Current Peak short-circuit

Prospective short-circuit or short-time current Asc kA(r.m.s.) (symmetrical breaking current) Factor of asymmetry to obtain the peak short circuit or making current Co s (p... 

In AC grids, the initial symmetrical short-circuit current, IK", defined as the rms value of the symmetrical AC component at the occurrence of the short-circuit, the peak short-circuit current, hr the maximum instantaneous value of the short-circuit current, and the steady state short-circuit current, Ik, defined as the rms value of the short-circuit current after fading of all transients, shall be differentiated in general. For far-from-generator short circuits, Ik" = ... 

Busbars are mounted on insulated bushes that are strong enough to withstand the peak short-circuit currents and forces. The busbars may be air insulated or enclosed in an insulating sleeve. 

These reactances are measured by creating a fault, similar to the method discussed in Section 14.3.6. The only difference now is that the fault is created in any of the phases at an instant, when the applied voltage in that phase is at its peak, i.e. at Vni- so that the d.c. component of the short-circuit current is zero and the waveform is symmetrical about its axis, as shown in Figure 13.19,... 

The peak value of a fault current will depend upon the content of the d.c. component. The d.c. component will depend upon the p.f. of the faulty circuit and the instant at which the short-circuit commences on the current wave. (Refer to Figure 13.27, illustrating the variation in asymmetry with the p.f. of the faulty circuit. For ease of application, it is represented as a certain multiple of the r.m.s. value of the symmetrical fault current /sc )... 

Table 13.11 Multiplying factors to obtain the momentary peak (maximum r.m.s. or dynamic) values of the short-circuit currents including the sub-transient d.c. component at different power factors (FI/Xl)...

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. 

From the oscillogram, shown in Figure 14.4 one can easily determine the average r.m.s. value of the short-circuit current, its duration and the momentary peak current. For easy evaluation, this oscillogram has been divided into ten equal parts (I to lO) and is redrawn in Figure 14.5 for more clarity. The short-circuit commences at point D and concludes at point A2, A A2 being the original zero axis. At the instant of short-circuit, the zero axis shifts to B A2- B) B is the initial d.c. component that decays to zero at A2 at the conclusion of the test. 

The d.c. component, /j ., at any instant should be a niininiuni of 50% that of the corresponding peak value of the a.c. component of the symmetrical fault current /.,c, /.,ci. /jctri. at any instant, during the period of the short-circuit condition, /jc should bo S 0..S V2 /jc- Otherwise the asymmetry may be ignored, being insignificant. 

In a typical monocrystalline module, the open circuit voltage is 21 volts and the short circuit current is about 5 amps. The peak power output of the module is 73 watts, achieved when the module is delivering a current of some 4.3 amps at a voltage of 17 volts. 

Fig. 7 Rescue of AF508-CFTR in HBE isolated from AF508-homozygous CF patients. A Representative short circuit current in AF508-HBE pre-treated for 48-hours with DMSO- (blue line) or 6.7 pM VRT-325 (red line). B Dose response to VRT-325 in FSK-stimulated AF508-HBE in the presence (filled circles) and absence (open circles) of the CFTR potentiator, VRT-532 (n = 5). C Maximum response to 10 iM FSK in AF508-HBE pre-treated with 1500 iM 4-PBA-, 6.7 iM VRT-422- (compoimd 1), 6.7 iM VRT-325-(compound 2), or 1 pM Corr-4a (compound 4), as well as 27°C-treated AF508-HBE. The peak response to forskolin was normalized to that in wild-type-HBE isolated from non-CF subjects (% wild-type CFTR). The dashed line indicates the level of residual (untreated) AF508-CFTR activity in AF508-HBE. D Cumulative data for uncorrected and VRT-325-corrected AF508-HBE with and without addition of the CFTR potentiator, VRT-532. Single asterisk = p<0.05 compared to un-treated controls double asterisk = p<0.01 compared to un-treated controls...

Two parallel busbars with a length I 1 m and a distance r = 50 mm shall withstand a short-circuit current (peak value) of 100 kA. Then the force F will be ... 

The short-circuit withstand performance may be important with certain types of equipment, e.g. generators, high-voltage motors, switchgear, power transformers. This should be described or stated in the data sheet. The rms and peak values of short-circuit currents may need to be described. 

An external short-circuit test was carried out on a 16P bank of cells with a load of 2 mQ [16]. No catastrophic failures were observed. The maximum temperature recorded was 89 °C and the total peak current observed was 361 A. The voltage dropped to 1.48 Vat short initiation, which then fell to approximately 0.41 V about 3 s into the shorting process and then decreased to less than 100 mV after 2 min into the whole process. The voltage then settled down to between 50 mV and 60 mV until the last cell was fully discharged. 

A PV cell is characterized by its open circuit voltage Vqc and its closed-circuit current /cc- Those two parameters correspond, respectively, to the voltage without any resistive charge between PV cell electrodes and to the maximal current proportional to the light intensity in the closed short circuit. A PV cell other important parameter is called the peak power Pc corresponding to the maximal power delivered, /mp and Vmp are current and voltage generating the maximal power. 

Current-Limiting Type. These power fuses are designed in such a way that the melting introduces high arc resistance into the circuit during the first half-cycle s peak current, thus restricting short-circuit current. 

Photovoltaic cells were prepared with a polymer layer sandwiched between electrodes with different work functions, as in polymer-based LEDs (Fig. 29.2). In the dark, the device exhibits a rectification ratio of 10 at 3.5 V. Under illumination, devices of this type show a strong photoresponse, with open-circuit voltages of 0.6 V and short-circuit currents that correspond to quantum efficiencies of up to 6%. Under forward or reverse biases, the quantum efficiencies rise rapidly, reaching 15% at a reverse bias of 3.5 V, 40% at 10 V. and considerably higher values under forward bias. These performance figures are very much better than those for devices made with aluminum electrodes and either MEH-PPV or CN-PPV alone. Thus, Halls et al. report values for the quantum yield of the short-circuit photocurrent in the MEH-PPV of 0.04% at the peak response wavelength (2.2 eV) and on the order of 10 %... 

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