magnetic bearings
TRANSCRIPT
Magnetic bearings
Bearings Bearings are machine elements
which constrains the relative motion to only desired motion and reduces friction between the moving parts
The word “bearing” from the word “to bear” is a machine element that allows one element to bear another
Magnetic bearings A magnetic
bearing is a bearing that supports a load using magnetic levitation
These bearings doesn’t have any physical contact with the moving parts
Magnetic bearings They levitate the
rotating shaft and permit relative motion with very low friction
They have minimum mechanical wear and support highest speeds when compared with all other bearings
They work effectively than all other bearings @ vacum and at high temperatures
Parts of a magnetic bearings: An electromagnet assembly Power amplifiers- supplies current
to the electromagnetic system Gap sensors - electronic circuit
which provide required feedback to control the position of position of rotor within the gap
A controller – controls the rotor motion within the gap
Parts of magnetic bearing :
Types of magnetic bearings :Active magnetic bearings
Passive magnetic bearings
Uses electro magnets for magnetic levitation
Carries varying load Requires input
power supply Easy to design More effective
Uses permanent magnet for magnetic levitation
Carries static load Doesn’t require
any input supply Difficult to design Less effective
Applications of magnetic bearings : Has several industrial
applications due to very low friction and ability to run without lubrication
Several applications of magnetic bearings are
watt-hour meters Maglev trains Centrifugal compressors Artificial hearts
Synchrony novaglide High temperature active magnetic
bearings used for aerospace and defence applications
Designed for using in next generation gas turbine engines where high temperature and high rotational speeds are already prevailing
They have optimized magnetic structure which reduces bearing size
Can operate at a temperature range of -70 F to 500 F
Parts of a novaglide system Two radial
bearings each with a stator and a rotor
One thrust bearing
Position sensors Magnetic bearing
controller
Uninterruptible power supply i.e., a battery backup
Auxillary bearings and bushings
Cables from controller to the bearing
Applications of novaglide High speed
compressors in large refrigeration systems
Expansion turbines Gas turbines High speed
generators Motors as a prime
mover
Zippe type centrifuges A centrifuge designed to enrich the rare fissile
uranium isotope uranium-235 from the mixuture of nature uranium containing u-238
This was first designed in Russia after world war 2
For isotopic seperation the centrifuge must rotate at a very high speed at about 90000 rpm
The shaft of the high speed rotor is supported by means of an active magnetic bearing
Design of zippie type centrifuge
Hollow cylindrical rotor filled with gaseous uranium
The magnetic field created at the bottom by means of supportive magnetic bearings enables the rotor to rotate at a high rpm without any frictional loss
The rotor spins in vacum
Artificial heart
A mechanical device that replaces heart
Artificial hearts bridge the time during heart transplantation
Design and parts of artificial heart : A centrifugal pump provided with
magnetic bearings or a similar axial flow pump can be used as a artificial heart
Artificial heart uses magnetic bearings as they have very less mechanical wear
The pump can regulate both pulmonary and systemic circulation
The centrifugal pump can produce continuous output
Material selection for artificial heart
The material must be flexible non toxic and must bear various stresses
The most commonly used material are silicones