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Dcmotor
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- 2. INTRODUCTION A motor isa machine which converts electrical energy into mechanical energy. A DC motor finds application in rolling mills, in traction system and overhead cranes. The principle of operation of DC motor is that when a current carrying conductor is kept in a magnetic field, a force is produced in that conductor. 2Electrical Machines
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- 5. ARMATURE REACTION If themagnetic field windings of a DC machine are connected to the power source and the rotor is turned by an external means, a voltage will be induced in the conductors of the rotor. 5Electrical Machines
- 6. ARMATURE REACTION This voltageis rectified and can be supplied to external loads. However, if a load is connected, a current will flow through the armature winding. This current produces its own magnetic field that distorts the original magnetic field from the machine’s poles. This distortion of the machine’s flux as the load increases is called armature reaction. 6Electrical Machines
- 7. TYPES OF DCMOTOR i) Permanent magnet DC motor ii) Separately excited DC motor iii) Series DC motor iv) Shunt DC motor v) Compound DC motor 7Electrical Machines
- 8. Permanent Magnet DCMotor In this type of DC motor, the field is made up of permanent magnet and hence, it requires no field winding. 8Electrical Machines
- 9. Separately Excited DCMotor Both the field winding and the armature winding are fed from two different sources, 9Electrical Machines
- 10. Series DC Motor Thefield winding is connected in series with the armature winding. 10Electrical Machines
- 11. Shunt DC Motor Thefield winding is connected in parallel with the armature winding. 11Electrical Machines
- 12. Compound DC Motor Acompound DC motor has both series and shunt field winding. It can be a short-shunt DC compound motor or a long-shunt DC compound motor. 12Electrical Machines
- 13. Speed of DCMotor Speed of a DC motor depends on the i) Supply voltage ii) Armature current iii) Armature resistance iv) Field flux. 13Electrical Machines
- 14. Characteristics of aDC Shunt Motor Speed versus armature current characteristics 14Electrical Machines
- 15. Characteristics of aDC Shunt Motor Torque versus armature current characteristics 15Electrical Machines
- 16. Characteristics of aDC Shunt Motor Speed–Torque characteristics 16Electrical Machines
- 17. Characteristics of aDC Series Motor Speed versus armature current characteristics 17Electrical Machines
- 18. Characteristics of aDC Series Motor Torque versus armature current characteristics 18Electrical Machines
- 19. Characteristics of aDC Series Motor Speed–Torque characteristics 19Electrical Machines
- 20. Characteristics of aDC Compound Motor Speed versus armature current characteristics 20Electrical Machines
- 21. Characteristics of aDC Compound Motor Torque versus armature current characteristics 21Electrical Machines
- 22. Characteristics of aDC compound Motor Speed Torque characteristics 22Electrical Machines
- 23. DC MOTOR STARTER Sincethe armature resistance is small, generally less than 1Ω, the current through the armature at the time of starting will be very high. This large current may damage the armature winding, brushes and commutator segments 23Electrical Machines
- 24. DC MOTOR STARTER Dueto the high inrush of current at the time of starting the motor, it becomes necessary to limit this current to a safe value, which is generally obtained by connecting an extra resistance in series with the armature winding. 24Electrical Machines
- 25. Three-point Starter forDC Shunt Motor 25Electrical Machines
- 26. Four-point Starter forDC Shunt Motor 26Electrical Machines
- 27. SPEED CONTROL OFDC SHUNT MOTOR The different methods of speed control of DC shunt motor are as follows: i) Shunt field control or flux control method. ii) Armature resistance control or armature control method. iii) Voltage control method. 27Electrical Machines
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- 29. Armature Control OR ArmatureResistance Control 29Electrical Machines
- 30. SPEED CONTROL OFDC SERIES MOTOR There are three methods of speed control for DC series motor, namely, i) Flux control method ii) Armature control method iii) Series-parallel control. 30Electrical Machines
- 31. ELECTRIC BRAKING Brakingis used to stop the motor quickly. There are three types of electric braking. i) Rheostatic or dynamic braking ii) Braking by plugging iii) Regenerative braking 31Electrical Machines