Electricity and Magnetism

by Elisha Gray

NIAGARA FALLS POWER—APPLIANCES.

Some years ago a company was formed for the purpose of utilizing, to some extent, this greatest of all water-powers. A tunnel of large capacity was run from a point a short distance below the falls on a level a little above the river at that point. The general direction of this tunnel is up the river; it is about a mile and one-half in length, terminating at a point near the bank of the river a mile or more above the falls. Above the end of this tunnel an upright pit comes to the surface, where a power-house of large dimensions has been constructed of solid masonry. It is long enough at present to contain ten dynamos of mammoth size. Along the side of this power-house a deep broad canal is cut, which communicates with the river at that point, and through which flows the water that is to furnish the power. Of course the water level of this canal is the same as that of the river.

The foundations of the power-house extend to the bottom of the tunnel, which at that point is 180 feet below the surface of the ground. To put it in other words, the cellar or pit under the power-house is 180 feet deep and communicates with the great tunnel, which has its outlet below the falls.

Each of the ten dynamos is driven by a turbine water-wheel situated near the bottom of the pit heretofore described. The turbine-wheel is on the lower end of a continuous shaft, which reaches from a point near the bottom of the tunnel to a point ten or fifteen feet above the floor of the power-house (which is about on a level with the surface of the ground).

This shaft is incased in a water-tight cylinder of such diameter as will admit a sufficient amount of water, and connects with the turbine wheel at the bottom in the ordinary way. The water is admitted into the top of this cylinder from the canal, so that the wheel is under the pressure of a falling column of water over 140 feet high. The water, forcing its way out at the bottom through the turbine, revolves it and its long, upward-reaching shaft with great power, and enables it to work the dynamos in the power-house above, as will be described. The water discharges through the wheel in such a manner as to lift the whole shaft, thus taking away the tremendous end-thrust downward that would otherwise interfere greatly with the running of the machine through friction. After the water has done its work it flows off through the tunnel into the river below the falls.

To the upper end of the power-shaft is attached a great revolving umbrella-shaped hood; to the periphery (circumference) of this hood is attached a forged steel ring, 5 inches in thickness, about 12 feet in diameter and from 4 to 5 feet in width. The whole of the revolving portion—including the ring upon which are mounted the field-magnets, the hood, and the shaft running to the bottom of the pit, where the turbine wheel is attached—weighs about thirty-five tons.

The dynamos belong to the alternating type, and are comparatively simple in construction. In a previous chapter upon the dynamo it was stated that the fundamental feature was the relation that the field-magnet and the armature sustained to each other, and that in some cases the field-magnet revolves while the part that is technically called the armature remains stationary. In other cases the armature revolves and the field-magnets are stationary. In the latter case brushes and commutators are used, to catch and transfer the generated electricity, while in the former these are not needed, which simplifies the construction of the machine.

As we have stated, the dynamos used at Niagara are constructed with revolving field-magnets that are bolted on to the inner surface of the steel ring that is carried by the hood, so that there are no brushes connected with the machine except the small ones used to carry the current to the field-magnets.

The current for power purposes is generated in a large stationary armature about ten feet in diameter and of the same depth as the revolving ring. The revolutions of the ring send out currents of alternating polarity, and each of the ten machines will furnish electrical energy equal to 5000 horse-power, so that when the work that is now under way is completed 50,000 horse-power can be furnished in the form of electricity. About 35,000 horse-power is now actually delivered to the various industrial enterprises. The dynamos are set horizontally, since the shaft which connects them with the turbine wheel stands in a perpendicular position.

Not all of the energy that is developed by the water-wheel is converted into electricity, but some of it appears as heat. In order to prevent the heat from becoming so great as to be dangerous to the machine it must be constructed in such a way as to admit of sufficient ventilation for cooling purposes. The armature is so constructed that there are air-passages running all through it, and on top of the revolving hood are two bonnet-shaped air-tubes set in such a way as to force the air down through the armature, which carries off the heat and warms the power-house, on the principle of a hot-air furnace. This great machine—which, in a way, is so simple in its construction—when in action conveys to the mind of the beholder a sense of wonderful power. It is only when we stand in the presence of such exhibitions as may be seen in this power-house, devised and executed by the genius of man, and in that greater presence, the mighty Falls of Niagara, that we get something of a conception of the power of the silent yet potent energy of the great king of daylight, the sun.