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DC Motors

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Motor construction is physically similar to a generator, in fact, a basic dc generator can also function as a dc motor. Both dc motors and generators use external magnetic field excitation, armature coil windings, and commutators.

Motors operate because of the interaction between magnetic and electromagnetic fields. A dc motor, like a dc generator, consists of end bells, frame, brush assembly, commutator assembly, armature assembly, and pole pieces. The stationary field is not always a permanent magnetic field. It may be supplied by an electromagnetic field, as with a dc generator. The field windings are excited from a dc power supply, and provide a steady electromagnetic field. The polarity of the field is determined by the direction of the current flow through the windings. Thus, the polarity is adjusted such that one of the pole pieces becomes an N pole and the other pole piece (in a two pole motor) becomes an S pole. This establishes the stationary field. However, a motor also requires dc excitation to the armature. This could be supplied by a separate dc power supply, but often the field windings (stator) and the armature assembly (rotor) are supplied from the same source. By adding more loops of wire to the armature, the motor principle is aided by Repulsion and Attraction. Actually, the repulsion and attraction effect becomes the dominant factor in dc motor operation when many loops of wire are used. There are three types of dc motors: SERIES,SHUNT, AND COMPOUND. This refers to the method in which the field coils and the armature coils are connected. It is important to know the characteristics of each type of motor in order to use them properly.


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Thanks Very Much for these sites because i got TEST next week, and i gonna prepare it with the HELP of these sites. Again THANKS for that..............


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On the topic of Direct current motors. could someone explain how they are able to make them with out brushes now?
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