Electric Subway Dangers.

Progress, Volume I, Issue 8, 1 June 1906, Page 211

Electric Subway Dangers.

Something of a sensation has been created in New York by Nikola Tesla, the great electrician, who has inveighed against the electric subways systems of that city in particular, and such systems in general. The danger to which we refer lies in the possibility of generating an explosive mixture by electrolytic decomposition and thermic dissociation of the water through the direct currents used in the operation of the cars. An expert found the percentage of free oxygen in the subway appreciably above that which might reasonably have been expected in a similarly stagnated channel. The total amperage of the normal working current in the tunnel is very great, and in case of flooding would be sufficient to generate not far from ioo cubic feet of hydrogen per minute. Inasmuch, however, as in railway operation the fuses must be set hard, in order to avoid frequent interruption of the service by their blowing out, m such an emergency the current would be of much greater volume, and hydrogen would be more abundantly liberated. One hundred thousand cubic feet of explosive might be formed before the danger is discovered, reported, and preventive measures taken. What the effect of such an explosion might be on life and property is not pleasant to contemplate. True, such a disaster is not probable, but the present electrical equipment makes it possible, and this possibility should be, by all means, removed. Ventilation will not do away with the danger. It can be completely avoided by discarding the direct current. We should say that city authorities, for this, if for no other reason should forbid its use by a proper act of legislation Meanwhile the owners of adjacent property should object to its employment and the insurance companies should refuse the grant of policies on such property except on their own terms.

The railway line from Murna to Oberammergau, which connects with the Bavarian State Railway from Munich, has a length of about 1 5 miles and a rise of nearly 30 per cent. It was originally designed to be worked with three-phase current, but m 1904 was altered for use with a single-phase alternating current. A power station, situated on the River Ammer, with a fall of 78 ft., generates a current equivalent to 335 h.p. The generating station contains two turbines each of 500 h.p. and two of 30 h.p. each. The former drive alternating current generators of 280 kw. each, and a continuous current generator of 150 kw. direct coupled. The alternating- current machines are for working the railway and the continuous current dynamos furnish the power for lighting the district. The overhead wires convey a current at 5,000 volts, and the return current passes along the rails which are arranged for the purpose. The

iiiotor carriages have three axles and each carry two alternating - series motors with compensa tion apparatus fed from the mam current. An oil transformer beneath the motor carriage serves to convert the 5,000 volt system to one of 270 volts. The usual summer cars, with complete electric fittings, weigh 27^ tons, and those for winter, 26 tons. In addition to the motor vehicle there is also a two-axle electric locomotive with similar fittings to the above, weighing 20 tons, and capable of being used on the steepest gradient to move a train weighing in all 70 tons. The maximum speed on the level and on down gradients is 24.8 miles per hour and on the most severe ascents 9 to 9J miles per hour. Eight trains on the average are run daily m each direction. The mean duty per ton-kilometre was found on the average of several trials to be 43 watt hours, and the mean power out-put equivalent to 71 per cent. The electrical apparatus was furnished by the Siemensschuckert Works in Berlin.