electrical drives and control,mechanical,iii sem,annauniversity

1. CONVENTIONAL AND SOLID STATE SPEED
CONTROL OF DC MOTORS

2. DC DRIVES
SOURCE POWER
CONVERTER
DC
MOTOR LOAD
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3. APPLICATIONS
 ELECTRIC TRACTION
 STEEL MILLS
 PRINTING MILLS
 TEXTILE MILLS
 PAPER MILLS
 HOISTS
 CRANES
 MACHINE TOOLS
 EXACAVATORS
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4. ADVANTAGES
 LOWER COSTS
 RELIABILITY
 SIMPLE CONTROL
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5. SPEED EQUATION OF DC MOTOR
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V-APPLIED VOLTAGE
Ia- ARMATURE CURRENT
Ra- ARMATURE RESISTANCE
Φ- FLUX

6. SPEED CONTROL OF DC MOTORS
1.Speed Control of Shunt Motor
 Flux Control
 Armature Voltage Control (Rheostat Control)
 Applied Voltage Control
2.Speed Control of Series Motor
 Flux Control
• Rheostatic Control
• Applied Voltage Control
3.Ward- Leonard System of Speed Control
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7. Speed Control of Shunt Motor
 Flux Control
 Armature Voltage Control (Rheostat Control)
 Applied Voltage Control
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8. Flux Control
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V-APPLIED VOLTAGE
Ia- ARMATURE CURRENT
Ra- ARMATURE RESISTANCE
Φ- FLUX

9. Flux Control
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11.  speed of the motor is inversely proportional
to flux
 The speed can be controlled by varying flux
 To vary the flux, a rheostat is added in series
with the field winding
 Adding more resistance in series with field
winding will increase the speed, as it will
decrease the flux
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12.  Field current is relatively small and hence I2R loss is
small
 This method is quiet efficient
 The speed can be reduced by using this method.
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13. Armature Voltage Control
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16.  Speed of the motor is directly proportional to the
armature voltage
 When armature voltage varies, the armature
current varies
 Speed is directly proportional to armature current
Ia
 If we add resistance in series with armature, Ia
decreases and hence speed decreases.
 The speed can be reduced by using this method.
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17. Advantages of armature control
 Simple method of speed control
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18. Disadvantages of armature control
 Input power constant
 Ouput power = backemf * armature current
 Lower speed,more power wasted
 Lesser efficiency
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19. BOTH ARMATURE AND FIELD CONTROL
METHOD FOR DC SHUNT MOTOR
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20. Speed Control of Series Motor
1. Flux Control
2. Rheostatic Control
3. Applied Voltage Control
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21. Flux control method for dc series
motor
1. Field diverter
2. Armature diverter
3. Tapped field control
4. Paralleling of field coils
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22. Field diverter
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23.  This method uses a diverter.
 Here the field flux can be reduced by shunting a
portion of motor current around the series field.
 This method gives speed above normal and the
method is used in electric drives in which speed
should rise sharply as soon as load is decreased.
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24. Armature diverter
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25. Tapped field control
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26.  This is another method of increasing the
speed by reducing the flux
 It is done by lowering number of turns of field
winding through which current flows.
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27. Paralleling of field coils
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30. Rheostatic Control (Variable resistance
in series with armature)
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31. 1. Introducing resistance in series with armature
2. voltage across the armature can be reduced.
3. speed reduces in proportion with it.
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32. Ward- Leonard System of Speed
Control
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35.  Ward Leonard control system is
introduced by Henry Ward Leonard in
1891.
 Ward Leonard method of speed control
is used for controlling the Speed of a DC
Motor
 It is a basic armature control method.
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36.  This control system is consisting of a DC
motor M1 and powered by a DC generator
G.
 In this method the speed of the DC
motor (M1) is controlled by applying
variable voltage across its armature.
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37.  The speed of motor M1 is to be controlled
which is powered by the generator G.
 The shunt field of the motor M1 is connected
across the DC supply lines. Now, generator G is
driven by the motor M2.
 The speed of the motor M2 is constant.
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38. Advantages of Ward Leonard System
 It is a very smooth speed control system over a
very wide range (from zero to normal speed of the
motor).
 The speed can be controlled in both the direction
of rotation of the motor easily.
 The motor can run with a uniform acceleration.
 Speed regulation is very good.
 It has inherent regenerative braking property.
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39. Disadvantages of Ward Leonard System
 The system is very costly because two extra
machines (motor-generator set) are required.
 Overall efficiency of the system is not sufficient
especially if it is lightly loaded.
 Larger size and weight. Requires more floor area.
 Frequent maintenance.
 The drive produces more noise.
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40. Application of Ward Leonard System
 This Ward Leonard method of speed control
system is used where a very wide and very
sensitive speed control is of a DC motor in both
the direction of rotation is required.
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41. Solid state speed control of DC
motor
 Motor speed can be controlled through power
semiconductor switches
 Power semiconductor switches are
SCR(THYRISTOR)
MOSFET
IGBT
TYPES
1.PHASE CONTROLLED RECTIFIER FED DC DRIVE
2.CHOPPER FED DC DRIVES
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42. PHASE CONTROLLED RECTIFIER FED DC DRIVES
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AC SOURCE
PHASE
CONTROLLED
RECTIFIER DC MOTOR LOAD

43. ADVANTAGES OF PHASE CONTROLLED DRIVES
 Simple
 Reliable
 Faster response
 Higher efficiency
 Small size
 Less weight
 Low initial cost
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44. DISADVANTAGES OF PHASE CONTROLLED DRIVES
 Higher ripple content
 Heating of motor
 Commutation problem
 Lower over load capacity
 Low power factor
 Complex control circuit
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45. Single phase half wave converter drives
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49. SINGLE PHASE SEMICONVERTER DRIVE OR
SINGLE PHASE HALF CONTROLLED CONVERTER
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54. Single phase fully controlled rectifier drive
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59. THREE PHASE SEMI CONVERTER
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63. THREE PHASE FULL CONVERTER
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