High-power applications

Focusing on the concept of the completely sealed system, the Sanyo Electric Co. developed sealed-type nickel-cadmium batteries in 1961. This type of battery enjoys a wide application range that is still expanding a large variety of nickel-cadmium batteries has been developed to meet user needs ranging from low-current uses like emergency power sources and semiconductor memories to high-power applications such as cordless drills. 

The Johnsonfigure of merit, based on saturated carrier velocity and dielectric strength (product of power x frequency squared x impedance), predicts the suitability of a material for high power applications. It is normalized with the value of one given to silicon. As shown in Table 13.2 below, diamond is clearly the preferred material on this basis. 

Johnson figure of merit (high-power applications) 1 7 16 1138... 

Fiber laser guide star systems. It is now widely appreciated that the heat- dissipation characteristics of fibers, coupled with the high efficiencies demonstrated (> 80%) and excellent spatial mode characteristics, make fiber lasers a preferred candidate for many high power applications. Based on these features, fiber laser technologies would provide a compact, efficient, robust, turnkey laser source, ideally suited for LGS applications. 

AIN is better described as an isolator due to its large direct bandgap of 6.28 eV. Its high melting point (3000°C) and high thermal conductivity (2.6W/cm/K) renders AIN an useful material for high power applications. 

The construction of a cell involves a number of variables such as the relative amount and nature of the cathodic mix, type of separator used, etc. Fig. 3.12 illustrates the difference in service life between a standard GP cell and a HD cell which has been designed for high power applications when both are subjected to a heavy discharge (30 minutes once a day through a 2 Q load). For a similar construction and composition, and a fixed duty schedule, higher capacities are obviously obtained by using cells of larger size. 

High-power applications for which batteries have a too high series resistance. 

A systematic investigation of intrinsic chemical stability was carried out on devices specially designed for high power applications [7]. For this purpose, accelerated ageing test procedures were developed for nc-DSCs and it turned out that, to first order, a separation can be made between the effects of visible light soaking, UV illumination and thermal treatment on long term stability. 

For high-power applications, the conductors in the workpiece may have to be cooled with water. Typical power supplies for induction curing applications range from 1 to 5 kW, depending on the parts and application requirements. 

Starved electrolyte battery — A -> battery with minimum amount of -> electrolyte. The electrolyte in starved electrolyte cells or batteries exists in the porous structure of the - electrodes and absorbed in the separator, so it contains little or no free fluid electrolytic solution. This type of batteries is used in certain constructions of sealed - lead-acid and -> nickel-cadmium batteries that rely on gas diffusion and recombination on the electrodes during charging or overcharging in order to maintain maintenance-free conditions, and to suppress pressure buildup. Starved electrolyte batteries benefit from larger - energy density due to the reduced amount of electrolyte. This design may suffer from poor heat dissipation compared with -> flooded batteries, thus for high power applications this point has to be taken into account. 

Figure 27 Comparison of the different battery technologies in terms of volumetric and gravimetric energy density. The share of worldwide sales forNi-Cd, Ni-MeH and Li-ion portable batteries is 23, 14, and 63%, respectively. The use of Pb-acid batteries is restricted mainly in automobiles or standby applications, whereas Ni-Cd batteries remain the most suitable technologies for high-power applications (for example, power tools). (Ref 47. Reproduced by permission of Nature Publishing Group (www.nature.com))...

While these materials still find some application, such materials as alumina, beryllia, and single-crystal corundum find increasing use in high-power applications for heat dissipation because of their relatively high thermal... 

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