The Westinghouse System.
The alternating current system of the Westinghouse Company has come to the front in the United States with extraordinary rapidity, and, although it is not three years since the first plant was erected, at the present time over 190,000 incandescent lamps are operated from a number of central-stations. The fundamental principles of the Goulard system have been retained in the Westinghouse converter; but the manner in which these principles are applied has been greatly modified, while most of the details have undergone a radical change at the hands of the engineers and electricians whose researches have been utilised by the Westinghouse Company. The form of converter as now designed consists of a number of thin sheet-iron plates, shaped like the letter E, they are slipped alternately from opposite directions over the primary and secondary coils, which are disposed side by side; the inductive core is, therefore, composed of a mass of detached plates insulated from each other by paper, and forming a discontinuous magnetic circuit. In order to protect the converter from mechanical injury as well as dampness, and also to avoid the possibility of contact with wires carrying currents of high potential, it is enclosed in a cast-iron case or box, made in two parts and adapted to be secured to any convenient support. [Fig. 12] is a transverse vertical section of such a converter box, with the converter in position. The terminals of the primary coil, P, of the converter are led into the compartment D¹, and the terminals of the secondary coil into D². The terminals are secured to bolts or couplings, f f, mounted upon insulating plates, e¹ and e². Fusible mica-foils, g, and switch plates, h and i, with plugs k, are provided for protecting and disconnecting the circuits. The open front of the compartments D¹ and D² are closed by glass plates, T, which permit inspection of the connections without entering the box. The converter box occupies little space, and may be placed in any convenient situation in or about the premises to be lighted, much the same as a gas-meter. The practice where overhead conductors are employed, is to mount the converter box on a pole in the vicinity of the premises to be lighted, as shown by [Fig. 13], and thus it is only necessary to lead the secondary or low potential wires into the building, the high potential wires remaining in an accessible position upon the pole. [Fig. 14] is a view of North Street, Pittsfield, Massachusetts, engraved from a photograph, and shows a very neat form of tubular pole with its converter box on top. This arrangement is used throughout the city, and is a great improvement on the ordinary form of telegraph poles which so greatly disfigure American cities, and are really the most objectionable feature of the overhead wire system.
Fig. 12.
Fig. 13.
Fig. 14.
The potential ordinarily employed in the main circuits of the Westinghouse installations is about 1000 volts, and that in the lamp circuits 50 volts, the ratio of conversion, therefore, being as 20 to 1; the dynamos are manufactured, as a rule, in three sizes, No. 1 for 650, 16 candle-power lamps; Nos. 2 and 3 for respectively 1300 and 2500 lamps. The converters are also made in three ordinary sizes to supply 20, 30, and 40 lamps of 16 candle-power each. A 40-light converter contains about 85 pounds of iron and 25 pounds of copper, so that the total weight of metal is less than 3 pounds per lamp; the electrical efficiency of the converter is said to exceed 95 per cent. when the potential is reduced from 1000 volts in the primary to 50 in the secondary. “It is claimed that the trifling loss of energy in conversion from high to low potential at the point of consumption is made up for by gain at other points, especially in the increased efficiency of the lamps, so that an alternating current plant may be counted on to give 10-16 candle-power lamps per indicated horse-power, as against 7 with the direct system;” the comparative gain is doubtful, but by using 50 instead of 100 volts the life of the lamps is increased, the former having a much stronger filament and consequently a longer life.