THE ELECTRIC LIGHT.

New Zealand Mail, Issue 907, 19 July 1889, Page 9

THE ELECTRIC LIGHT.

The final and full installation of the electric lighting of the City of Wellington took place last Friday night. There have been several delays in connection with the installation. In the first jflace, the water mains laid down by the Corporation were found to be insufficient to drive the turbines at a proper rate of speed. Then some time was taken in discussing the matter in the City Council. At last it was decided to lay down the larger main. This was completed laat week. The installation can only be classified as a thorough success, aud Wellington now occupies the proud position of being the best lighted city in the whole of the colonies, and perhaps, considering her size and number of inhabitants, the best lit city in the world. The lamps, 500 in number, are well distributed all over the city, although there are several streets where it will be found by experience that more lamps are required, and some of the outlying suburbs—such as Mitchelltown, for, example—will sooner or later have to be supplied with this brilliant light. ! : i Wellington is indebted to Mr Samuel Brown, ex-Mayor, for this great boon. When he first mooted his ideas in public on the matter he was met generally with the cold shoulder, but feeling convinced that the time had arrived when the Empire City of tbe Colony had advanced enough in civilisation to adopt the best and latest devised scheme of street lighting, he set his mind resolutely to the task, and in spite of all opposition carried his point so far that the city is in full possession of one of the most perfect lights yet invented. On Friday night, although the weather was most miserable for out-door traffic, and as in wet weather electricity is produced with more difficulty, the street lights were in splendid working order. The new large mains recently laid down afford ample pressure at the Panama-etreet station to drive the turbines at a rate of speed sufficient to develop in the dynamos enough electricity to light the number of lamps belonging to that station. The view of the town from the heights of Mount Victoria was a charming one; ■■ The whole city lay spread at the feet of the spectator like a huge map on the projection system. The eye ranged from the far end of Thorndon to, the confines of the Newtown Park. . Scon'after dusk, as far as the eye could see, street after street was dotted suddenly with tiny glowing glints of light, resembling' so many isolated knitting needles heated to a dull red heat. Then these gradually increased in depth of colour, passing from the dull, cherry red into a crimson-like flame, verging rapidly into the full, pure white blaze of electricity. Then tho city was brilliantly lit. The sheen of the light gleaming upon the wet pavements and roadways of the city was reflected more brilliantly upon the masses of houses than it would have been on an ordinary fine weather evening. The city, despite the wet night, had a very pretty effect. Street after street in long straight lines or mazing into intricate perspicuity appeared fringed with glowing stars of flame, while above the tops of the houses hung a luminous cloud of soft lambent light. Great credit is due to the contractors of the Giilcher Light Company for the very successful installation. They have spared no pains or expense to make Wellington the best lit city south of the Line. Mr A. J. Baron, the representative electrician of the Company, arrived here in November last, and since that date has worked very hard, and for the last few weeks almost day and night, ia one to bring to a successful issue the work he had undertaken. In this he was very ably assisted by Mr Cederholm, representing the agents for the Company, Messrs Miles and Co., of Christchurch, Mr Baron will shortly leave for another part of the Colony, and Mr Cederholm will remain here as resident engineer in charge. Mr Baron returns here when the Company have undertaken the task of supplying the electric light for private houses and business premises. We feel assured that from the success of the street lighting, there will be a large number of applications for this delightful light in private residences. In order to give our readers some idea of the plant required for lighting this city fcy electricity, we give the following descriptions of the two dynamo stations—one erected in Panama-street and the other in Mannersstreet :—The turbines are of the vortex type, invented by Professor James Thomson, LL.D., F.R.S., are of 30 horse-power, adapted to a fall of 276 ft, or a minimum pressure of 1201bs to the square inch ; at which pressure they will work at an efficiency of 75 per cent. The turbine consists of a movable wheel of wrought steel, 14in in diameter by about lin wide, with radiating vanes, some of which do not extend to the central orifice, the object being that they may not too much fill up the contracted part of the passage and thu3 impede the flow of the water. The wheel is screwed to a shaft two aud a half inches in diameter, which passes through stuffing 'boxes and glands at either side of the centre and revolves in two bearings of gunmetal ; it ia also provided with fast and loose pulleys 17im in diameter. The wheel ia

surrounded by an annular case of cast-iron, closed externally, but having on its internal circumference four curved guide bliyles of bronze. They are designed to use, when full open, 109 cubic feet of water per minute. When closed they lap over and completely cover the circumference of the wheel, the whole being watertight. Hand wheel gear is used to control these guide blades, and is so arranged that a very accurate adjustment can be made to meet the varying pressure of the mains. The water is admitted to the case fay one or more pipes, aud issuing through the guide passages, acts against the vanes of the wheel, driving it round at a velocity depending on the height of the fall. Having expended its force on the vanes of the wheel, the water passes out at either side of the centre into suction bends which convey it into a Y pipe, thence it is conveyed to a wastewater drain. The power is transmitted from the turbines by means of buffalo hair belting 9in wide, to pulleys 6ft 6in in diameter, and 12in on the face, bolted Tound and tied to the countershaft.

Tbe countershaft is provided in all with eight Rogers' wroughfc-iron pulleys, 2ft 6iu in diameter, at either end connecting with the fast and loose pulleys of the turbines, and nearer the centre two 3ft pulleys for tte alternating dynamos, and two 2ft Gin pulleys connected by an inch belt to a Schaffer and Budenberg tachometer, which gives an instantaueous reading of the speed of the countershaft, which is nominally 300 revolutions per minnte. The countershaft, which is 32ft long and 4in in diameter, was imported iu three pieces, which are coupled together by an ordinary coupling, runs in bearings, the plummer blocks of which are supported by five standards bolted to blocks of conarete by iron cotter bolts, 4ft long by lin square. The dynamos for generating the alternating current which is supplied to the street lamps are of the class L, Giilcher .type, and are provided with pulleys "in diameter, which are driven from the 3ft pulleys on the countershaft by means of S-ineh buffalo hair belting. Both in their mechanicals aud electrical details they represent a simplicity far greater than is possible with any dynamo generating a direct current. The magnetic field is composed of a series of twelve palp pieces, having alternate polarity, the cores of which are of the best wrought iron, turned down and fitted with circular nuts, so as to i-ecare large contact surface with the yokes. The magnet are a series of bobbins, each connected iu circuit with all the others, and are wound with many turns of thick cotton covered round copper wire. The armature or ring in which the electrio current is generated is built up of the best soft Swedish rectangular charcoal iron wire wound upon a gun-metal pulley and forming a core of nearly square section. This is overwound with 12 coils of insulated copper wire (corresponding with the 12 pole pieces of the field magnets), the end of each coil and commencement of the next being connected together, the two ends of the whole length of wire being carried along the shaft, to which the armature is screwed through tubes of vulcanite to two brass collecting rings heavily insulated from one another, and from the shaft by fibre and asbestos. The whole dynamo rests upon sliding bedrails, which are insulated from the concrete foundation by baulks of kauri 4in by 12in, boiled in paraffine wax. The bolts holding the bed-rails down are also covered with ljin rubber hose for the purpose of insulation. Theoutput of these.machines is 20 amperes, or units of current, aud 1400 to 1500 volts, or units of electrical pressure. As the current generated in the armature is not commuted into a continuous current by means of a commutator. it 13 of mo use for producing magnetism in the cores of tbe field magnets, for the current is reversed in direction some 8090 times in a minute, consequently the magnetism produced by one alternation is cancelled by the next. It is, therefore, necessary..to excite these cores with a continuous current from another source. This is done in the present case by small continuous current dynamos of the A class Giilcher type, which are driven at a speed of 1100 revolutions per minute by means of a 3Jin hair belt from the 2ft 6in pulleys on the countershaft, the output being fifty volts or units of electrical pressure and sixty amperes or units of electrical current. Tbe dynamos have only four pole pieces,- and the current, which is alternating in the armature, is commuted into a continuous current by means of a commutator or copper cylinder, consisting of a number of striijs or segments of copper, insulated from each other by mica, the number of strips corresponding with the number of coils of wire on the 'armature. The brushes which rub upon the collector rings of the alternate dynamo for the purpose of collecting the current from the armature as it rotates.

are connected by insulated wires, which are led enclosed in wooden casing to a switch board about 12ft square placed against one of the walls of the building, from whence the main current is distributed by means oE switches to the different circuits leading away through the roof of the central station to different parts of the city. There are two rows of switehes, four in each row, by the turning of any of which from 100 to 150 lamps distributed in the streets of the various wards are instantaneously lighted. By means of switehes on the bottom row the who’e of the lights may be thrown on to either one dynamo or the other in case of accident, in the same way with the switches of the upper row. Just as a train cau be switched from one line of rails by means of points, so can the electric current be switched from one line of wires to the other, according to the will of the operator. Before we proceed further, we may state that the whole question of electrical distribution has been popularly illus. trated by its analogy to hydraulics. The dynamo is essentially a rotary pump, but pumping electricity instead of water. If the discharge pipe of a rotary pump be carried around through a given circuit and connected into the suction side, both pump and pipes being fullof water, the movement of the pump will obviously cause the water to flow in one direction, producing a continuous current of water. Now substitute dynamo for pump, wire for pipe, and electricity for water, and the conception of electrical transmission by continuous current ia at onca

clear aa to itß elementary phenomena. Bracket analogous electrical terms, and it >may be said that a certain number ®f pounds (volts) of pressure is required to overcome the friction (resistance) of the pipe (wire) in order that the water (current) may flow at the rate of so many gallons (amperes) per minute. The larger the pipe (wire) the more water (current) caa be carried, and the less will be the friction (resistance or drop), or per contra. The smaller the pipe (wire) the less quantity (amperes) per minute, and the greater will be the friction (loss or drop). Manifestly the pipe (wire) might be so small that the friction (resistance) would absorb a very large proportion of the power of the pump (dynamo), leaving but little remaining for useful effect, therefore the two horns of the dilemma are : If the pipe (wire) be too darge it will cost too much; if too small, fche loss (drop) will be too great, and right at that point all electrical advance has balked until the advent of the alternating system. In this system the alternating current leaves the station at a high pressure and small quantity by the various so-called primary mains, and is conveyed to some forty or fifty transformers or converters, which are practically the heart of the alternating system, and is there transformed down to a small tension or electro motive force, and a larger current or quantity for use in the lamps. The Giilcher transformer or converter, which is one of the simplest and bestconstructed in the market, consists essentially of fourooils, two of great length of fine wire called the primary coils and receiving the • current from the dynamos, and the others v of a short length of large wire, in which is induced the secondary current for the lamp service. These coils are wound upon two cores of the softest laminated sheet iron, and are completely insulated from one another. The cores are placed in an upright position side by side, and serve to confine the lines of foioe and greatly increase the efficiency of action. The transformers are of different sizes, and are capable of supplying from 10 to 50 lamps of 20-candle power. The transformer, which is bolted to a piece of inch dry wood, is placed-in a cast-iron box, on the face of which is bolted a flat cover, making a waterproof joint, the top of the case being covered with a weatherboard, in order to prevent the water from settling on the top. The connections having been made through safety fuses of lead-tin wire mounted on Blate bases, are brought through watertight and insulated glands to the outside of the case, the two wires from the secondary coils being connected to the two secondary mains, and the two from the primary coils to the two primary mains, supported by insulators on the crossarms above. The reason for using this high tension or transformer system is that there iB very little loss of power over long distances in comparison with the lower tension continuous current system. Tne cost of the copper mains in an installation covering the area that is lighted by electricity in this city would be quite prohibitive.

It may be interesting to the public to know that there are two central electric light stations—one in Panama-street and the other in Manners-street. Both are as nearly alike in every detail as possible, no expense having been spared by the Company to make them as complete as a modern central station can be made, everything being of the very latest design and best workmanship. In the erection of the installation there have been 86 miles of insulated copper wire, of No. 10, 12, 14, and 18, Birmingham wire gauge, used to convoy the current to the 500 incandescent lamps in the city. To support the wire, it was found necessary to use 1190 poles of heart of totara, 6iu by Gin, and some Sin by Sin. The number of rata crosß arms requisite was 2500, with the same number of galvanised iron bolts and nuts, and 7000 insulators. The lamps themselves are enclosed in a four-sided lantern, with Blightly fluted glass sides, surmounted by a neat and ornamental top, painted white inside, which reflects the light down upon the street ; the whole being suspended from the pole about 14ft from the ground by a ourved iron bracket, which is hollow, and through which the wires which supply the lamp pass. The whole installation is the property of the Giilcher Electric Light and Power Company, Limited, of Battersea Foundry, London, and has been erected by Mr A. J. Baron, one qf the Company’s electrical engineers, who came out’ from Home last November for the purpose, and Mr H. S. Cederholm, who has carried out several installations in the Colony for Messrs Miles and Company, the Giilcher Co.’s agents for New Zealand.