MOTOR name plate and motor types ppt.pptx

motor data and all information of name plate and all information of motor types

1. Motor Power (kW) Motor Current (Amps) Frame Size 0.37 1 71 0.55 1.5 80 0.75 2 80 1.1 2.5 90 1.5 3.3 90 2.2 4.8 100 3 6.3 100 4 8.2 112 5.5 11 132 7.5 14.5 132 11 20.5 160 15 28.5 160 18.5 34 180 22 41 180 30 56 200 37 68 225

2. D.C. MOTORS

3. CONTENTS: Introduction Principle of operation – Back E.M.F Torque equation – characteristics Application of shunt, series and compound motors Armature reaction and commutation Speed control of D.C. Motors Armature voltage and field flux control methods Motor starters (3- point and 4- point starters) Testing of D.C. machines Losses – Constant & Variable losses Calculation of efficiency – condition for maximum efficiency

4. 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 g ive mechanical work. INTRODUCTION

5. PRINCIPLE OF DC MOTOR 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.

6. CONSTRUCTION OF DC MOTOR

7. CONSTRUCTION OF DC MOTOR

8. Function of each part of DC Motor: Yoke: It is outer cover of dc motor also called as frame. It provides protection to the rotating and other part of the machine from moisture, dust etc. Yoke is an iron body which provides the path for the flux to complete the magnetic circuit. It provides the mechanical support for the poles. Material Used: low reluctance material such as cast iron, silicon steel, rolled steel, cast steel etc.

9. Poles and pole core: Poles are electromagnet, the field winding is wound over it. It produces the magnetic flux when the field winding is excited. The construction of pole is done using the lamination of particular shape to reduce the power loss due to eddy current. pole shoe: Pole shoe is an extended part of a pole. Due to its typical shape, it enlarges the area of the pole, so that more flux can pass through the air gap to armature. Material Used : low reluctance magnetic material such as cast steel or cast iron is used for construction of pole and pole shoe.

10. Field winding: field coil wound on pole The coil wound on the pole core are called field coils. Field coils are connected in series to form field winding. Current is passed through the field winding in a specific direction, to magnetize the poles and pole shoes. Thus magnetic flux is produce in the air gap between the pole shoe and armature. Field winding is also called as Exciting winding. Material Used for copper conductor is copper. Due to the current flowing through the field winding alternate N and S poles are produced.

11. Armature core: Armature core is a cylindrical drum mounted on the shaft. It is provided with large number of slots all over its periphery and it is parallel to the shaft axis. Armature conductors are placed in these slots. Armature core provides low reluctance path to the flux produced by the field winding. Material used: high permeability, low reluctance cast steel or cast iron material is used. Laminated construction of iron core is used to minimize the eddy current losses.

12. Armature winding: Armature conductor is placed in a armature slots present on the periphery of armature core. Armature conductor are interconnected to form the armature winding. When the armature winding is rotated using a prime mover, it cuts the magnetic flux lines and voltage gets induced in it. Armature winding is connected to the externalcircuit (load) through the commutator andbrushes. Material Used: Armature winding is suppose to carry the entire load current hence it should be made up of conducting material such as copper.

13. Commutator: It is a cylindrical drum mounted on the shaft along with the armature core. It is made up of large number of wedge shaped segments of hard- d r a w n c o pp e r . The segments are insulated from each other by thin layer of mica. Armature winding are tapped at various points and these tapping are successively connected to various segments of the commutator. Function of commutator: It converts the dc emf generatedinternally into ac It helps to produce unidirectional torque. Material Used: it is made up of copper and insulating material between the segments is mica.

14. Brushes: Current are conducted from the armature to the external load by the carbon brushes which are held against the surface of the commutator by springs. Function of brushes: To collect the current from the commutator and apply it to the external load in generator, and vice versa in motor. Material Used: Brushes are made of carbon and they arerectangular in shape.

15. Action of commutator: The commutator converts DC in the supply terminals to the AC in the armature conductors. Therefore the commutator behaves as mechanical rotating inverter and the frequency of armature current, f=PN/120 . This conversion of DC into AC is accomplished through the use of a commutator (split rings). The conductors of the armature of a DC motor are connected to commutator segments.

16. WORKING PRINCIPLE OF DC MOTOR

17. Back E.M.F: When the armature winding of dc motor is start rotating in the magnetic flux produced by the field winding, it cuts the lines of magnetic flux and induces the emf in the armature winding. According to Lenz’s law ( The law that whenever there is an induced electromotive force (emf) in a conductor, it is always in such a direction that the current it would produce would oppose the change which causes the induced emf . ), this induced emf acts in the opposite direction to the armature supply voltage. Hence this emf is called as back emf. 60 𝐴 𝐸 𝑏 = ∅ 𝑍 N 𝑃 Volts + 𝑁 = speed in rpm ∅ = flux per pole armature supply voltage A1 𝑍 = no of conductors 𝑃 =no of pole pairs 𝐴 =area of cross section of conductor 𝐸 𝑏 = back emf 𝐸 𝑏 A2 _

18. V o l t ag e Equation E g = V + I a R a (Generator) V = E b + I a R a (Motor)

19. Voltage and Power equation of DC Motor: 𝑉 = 𝐸 𝑏 + 𝐼 𝑎 𝑅 𝑎 If we multiply the above equation by 𝐼𝑎 , we will get 𝑎 𝑉𝐼 𝑎 = 𝐸 𝑏 𝐼 𝑎 + 𝐼 2 𝑅 𝑎 𝑉𝐼𝑎 = 𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑝𝑜𝑤𝑒𝑟 𝑠𝑢𝑝𝑝𝑙𝑖𝑒𝑑 𝑡𝑜 𝑡 h 𝑒 𝑚𝑜𝑡𝑜𝑟 𝐸𝑏𝐼𝑎 = 𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑒𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑡 𝑜𝑓 𝑡 h e 𝑚𝑒𝑐 h 𝑎𝑛𝑖𝑐𝑎𝑙𝑝𝑜𝑤𝑒𝑟 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑 𝑏𝑦 𝑡 h 𝑒 𝑚𝑜𝑡𝑜𝑟 𝐼𝑎 2 𝑅𝑎 = 𝑝𝑜𝑤𝑒𝑟 𝑙𝑜𝑠𝑠 𝑡𝑎𝑘𝑖𝑛𝑔 𝑝𝑙𝑎𝑐𝑒 𝑖𝑛 𝑎𝑟𝑚𝑎𝑡𝑢𝑟𝑒 𝑤𝑖𝑛𝑑𝑖𝑛𝑔 Thus, 𝑎 𝐸 𝑏 𝐼 𝑎 = 𝑉𝐼 𝑎 − 𝐼 2 𝑅 𝑎 =input power- power loss thus, 𝐸 𝑏 𝐼 𝑎 = Gross mechanical power produce by the motor = P m

20. T o r q u e equation of DC Motor: 𝐸 𝑏 𝐼 𝑎 = 𝑇𝜔 𝑚𝑒𝑐 h 𝑎𝑛𝑖𝑐𝑎𝑙 𝑝𝑜𝑤𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 𝑡𝑜 𝑟𝑜𝑡𝑎𝑡𝑒 𝑡 h 𝑒 𝑠 h 𝑎𝑓𝑡 𝑜𝑛 𝑚𝑒𝑐 h 𝑎𝑛𝑖𝑐𝑎𝑙 𝑠𝑖𝑑𝑒 = 𝑇𝜔 ……………………………………………… 1 T =Torque in Newton- meter 𝜔 = angular velocity in radian/second 𝑔𝑟𝑜𝑠𝑠 𝑚𝑒𝑐 h 𝑎𝑛𝑖𝑐𝑎𝑙𝑝𝑜𝑤𝑒𝑟 𝑝𝑟𝑜𝑑𝑢𝑐𝑒 𝑏𝑦 𝑡 h 𝑒𝑚𝑜𝑡𝑜𝑟 𝑜𝑛 𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑠𝑖𝑑𝑒 = 𝐸𝑏𝐼𝑎 ………………………………………………… 2 E b = back emf in volts I a = armature current in ampere equating eqnuation 1 and 2 , we get

21. 𝜔 = 2 𝜋 𝑁 ……………………………… 60 And 𝐸 𝑏 = ∅ 𝑍𝑁𝑃 60 2 𝜋𝑁 = Speed in rpm 60 𝐴 𝑇 = 0.159 𝑃𝑍 2 𝜋 𝐴 𝐴 𝐴 ∅ 𝐼𝑎𝑍𝑃 = 0.159 𝑃 ∅ 𝑍𝐼𝑎 = ∅ 𝐼𝑎 𝑃 , 𝑍 𝑎𝑛𝑑 𝐴 are constant, hence we can say 𝑇 ∝ ∅ 𝐼𝑎 Thus, torque produce by the DC Motor is proportional to the main field flux ∅ and armature current 𝐼𝑎 Thus, equation 3 become ∅ 𝑍𝑁𝑃 𝐼𝑎 = 𝑇 2 𝜋𝑁 60 𝐴 60

22. Types of Self Excited DC Motors: Classification of the d.c. motor depends on the way of connecting the armature and field winding of a d.c. motor: DC Shunt Motor DC Series Motor DC Compound Motor Short shunt compound Long shunt compound Cumulative Differential Cumulative Differential compound compound compound compound motor motor motor motor

23. 1. DC SHUNT MOTOR Armature The parallel combination of two windings is connected across a common dc power supply. The resistance of shunt field winding (R sh ) 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.

24. I L =I a + I sh Shunt field current, I sh = V/R sh Back emf, E b = V- I a R a Gross mechanical Power developed, P m = E b ×I a Net electrical power input Power, P net = V×I a Voltage and current relations:

25. 2. DC SERIES MOTOR The field winding is connected in series with the armature. The current passing through the series winding is same as 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.

26. Voltage and current relations: I a = I se = I L Back emf, E b = V- I a R a - I a R se Net electrical power input Power, P in = V×I a

27. 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.

28. Voltage and current relations: I L = I a +I sh Shunt field current, I sh = V/R sh Back emf, E b = V- I a R a - I a R se Net electrical power input Power, P in = V×I a

29. II. SHORT SHUNT COMPOUND MOTOR In short shunt compound motor the series winding is 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.

30. Shunt field current, I sh = V- I L R se /R sh Back emf, E b = V- I a R a - I L R se Voltage and current relations: I L = I a +I sh I L = I se

31. Armature T o r q u e Equation Derivation

32. Armature T o r q u e of a D.C. Motor

33. Shaft T o r q u e Equation Derivation The difference ( T a − T sh ) is known as lost torque and is due to iron and friction losses of the motor.

34. Speed of a D.C. Motor Speed Regulation

35. D.C. Motor Characteristics Torque and armature current i.e. T a /I a characteristics. It is known as electrical characteristics . Speed and armature current i.e. N/I a characteristics. Speed and torque i.e. N/T a characteristic. It is also known as mechanical characteristics .

36. Characteristics of DC Shunt Motors 1. T o r qu e and armature current i.e. T a / I a characteristics. It is known as electrical characteristics . Assuming (though somewhat reaction) Φ at heavy to be practically loads, φ dueto increased constant decreases armature Hence, the electrical characteristic is practically a straight line through the origin. Shaft torque is shown dotted. Since a heavy starting load will need a heavy starting current, shunt motor should never be started on (heavy) load. As Φ is practically constant

37. Characteristics of DC Shunt Motors 2. Speed and armature current i.e. N/I a characteristics. As Φ is practically constant As E b is also practically constant, speed is, for most purposes, constant Here, both E b and Φ decrease with increasing load. However, E b decreases slightly more than φ so that on the whole, there is some decrease in speed. The drop varies from 5 to 15% of full- load speed , being dependent on saturation, armature reaction and brush position. slightly Hence, the actual speed curve is drooping as shown by the dotted line. But, for all practical purposes, shunt motor is taken as a constant- speed motor.

38. Characteristics of DC Shunt Motors 3. Speed and torque i.e. N/T a characteristic. It is also known as mechanical characteristics . When speed is high, torque is almost constant. As Φ is practically constant

39. Characteristics of DC Series Motors 1. T o r qu e and armature current i.e. T a / I a characteristics. It is known as electrical characteristics . At light loads , Ia and hence Φ is small. But as Ia increases, Ta increases as the square of the current. Hence, Ta / Ia curve is a parabola . After saturation/heavy Loads, Φ is almost independent of Ia hence Ta ∝ Ia only. So the characteristic becomes a straight line. The shaft torque Tsh is less than armature torque due to stray losses. As practically Φ is equals to Ia

40. Characteristics of DC Series Motors 2. Speed and armature current i.e. N/I a characteristics. As practically Φ is equals to Ia With increased I a , Φ also increases . Hence, speed varies inversely as armature current. When load is heavy , I a is large. Hence, speed is low (this decreases Eb and allows more armature current to flow). But when load current and hence I a falls to a small value, speed becomes dangerously high. Hence, a series motor should never be started without some load on it mechanical (not belt- driven) otherwise it may excessive speed and get damaged develop due to heavy centrifugal forces so produced. It should be noted that series motor is a variable speed motor.

41. Characteristics of DC Series Motors 3. Speed and torque i.e. N/Ta characteristic. It is also known as mechanical characteristics . When speed is high, torque is low and vice- versa.

42. Compound Motors These motors have both series and shunt windings. If series excitation helps the shunt excitation i.e. series flux is in the same direction (a) then the motor is said to be cumulative compound motor. If on the other hand, series field opposes the shunt field (b) , then the motor is said to be differential compound motor .

43. Characteristics of DC Compound Motors i). Speed versus armature current characteristics

44. Characteristics of DC Compound Motors ii). Torque versus armature current characteristics

45. iii) Speed - Torque characteristics Characteristics of DC Compound Motors

46. A PP L I C A T I O N S OF DC MOTORS MOTORS.. APPLICATIONS… D.C. SHUNTMOTOR Lathe Machines, Centrifugal Pumps, Fans, Blowers, Conveyors, Lifts and Spinning machines, etc. D.C. SERIES MOTOR Traction, Hoists and Lifts, Cranes and Rolling mills, etc. D.C. COMPOUND MOTOR (Cumulative) Elevators, Rolling mills, Punches, Shears and planers, etc.

47. Speed Control of DC Motor The speed equation of dc motor is 𝑁𝛼 𝛼 𝐸 𝑏 (𝑉 − 𝐼 𝑎 𝑅 𝑎 ) ∅ ∅ But the resistance of armature winding or series field winding in dc series motor are small. Therefore the voltage drop 𝐼𝑎𝑅𝑎 or 𝐼𝑎 ( 𝑅𝑎 + 𝑅 𝑠 ) across them will be negligible as compare to the external supply voltage V in above equation. since V>>>> 𝐼𝑎𝑅𝑎 Therefore 𝑁𝛼 𝑉 ∅ Thus we can say Speed is inversely proportional to flux ∅ . Speed is directly proportional to armature voltage. Speed is directly proportional to applied voltage V. So by varying one of these parameters, it is possible to change the speed of a dc motor

48. Factors Controlling Motor Speed ▶ The speed can be controlled by varying Flux/pole, Φ ( Flux Control ) Resistance R a of armature circuit ( Rheostatic Control ) Applied voltage V ( Voltage Control )

49. 1. Flux Control Method ▶ To control the flux, a rheostat is added in series with the field winding, as shown in the circuit diagram. Adding more resistance in series with the field windingwill increase the speed as it decreases the flux. constant, armature resistance R a are speed is directly proportional to the armature current I a . Thus, if we add a resistance in series with the armature, I a decreases and, hence, the speed also decreases. 2. Armature Control Method When the supply voltage V and the kept Speed Control of DC Shunt Motor

50. 3. Applied Voltage Control Method Multiple voltage control: In this method, the shunt field is connected to a fixed exciting voltage and armature is supplied with different voltages. Voltage across armature is changed with the help of a suitable switchgear.

51. Speed Control Of Series Motor: 1. Flux Control Method:

52. 2. Rheostatic Control Method:

53. 3. Applied Voltage Control Method:

54. Need of Starter: We know that, V = 𝐸 𝑏 + 𝐼 𝑎 𝑅 𝑎 .........for dc shunt motor and V = 𝐸 𝑏 + 𝐼 𝑎 ( 𝑅 𝑎 + 𝑅 𝑠 e ) ….for a dc series motor Hence, the expression for 𝐼 𝑎 are as follows : 𝐼 𝑎 = 𝑉 − 𝐸 𝑏 …………… for dc shunt motor 𝑅 𝑎 𝑉 − 𝐸 𝑏 𝑎 𝐼 = ( 𝑅 𝑎 + 𝑅 𝑠 e ) ……….. for dc series motor At the time of starting the motor speed N=0 and hence the back emf 𝐸 𝑏 =0. Hence the armature current at the time of starting is given by, 𝑅 𝑎 𝐼 𝑎 ( 𝑠𝑡𝑎𝑟𝑡𝑖𝑛𝑔 ) = 𝑉 ………….for dc shunt motor 𝑎 ( 𝑠𝑡𝑎𝑟𝑡𝑖𝑛𝑔 ) 𝐼 = 𝑉 ( 𝑅 𝑎 + 𝑅 𝑠 e ) ……for dc series motor

55. Since the values of 𝑅 𝑎 𝑎𝑛𝑑 𝑅 𝑠 e are small , the starting currents will be tremendously large, if the rated voltage is applied at the time of starting. The starting current of the motor can be 15 to 20 times higher than the full load current. Due to high starting current the supply voltage will fluctuate. Due to excessive current, the insulation of the armature winding may burn. The fuses will blow and circuit breakers will trip. F o r d c series m o t o r s the torque T ∝ 𝐼 𝑎 2 . S o a n excessive large s t a r ti n g torque i s produced. This can pu t a heavy mechanical stress o n the w i n d i n g a n d shaft o f the m o tor resulting i n the mechanical damage t o the motor. So to avoid all these effects we have to keep the starting current of motor below safe limit. This is achieved by using starter.

56. Principle of starter: Starter is basically a resistance which is connected in series with the armature winding only at the time of starting the motor to limit the starting current. The starter of starting resistance will remain in the circuit only at the time of starting and will go out of the circuit or become ineffective when the motor speed upto a desire speed.

57. At the time of starting, the starter is in the start position as shown in fig. so the full starter resistance appears in series with the armature. This will reduce the starting current. The starter resistance is then gradually cut off. The motor will speed up, back emf will be developed and it will regulate the armature current. The starter is not necessary then. Thus starter is pushed to the Run position as shown in fig under the normal operating condition. The value of starter resistance is zero in this position and it does not affect the normal operation. Types of starters: Three point starter Four point starter

58. Three-point Starter:

59. Three-point Starter Animation:

60. Four- point Starter:

61. Q: Why testing is required ? Ans: Machines are tested for finding out losses, efficiency and temperature rise. For small machines we used DIRECT METHOD of testing and for large machines, INDIRECT METHOD of testing are used. Testing of D.C. machines

62. Power Stages in DC Motor

63. Losses in a D.C. Motor 1- COPPER LOSSES ARMATURE Cu LOSS SHUNT FIELD Cu LOSS SERIES FIELD Cu LOSS 2- IRON LOSSES HYSTERESIS LOSS EDDY CURRENT LOSS 3- MECHANICAL LOSSES FRICTION LOSS WINDAGE LOSS 4- STRAY LOAD LOSSES

64. Copper losses Cupper losses are mainly due to the current passing through the winding. Thus copper losses consists of Armature copper loss, Field copper loss and Loss due to brush contact resistance.

65. Copper losses- Armature Cu Loss Armature copper loss = I a 2 R a (Where I a is Armature current and R a is Armature resistance) This loss is about 30 to 40% of full load losses.

66. Copper losses- Field Cu Loss Field copper loss = I 2 R f f (where I f is field current and R f is field resistance) In case of shunt wounded field, this loss is practically constant. Field copper loss is about 20 to 30% of full load losses. Shunt field copper loss = I 2 R sh sh Series field copper loss = I 2 R se se

67. Copper losses - Loss due to Brush Contact Resistance There is also brush contact loss due to brush contact resistance (i.e., resistance between the surface of brush and surface of commutator). Generally this loss is included into armature copper loss.

68. Iron losses (Magnetic losses) As iron core of the armature is continuously rotating in a magnetic field, there are some losses taking place in the core. Therefore iron losses are also known as Core losses. This loss consists of Hysteresis loss and Eddy current loss .

69. Hysteresis loss (W h ): The loss is due to the reversal of magnetization of the armature core. Every portion of the rating core passes under N and S poles alternately. The core undergoes one complete cycle of magnetic reversal after passing under one pair of poles. P = No. of poles N = Armature speed in rpm frequency of magnetic reversals f = PN 120 The loss depends upon the volume and B max and frequency of reversals. Hysteresis loss is given by steinmetz formula W h =η B 1.6 max f V watts V=Volume of the core in m 3 η= Steinmetz hysteresis coefficient

70. Hysteresis loss

71. Eddy current loss (W e ): When the armature core rotates in the magnetic field, an emf is also induced in the core, according to the Faraday's law of electromagnetic induction. Though this induced emf is small, it causes a large current to flow in the body due to its small resistance of the core. This current is known as “ Eddy Current ”. The power loss due to this current is known as “ Eddy current loss” . Eddy current loss W e is given as: W e = k B 2 max f 2 t 2 v 2 watts B max = Maximum flux density F = Frequency of the magnetic reversals v = Volume of the armature core t = Thickness of lamination

72. Eddy current loss

73. Stray Losses Iron losses and mechanical losses together are called stray losses. Mechanical Losses Mechanical losses consists of the losses due to friction in bearings and commutator. Air friction loss of rotating armature also contributes. These losses are about 10 to 20% of full load losses.

74. Stray Load Loss The stray load losses are produced as a result of the distortion of the magnetic field by the armature and the interpoles. The distortion causes the flux in the field poles to be unevenly distributed and thereby produces a hysteresis loss. It is generally neglected in motors of 200 hp or less. In larger rated dynamos the stray load loss is assumed to be 1% of the output.

75. Constant and Variable Losses The losses in a d.c. motor may be sub-divided into Constant losses, Variable losses. (i) Constant losses: Those losses in a d.c. motor which remain constant at all loads are known as constant losses. The constant losses in a d.c. motor are: iron losses mechanical losses shunt field losses

76. Constant and Variable Losses Variable losses: Those losses in a d.c. motor which vary with load are called variable losses. The variable losses in a d.c. motor are: Copper loss in armature winding ( I a 2 R a ) Copper loss in series field winding ( I se 2 R se ) Total losses = Constant losses + Variable losses Note : Field Cu loss is constant for shunt and compound motors.

77. Condition for Maximum Efficiency The load current corresponding to maximum efficiency is given by the relation Generator efficiency is maximum when, Variable loss = Constant Loss I L  W c / R a