Direct-Current (DC) Machines

• A DC machine is a versatile machine- same machine can be used as generator or motor

• Use of dc machine as dc generators to produce bulk power has rapidly disappeared due to economic advantages involved in the use of ac generator, and T & D

• Today, the need for dc power is often met by the use of solid state–controlled rectifiers.

• Extensive :

  • constant mechanical power output or constant torque

  • adjustable motor speed over wide ranges

  • precise speed or position control

  • efficient operation over a wide speed range

  • rapid acceleration and deceleration

  • responsiveness to feedback signals

• Wide variation in the size of DC Motors based on short-term or continuous application

• - used for small control devices, windshield-wiper motors, fan motors, starter motors, and various servomotors

• - conveyors, pumps, hoists, overhead cranes, forklifts, fans, steel and aluminum rolling mills, paper mills, textile mills, various other rolling mills, golf carts, electrical cars, street cars or trolleys, electric trains, electric elevators, and large earth-moving equipment

• Dc machine applications are very significant, but and the associated with its brush-commutator system.