« PreviousContinue »
that is, it automatically adjusts its speed to its load. If the weight of the train is increased, or the grade becomes steeper, the speed slows in proportion. If the load and the grade remain constant the speed will not vary unless the voltage applied to the motor is increased. But the system of current supply implies a fixed voltage, and therefore even in emergencies it would be impossible to get a speed much above that for which the motor was constructed. On the other hand, the speed may be cut in half or it may be quartered. This is done by connecting the motors in series, dividing the pressure between two or between four motors, and by the use of electrical resistance. There are other practical objections to this system.
The motor of the three-phase system is inherently a constant-speed machine. With a light load or a heavy load it runs at the same rate of speed. Upgrade or on a level track it makes approximately the same speed also. But the high power required to climb the grade may be several times that needed on the level. On the other hand, however, the motor makes no greater speed on the level track than on an ascent. There are
various devices by which lower speeds can be secured, all of them involving complications and losses. In no way can the speed be more than a trifle higher with a light load than with a heavy train. The motors are comparatively simple in construction, and when on a down grade they may return current to the line, a valuable thing among the mountains.
The speed characteristics of the single-phase series motor are similar to those of the direct-current motor. The speed at a given voltage is more or less as the load is lighter or heavier. But this motor has the advantage over others that by a simple controller its speed may be greatly varied according to conditions. Many voltages lower than the normal may be provided for lower speeds and various higher voltages to produce speeds above the normal. The steam locomotive has its throttle lever, and the single-phase electric its control lever, and in both cases the lever may be placed in any one of many notches to keep the required speed. The current comes aboard the locomotive at a voltage of 11,000 volts on the New Haven lines. But the motors do not use the current at such a high voltage. It is reduced by the transformers which are installed in the locomotives. As will be noted farther on, this means the elimination of the substation, a bold departure, with many advantages. It is the possibility of adjustment, of setting the lever for different speeds, which is a very valuable feature of this system. The limit of endurance with the vast supply of energy thus made available is determined by the safe temperature of the motor. In the steam locomotive ability to maintain speed with heavy loads depended upon the capacity of the boiler.
When it comes to the expense consideration the differences in these three systems is a matter not of motors primarily or of power-houses, but of the transmisTrain The
sion of the power from the latter to the former. In the power-houses almost always the current that is generated is the alternating and at high tension. It is cheaper to transmit it even when for use it has to be converted into direct current.
Each of the systems has a number of links or elements through which the power must pass between the moment of its generation in the power house and its application in the locomotive.
In the continuous current system using alternating current for transmission there must be a sub-station between the power-house and the locomotive. The current is generated in the power-house, raised by transformers to high voltage, carried by wires to sub-stations miles away, where transformers or motor generators step it clown to a voltage low enough to use and converters change it from alternating to direct current: it is then carried by wires to the third rail or trolley wire.
In the case of the three phase system the current once generated is raised by transformers to high voltages, carried to substations about eight miles apart, and stepped down by transformers to low voltage, or the high voltage current may be carried directly to the two overhead trolley wires. In the latter case the voltage is stepped down by transformers on the locomotive. The low voltage three phase current is then fed directly to the motor. Two overhead wires are used and this involves a double system of overhead construction, which becomes quite complicated at cross-over switches. The wires have to be kept well separated and insulated from each other at equal heights above the train. The track in this system acts as a third wire or conductor. In the direct current system the return circuit is furnished by the track.
To get the current aboard the locomotive in the single-phase system, it may
For Suburban Srsvicb On The New Haven Line. new form of overhead construction is clearly shown.
be generated in the power-house, raised by transformers to high voltage, carried by wires to sub-stations, widely-separated, where it is stepped down to a usable tension, and carried to a single wire strung over the railroad tracks. The single wire permits a wide range in height as the trolley adjusts itself automatically to the position of the wire. Usually the wire is strung on lines twenty-two feet above the track but passes under bridges at a height of fifteen and one-half feet. Once more the track acts as one side of the circuit.
But a remarkable part of the great feat of the New Haven was that it abolished the sub-station where the transformers intervened between the locomotive and the power-house. It took the current at high tension aboard the locomotive itself. This it could do because the length of the line on which the service was installed 'was but twenty-one miles. It was a daring bit of pioneer work to take the high voltage alternating current aboard the locomotive and lower it there to the low voltage current required for the motors, doing aboard the speeding locomotive what had been done in the sub-stations scattered along the railroad lines. This saved the great expense of direct-current work and it secured a very high degree of efficiency.
If railroads consider electrification they ask of course about such matters as the cost of the respective systems and their comparative losses of power between generatois and locomotives. The first cost of the single-phase installation is much less than either of the others. Although the locomotives cost a little more, the cost of operation is considerably less in case of the single-phase system.
This outline of the situation indicates what the problems of the electrical railway engineer are going to be. As the crocuses promise the spring so the electrifications already made presage the coming of the vast electric systems of the future. Almost every week witnesses some installation. The Michigan Central has just started its electric operation in the tunnel under the Detroit River. The very first thing that was done by the president of the New Haven lines when he became the actual president of the Boston and Maine was to send an engineer to the Hoosac Tunnel to devise plans for the electrification of the miles of underground line at that point
In a comparatively short time the railroad work of all New England will be done by electricity? New York will soon be linked with Philadelphia, Philadelphia with Baltimore, Baltimore with Washington, by electric railways. Electricity will supersede steam between such cities as Cleveland and Toledo, Cincinnati and Columbus, Chicago and Milwaukee. Centers of electrification will come into being in various parts of the country. At last some long trunk line will come forward with electric power in use from terminal to terminal. And so, step by step, the complete, or nearly complete, electrification will arrive. How enormously desirable that this outcome shall be anticipated and that broad-minded and statesmanlike plans shall be made.
There are a few words to say about the work done on the New Haven line. On express trains and trains of great length two locomotives are used. This is not due, as rumor had it, to any error of design. The locomotives were made to develop eighty per cent, of the power for a maximum train load. The ordinary train load is not of the maximum weight. To have made more powerful engines would have been to waste them on trains so light as to leave unused a large fraction of their capacity. It is greater economy to double up the locomotives on the comparatively few trains that require that power in excess of what one will develop. The two may be operated without any additional crew, it must be understood.
These locomotives are very interesting. Tender, cab, cylinders, connecting rods, dome, smokestack, have disappeared. They look to be all cab. Only the cowcatcher and the headlight of the old order remain. The engineer and his assistant have about them only a few knobs and handles. The corridor running from end to end—for these locomotives have no front and rear; they are doubleheaders, needing no turntable at the end of the run—these corridors are walled with steel. Behind these walls are muzzled cyclones hard at work.
The countless millions of electrons rush from the transmission line to the
motors, which are the essence of being of the locomotive. Here their energy is wrested from them and they are made to do work in driving the train, after which they return to the line to again complete their cycle.
It is true that direct current and alternating current in combination had been used before for light service on certain unimportant lines. But the enormous weight of the trains, the volume of the traffic, and the character of the service, make the New Haven's a real pioneer work. When its experts began to study the problem of electrifying these twentyone miles they were told to keep in mind the ultimate electrification of the whole Shore Line route between New York and Boston. It now seems likely that this railroad thus has made a very valuable contribution to the great railway problem of the future—a uniform system of electrification.
When love with unconfined wings
Hovers within my gates, And my divine Althea brings
To whisper at my grates; When I lie tangled in her hair
And fettered with her eye, The birds that wanton in the air
Know no such liberty.
When flowing cups pass swiftly round
With no allaying Thames, Our careless heads with roses crowned.
Our hearts with loyal flames; When thirsty grief with wine we steep,
When health and draughts go free— Fishes that tipple in the deep
Know no such liberty.
"TOW you see it, and now you l^k 1 don't," is a sign that Nature I I might well display over a j| ^1 little group of islands in X. i Bering Sea, where the great Mother of the Universe plays the part of sorceress, coaxing mountain-tops from the depths of the ocean and making them disappear again in the twinkling of an eye, amid a demonstration that only a favored few have witnessed. The stage that Nature uses for her works of magic is apart from the main lanes of ship travel just to the northward of the long string of Aleutian islands that swings from America almost to the Asiatic
shore. In no part of the world do remarkable seismic disturbances more frequently recur than in this isolated spot. So often do these large-scale acts of legerdemain transpire that no visitor at Nature's black art theatre ever expects to see the conjured islands in the same form upon a second visit.
It was in September of this last season that the most recent performance was given at the Bogoslofs—for such is the name of the enchanted Bering Sea group. The officers and crew of the revenue cutter Tahoma, which had recently returned to Puget Sound from a summer cruise in the vicinity of Pribilof seal