Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . er, will supply electrical energy to thecircuit connected to it. Thus, a dynamo and motor are con-vertible machines, and the previous lessons upon the con-struction of dynamos will apply equally as well to the electricmotor. Motors are classified in the same manner as dynamosand may be, (a) Series wound, (b) Shunt wound, (c) Covipound woimd, 393 394 PRACTICAL ELECTRICITY. The fields may be either bipolar or multipolar, and sincethe number of poles determines the number of neutral poi
Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . er, will supply electrical energy to thecircuit connected to it. Thus, a dynamo and motor are con-vertible machines, and the previous lessons upon the con-struction of dynamos will apply equally as well to the electricmotor. Motors are classified in the same manner as dynamosand may be, (a) Series wound, (b) Shunt wound, (c) Covipound woimd, 393 394 PRACTICAL ELECTRICITY. The fields may be either bipolar or multipolar, and sincethe number of poles determines the number of neutral points,there must be as many brushes as poles, except when thecommutator is cross-connected, page 333. 357. Principles of the Motor.—The principles involvedin the rotation of the armature conductors, when placed in amagnetic field, are fully discussed under the subject of elec-trodynamics, Lesson XXIII. It was there experimentallyshown how a single loop, placed in a magnetic field, could bemade to rotate, by commutating the current through it at theproper instant in a revolution, U 275, and how the turning-. Fig. 372.—Parts of a 20-H. P. Direct Current Slow Speed Motor. K. W., 15. Volts, 250. Amperes, 60. Speed, 600 revolutions per minute. Average netweight, 2460 pounds. Diameter of pulley, 14 inches; face, 8 inches. effort was increased by increasing the number of loops orcoils and arranging them at different angles with reference tothe field.* When the loops are angularly disposed around aniron core, as in a Gramme or drum ring armature, and thenplaced in a powerful magnetic field and a current passedthrough them, each loop tends to move to the position inwhich it encloses the greatest number of the lines of thefield. The direction in which each loop will move will be suchthat its lines of force will be in the same direction as the * The student is advised to agaiq read If 275, DIRECT CURRENT MOTORS. 395 lines of force of the field ; the force with which it will move,or the
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