Pastor Present

8/2/2019 Pastor Present

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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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