Electric Motor The Transmiss PDF Download

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. 1906 edition. Excerpt: ...the load. The connections of a series-wound motor are shown in Fig. 27. Here the magnet Fig. 27.--Diagram Of Series Winding. coil M, is in series with the armature A, between the mains a and// that is to sny the current from the mains passes successively through the magnet M, and armature A. When such a machine is on light load, with a small torque, the current strength passing through the machine will be comparatively small, and the M. M. F. of this current in the field coils will be small, producing thereby a small magnetic flux through the armature. The speed of the armature will, therefore, be comparatively great. If, however, the torque on the motor; /. e., its load, be increased, the current passing through the motor will automatically increase, increasing thereby the M. M. F. and flux through the armature, thus reducing the speed. On this account, as well as owing to the drop of pressure iu the resistance of the armature, a series-wound motor is much more variable in its speed than is a shunt-wound motor, but a series-wound motor, especially in small sizes, is simpler to construct; for, its field-winding consists of but comparatively few turns of coarse wire, while a shunt motor field-winding consists of many turns of fine wire, in order to reduce as far as possible the current strength employed in magnetizing them. A compound-wound motor is a motor whose field magnets are partly series Fig. 28.--Diagram Of Compound Winding. wound and partly shunt-wound. Such a winding is diagrammatically represented in Fig. 28. Here the armature A, is iu series with the coarse wire coils m, and these two are connected in shunt with the fine wire coil M. When no current passes through the armature, the field magnet M, is excited, while the series...