DEVELOP MENT, the term by which the engineering profession has come to designate the production of water power and its electrical distribution for use as power, light and heat. ABout 1890 it was recognized by some that a change in motive power was imminent, and that gradually the steam-engine and boiler depending on coal would be replaced by water wheels, utilizing the largely wasted forces of the rivers, streams and waterfalls, and converting these into elec tricity, to be sent out at high pressure, over hundreds of miles of wires, and thus distributed to lighting plants and electric motors for use where needed. Gradually capital was inter ested, and power sites have been acquired, and now there has come to be competition for the remaining good water powers, and the public has even been alarmed at the suggestion of monopoly of the important natural resource represented by the potential power of its flow ing waters.
The Niagara Falls power plants settled the question of economical utilization of water power on a large scale. The latent power of the great waterfall was utilized in 1877 in a small way, and in 1886 the Niagara Falls Power Company was chartered to utilize the power on a large scale. It took them 10 years to get going, and the leading engineers of the world were consulted as to the best mechanical means of using the tremendous head and mighty volume of descending water. The difficulty of the problem lay in the fact that there was so much power that ordinary machinery was likely to be broken up by the mighty force it was desired to harness. But the cataract yielded to man's genius just as has the harnessed lightning. A side channel was dug by the Falls, and a pit sunk so as to allow of using a head of 136 feet, and at the foot of these were placed turbines, with shafts running up to the top of the pit, and directly connected to dynamos,. each of 5,000 horse power, far the largest that had then been constructed. To support the weight of this great 136-foot steel shaft, carrying the heavy dynamo and turbine, and whirl it around at a peripheral speed far exceeding that of the fastest railway train, without wearing itself out with friction was indeed a problem. No known bearing would stand such tremendous friction, therefore a new form of bearing had to be devised; and the form decided on was highly admirable. As constructed the heavy column and revolving machinery rest on the flowing water itself. The water comes down the interior of the columnar pipe, strikes the lower surface, rebounds or reacts against the blades of the turbine, causing it to rotate and at the same time lifting or suovorting it in an almost frictionless manner. Thus was solved
the problem of using the turbine wheel for comparatively high heads of water to gain very large power for a single unit machine.
One other important invention was needed to make the utilization of great water power complete, and that was means for sending out a great voltage of electricity to a long distance. This was accomplished by Nikola Tesla, in his notable discovery of the rotating magnetic field. He reversed the arrangement of the dynamo as constructed before his time, making the core stationary, and arranging the magnetic field to revolve around it. This made possible a dy namo for high service, and with the develop ment of improved methods of insulation and minor details, the mechanism for long-distance power, light and heat transportation was com plete.
It is true that before 1891 two fair-sized hydroelectric plants had been established. one sending electricity 13 miles from Oregon City to Portland, Ore., and the other 29 miles from Pomona to San Bernardino, Cal., but these were single phase currents, of not more than 10,000 voltage, adapted to running street cars and electric lights, but not for miscellaneous purposes, for which a polyphase current is req uisite. It should be understood that an alter nating current generator can be constructed to generate two or more currents alternating at the same rate but not at the same time. One current will be just stopping and changing its direction when the other current is flowing with full force; the next instant the first cur rent will come up to its full strength, and the second current will stop and reverse. Three as well as two alternating currents can be com bined and transmitted in this way to a distance, and this system is called three-phase or poly phase transmission. A polyphase current ap plied to an alternating current motor produces a balanced rotation of the armature very much as three or more cranks on an engine-shaft balance each other. One current in the motor will be doing its maximum work while another is at or approaching zero, just as in the engine one crank is exerting its maximum push as another is at or approaching its dead centre. Three-phase transmission was first successfully accomplished in 1891 at Frankfort, Germany, and is now universal.