Working,construction,History Types and Applications of DC motors

This ppt includes Working,construction,History Types and Applications of DC motors

1. DC MOTORS

2. CONTENTS: History Introduction Construction Working Types of DC Motors Applications DC MOTOR |

3. HISTORY OF DC MOTOR: In 1834, Russian engineer Moritz von Jacobi went on to invent the very first rotating DC motor. His invention became famous for being incredibly powerful, which later set a world record. Incredibly, he broke his own world record in 1838 with a new and improved version of his DC motor invention. This motor motivated others to produce DC motors of the same powerful standard, with the ability to drive a boat with a capacity of 14 people across a river. DC MOTOR |

4. WHAT IS AN ELECTRIC MOTOR? An electric motor is an electromechanical device which converts electrical energy into mechanical energy. WHAT IS A DC MOTOR? A direct current (dc) motor is a type of electric machine that converts electrical energy into mechanical energy. DC motors take electrical power through direct current, and convert this energy into mechanical rotation . DC MOTOR |

5. CONSTRUCTION DC MOTOR |

6. CONSTRUCTION: A DC motor or machine consists of two windings namely field winding and armature winding. The field winding is stationary and the armature winding can rotate. The field winding produces a magnetic flux in the air gap between the armature and field windings and the armature is placed in this magnetic field. The construction of DC motor or machine is shown in the previous slide. Parts used in construction of dc motor: Y oke, Poles, Field winding, Commutator, Carbon brushes Bearings, etc … A brief description of the various parts is given in the next slide: DC MOTOR |

7. YOKE : The yoke acts as the outer cover of a DC motor and it is also known as the frame. The yoke is an iron body, made up of low reluctance magnetic material such as cast iron, silicon steel, rolled steel, etc. Yoke serves two purposes, firstly it provides mechanical protection to the outer parts of the machine secondly it provides a low reluctance path for the magnetic flux. DC MOTOR |

8. 2. POLES AND POLE SHOE : The pole and pole shoe are fixed on the yoke by bolts. These are made of thin cast steel or wrought iron laminations that are riveted together. Poles produce the magnetic flux when the field winding is excited. A Pole shoe is an extended part of a pole. Due to its shape, the pole area is enlarged and more flux can pass through the air gap to the armature. DC MOTOR |

9. 3.FIELD WINDING The coils around the poles are known as field (or exciting) coils and are connected in series to form the field winding. Copper wire is used for the construction of field coils. When the DC is passed through the field windings, it magnetizes poles that produce magnetic flux. DC MOTOR |

10. ARMATURE WINDING The armature winding plays a very important role in the construction of a DC motor because the conversion of power takes place in the armature winding. Based on connections, there are two types of armature windings named: 1. Wave Winding 2. Lap Winding DC MOTOR |

11. COMMUTATOR It is mounted on the shaft. It is made up of a large number of wedge-shaped segments of hard drawn copper, insulated from each other by a thin layer of mica. The commutator connects the rotating armature conductor to the stationary external circuit through carbon brushes. It converts alternating torque into unidirectional torque produced in the armature. DC MOTOR |

12. CARBON BRUSHES The current is conducted from the voltage source to the armature by the carbon brushes which are held against the surface of the commutator by springs. They are made of high-grade carbon steel and are rectangular. DC MOTOR |

13. BEARINGS The ball or roller bearings are fitted in the end housings. The friction between stationary and rotating parts of the motor is reduced by bearing. Mostly high carbon steel is used for making the bearings as it is a very hard material. DC MOTOR |

14. WORKING PRINCIPLE OF DC MOTOR: PRINCIPLE: A current-carrying conductor, when kept in a magnetic field, gains torque and develops a tendency to move. In short, when electric fields and magnetic fields interact a mechanical force arises. This is the principle on which the DC motors work. DC MOTOR |

15. WORKING: DC MOTOR |

16. WORKING: A magnetic field arises in the air gap when the field coil of the DC motor is energised . The created magnetic field is in the direction of the radii of the armature. The magnetic field enters the armature from the North pole side of the field coil and “exits” the armature from the South pole side of the field coil. The conductors located on the other pole are subjected to a force of the same intensity but in the opposite direction. These two opposing forces create a torque that causes the motor armature to rotate. DC MOTOR |

17. TYPES OF DC MOTORS: DC motors have a wide range of applications ranging from electric shavers to automobiles. To cater to this wide range of applications, they are classified into different types based on the field winding connections to the armature as: Self Excited DC Motor: Shunt wound DC motor Series wound DC motor Compound wound DC motor Separately Excited DC Motor: Brushed DC Motor Brushless DC Motor DC MOTOR |

18. Self Excited DC Motors: Shunt wound DC Motor DC MOTOR |

19. 2. Series wound DC Motor DC MOTOR |

20. 3. Compound wound DC Motor DC MOTOR |

21. Separately excited DC Motor: Brushed DC Motor 2. Brushless DC Motor DC MOTOR |

22. APPLICATIONS: 1. Shunt DC Motor   Characteristics: Speed  is fairly constant and medium starting torque.   Applications: 1. Blowers and fans 2. Centrifugal and reciprocating pumps 3. Lathe machines 4. Machine tools 5. Milling machines 6. Drilling machines   DC MOTOR |

23. 2. Series DC Motor   Characteristics: Series High starting torque. No load condition is dangerous. Variable speed.   Applications:  1. Cranes 2. Hoists, Elevators 3. Trolleys 4. Conveyors 5. Electric locomotives     DC MOTOR |

24. 3 . Cumulative compound DC Motor   Characteristics: High starting torque. No load condition is allowed.   Applications: 1. Rolling mills 2. Punches 3. Shears 4. Heavy planers 5. Elevators   Differential compound DC Motor   Characteristics: Speed increases as load increases.   Applications: Not suitable for any practical applications DC MOTOR |

25. CONCLUSION : Machines play a vital role in the improvisation of our day to day lifestyle and DC Motor is one of them. Can you imagine climbing a 30 storeyed building all by yourself without making use of elevator or peddling a boat for 24 hours just to reach your destination? Believe it or not, DC Motors have actually made our life much easier with its widespread applicattions in our day to day life. Hence I’d like to conclude by quoting that- “ MACHINERY IS THE SUBCONSIOUS MIND OF THE WORLD” DC MOTOR |

26. REFERENCE: “A TEXTBOOK OF ELECTRICAL TECHNOLOGY” - B. L. Theraja , A. K. Theraja . “ELECTRIC MOTOR DRIVES” -Krishnan. DC MOTOR |