“DESIGN OF ACTIVE MAGNETIC BEARING”

Presented ByJADHAV

MANORANJAN A.Guided By

Prof . S. B. BELKAR

Introduction

MagnetismMagnetic field

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

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

Magnetism Lorentz Force

f = forceQ = electric chargeE = electric fieldV = velocity of charge

QB = magnetic flux

density

BvEQf

Magnetism Lorentz Force

Simplification:

BvQf

Source: MIT Physics Dept.

website

BvEQf

BvE

Magnetism Lorentz Force

Further simplification:

Bif

BvQf

vQi

force perpendicular to flux!

f

i

B

Analogous Wire

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

MAGNETIC BEARING TYPESPASSIVE MAGNETIC BEARING Not electrically controlled, Permanent magnets

ACTIVE MAGNETIC BEARING Electrically controlled, Electromagnets

Principle of operation: Magnetic Levitation

Model of Active Magnetic Bearing

Active Magnetic Bearings Elements of System

Electromagnet Rotor Stator Position Sensor Controller Amplifier

Radial Bearing Configuration: for radial force balancingAxial Bearing Configuration: for axial force balancingPosition Transducers:

Auxiliary Bearing System

Sensors

Controller

Power Amplifiers

Control system:

Principle of radial and axial force

Where ,

magnetic flux in the air gap

The axial force

permeances of bias & axial control fluxes Pb & Px

Analysis of AMB system using Finite Element Method

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

ADVANTAGES OF AMB

•NON CONTACT MOTION

•HIGH ROTATING SPEED

•NO LUBRICATION

•INCREASE IN OPERATING TEMPERATURE

RANGE

•ACTIVE NATURE

DISADVANTAGES OF AMB

•NO LINEARITY

•ROTOR HEATING

•LARGER SIZE

•HIGH COST

APPLICATIONS OF AMB

•Image display unit

•High precision lathe

•Turbo expander

•Turbo compressor

•High speed milling

•Machine tool spindle

•Maglev Trains

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

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

THANK YOU