The electric current : how produced and how used / by R. Mullineux Walmsley.

  • Walmsley, R. Mullineux (Robert Mullineux)
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: The electric current : how produced and how used / by R. Mullineux Walmsley. Source: Wellcome Collection.

    683/800 (page 667)
    Alternate-current systems.—In by far the most important high-pressure transmissions of power alternate currents are used. In fact, it is their adaptability to this work that has led to the very rapid development of their application in practice, for with them very much higher pressures can be used than have yet been found possible with continuous currents, and thus the economy due to high pressures becomes more pronounced. This is more especially the case where the source of energy is at a great distance from the place where it is desirable to utilise it. We have already sufficiently described the first method of Alternate-Current high-pressure transmission, referred to in Table X. With regard to the second method, which contains the most widely-used systems, the diagram already given in Fig. 336, of feeders and distributors, sufficiently well depicts the general arrangement of the high-pressure part of the system. The only difference is that neither A nor B can now be called the positive or negative terminal of the station, since each is alternately positive and negative. Another difference in practice will be that the method of laying and insulating the distributing mains and feeders will be altogether changed. Last, but not least, the consumers, instead of being directly connected to the distributors, are connected to them through induction coils or alternate- current transformers. The primary terminals of the induc- tion coils are permanently joined to the mains, and covered up so as to be inaccessible to the consumer, who is, instead, supplied with two wires coming from the secondary ter- minals of the coil. As the electric pressure on these wires seldom exceeds 100 volts, and sometimes is only 50, they can be handled with comparative safety. It will be noticed that whether the consumer is using energy or not, the primary circuit of his transformer is always connected up to the mains, and, therefore, some current must always be passing through it. This leads to