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DC Machine DC Generator DC Motor DC Machine: Conductor carrying - - PDF document
DC Machine DC Generator DC Motor DC Machine: Conductor carrying - - PDF document
DC Machine DC Generator DC Motor DC Machine: Conductor carrying current when placed in a magnetic field experience Mechanical force. B Flemings Left hand Rule F I DC M/C : Principle of Operation a 1 Field a 2 winding N a a S
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Conductor carrying current when placed in a magnetic field experience Mechanical force. Fleming’s Left hand Rule
B I F
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N S a a
1 2
V
f
a a
1 2
DC M/C : Principle of Operation Field winding Armature Armature Conductor
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DC M/C : Principle of Operation N S a a
1 2
F F
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N S a a1
2
F F DC M/C : Principle of Operation
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N S a a
1 2
F F V
a
DC M/C : Principle of Operation Commutator & Brush
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DC M/C : Principle of Operation N S a a1
2
F F V
a
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sin 90
a
F BIL T I θ θ φ = ∝
- N
S a a1
2
F F V
a
Ia
DC M/C : Principle of Operation
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Contradiction from Faraday’s Law
2 sin
b b
E BLv E θ φω = ∝
N S a a1
2
F F V
a
Fleming’s right hand rule assigns the polarity of induced voltage, E
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N S a a1
2
F F V
a
+ _ I _ +
a
DC M/C : Principle of Operation Fleming’s right Hand rule B I F (Eb)
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A Realistic DC Machine N S V
a
+ _
Eb
+ _
Ia
e b e
T K I E K φ φω = =
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DC Machine: Steady state model and behaviour
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Speed-Torque Characteristics
+ _ + _
a I I a a
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Feed back between electrical and mechanical world
L
d T T J dt ω = +
Motor Load
T
TL
ω
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DC Machine: Torque vs. speed Characteristics
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For Sep. Excited Motor:
a
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For Series Motor:
a
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Speed – Torque Characteristic
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Speed Control of Separately excited dc motor
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Armature Resistance Control
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Armature Resistance Control
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Combined Armature Voltage & Field Control
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Combined Armature Voltage & Field Control
Control Philosophy:
- For obtaining speeds lower than the
base speed: Vary armature voltage
- For obtaining speeds higher than the