A1912866255_25035_16_2019_UNIT-III DC Machines (1).pdf - UNIT-111 DC MACHINES Content q q q q Working principle Classification Speed control of DC Motor

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UNIT-111UNIT-111DC MACHINES DC MACHINES DC MOTORContentqWorking principleqClassificationqSpeed control of DC MotorqApplications of DC Motors
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Review Review of magnetismof magnetism3The magnetic lines around a current carrying conductor leave from the N-pole and re-enter at the S-pole. "Left Hand Rule" states that if you point the thumb of your left hand in the direction of the current, your fingers will point in the direction of the magnetic field. Lines of flux define the magnetic field and are in the form of concentric circles around the wire.The flow of electrical current in a conductor sets up concentric lines of magnetic flux around the conductor.
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Fleming’s left hand rule
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Fleming’s left and right hand rule The thumb, fore finger and middle finger of the hand are kept at right angles to one another .The middle finger represent the direction of currentThe fore finger represent the direction of magnetic fieldThe thumb will indicate the direction of force acting on the conductor .
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Fleming’s Right hand rule Used to determine the direction of force acting on a current carrying conductor placed in a magnetic field .Used to determine the direction of a current when a conductor moves in magnetic field .This rule is used in motors.This rule is used in generators.
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qDC motors are found in many special industrial environmentsMotors drive many types of loads from fans and pumps to presses and conveyorsqThe major advantages of dc machines over generators are easy to control speed and torque regulation. qHowever, their application is limited to mills, mines and trains. As examples, trolleys and underground subway cars may use dc motors. qIn the past, automobiles were equipped with dc dynamos to charge their batteries, but now dynamos are replaced by alternators.
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  • Winter '18
  • ghars
  • Magnetic Field, DC MOTORS, Electric motor

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