Publisher's Synopsis
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1892 edition. Excerpt: ... CHAPTER V. Compound Machines. The general principle of the compound winding is as follows: In a simple shunt machine, the greater the current in the external circuit or in the armature, the greater will be the fall of potential in the armature itself, due to its resistance, and therefore the loss will be the difference of potential at the terminals of the shunt coils. This decreases the current in them, thus diminishing the magnetism, which again decreases the potential. The potential at the poles of the shunt machine must, therefore, fall a certain definite amount with an increase in the number of lamps in circuit. When the armature resistance is very small, this decrease of potential will be correspondingly small. The increased "countermagnetism" of the armature, due to its own current, also tends to decrease the potential for an increased current. If by some means these losses of potential, due to an increased current, could be generated again automatically by an exactly equal amount by increasing the magnetism proportionally, it is evident that the potential at the poles could be made to remain constant or nearly so. This may be done by adding series coils to such an amount that the total magnetism of the field increases with an increasing current in the external circuit, thus maintaining constant the potential at the poles of the machine. The connections of the shunt coils may be made in one of two ways. In the first of these, called the ordinary compound machine connections, and shown in Fig. 3, the terminals of the shunt coils are connected to the poles of the armature, or, what is the same thing, to the brushes. The current in the series coils is, therefore, not the total current of the armature, but is the current in the...
