Transient voltage waveform

By the immediate first current zero it is assumed that the contacts have travelled sufficiently apart to achieve the required deionization and have built up adequate dielectric strength to withstand at least 0.95 V, . If the circuit does not interrupt at the immediate current zero at a which is so near to the point of chopping Vt , the interruption will take place only by the next current zero at point h and result in another 260 strikes by then. To study more accurate behaviour of an intenupter, with the number of restrikes and the formation of the actual transient voltage waveforms on current chopping, oscillograms similar to those during a short-circuit test may be obtained (Section 14.3.6). 

Transient — Subcycle disturbance in the AC waveform evidenced by a sharp, brief discontinuity of the waveform. This may be of either polarity and may be additive or subtractive from the nominal waveform. Transients occur when there is a sudden change in the voltage or the current in a power system. Transients are short-duration events, the characteristics of which are predominantly determined by the resistance, inductance, and capacitance of the power system network at the point of interest. The primary characteristics that define a transient are the peak amplitude, the rise time, the fall time, and the frequency of oscillation. Figure 1.12 shows a transient voltage waveform at the output of a power transformer as the result of switching-in of a motor containing power factor correction capacitors. 

FIGURE 1.12 Motor starting transient voltage waveform. 

When a line is transposed, all the aerial modes become identical. Thus, a number of different characteristic modes are reduced to two in the three-phase line case and to three in the twin-circuit line case. The different velocities of the aerial modes in an untransposed line cause a spike voltage on a transient voltage waveform, which is characteristic to the untransposed line. 

The Transient Analysis uses the sinusoidal voltage waveform when it performs the simulation. This circuit would not work if an AC Sweep were used. To set up a Transient Analysis, select PSpice and then New Simulation Profile from the Capture menus ... 

Figure 4.11 Transient current and voltage waveforms showing effect of trapping and detrapping, (a) No trapping, (b) Trapping, no detrapping, (c) Trapping and detrapping (from Ref. [13]).

The major reasons for ASD shutdown are transients, interruptions, sags (under-voltages), swells (over-voltages), waveform distortions, voltage fluctuations, and frequency variations [11-13]. These problems can cause ADS symptoms such as premature trips or shuts down, resets and restarts, frequent repairs and replacements, erratic control of process parameters, unexplained fuse blowing and/or component failures, and frequent motor overheating trips and/or continuous operation of motor cooling systems. 

Multiple horizontal plates Figure 7.45b shows the transient voltage of an electrode composed of two horizontal circular plates. The voltage waveform is similar to that of an electrode with one horizontal plate as shown in Figure 7.45a. Thus, it is concluded that an electrode with multiple horizontal plates has no practical value. 

It is important to realize the difference between the AC Sweep and the Transient Analysis discussed in Part 6. The AC Sweep is used to find the magnitude and phase of voltages and currents. The Transient Analysis is used to look at waveforms versus time. An example of a waveform versus time is ... 

This graph shows us a voltage versus time. Use the Transient Analysis to obtain a waveform versus time. In the time domain the equation for this waveform is vx(t) = 5sin(2/r lOOOf + 0°). This waveform has an amplitude of 5 V and a frequency... 

The Transient Analysis is used to look at plots of voltages and currents versus time. This simulation displays waveforms as you would see them on an oscilloscope screen. 

The time step Tstep = lOu determines each point in time starting from zero that the transient solver will calculate a solution. A safe estimation of the time step is an order of magnitude less than the period of a switching waveform. For example, the time step for a 100 kHz oscillator (period = 10 /xs) should be approximately 1 /xs. Tmax, the maximum time step, can be left out (at default) or specified to increase (decrease TMAX) or decrease (increase TMAX) simulation accuracy. This allows the simulator to take larger steps when the voltage levels in the circuit experience little change. A transient time domain analysis can prove to be the most difficult to get to converge. 

For each event, the analysis was done for the waveform recorded by the transducer closest to the crack tip. The closest transducer was assiuned to have an incidence angle that is nearly normal, thus simplifying analysis. Measured voltage transients were converted to displacement transients by applying the manufacturer s calibration data and using frequency division ... 

Transient disturbance A voltage pulse of high energy and short duration impressed upon the ac waveform. The overvoltage pulse can be one to 100 times the normal ac potential (or more) and can last up to 15 ms. Rise times measure in the nanosecond range. 

Figure 3.14d shows the transient response of the core voltage in a solidly bonded cable. It shows a stair-like waveform with a length of 70 ps. This length is determined by the round-trip time shown in Equation 3.89. Sheath voltages of the solidly bonded cable are much smaller than those of the cross-bonded cable. The results indicate that not all cross-bonded cables can be simplified by a solidly bonded cable from the viewpoint of not only the sheath voltages but also the core voltages. 

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