THE LAUFFEN-FRANKFORT TRANSMISSION.

In our issue of Aug. 28 will be found a description, with illustrations, of the Oerlikon apparatus for the transmission of power, except so far as regards the transformers. We are now, by the courtesy of Mr. C. E. L. Brown, enabled to supplement the previous information with other details. In the first place, there seems to be in some quarters a difficulty in comprehending the winding of the armature adopted. This point may be made clearer by an examination of the accompanying diagrams. There are three distinct windings upon the armature, represented diagrammatically in the sketch, Fig. 1. The shaded rectangles represent the poles, those, say, at the right-hand side being alternately S and N. The three circuits are represented

connection.

We further give on opposite page an illustration of the large high-pressure transformers employed in the LauffenFrankfort experiments.

The magnetic circuit is composed of three laminated iron columns of circular section, whose ends are connected by two flat laminated rings similar to a Brush armature core. Over each column are slipped the high and low tension coils. As the drawing clearly shows, the high-tension coil is boxed between the low-tension one. This disposition reduces the inductive drop, and simplifies the way of making the low-tension connections.

The construction of the whole transformer is such that any part of it can in a very short time be replaced. This transformer was designed to have an output of 200 kilowatts, and working with a normal pressure of 13 to 15 thousand volts. To ensure a very good insulation, the transformer is completely plunged in oil, but without this precaution the insulation is so good that the transformer can stand the high pressure of 15,000 volts, as has been proved by practical tests. The commercial efficiency at full load will be about 98 per cent,

In the early part of the year Mr. Brown read a paper at Frankfort on this subject, which appeared in the Elektro technische Zeitschrift, No. 11, an abstract of which we give elsewhere. It is somewhat generally thought that the multiphase current was the means of enabling the successful experiments at Frankfort. Mr. Brown says the multiphase current made the undertaking more difficult, as it involved many new complications in the dynamo, transformer, switchboards, and line. It was only chosen because of the possibility of driving self-starting motors without commutators.

ELECTRIC TRAVELLING CRANES.

The substitution of electric driving for other modes at present in use can be carried out upon any design of crane without necessitating important modifications. Excellent results are obtained, on the condition, of course, that the apparatus employed is carefully constructed and the arrangement is properly designed for the purpose required.

The application of electric motors to cranes has recently been carried out, says M. Desquieux, in the Genie Civil, by Messrs. Schneider et Cie. on several forms of their travelling cranes, notably upon a 60-ton crane used in their artillery works.

of

This crane was originally employed to serve a space 50ft. wide and 330ft. long; worked by cables it could only raise 35 tons continuously with a speed of 2ft. per minute. With this load the speed of translation was 50ft. per minute. It was found that over 35 to 40 tons the rope slipped on all the pulleys and rapidly became charred. The life of the cable was hardly more than 10 months.

Recently the problem presented itself of making this crane serve 230ft. more, in all 560ft. The further use of cables could not be entertained, the inertia at starting being very considerably increased. It was necessary, therefore, to find other means of setting the gear in movement rapidly, and at the same time utilising the full power of the

crane.

Very satisfactory results having been obtained with a travelling crane of 15 tons, it was finally decided to adopt as driving gear the electric motors of Ganz and Co., constructed at Creusot.

The following are the details of the arrangement: A Ganz continuous-current dynamo, type D 5, of 45,000 watts power, is fixed on the framework of the crane on the opposite side to the gearing, and drives the axle by a belt. The current is led from the dynamo by two bare cables of 12 mm. diameter, fastened at the two ends of the workshop and held up every 10 yards on porcelain pulleys; the current is taken off simply by two shoes

fixed on the crane.

The accessory apparatus for starting and regulation, such as resistances, switches, ammeter, and voltmeter, are placed within the cage within the reach of the driver.

The current is produced by a dynamo, type D 5, of the same capacity as the motor. It also supplies current for a 15-ton crane carrying a D3 motor, a wood-working shop which contains a D 3 motor, and several electric drills.

Under these conditions the crane raises with ease 40 tons with a speed of 7ft. per minute, and a load of 60 tons at 3ft. per minute. The speed of translation is about 90ft. per minute, so that to cross the entire space only requires about six minutes.

Owing to the method of exciting the dynamos, the voltage of transmission, which is 220 volts, remains constant, and the variations of speed of the motor empty and at full load do not exceed 5 per cent. Further than this no special precaution is taken for the running of the crane, and the maximum load is put on quickly without the least inconvenience.

Besides these advantages, the electric transmission has enabled an effective safety apparatus to be added to the crane gearing for the purpose of preventing any accidental fall of the chain in case of prolonged or involuntary descent. This apparatus breaks the main circuit to the crane, which at the moment of descent is always weak, while yet keeping the dynamo excited, with the result of a very quick stoppage.

opposite conditions a difficulty results which is evidently insurmountable. The proof of this may be seen in the multiplicity of axle arrangements which have been devised from time to time to realise each of these conditions without too far interfering with the other. The problem of the steam locomotive is not solved; the fault lies in its nature itself. We do not need to mention a further defect and one not less grave-the reciprocating nature of the movement.

RAILWAY TRAINS.

We have already urged the advantages of electric traction for tramway and underground railways with sufficient frequency for there to be any need to dwell further upon this side of the question. The smoocaness of motion, the absence of vibration, the facility of starting, are all points which characterise this mode of traction. If, added to these advantages, economy and greater speed could be demonstrated, it would need no efforts on our part to draw attention to its extreme importance.

M. J. J. Heilmann has, as we have recently had occasion to mention, set himself the problem of applying this method of traction for ordinary long-distance railways without changing the present permanent way to any appreciable extent. The solution proposed by M. Heilmann, which is at the present moment in a fair way towards execution, consists in the daring scheme of carrying along with the train itself its own electric station-engines, boiler, and dynamo-and distributing the energy so generated to the various axles by means of directly-geared electric motors. The power for the train will be thus generated along the route, as is the case with the present locomotives, but with the additional benefits of speed, economy, and safety that can be obtained from the use of electrical means of traction.

The company formed by M. Heilmann in Paris, under the name of "Traction Electrique Système Heilmann," having offices at 30, rue de Grammont, proposes to carry out this project in two different manners, and the construction of one form of electric locomotive has already been commenced. This is formed of one long vehicle mounted upon two trucks, articulated together to form one loco motive, carrying boiler, steam engine, and generating dynamo, the current being transmitted by way of a switchboard to motors mounted on all the axles of this locomotive.

The second project is an extension of the first. It consists in furnishing the entire train with electric motors driving the axles of every waggon. As the details of the second project are yet being arranged, we shall speak more particularly of the first scheme.

It seems extraordinary, in the first place, that any advantage could be gained by transforming the mechanical energy of the locomotive into electrical energy and transforming this once more back again into mechanical energy, and at the same time increasing the weight of the train by the weight of the dynamos and motors. There does, however, exist such an advantage, and the reasons below serve to demonstrate this fact.

the former, and the recent experiments carried out in America have shown the destructive influence of counterbalance weights both upon the tyres themselves and upon the rails

With the electric motor, nothing similar occurs; the movement is continuous and the energy constant. The motor is symmetrical around the axle and follows it in all its movements. Nothing prevents the possibility of allowing the necessary play between axle and bearing for describing the curves and the various displacements necessitated by the state of the road.

The electric motor allows the total adherence of the locomotive to be utilised, each axle being fitted with its own motor and exerting a tractive force.

The difficulty of getting rid of steam at very high speeds may also be mentioned.

The Heilmann electric locomotive presents externally the form of a car of 15 metres (49ft.) long, mounted upon two bogies of four wheels each. All the wheels are driving wheels. Their diameter is 104 metre (3ft. 5in.). All heavy parts rest, so to speak, above the bogie cars, so that the framework is relatively light. The boiler is placed behind and works the opposite way to those of the ordinary locomotive boilers. It is of the Lentz type, already applied with advantage to ordinary locomotives. Its chief features are a corrugated furnace, followed by a combustion chamber. The tubes are relatively short, and the boiler is without stay-pieces. The length it occupies upon the vehicle is about eight metres (26ft.). A free space follows for the stoker, then comes the steam engine, which is a high-speed machine coupled direct to the dynamo. Special arrangements have been provided for starting, stopping, reversing, etc., together with a special type of motor.

The front part of the Heilmann locomotive finishes in a conical point, to reduce the resistance of the air to a minimum. The driver will be seated within this projection, and will have before him all the apparatus and handles, both of the switches and of the brake.

Without entering further at the present moment into the details of the subject of this interesting system of traction, we may add only that it permits the attainment of any speed, however high, that can be borne by the rails, with trains of unlimited tonnage. The inventor states his confidence in being able easily to achieve the speed of 130 kilometres, or 80 miles an hour. The experiments_which are shortly to be undertaken on the lines of the French State Railway, will inform us whether these expectations are capable of being realised.

CONDUCTION, AND APPLICATION.*

It is unnecessary in the course of this paper to go into the theoretical reasons why a given amount of electrical energy can be transmitted by thinner conductors, and with less loss, in proportion to the increase in the tension of the current. The simplest calculation shows that if we were not bound down within practical limits as regards the highness of the tension, immense effective energy could be transmitted by quite thin conductors with insignificant loss and to the greatest distances. But in this field, as in others, there are practical limits which cannot be exceeded. These limits are determined by the following points: Firstly, what is the highest tension which can be produced for industrial purposes by safe apparatus; secondly, what

*Abstract of a paper read by Mr. C. E. L. Brown before the Electrical Society of Frankfort-on-the-Maine on 9th February, 1891.

is the highest tension which can be transmitted over long distances with the means at disposal; and thirdly, to what extent can protective measures be adopted against the dangerous effects of a high-tension current.

Up to the present, currents of 2,000, 3,000 and perhaps 4,000 volts were considered the highest in practical use. However, the author's activity in the field of the electrical transmission of power and the ever-increasing scope of new projects, the carrying out of which would cause a great advantage in national economy, showed that the extreme limits of practicability had by no means been reached. The author has consequently endeavoured for several years past to introduce higher-tension currents for practical purposes, and the question has arisen as to the best means of producing them.

In considering closely the subject of our ordinary continuous-current dynamos, the limits of practical possibility is soon reached. The arrangement of the armature winding

and the necessity of a commutator render it difficult to construct machines for high tension, at least with the insulating materials available up till now. The author has constructed continuous current dynamos up to 2,000 and 2,500 volts, which could be run uninterruptedly day and night without causing difficulties. The construction of these, however, showed the author that if higher tension currents were not impossible, yet they led to circumstances, and particularly between the insulating material and the working copper of the armature, which would cause the machines to reach an uneconomical size.

More favourable results are obtained with alternatingcurrent dynamos which deliver a high-tension current direct. The separate and complete divisions of the armature winding, each of which produces only a fraction of the total current, the dispensing of the commutator, and the possibility of allowing the armature to stand still and to rotate the magnetic field, render the alternating-current machine essentially more suitable for the direct production

of high-tension currents. An excellent example of this is to be found up to the present in the large Ferranti dynamos. But however well constructed, all dynamos for the direct production of high-tension currents have the disadvantage that they require manipulation while running, thus not quite avoiding a certain danger of interruption and to the workmen. The ideal apparatus for our purpose is one which is not in motion, which does not require continual attention, and which will perhaps work without interruption for years, and without having to be touched outwardly. We thus come to the transformer. The object and manner of working of the transformer are well known, and the author therefore gives the points which have guided him in the construction of his transformers. A transformer should be so made that it can readily be taken to pieces. The primary and secondary coils should be independent, and both easily removable from the mass of iron and from each other. The construction of the coils should be of such a nature that they can be made without special expert labour on any lathe, as faultless work at the beginning gives the best results, and allows of repairs being easily effected. The insulation should be such that an arc, or contact between the two windings, may be regarded as impossible. Lastly, the general arrangement and the external protection should allow of the apparatus being fixed without danger in any place and under any circumstances. That the construction of a transformer which will fulfil all these conditions is possible is shown by those made by the Oerlikon Engineering Works. There is now, of course, the usual transformer for pressures of 2,000 to 3,000 volts, but none of that kind for tensions of 20,000, 30,000, and 40,000 volts. But if it is possible to make one to work after the ordinary type for very high tensions fresh from the workshop, its working safety would be interrupted, first of all, in consequence of the influence of the atmosphere, out of which all usual insulating materials absorb more or less water. Against this a new factor must arise-namely, oil as the insulating material. Oil is one of the most perfect non-conductors, and the high insulating properties of a thick resinous oil can be shown by a simple experiment. The ends of two cotton-covered wires are twisted together, and placed in a vessel containing oil, see Fig. 1. This is then heated highly for a long time, so as to expel all the water from the cotton and from the oil. Glass tubes are placed over the wires where they project from the oil, and the tubes reach below the surface of the oil. Water can then be poured upon the oil. On connecting the upper free ends of the wires with, for instance, the poles of an influence machine, sparks several centimetres in length can be obtained between the wires in the air without any arc being formed between the twisted parts of the wire immersed in the oil. This is certainly a striking proof of the insulation attainable, and of the resistance to the formation of an arc, afforded by the use of oil.

The first use of oil in this way was probably by Brooks, in connection with underground conductors. The author was the first to introduce oil as an insulating means for high-tension transformers. He places, first of all, the whole apparatus in a cast-iron box, which is then filled with oil, and subjected for a long time to a temperature of up to and over 150deg. C. The advantages of this are the oil forces its way into all pores and crevices of the apparatus, expelling all air and moisture, and covering the whole transformer. By this means the possibility of the piercing of the insulation is greatly minimised, and the transformer is absolutely protected against the external influences of the weather, dust, etc. These influences affect only the upper surface of the oil filling, and the oil always remains a compact mass, and is thus preferable to paraffin, for instance, which in time cracks and absorbs moisture. Great care is, in addition, necessary in +1 winding of the coils with the thin wire, and in the i each layer from one another. Special attenti be devoted to the manufacture of the lead For low-tension currents the coils are usual simple. The first of the transformers mad pointed out by the author, could at once be 40,000 volts without causing any difficulty.

By means of transformers exceptionally