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Radio Power for Transport

20th October 1944
Page 32
Page 32, 20th October 1944 — Radio Power for Transport
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Which of the following most accurately describes the problem?

Conductorless Transmission of Electrical Energy for Operating Road Vehicles has been Successfully Achieved on an Experimental Scale in Russia. Its History and Future Possibilities are Outlined

CUNDAMENTAL limitations of elec

trical power for transport purposes are, in general, the need for the establishment of some system of connection between the vehicle itself and a fixed external source of supply, or the necessity of increasing deadweight by the employment of storage batteries.

In either case, whilst it is known that matters may he so arranged that neither of these factors exerts any apparent influence on the utility of electrical propulsion for commercial vehicles, tacit ignoring of the real state of affairs does not, in fact, solve the problem.

For this reason, "attempts have been made in two directions to profit by the advantages of electricity as a source of motive power : first, by the familiar combination of a prime-mover, such as an oil or petrol engine, in combination with a generator; secondly, by radical improvements in storage batteries (mainly with the object of increasing 'what might be termed their powerweight ratios). Both these devices, however, successful as they are for the specialized fields for which they have principally been developed, offer no real solution to the difficulty.

Harnessing Lightning

Benjamin Franklin may be credited, with beingone of the first to realize the advantages of tapping an external source of power without the intermediary ot , any direct connection. His experiment of sending up a steel wire on a kite into a thundercloud was repeated later by others (sometimes with disastrous results) who performed various chemical and metallurgical operations with the " free " energy so obtained. Moving parts were actuated, but unexpected surges and uncontrollable variations in " line voltage " forbade, from the start, any attempts to run the simple electric motors developed around this date from " cloud " electricity.

Not until the middle of the nineteenth century was it •shown by Maxwell that, in certain circumstances, electrical energy could be propagated through space in a controlled form as distinct from the disruptive discharge of a spark, which needs air for its formation.

Hertz, in Germany, demonstrated a few years later on the basis of Maxwell's calculations, that the theory could be realized in practice. His work was confined to relatively low energy levels and formed the foundations of Marconi's later work on wireless telegraphy.

Tesla has the honour of being the pioneer in the transmission of appreciable power from a generator through space to a distant point where its effects could be made visible. Working on the data provided by Maxwell and Hertz, he devised the first highfrequency transformer. By means of this, he caused unconnected bulbs to glow while he held them in his hand. Nevertheless, experience soon showed that there were many snags to be overcome. Where power was required to be transmitted f or any appreciable distance, the efficiency of the system dropped off so markedly that it became useless for anything but telegraphic or telephonic purposes.

Russian Experiments More recently, intensive study of high-frequency currents and apparatus for producing and controlling them seems to indicate that former difficulties may, in the near future, be overcome, as the following acconnt shows.

On June 16, 1943, in the courtyard of a Moscow factory, the first trip was made by a vehicle driven by power transmitted through space without intermediary contact wires. .This " vechemobile," as Stalin Prize winner G. Rabat's invention was called, was an ordinary baby car in which the internal-combustion en gine was replaced by a direct current electric motor. A receiving spiral was installed on its roof, and, on the back seat, a rectifier, which transformed the highfrequency current picked up by the receiver into the direct current needed by the motor The power line was a copper wire stretched about 12 ft. above the roadway. It carried a 100-amp, current with a frequency of 100,000 cycles a second, The voltage used was not stated.

Further experiments were made by the Power Institute of the Academy of Sciences of the Soviet Union. In the summer of 1943, an experimental highfrequency transport power line was built on the territory of a large Moscow factory. Considerable research was undertaken by G. Babat and A. losifan to improve the old design and obtain the best results.

This time the overhead power line was replaced by an underground cable. Tests were made to ascertain optimum frequency (if the frequency be too high the electro-magnetic field does not spread far beyond the cable, whilst if it be too low there is a tendency for the power to be absorbed by neighbouring underground ;cables), and to perfect the design of the transmission and receiving system, so as to reduce power loss to a minimum. Different types of oscillator and rectifier were tested and, 'for the latter, a novel design of great robustness was evolved. In the early part of this year, " vechecars " driven by a high. frequency current began to be used in this factory for inter-works goods transport.

This new method needs no rails or cumbersome overhead power lines. It is necessary only to lay high-frequency cables underneath the main thoroughfares of the town to enable " vechemobiles " to run with energy supplied direct from road level at any point.

" Vechemobiles " may be supplied with auxiliary accumulators which will allow them to make trips of a mile or -two away from the power mains, and which can be recharged again by returning and moving along the cabled thoroughfares. It is estimated that the running cost for " vechemobiles," including installation charges for the high-frequency generators (sub-stations, cable, etc.), will be less than that of internal-combustion vehicles, or ordinary tramcars. The vehicles themselves can be built more simply. Gearboxes, differentials, and transmission shafts become superfluous; clutch, brake, rheostat and steering, as well as a motor. are all that is required.

This new method of transport, whilst intended primarily for the carriage of heavy freight and passenger traffic. does not preclude the development of a private car, designed also to operate from what might be called "public h.f. mains."

Power from Clouds ?

It may very reasonably be asked whether, at this stage in the development of electrical engineering science, it may not be worth considering, once again, the possibility of harnessing atmospheric elearicity at present allowed to dissipate itself in the form of thunderstcons. Static electricity stored in the condenser formed by the surface of the earth and the clouds is discharged in the form' of lightning flashes at pressures of tens or hundreds of millions of volts. Even though the duration of a flash be less than a thousandth of a second, the energy dissipated per flash amounts to thousands of horse-power.

Until recently, apparatus for handling pressures of the order of 10 megavolts and upwards was not available.

Nowadays, however, we are somewhat more fortunate than Franklin. Commercial equipment is in use which is designed to operate at voltages up to a million and generators can be obtained for the production of up to 10,000,000 volts.

With this apparatus behind us, and a decade or so of experience in superhigh voltage currents, we may yet manage to harness lightning. Limitless high-frequency current will then becom3 available, not for nothing. but, at least, demanding no consumption of' coal, oil or water-power for its generation. When pat day comes, the relative inefficiency of wireless power transmission for transport-vehicle Operation will come to be a decidinp factor in the general commercial adoption of the system described.

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