Kuliah Rangkaian Magnet 270809 11
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Transcript of Kuliah Rangkaian Magnet 270809 11

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RANGKAIAN MAGNETIK
A ma Den u ya
Jurusan Teknik Konversi Energi
Politeknik Negeri BandungBandung – September 2009

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History Electricity

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To be able to convert Energy,
we nee a oup ng e

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MAGNETIC CIRCUITS
• Magnetic Fields
• Magnetic Circuits
• Magnetic Materials
• Inductance and Mutualnductance and MutualInductance

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Magnetic Circuit
1. Understand magnetic fields and their interactions with moving
.
1. Use the right-hand rule to determine the direction of the magneticfield around a current-carrying wire or coil.
.
to magnetic fields.
4. Calculate the voltage induced in a coil by a changing magnetic fluxor in a conductor cuttin throu h a ma netic field.
5. Use Lenz’s law to determine the polarities of induced voltages.
6. Apply magnetic-circuit concepts to determine the magnetic fields in
practical devices.7. Determine the inductance and mutual inductance of coils given their
physical parameters.
8. Understand hysteresis, saturation, core loss, and eddy currents in
cores compose o magne cma er a s suc as ron.

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Magnetic Fields
Konsep Induktansi
dS.BΨ = ∫
d
atauIL,I
λ
λλ =
=
dI=

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Magnetic Fields

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Illustrations of the ri ht-hand rule

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Concentric magnetic flux around a
curren -carry ng con uc or.

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-

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Example of Ampére’s Law
Find the magnetic field along a circular path around an infinitely longConductor carrying ‘I’ ampere of current.
900
B,H
r
Since both→
dl
→
Hand are perpendicular to radius ‘r’ at any point ‘A’
on the circular path, the angle θ is zero between them at all points. Also since all
the points on the circular path are equidistant from the current carrying
conductor is constant at all points on the circle→
Ir 2HdlHdl.H =π==→→→→→
∫ ∫ or
r 2
IH
π=
→

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Magnetic Field Intensity andagnetic Field Intensity and
Ampère’s Law
7−=
’µ µ =
r
=⋅ id lH

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Magnetic Field Around a Longagnetic Field Around a Long
Straight Wire
I
H B µ == r π

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Flux Density in a Toroidal Core
NI
B
µ
=

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Flux Linkages and Faraday’s Law
AB d ⋅=φ φ λ N = A
Faraday’s law of magnetic induction:
d λ
dt =

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close together where the field is strong and.
-
magnet and enter the south-seeking end.
When placed in a magnetic field, a compass
.

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Magnetic Circuit

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Magnetic Circuits
F =NI= Magneto Motive Force or MMF = # of turns * Current passing through it
F = NI = Hl (why!)
NI=µlor NI
A=
µlor
or
)A/(µ=Φl
ℜ=Φor
ℜ = Reluctance of magnetic path

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Magnetic Circuits (1)
w
I
N
d
l= mean length

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Magnetic Circuits (2)
F =NI= Magneto Motive Force or MMF = # of turns * Current passing
through it
F = NI = Hl (why!)
NIB
=
µ
lor NI
A
=
µ
Φlor
or
)A/(
NI
µ=Φl
ℜ=Φ
NIor
ℜ = Reluctance of magnetic path

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Magnetic Equivalent Circuits

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Analogy between Electric circuit
an agne c rcu

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The magnetic circuit for the toriodal coil

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Analogy between Electric circuit

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Analogy between Electric circuit
Φ
ℜ
F =MMF is analogous to Electromotive force (EMF) =E
Φ = Flux is analogous to I = Current
= Reluctance is analo ous to R = Resistance
P = Permeanceℜ
=1
= Analogous to conductanceR
1G =

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Analogy between 'magnetic circuits'
and electrical circuits

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Analogy between Electric circuit
and Magnetic Circuit

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Equivalent circuits for the electrical

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Magnetization Curve

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Basic magnetic circuit

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Simple Magnetic Circuit

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Magnetic Circuit with Air Gap

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Fringing
We approximately account for fringing byaddin the len th of the a to the de th and
width in computing effective gap area.

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• Ratio of iron vs. stack areas
• Lamination thickness 0.35 ...
0.65 mm <-> stacking factor . ... . .
• Amorphous steel
– 80% iron, 20% boron
– cheap (less than silicon steel),
– low losses (1/5’th of best
– hard to punch

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Composite Magnetic Circuit with
r-gap
Magnetic Circuit

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Magnetic Circuit

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Flux linkage & generated voltage

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Flux linkage & generated voltage