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THREE PHASE INDUCTION MOTORS
RODRIGUE
KAMBA
208231196
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INTRODUCTION
DEVELOPMENT
3. 3-Phase,72 slots 50Hz 10 pole machine4. Motor's type of connections5. Star delta starter circuit
6. Fault finding
CONCLUSIONS ANDRECOMMENDATIONS
2. 4 pole stator's design with 72 slots using PCAD
1. Main parts of a three phase induction Motor
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3-phase induction motors are simple, rugged, low cost, and easy tomaintain. They run at essentially constant speed from zero-to-full load.Therefore, they are the motors most frequently encountered in industry.
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1. Main parts of a three phase induction Motor
*A stator consisting of a steel frame that supports a hollow, cylindrical core ofstacked laminations. Slots on the internal circumference of the stator house thestator winding.
Steel core
cylindrical core
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. Slots
. Slots
Laminated paper
Laminated paper
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Copper wires
Copper wires
*Wired stator
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*Rotor: consists of a shaft (which provides the mechanical energy),rotoriron and windings in the case of a wound rotor type(also called slip ringmachine) or a cage made of copper or aluminum for so called squirrel
cage machines. Both, stator and rotor must be wound for the samenumber of poles to guarantee proper functioning of the machine
shaft shaft
iron
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* 2 Pole generator stator and 2 pole wound rotor
2 Pole rotor windings
24 slots 2 pole stator
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2. 4 pole stator's design with 72 slots using PCAD
Pole phase groups
Q=pm (number of coils per group)
Phase group=Z/2Q
Z/number of pole
Pole pitch=Z/2P
Coil Coil pitch
Pole pitchCoil pitch= 2/Z
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3. 3-Phase, 72 slots 50Hz 10 pole machine
Phase
4
125
10
105
10
a
25
Phase
c'
8
80
a
[c]
a'
Slot No
b'
26
b
30
a
c
150
b
14
Angle
c'
Phase
31
11
65
23
35
b'
[a]
115
a
a'
Phase c
145
b
Pole Pitch 2
1
12
a
Pole Pitch 5
15
17
a
70
[b]
32
5Slot No
c
Slot No
13
c'
18 21
130
0
a
140
Angle
15
90
b
27
Pole Pitch 4
Slot No
20
c
b
170
M=72/(3*10)=2.4(Fractional)
19
Phase
24
P'=5 (Basic unit)
50
28
S/P=72/10=36/5=S'/P'
30
c'
Angle
(3,2.2,2,3)=12
6
a
Pole Pitch 1
b
S'=36
75
95
40
29
16060
a'
45
(3,3,2,2,2)=12
33 36
25
22 Angle=(10*180)/72=25
175
55 Phase b
3
165
Angle
2
c
34
Pole Pitch 3
20
110
Phase
16
Phase a
36 Coils
c'
100
b'
c'
Angle
b'
b'
35
5
c'
9
(2,2.3.3.2)=12
Phase Sequence abc
85
a'
b
c
155
7
Slot No
135
120
Formulas used
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4. Motor's type of connections
Star connectionDelta
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5. Star delta starter circuit
Three phase contactors star deltaconnection
Relay control circuitand switches
Power lines
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*Star Delta starter Circuit diagram
Contactor 3
L2 L3
Contactor 2
Overload
L1
Contactor 1
30KW motor
Fuses
.Power circuit
C2
Start
T1
Overload
C1
C1 T1
FUSE
C3
C2C3
Stop
T1
E/S
Set time
Relay circuit
3 Phase incoming voltage
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Motor will not start.
Supply or Starter trips out at start.
Motor Starts but has not torque.
Motor does not reach full speed.
Motor takes a long time to reach full speed.
Motor overheating.
No load amps in excess of Full load amps.
Mechanical noise or Vibration.
Noisy bearings.
Bearing Overheating
Motor amps in excess of nameplate full load
amps on load.Excessive electrical noise.
Unbalanced amps in different phases when
motor on load.
Motor runs wrong direction.
6. Fault finding
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Heat radiation of the windings, burning of winding old copper windings. Thethree phase impedances will be modified. One needs to measure the voltages,
currents, and powers in order to see if the system connection is right.
Burned copper wires
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If the electrical wiring installation is old, or has been extensively altered or
extended, or appears suspect, a Surveyor is likely to recommend that it isinspected and tested by an electrician
Whenever one gets across burned conductors, or old copper wires, themotor's stator will need to be rewind. To alleviate heat radiation the stator ismade of fins which increase the effective surface.
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