Dcmotor

WELCOME

By: Manoj Gupta

Lecture Outline 1. ELECTRICAL MACHINES-MOTOR, GENERATOR, TRANSFORMER

2. DC/AC MACHINES 3. FARADAY'S LAW of Electromagnetic Induction 4. DC GENERATOR/MOTOR- Operating Principle 5. DC MACHINE- CONSTRUCTION 6. DC MACHINE-TYPES 7. CONCLUSION

By: Manoj Gupta

DC Motors Lorentz Force Law: F=IxB

N

S

F = force on wire I = current B = magnetic field Right hand rule: index finger along I, middle finger along B, thumb along F By: Manoj Gupta

Right Hand Rule Force

Electric Currents & Magnetism  Force t

ren r u C

tic ne ag M el d Fi By: Manoj Gupta

By: Manoj Gupta

By: Manoj Gupta

By: Manoj Gupta

Commutator

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By: Manoj Gupta

Eo = 0 PN 60

* Z A By: Manoj Gupta

By: Manoj Gupta

DC MACHINE CONSTRUCTION Main Parts : 2. Magnetic Frame or Yoke 3. Pole-Cores and Pole-Shoes 4. Pole Coil or Field Coil 5. Armature Core 6. Armature Winding or Conductors 7. Commutator 8. Brushes and Bearings By: Manoj Gupta

DC Machine Construction

Figure 8.1 General arrangement of a dc machine By: Manoj Gupta

Armature of a DC Motor

By: Manoj Gupta

By: Manoj Gupta

By: Manoj Gupta

By: Manoj Gupta

By: Manoj Gupta

DC Machines • The rotor has a ring-shaped laminated iron core with slots. • The commutator consists of insulated copper segments mounted on an insulated tube. • Two brushes are pressed to the commutator to permit current flow. • The brushes are placed in the neutral zone, where the magnetic field is close to zero, to reduce arcing.

By: Manoj Gupta

DC Machine Construction

Figure 8.3 Details of the commutator of a dc motor. By: Manoj Gupta

Inside a DC Motor

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Electric Motor

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Simple DC Motor

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TYPES OF DC MACHINES

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Separately Excited DC Machine RA

+ Vf

-

Armature

Field Coil

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Shunt Excited DC Machine

Shunt Field Coil

Armature RA

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Series Excited DC Machine RA

Armature

Series Field Coil

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Compound Excited DC Machine Series Field Coil

Shunt Field Coil

Armature RA

•If the shunt and series field aid each other it is called a cumulatively excited machine •If the shunt and series field oppose each other it is called a differentially excited machine By: Manoj Gupta

Questions ?

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THANKS

By: Manoj Gupta