Electrical Transmission by Oerlikon machines

[Trade Journal]

Publication: Electrical World

New York, NY, United States
vol. 11, no. 4, p. 42, col. 1-3


Electric Transmission of Energy by Oerlikon

Machines.


Our columns have already contained an account of experiments made at Zurich, Switzerland, with Oerlikon dynamos, designed to transmit the power of a waterfall a distance of five miles from Kriegstetten to Solothurn. These experiments were made by a committee of engineers and scientific men, with a view to ascertain the total commercial efficiency of the transmission plant; but as the machines were in this case placed side by side, the results could only be taken as approximately correct. It is evident that, in such an arrangement of machines and resistances erected within the limits of a covered workshop, the insulation of the circuits presents no difficulty whatever, whereas in the actual installation, when many miles of overhead wires must be used, the insulation becomes a matter of some difficulty, and atmospheric influences may also have some effect upon the performance of the plant. These considerations induced the makers to arrange for some further trials with the plant as actually installed. A committee was appointed, under the presidency of Professor Amsler, of Schaffhausen, the well known inventor of the planimeter, and other well-known gentlemen were members, among them Prof. Weber of the Zurich Polytechnic School. This committee have just issued their official report on the trials made on the 11th and 13th of October last with the plant as actually installed. Before quoting the results of these trials, it will be well to briefly refer to the general arrangement of this installation. At Kriegstetten there is a water power available, representing about forty actual horse-power, and the problem was to carry as much of this power as possible to a mill in Solothurn, the distance being 4 3/4 miles as the crow flies; but, allowing for deviations, the length of each circuit may be taken as about five miles. There are at Kriegstetten two generating dynamos, and at Solothurn two motors, coupled up on the three-wire system, as shown in the above illustration taken from Industries. Each dynamo weighs 8 tons 12 cwt., and has a Gramme armature 20 in. diameter and 14 in. long, the normal speed being 700 revolutions per minute; Referring to the diagram of connections, G1 and G2 are the generators at Kriegstetten, and M1 and M2 are the motors at Solothurn. R1 and R2 are electro-magnetic switches which automatically come into action and short circuit the exciting coils in case of the current rising beyond a certain limit. This provision was introduced in order to guard against the destruction of the generator in case a short circuit should take place somewhere in the line. The current from each of the generators passes through an ammeter and then to a plug switch-board P. to which is also connected the balancing wire joining the negative brush of G2, with the positive brush of G1. The balancing wire is then carried direct to the middle one of the three lightning arresters L. and then to the middle wire of the line, while each of the outside wires is led through a liquid switch S1S2 then to a lightning arrester, and to the line. Each lightning arrester consists of a circular metal disc, the edge of which is provided with projecting teeth, and situated in a concentric metal ring, the internal circumference of which is also provided with teeth, but not touching the teeth of the disc. All the discs are connected with a common earth wire and two earth plates E E. The same provision against lightning is made at the motor station. The switches S1 S2 are of peculiar construction, and consist of a vessel containing a conducting liquid and a perforated metal ball dipping into it. When the current is to be switched off, the handle is turned so as to raise the ball out of the liquid: but the circuit is not immediately interrupted, since the liquid within the balls issues in fine streams out of the perforations, and so maintains the connection for a short time after