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Show 4 INTER-MOUNTAI- JOINING REVIEW. N electric generators (a) Disappears (b), (c), steam or water-powe- r, (i), same as under I, and II. switch board and motors seldom exceeds $i5j ROCKY where power is used, ELECTRIC MINING IN THE (d), (e), (f), (g), (h MOUNTAINS. per kilowatt, it is evident that when a distance Against the advantages enumerated in the is reached that makes the cost of wire (anj COUNTER CONSIDERATIONS. By Irving: Ilalc, Denver, Colorado preceding section must be charged interest, insurance, taxes and depreciation on the excess of cost of water power and electric plant over a steam plant for doing the same work ; also the greater cost of attendance, if any, due to the location of machinery at two places, although this will in many cases be more than offset by the saving in attendance on motors, as compared with steam engines and boilers. The superiority of electric power for mining purposes was recognized in a general way as soon as the electric motor became a practical success, but it has required time and experience to amplify and fully develop its advantages and to overcome the minor difficulties that arose. The advantages of electrical power may be considered under three heads, based on the ature of the generating power : ; transformers, if used) exceed that amount, or the entire cost of the remainder of the plant that distance may be considered to be near, if not beyond, the economical limit, unless the conditions are peculiarly favorable for electric power. With 500 volts this condition is reached inside of three miles; with 1,000 volts, inside of gix miles; with 3,000 volts, at about seventeen miles and with 10,000 volts, at about fifty miles (allowing for trans--! ! i ! 1 i formers). It is evident from the foregoing principles and figures that the key to long distance mission is high voltage. ; trans. SYSTEMS. Direct current. Direct generators, suitable for power purposes, cannot be made to operate successfully at a . cur-re- nt much higher electro-motiv- e ' ; force than 1,000 volts, on account of; the arching and short circuiting of the commutator and its con-- ' 1 nections required the current. to rectify The direct current cannot be ! transformed to a higher voltage, except in a machine similar in construction to a generator and open to the same objections The expedient of connecting several generators in series, thus multiply the voltage, has ' ' ' , POWER HOUSE. - . ' 5 - Caroline Mining: Company, Ouray, Colorado. J 1 ' ' CONDITIONS AFFECTING THE COST OF PLANT. I. Electricity generated by water power, (a) The cost of an electric transmission plant deSaving of coal, water from steam, firemen, etc. (b) Require less attendance and repairs than pends chiefly on three conditions. First. Nasteam or compressed-ai- r (assuming such power to be engines, (c) Under- ture of water-powground wires more convenient than pipes, (d) used) and cost developing it. Second. Disun- tance of transmission. Third. Electromotive Avoidance of losses by ; er steam-condensati- derground. bad effects on - large units. ! j ' i i ; been tried in a few cases, but it is suitable only where power is to be transmitted and used in It would be manifestly impracti- - ; i ; ' cable to connect several motors in series for small powers, and especially for such purposes as running hoists, pumps, blowers and other mining machinery, Single phase alternating current. The single j ; e Avoidance of of steam under- (e.) ground. (f) More efficient than the small steam and compressed air engines used on hoists, pumps, etc. (g) Rotary motion of electric motor of engine, (h) Electric locomotives peculiarly adapted to underground haulage where steam is impracticable. II. Electricity generated by steam, at some distant point where fuel and water are cheaper. (a) Saving of difference in cost of fuel and water between places where power is generated and used, (b), (c), (d), (e), (f), (g), (h), same as under I. (i) Sup- erior economy of large compound and, where practicable, condensing engines, over the small, inefficient engines used on most mining machinery, proper, al- lowance being made for losses in INTERIOR OF POWER HOUSE, tranforming and transmitting Caroline Mining Company, Ouray Colorado. electric power. can be III. Electricity generated by steam at place force of voltage used. current generator phase alternating vo f for wound without CONCLUSIONS. 3,000 to difficulty Read at the September meeting: of tlie American as necessary, if and considerably higher the fact Institute of Mining Engineers. that cost the total of Considering t 5 . |