Leakage Current Effects

Minimizing dielectric thickness is an alternative to increasing the capacitance of these hlms snbject to the constraint of acceptable leakage currents, effective insulation of the gate, and snfficient dielectric breakdown strength. 

The greatest effect of ageing is reflected by the variation in its resistive current, which is rich in the third harmonic. Variation in is used in assessing the condition of an arrester. By conducting laboratory tests to determine the characteristics of an arrester, we can establish a ratio between the total leakage current, IZnO and the content of If, to assess the condition of the arrester. If we can monitor this current, we can monitor the condition of the arrester. Below we discuss briefly one such method by which this component can be separated out. 

Figure 21.1 as in lEC 60479-1 illustrates the various zones of ground leakage current versus duration of fault and its effect on a human body. 

Satisfactory agreement of experiments with kinetic laws, described by Eqs. (44) and (45), are observed only for tantalum and niobium, when the current efficiency approaches 100%. Even for these metals, certain deviations occur which could be attributed to space charge effects,82 electronic leakage currents,83 or other factors. In the case of aluminum, these deviations are relatively large, as, even in barrier-forming electrolytes, some oxide dissolution takes place from the very beginning of voltage supply to an anodized sample.32... 

Incidentally, Schottky diodes do not have any reverse recovery current issues, but they do have some body capacitance, which can produce similar effects. However, that fear has always proven to be exaggerated. I have personally not seen any application having a performance issue explicitly related to a bad Schottky. The only exception was a case where the leakage current of the Schottky was so high, it was prematurely tripping the current comparators inside the switcher IC. And there was also a reliability issue once, concerning the dV/df rating of a commercial Schottky. Both these issues are discussed elsewhere in this book. 

To work with high power, it is necessary to have a low ESR to limit the ohmic losses. The parallel resistance, Rv, has an effect visible only at ultralow frequency (below the millihertz range). It is responsible for the capacitor self-discharge. Its value must be as high as possible to limit the leakage current. The time constant x of the self-discharge is equal to x = RVC. 

The total effective area of the ten plates is 503 square inches, and the length of the boundary lines 3 inches. The residual current, or leakage current, at 110 volts was. 0005 amperes, which leaked through the insulation at the boundary line. The distance between the plates was about 3/16 of an inch. In this condenser, five plates were used for each side of the circuit and as each set of plates is of aluminum, it makes no difference which way the condenser is connected in the circuit. The following table shows the measured capacities with different formation-voltages ... 

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