basic principles of...

EE 209 Fundamentals of Electrical and Electronics Engineering, Prof. Dr. O. SEVAİOĞLU,

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Basic Principles of Electromechanics

by Prof. Dr. Osman SEVAİOĞLU

Electrical and Electronics Engineering Department



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Left Hand Rule - Principle of Electric Motors

EE 209 Fundamentals of Electrical and Electronics Engineering, Prof. Dr. O. SEVAİOĞLU, Page 2

Left Hand RuleA force is created in the vertical direction shown, in a conductor carrying a current I in a magnetic field as shown in the figure on the RHS

F = ( I L ) x B

This principle is best explained by Left Hand Rule• Thumb finger of the left hand points

the direction of the force generated,• Index finger points the direction of

magnetic field,• Middle finger points the direction of

current applied,

F

I

BL

90O


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Left Hand Rule

F = ( I L ) x B

F (Force created)

I

B

L90O

V

F

I

B

L90O

Left Hand Rule - Principle of Electric Motors

A force is created in the vertical direction shown, in a conductor carrying a current I in a magnetic field as shown in the figure on the RHS

B


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Right Hand Rule

F = - ( I L ) x B

This principle is best explained by Right Hand Rule• Thumb finger points the right hand

points the direction of the force applied,• Index finger points the direction of

magnetic field,• Middle finger points the direction of

current generated,

Right Hand Rule - Principle of Electric Generators

A current is induced (generated) in the direction shown, on a conductor moving vertically in a magnetic field as shown in the following figure

F

I

B

L 90O


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Right Hand Rule - Principle of Electric Generators


Right Hand Rule

A current is induced (generated) in the direction shown, on a conductor moving vertically in a magnetic field as shown in the following figure

F = -( I L ) x B

F (Force applied)

I

B

L90O

F

B

L90O

V

B


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Please do not Confuse

Left Hand Rule-Electric Motor

F = ( I L ) x B

Right-Hand Rule-Electric Generator

F = - ( I L ) x B

F

I

B

L90O

F

I

B

L90O


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Generation of AC Voltage

I(t)

I(t)

Fixed Stator Coils, Rotating Poles Fixed Poles, Rotating Coils


Rotating Poles Fixed Stator PolesAC Rotating Rotor CoilFixed Stator Coil


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Fixed Poles, Rotating CoilsFixed Stator PolesAC Rotating Rotor Coil


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Generation of AC Voltage - Synchronous Generator

Hydroelectric Dam Generating Units


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Atatürk Hydroelectric Dam (2400 MW)


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Francis Turbine Generator Set

Cross Section View

http://en.wikipedia.org/wiki/Image:Water_turbine.jpg


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Francis Turbine - Generator

Water Flow


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Itaipu Generating Unit - Stator


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Generation of DC Voltage

Fixed Poles, Rotating CoilsSplit Ring Rotating Rotor Coil Fixed Stator Poles

Split Rings

DC Windings


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Generation of DC Voltage

Fixed Poles, Rotating CoilsFixed Stator Poles

VDCSplit RingsRotating Rotor Coil

DC Windings

+ -


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Generation of DC VoltageFixed Poles, Rotating Coils


Split Ring Rotating Rotor Coil

Average Voltage

-505

10152025

5 10 15 200

V (V

olts

)Fixed Stator Poles

T=10 msec

10

V average = (1/T) ∫ V(t) d/dt 0

5

= (1/5) ∫ Vpeak cos wt dt 0

= (2 / π ) Vpeak = 0.63 Vpeak

Vaverage = VDC

Vpeak = 22 V


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Squirrel Cage AC (Induction) MotorsFixed Poles, Rotating Coils


Rotor Coils (Fixed Bars)Fixed Stator Poles

Line Voltages Applied


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Squirrel Cage AC (Induction) MotorsFixed Poles, Rotating Coils


Rotor Coils (Fixed Bars) Fixed Stator Poles

Line Voltages Applied

http://upload.wikimedia.org/wikipedia/commons/a/a4/Induction-motor-3a.gif


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DC Motors

Fixed Poles, Rotating Coils


Split Ring Rotor Coils Fixed Stator Poles

DC Voltage Applied

Time (Sec)

20

1 2 3 4 5 6

80

07

40

60

DC (mean) Voltage

DC Voltage (Volts)


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Stator Shell

Arrangement of Windings

Conductors in Stator Coil

I I


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Conductors

Generation of AC Voltage Synchronous Generator

Stator Coils Configuration


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Coil

Magnetic axis of coil

Magnetic axis of magnet

θ = Angle between magnetic axes


Basic Principles of Synchronous Generator


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Basic Relation

φcoil = φmax x cos θθ = wt φcoil (t) = φmax x cos wt

Lenz LawV(t) = - N d/dt φcoil (t)

= - N d/dt φmax x cos wt= N w φmax sin wt= V max sin wt

Sinusoidal voltage is generated


Synchronous Generator


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N

S

I(t)I(t)

N S

-25-20-15-10-505

101520

0,005 0,01 0,015 0,02Time (Sec)

25

0

-25-20-15-10-505

101520

0,005 0,01 0,015 0,02Time (Sec)

25

0

Conductors Conductors

φcoil (t) = φmax x cos wt = φmax φcoil (t) = φmax x cos wt = 0

Generation of AC VoltageBasic Principles of Synchronous Generator

V (V

olts

)

V (V

olts

)


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