Voltages and currents

Of ah the rare gases, the discharge of neon is the most intense at ordinary voltages and currents. 

Fig. 10. Power factor at 1 MHz vs temperature for some commercial glasses. Courtesy of Corning Inc. The power factor is the ratio of the power ia watts dissipated ia a material to the product of the effective siausoidal voltage and current ia volt-amperes. When the dissipation factor is less than 0.1, the power...

Impedance. Impedance defines the relationship of voltage and current in a coaxial cable. The electrical requirements of the hardware dictate the impedance values for the interconnecting cables. Most coaxial cables are designed to match the impedances required by electronic hardware. 

PLCs are classified by the number of the I/O functions supported. There are several sizes available, with the smallest PLCs supporting less than 128 I/O channels and the largest supporting over 1023 I/O channels. I/O modules are available that support high-current motor loads, general-purpose voltage and current loads, discrete inputs, ana-... 

The apphcation of an impressed alternating current on a metal specimen can generate information on the state of the surface of the specimen. The corrosion behavior of the surface of an electrode is related to the way in which that surface responds to this electrochemical circmt. The AC impedance technique involves the application of a small sinusoidal voltage across this circuit. The frequency of that alternating signal is varied. The voltage and current response of the system are measured. 

Table 4.1 Comparison between an open and a closed transient switching in terms of voltage and current...

These are unidirectional and uncontrollablet static electronic devices and used as static switches and shown in Figure 6.14. A diode turns ON at the instant it becomes forward biased and OFF when it becomes reverse biased. By connecting them in series parallel combinations, they can be made suitable for any desired voltage and current ratings. Whether it is a transistor scheme or a thyristor scheme, they are used extensively where a forward conduction alone is necessary and the scheme calls for only a simple switching, without any control over the switching operation. They are used extensively in a rectifier circuit to convert a fixed a.c. supply to a fixed d.c. supply. 

The triac may, however, have some limitations in handling frequencies higher than normal. In such cases, they can be simulated by using two SCRs in inverse parallel combinations as illustrated in Figure 6.22(b). Now it is known as a reverse conducting thyristor. An SCR has no frequency limitations at least up to ten times the normal. The required voltage and current ratings are obtained by series-parallel connections of more than one thyristor unit. 

A switched static device (particularly a thyristor) produces voltage and current transients similar to inductive or... 

When the short-circuit occurs at a current zero, i.e., when the applied voltage is almost at its peak, the voltage and current waves will follow Figure 13.19, the cuiTent lagging the voltage by almost 84°. The current will now be almost symmetrical. 

Figure 13.27 Approximate illustration of a short-circuit condition occurring when both voltage and current waves are not at their natural zeros. Current shifting its zero axis from A, Aj to B B2 to rise from zero again at the instant of short-circuit...

In an alternating current system the voltage and current components travel in the shape of a sinusoidal waveform (Figure 17.9) and oscillate through their natural zeros, 100 times a second for a 50 Hz system. 

Figure 18.6 Arrester voltage and current oscillograms for 10 kA, 8/20 /iS current impulse lest...

Figure 19.27 Approximate representation of assumed voltage and current waveforms illustrating a current-chopping effect and its attenuation while interrupting a circuit having 0,3 p.f.

The basic principle of this relay is the sensing of the phase displacement between the fundamental waveforms of the voltage and current waves of a power circuit. Harmonic quantities are filtered out when present in the... 

A capacitive circuit magnifies the harmonic effects when present in the system, as discussed in Section 23.5.2, and gives rise to spurious voltages and currents, raising the normal V, and Ji to and respectively,... 

Figure 24.12 Voltage and current profiles when the line at the far end is open-circuited...

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