits storage of electric charge in proportion to the voltage difference between the conductors. The SI unit is the farad (F). A capacitor storing one coulomb of charge at a potential difference of 1°V has a... 

Life Tests. The high humidity bias test is the most commonly used test to determine rehabihty of a conductor/dielectric system. The most commonly used test conditions are 85 percent relative humidity, 85°C, and 10- or 30-V bias voltage. Typically, the test is run for 1000 h. This test simulates more than 20 years life at average ambient conditions. 

The resistance of most plastics to the flow of direct current is very high. Both surface and volume electrical resistivities are important properties for applications of plastics insulating materials. The volume resistivity is the electrical resistance of the material measured in ohms as though the material was a conductor. Insulators will not sustain an indefinitely high voltage as the applied voltage is increased, a point is reached where a drastic decrease in resistance takes place accompanied by a physical breakdown of the insulator. This is known as the dielectric strength, which is the electric potential in volts, which would be necessary to cause the failure of a 1/8-in. thick insulator (Chapter 4, ELEC-TRICAL/ELECTR ONICS PRODUCT). 

The electrical properties of materials are important for many of the higher technology applications. Measurements can be made using AC and/or DC. The electrical properties are dependent on voltage and frequency. Important electrical properties include dielectric loss, loss factor, dielectric constant, conductivity, relaxation time, induced dipole moment, electrical resistance, power loss, dissipation factor, and electrical breakdown. Electrical properties are related to polymer structure. Most organic polymers are nonconductors, but some are conductors. 

A variety of transmission line structures can be fabricated in planar layers of conductor and dielectric (Figure 9). The stripline and offset stripline are best suited for multilayer structures. The offset stripline, with two orthogonal signal layers between a pair of reference voltage planes, eliminates one intermediate plane and achieves higher characteristic impedance for a given dielectric thickness than do two stripline layers but increases the possibility for crosstalk between layers. 

Fig. 5.17 Transient currents from step voltages across (a) a loss-free dielectric, (b) a conductor, (c) a dielectric with dipolar relaxation, and (d) a dielectric with dipolar relaxation and conduction.

FIG. 19-55 Schematic representation of charging mechanisms. (A) Contact electrification. (B) Conductive induction. (C) Ion bombardment. Cond. = conductor particle diel. = dielectric particle = high-voltage dc electrode 0 = ions from corona discharge at high-voltage electrode. 

We shall consider two extreme kinds of systems. In the first kind, the system is a conductor and by application of a voltage between two electrodes (for the sake of simplicity the two electrodes will be taken parallel) a current flows from one electrode to another. The failure occurs when the current density becomes larger than a threshold value. Consequently, the system becomes nonconducting. The system behaves exactly as a fuse which is destroyed when the current is too large. We shall call this failure the fuse failure. In the second case, the system is a perfect insulator and a voltage is applied between the two electrodes. Again, beyond a definite (threshold) value of the electric field, the system breaks down and becomes conducting. This phenomenon is well-known in the physics of dielectrics, since it limits the application of dielectrics as insulators. We shall talk about the dielectric problem for this kind of failure. 

---