Electric Light Installations and the Management of Accumulators (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1890. Excerpt: ... field, and resistance of the armature, are the data which determine the E.M.F. and curve; and the diameter of the armature wire limits the current, which can be produced without injury to the machine. The general behaviour and qualities of the dynamo have now been considered. As to the cells, it has been shown their E.M.F. is practically constant, but rises somewhat as the charging proceeds, and mostly at the end of the charge. Three things may occur when the dynamo and cells are combined. 1. The dynamo may have an E.M.F. higher than that of the cells. In this event, they will charge. 2. The E.M.F. of the two may be equal, consequently, no current passes. 3. The E.M.F. of the dynamo may be less than that of the accumulator. In this case the cells will discharge into the machine, and run it as a motor. Appliances should be placed in the installation to prevent this. Since the mains are branched from the ends of the accumulator--or, in other words, it would be more correct to say that the house and dynamo leads are one and the same, with the accumulator placed between them, in the same way as a lamp--it is necessary to examine what occurs when a current is flowing in these mains. Case 3 may be passed over, because, should it occur, it must be regarded as due to neglect or accident. In case 1, it is evident that, so long as the E.M.F. is higher than that of the cells, all currents going to house mains must come from the dynamo: this, in fact, supplies the light and charges at the same time. In case 2, half the current is supplied from the cells and half from the dynamo. But it does not, in practice, necessarily follow in this proportion, unless the resistance of the dynamo leads be extremely small and the internal resistance of the battery very low. There is...