The West End Company, with two hundred miles of track in and around Boston, began to equip its lines in 1888 with the Thomson-Houston plant. The success of this great undertaking left no doubt of the future of electric traction. The difficulties which had seriously threatened future success were gradually removed.
The electric railway progress was so great in the United States that about January 1, 1891, there were more than two hundred and forty lines in operation. About thirty thousand horses and mules were replaced by electric power in the single year of 1891. In 1892 the Thomson-Houston interests and those of the Edison General Electric Company were merged in the General Electric Company, an event of unusual importance, as it brought together the two great competitors in electric traction at that date. Other electric manufacturers, chief among which was the Westinghouse Company, also entered the field and became prominent factors in railway extension. In a few years horse traction in the United States on tramway lines virtually disappeared. Many cable lines were converted to electric lines, and projects such as the Boston Subway began to be planned. Not the least of the advantages of electric traction is the higher speed attainable with safety. The comfort and cleanliness of the cars, lighted brilliantly at night, and heated in winter by the same source of energy which is used to propel them, are important factors.
All these things, together with the great extension of the lines into suburban and country districts, and the interconnection of the lines of one district with those of another, cannot fail to have a decidedly beneficial effect upon the life, habits, and health of the people. While the United States and Canada have been and still are the theatre of the enormous advance in electric traction, as in other electric work, many electric car lines have in recent years been established in Great Britain and on the continent of Europe. Countries like Japan, Australia, South Africa, and South America have also in operation many electric trolley lines, and the work is rapidly extending. Most of this work, even in Europe, has been carried out either by importation of equipment from America, or by apparatus manufactured there, but following American practice closely. The bulk of the work has been done with the overhead wire and under-running trolley, but there are notable instances of the use of electric conductors in underground slotted conduits, chief of which are the great systems of street railway in New York City.
In Chicago the application of motor-cars in trains upon the elevated railway followed directly upon the practical demonstration at the World’s Fair of the capabilities of third-rail electric traction on the Intramural Elevated Railway, and the system is rapidly extending so as to include all elevated city roads. A few years will doubtless see the great change accomplished.
The motor-car, or car propelled by its own motors, has also been introduced upon standard steam roads to a limited extent as a supplement to steam traction. The earliest of these installations are the one at Nantasket, Massachusetts, and that between Hartford and New Britain, in Connecticut. A number of special high-speed lines, using similar plans, have gone into operation in recent years. The problem of constructing electric motors of sufficient robustness for heavy work and controlling them effectively was not an easy one, and the difficulties were increased greatly because of the placing of the motors under the car body, exposed to wet, to dust and dirt of road. The advantage of the motor-car, or motor-car train, is that the traction or hold upon the track increases with the increase of the weight or load carried. It is thus able to be accelerated rapidly after a stop, and also climb steep grades without slipping its wheels. Nevertheless, there are circumstances which favor the employment of a locomotive at the head of a train, as in steam practice. This is the case in lines where a train of coal or ore cars is drawn by electric mining locomotives. Many such plants are in operation, and, at the same time the electric power is used to drive fans for ventilating, pumps for drainage, electric hoists, etc., besides being used for lighting the mines. The trains in the tunnels of the Metropolitan Underground Railway of London have for many years been operated by steam locomotives with the inevitable escape of steam, foul, suffocating gases, and more or less soot.
A number of years ago the tunnel of the City and South London Railway was put into successful operation with electric locomotives drawing the trains of cars, and the nuisance caused by steam avoided. This work recalls the early efforts of Field, of Daft, and Bentley and Knight in providing an electric locomotive for replacing the steam plant of the elevated roads in New York City. Well-conceived as many of these plans were, electric traction had not reached a sufficient development, and the efforts were abandoned after several more or less successful trials. It is now seen that the motor-car train may advantageously replace the locomotive-drawn train in such instances as these elevated railways.
The three largest and most powerful electric locomotives ever put into service are those which are employed to take trains through the Baltimore and Ohio Railroad tunnel at Baltimore. They have been in service about seven or eight years, and are fully equal in power to the large steam locomotives used on steam roads. Frequently trains of cars, including the steam locomotive itself, are drawn through the tunnel by these huge electric engines, the fires on the steam machines being for the time checked so as to prevent fouling the air of the tunnel. There was opened, in London, in 1900, a new railway called the Central Underground, equipped with twenty-six electric locomotives for drawing its trains. The electric and power equipment, which embodied in itself the latest results of American practice, was also manufactured in America to suit the needs of the road. Other similar railways are in contemplation in London and in other cities of Europe. As on the elevated roads in New York City, the replacement of underground steam traction, where it exists, by electric traction is evidently only a question of a few years.
An electric railway may exemplify a power-transmission system in which power is delivered to moving vehicles. But the distances so covered are not generally more than a few miles from the generating station. Where, however, abundant water-power exists, as at Niagara, or where fuel is very expensive and power is to be had only at great distances from the place at which it is to be used, electricity furnishes the most effective means for transmission and distribution. Between the years 1880 and 1890 the device called alternating current transformer was developed to a considerable degree of perfection. It is, in reality, a modified induction coil, consisting of copper wire and iron, whereby a current sent through one of its coils will induce similar currents in the other coils of apparatus. It has the great advantage of having no moving parts. Faraday, in 1831, discovered the fundamental principle of the modern transformer. Not only, however, will the current in one coil of the apparatus generate by induction a new current in an entirely separate coil or circuit, but by suitably proportioning the windings we may exchange, as it were, a large low-pressure current for a small but high-pressure current, or vice versa. This exchange may be made with a very small percentage of loss of energy. These valuable properties of the transformer have rendered it of supreme importance in recent electrical extension. The first use made of it, in 1885–86, was to transform a high-pressure current into one of low pressure in electric lighting, enabling a small wire to be used to convey electric energy at high pressure, and without much loss, to a long distance from the station. This energy at high pressure reaches the transformer placed within or close to the building to be lighted. A low-pressure safe current is conveyed from the transformer to the wires connected to the lamps. In this way a current of two thousand volts, an unsafe and unsuitable pressure for incandescent lighting, is exchanged for one of about one hundred volts, which is quite safe. In this way, also, the supply station is enabled to reach a customer too far away to be supplied directly with current at one hundred volts, without enormous expense for copper conductors.
The alternating current transformer not only greatly extended the radius of supply from a single station, but also enabled the station to be conveniently located where water and coal could be had without difficulty. It also permitted the distant water-powers to become sources of electric energy for lighting, power, or for other service. For example, a water-power located at a distance of fifty to one hundred miles or more from a city, or from a large manufacturing centre where cost of fuel is high, may be utilized as follows: A power-station will be located upon the site of the water-power, and the dynamos therein will generate electricity at, say, two thousand volts pressure. By means of step-up transformers this will be exchanged for a current of thirty thousand volts for transmission over a line of copper or aluminum wire to the distant consumption area. Here there will be a set of step-down transformers which will exchange the thirty-thousand-volt line current for one of so low a pressure as to be safe for local distribution to lamps, to motors, etc., either stationary or upon a railway. The same transmission plant may simultaneously supply energy for lighting, for power, for heat, and for charging storage batteries. It may, therefore, be employed both day and night.
These long-distance power transmission plants are generally spoken of as “two-phase,” “three-phase,” or “polyphase” systems. Before 1890 no such plants existed. A large number of such installations are now working over distances of a few miles up to one hundred miles. They differ from what are known as single-phase alternating systems in employing, instead of a single alternating current, two, three, or more, which are sent over separate lines, and in which the electric impulses are not simultaneous, but follow each other in regular succession, overlapping each other’s dead points, so to speak. Early suggestions of such a plan, about 1880, and thereafter, by Bailey, Deprez, and others, bore no fruit, and not until Tesla’s announcement of his polyphase system, in 1888, was much attention given to the subject. A widespread interest in Tesla’s work was invoked, but several years elapsed before engineering difficulties were overcome. This work was done mainly by the technical staffs of the large manufacturing companies, and it was necessary to be done before any notable power transmissions on the polyphase system could be established. After 1892 the growth became very rapid.