Electrical news and engineering . e Fig. 7. Occasionally where notrolley is available, a cable is carried by the locomotivewhen it leaves the main slope. Traction-reel types of loco-motives are also supplied where necessary. On the surface,heavy electric locomotives can haul very large loads andthese can be either alternating or direct current. Fig. 8shows an electric train emerging, with direct cmrcnl loco-motive supplied by current from the iriilky. Where electricity is to replace large winding enginethe matter is more serious and the question of design mu-ibe carefully considered. In order
Electrical news and engineering . e Fig. 7. Occasionally where notrolley is available, a cable is carried by the locomotivewhen it leaves the main slope. Traction-reel types of loco-motives are also supplied where necessary. On the surface,heavy electric locomotives can haul very large loads andthese can be either alternating or direct current. Fig. 8shows an electric train emerging, with direct cmrcnl loco-motive supplied by current from the iriilky. Where electricity is to replace large winding enginethe matter is more serious and the question of design mu-ibe carefully considered. In order to show a saving withelectric hoisting over steam hoi-ling, it is necessary that there be a reduced consumption of coal under the boilersper ton of ore hoisted. It is often hard Ui get a statementlliat will take account of all the factors, but it is well knownthat the ordinary steam hoisting engine is a very inefficientdevice operating as it does at varying speeds and loadsand its elTiciency being under the conirol of an operator. Fig. 9.—Motor Generator Set Changes A. C. to D. C. who, as a rule, is unskilled. It is often impossible to takeadvantage of higher grade of steam hoisting engines on thisaccount. Characteristics of Load Vary Where there are several winding engines fed by onecentral electric power station, it can easily be seen that theloads in different cases will so overlap that a comparativelyeven load will result upon the power house, with the addedresult that the boiler and engine capacity at that point isless than the aggregate of the individual plants. Again, asthe power house units operate at better efficiency, economycan be shown in this connection. High pressures,superheat, and low vacuum can be introduced intoone central power station where expert operatorscan pay attention to these details, which make defi-nite savings in any plant. Electric hoisting hasbeen thoroughly developed and is no longer a matter ofexperiment; it is necessary, however, to use that
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