Two-conductor system

Let us consider the lossless two-conductor system illustrated in Figure 1.46. The surge impedance matrices of the lines are given by... 

FIGURE 1.47 Analytical voltage waveforms on a two-conductor system. 

The voltage transformation matrix A for a symmetrical two-conductor system is given by... 

For instance, a bus system with 4 x 152.4 x 6.35 mm conductors may be arranged into two groups of two conductors each, according to Figure 28.29(b). Then the improved rating of this system as in Table 30.4 will be... 

Most electrochemical reactions occur at an interface between an electronic conductor system and an ionic conductor system. An interface has three components the two systems and the surface of separation. The electronic conductor stores one of the required chemicals electrons or wide electronic levels. The ionic conductor stores the other chemical needed for an electrochemical reaction the electroactive substance. A reaction occurs only if both components meet physically at the interface separating the two systems. 

Figure 52. The free enthalpy of mixing of the fast ion conductor Nasicon (Nai+ ZiyPsyM/tiJ (y= x/3) obtained from emf measurements as a function of composition.272 The shape of the curves indicates the stability of a thermodynamic two phase system at T< 615 K. Reprinted from U. Warhus, J. Maier, and A. Rabenau, J. Solid St Chem., 72 (1988) 113-125. Copyright 1988 with permission from Elsevier.

The first is one in which there exists an extra quinone molecule for every free radical ion, i.e., a crystal made up of two quinone molecules constituting one of these free radical ions and one cation. These materials have conductivities of the order of unity, varying with the cation, but they are all very good conductors. Thus, this material is a solid with more than one quinone for each odd electron. Presumably it has alternating neighbors with occupied and unoccupied orbitals so that one can get the electron to move from one into another. If, however, the crystals are made with only one quinone per odd electron and not the extra one, the conductivity drops by a factor of 104. This is exactly the kind of thing that one would have predicted from the results on the two-phase system which was just described. 

Here is the radius of the localized state wavefunction, N f) is the density of localized states, A is the area of the compressed pellet, and k is Boltzmann constant. Plots of this type have been observed for a number of known one-dimensional systems and taken as evidence for onedimensional hopping conductivity between localized states (38-47, 56-64). For comparison, the hopping conductivity for a two-dimensional system can be characterized by the relation In R/Ro = (T/To) where To = 8a / kDN F)) (here D is the thickness), whereas the hopping conductivity for a three-dimensional system follows the relation In R/Ro = (T/To) / where To = 16a / kN F)). This theory has been questioned recently by Mott (64). Nevertheless, this type of plot can be used to characterize the conductivity of these materials. The To values of 1.7 X 10 K observed for both compounds are, however, significantly higher than that generally observed for one-dimensional conductors or semiconductors (range 0.5 5 X 10 K) 24-26, 38-47, 56-64). 

A SELV system is an extra-low voltage system (50 Vac or 120 Vdc free of ripple when measured between any two conductors), which is electrically separated from the earth (or ground) and other systems (such as the primary winding of an isolating transformer) in such a way that a single fault cannot give rise to the risk of electric shock. A PELV system is also an extra-low voltage system, but is one that is not electrically separated from earth. In all other respects it must satisfy the requirements of a SELV system. 

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