ROTORUA'S ELECTRICITY THE POWER-HOUSE AT OKERE FALLS.

Auckland Star, Volume XXXIII, Issue 112, 13 May 1902, Page 2

ROTORUA'S ELECTRICITY THE POWER-HOUSE AT OKERE FALLS.

The Thames "Star" gives an interesting account of a recent visit paid to Rotorua by a party in connection with the Thames School of Mines electrical class, an-d the following description, furnished "oy members of the party, of the source of Rotorua's electric light supply:

The power-house at Okere Falls is a typical exaar n jlfe of the way man has begun to harness nature for power and lig-hting purposes. Thoug-h not so large as Niagara, the plant at Rotorua may claim to be ;'ust as up-to-date and efficient as any work the Americans have. From a British point of view this is very satisfactory, for with the exception of one or two minor details, the whole of 'the plant is of British manufacture. The -power-house Is thirteen-'miles from Rotorua, and is situated at the outlet of Lake Rotoiti. A head of fourteen feet -is obtained by constructing a large flume lSft wide, Sft deep, and 209 ft long", of kauri. The intake of this is placed above the higher of the two falls, one eight feet high and the other six feet. The power-house, is situated on the bank of the river just below the lower fall. It is interesting to know that at the time of the visit the amount of water being used was but a small fraction of. the total available, so that there is power for nrnch more plant than at present being usefl.

There are two turbines, each of one hundred horse-power, driving two large dynamos of the latest pattern, known as "Mordey's Inductor.1' A novel feature of these machines is that they have'no moving coils of wire, as in the ordinary dynamo. Simply, they are two separate coils of wire wound inside a' huge steel casting, a large steel magnet revolves between them, a current of electricity,, generated by a small, ordinary dynamo, mounted on the name shaft as the magnet, is sent round one of the coils, the magnet revolving causes a disturbance of this current, and a much larger current is induced in the other coil. The latter current is the one'"used for transmission .to P.otorua, and is at a pressure of 4000 volts. It does not flow in one direction the whole time, but rapidly merges backwards and forwards many times a second—in the case of these machines fifty times. The change is so quickly done that like a pendulum oscillating rapidly it cannot be followed by the eye.

The' current is conveyed to Rotorua by two wires, each 1-5 of an inch in diameter. The power lost in overcoming the resistance of the wire is 1000 volts; 3000 volts are thus delivered for use at the Rotorua end of the line. At this high pressure it would both be unsafe and useless for ordinary work. A device known as a transformer is brought into use. This consists of" two coils of vvire wound round a number of iron sheets, one of the wires is connected to the supply mains, the other to the customers' wires, the latter getting only 100 volts. The voltage the customer gets is regulated by the number of turns of wire connected to his" lamps, that are wound on the transformer.

That the electric light is a great improvement there cannot be any doiiibt. The streets and gardens are brilliantly lit by arc lamps, and many of the shops and. private houses.are adopting it. The price,..too, is reasonable, being sixpence per board oi trade unit. A unit will light an eight-candle-power lamp for 3G hours.