Download - Active Magnetic Bearing
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“DESIGN OF ACTIVE MAGNETIC BEARING”
Presented ByJADHAV
MANORANJAN A.Guided By
Prof . S. B. BELKAR
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Introduction
MagnetismMagnetic field
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Magnetism Magnetic Flux Density
B = magnetic flux densitym = magnetic permeability
H = magnetic field
HB
r 0m0 = permeability of free
spacemr = relative permeability
1
1
diamagnetic
paramagnetic
ferromagnetic
r
niH
2
multiple loops of wire, n
1
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Magnetism Magnetic Field
Magnetic field, H, is found around a magnet or a current carrying body.
r
iH
2
idsH
(for one current loop)
H
i
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Magnetism Lorentz Force
f = forceQ = electric chargeE = electric fieldV = velocity of charge
QB = magnetic flux
density
BvEQf
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Magnetism Lorentz Force
Simplification:
BvQf
Source: MIT Physics Dept.
website
BvEQf
BvE
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Magnetism Lorentz Force
Further simplification:
Bif
BvQf
vQi
force perpendicular to flux!
f
i
B
Analogous Wire
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MAGNETIC BEARINGBearing which supports a load using magnetic levitation
Advantages of magnetic bearings: contact-free no lubricant (no) maintenance tolerable against heat, cold, vacuum, chemicals low losses very high rotational speeds
Disadvantages: complexity high initial cost
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MAGNETIC BEARING TYPESPASSIVE MAGNETIC BEARING Not electrically controlled, Permanent magnets
ACTIVE MAGNETIC BEARING Electrically controlled, Electromagnets
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Principle of operation: Magnetic Levitation
Model of Active Magnetic Bearing
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Active Magnetic Bearings Elements of System
Electromagnet Rotor Stator Position Sensor Controller Amplifier
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Radial Bearing Configuration: for radial force balancingAxial Bearing Configuration: for axial force balancingPosition Transducers:
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Auxiliary Bearing System
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Sensors
Controller
Power Amplifiers
Control system:
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Principle of radial and axial force
Where ,
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magnetic flux in the air gap
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The axial force
permeances of bias & axial control fluxes Pb & Px
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Analysis of AMB system using Finite Element Method
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Performance relative to hydrodynamic bearing
REQUIREMENTS
MAGNETIC BEARING
HYDRODYNAMIC BEARING
High loads low high
Speed high low
Sealing Not required required
Unbalance no yes
Losses Very low high
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ADVANTAGES OF AMB
•NON CONTACT MOTION
•HIGH ROTATING SPEED
•NO LUBRICATION
•INCREASE IN OPERATING TEMPERATURE
RANGE
•ACTIVE NATURE
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DISADVANTAGES OF AMB
•NO LINEARITY
•ROTOR HEATING
•LARGER SIZE
•HIGH COST
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APPLICATIONS OF AMB
•Image display unit
•High precision lathe
•Turbo expander
•Turbo compressor
•High speed milling
•Machine tool spindle
•Maglev Trains
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Applications Maglev Trains
Maglev = Magnetic Levitation150 mm levitation over guideway track
undisturbed from small obstacles (snow, debris, etc.)
typical ave. speed of 350 km/h (max 500 km/h)what if? Paris-Moscow in 7 hr 10 min (2495 km)!
stator: track, rotor: magnets on train
Source: DiscoveryChannel.com
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Applications Maglev Trains
Maglev in Shanghai- complete in 2004- airport to financial district (30 km)- world‘s fastest maglev in commercial operation
(501 km/h)- service speed of 430 km/h
Source: www.monorails.org
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THANK YOU