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DC MOTORS • Presenter… Sumeet Patel (99) TOPICS TO DISCUSS Introduction to DC MOTORS Principle Construction Working Types Applications DC MOTOR • A DC motor or Direct Current Motor converts electrical energy into mechanical energy • A direct current (DC) motor is a fairly simple electric motor that uses electricity and a magnetic field to produce torque, which turns the rotor and hence give mechanical work PRINCIPLE OF DC MOTORS • In any electric motor, operation is based on simple electromagnetism • When a current-carrying conductor is placed in an external magnetic field, it will experience a force i.e Lorentz force • Due to this force torque is produced which rotates the rotor of motor and hence a motor runs CONSTRUCTION • DC motor consist of windings… Field winding Armature winding • Field winding is stationary and armature winding can rotate freely • Field windings when given DC supply, magnetic field is produced • Armature winding when connected to DC source, shaft connected to it rotates due to Lorentz force WORKING OF DC MOTORS TYPES OF DC MOTORS • DC motor are of types they are… DC SHUNT MOTOR DC SERIES MOTOR DC COMPOUND MOTOR • DC SHUNT MOTOR The parallel combination of two windings is connected across a common dc power supply • The resistance of shunt field winding (Rsh) is always higher than that is armature winding • This is because the number of turns for the field winding is more than that of armature winding • The cross-sectional area of the wire used for field winding is smaller than that of the wire used for armature winding Armature DC SERIES MOTOR • The field winding is connected in series with the armature • The current passing through the series winding is same asClick to edit Master text styles the armature current • Therefore the series field winding has fewer turns of thick wire than the shunt field winding • Also therefore the field winding will posses a low resistance then the armature winding Second level Third level Fourth level Fifth level DC COMPOUND MOTOR I • LONG SHUNT COMPOUND MOTOR In this the series winding is connected in series with the armature winding and the shunt winding is connected in parallel with the armature connection Click to edit Master text styles Second level Third level Fourth level Fifth level II • SHORT SHUNT COMPUND MOTOR In short shunt compound motor the series Click to edit Master text styles Second level Third level winding is Fourth level Fifth level connected in series to the parallel combination of armature and the shunt winding • This is done to get good starting torque and constant speed characteristics a) • CUMULATIVE COMPOUND DC MOTORS If the two field windings i.e series and shunt are wounded in such a way that the fluxes produced by them add or assist each other b) • DIFFERENTIAL COMPOUND DC MOTORS If the two field winding i.e series and shunt are wounded in such a way that the fluxes produced by them always try to oppose and try to cancel each other APPLICATIONS OF DC MOTORS MOTORS APPLICATIONS… LATHES , FANS, PUMPS DISC AND BAND SAW DRIVE REQUIRING D.C SHUNT MOTOR MODERATE TORQUES D.C SERIES MOTOR ELECTRIC TRACTION, HIGH SPEED TOOLS ROLLING MILLS AND OTHER LOADS REQUIRING LARGE D.C COMPOUND MOTOR MOMENTARY TORQUES BIBLIOGRAPHY www.google.com en.wikipedia.org Electrical technology – B.L Theraja – A.K Theraja THANK YOU ANY QUESTIONS ??? ?
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