Magnetic bearings support rotating machinery without physical contact using magnetic levitation. They have advantages over conventional bearings like eliminating friction, lubrication needs, and contamination. There are two types - passive bearings that operate like mechanical bearings without control, and active bearings with sensors and controls that monitor shaft position and feed information back to continuously adjust the magnetic fields holding the rotor in place. Magnetic bearings enable more efficient, smaller, and lower maintenance machines.

1. Magnetic Bearing
Technology For High
Power Machines

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A magnetic bearing is a bearing that balances a load using
magnetic flotation. Magnetic bearings support moving parts
without any physical contact. Hence magnetic bearings have
been utilized by a variety of industrial sectors for over a
decade with benefits that include non­contact rotor support,
no lubrication and even no friction.
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Conventional mechanical bearings physically interface with
the shaft and require some form of greasiness, can be replaced
by a technology that suspends a rotor in a magnetic field,
which eliminates all friction losses.
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Today there are two types of magnetic bearing technologies in
use. They are Passive and Active. Now the passive bearings
are similar to mechanical bearings and don’t need any active
control for operation. In active systems, with no contact
position sensors can continually monitor shaft position and
feed this information to the control system.

4. Additional advantages of magnetic
bearings
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Frictionless
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No need of lubrication
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No oil contamination
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Low energy consumption
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Able to operate within a wider temperature range
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No need for seals, pumps,filters, piping, coolers or tanks
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Eco friendly workplace
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Cost savings

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In practice, these attractions are balanced in order to
maintain a gap between the shaft i.e. rotor and static parts i.e.
stator. The function of the magnetic bearing is to locate the
shaft’s rotation axis i.e. in the center, reacting to any load
variation or any external disturbing forces.
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Conventional centrifugal compressors are based on
mechanical gears, low­speed drives and oil­film bearings
yielding in high running costs because of their high losses,
wear and need to maintain.
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The new compressor drive uses a permanent magnet motor,
operating at an efficiency of around 97%, to drive a rotor
“floating” on magnetic bearings, which spins the compressor
impeller at speeds of around 60,000 rpm. These drives
experience almost no friction or wear, and need very little
maintenance. They also minimize the risk of oil
contamination, and result in compressors that are about half
the size of conventional designs.

8. Working
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Magnetic bearings are basically a system of bearings which provide non­
contact operation, virtually removing friction from rotating mechanical
systems. Now magnetic bearing systems have many components. The
components consist of the electromagnets, rotors and position sensors. The
electronics consist of a set of power amplifiers that supplies current to
electromagnets. A controller works with the position sensors which provide
feedback to control the position of the rotor within the gap.
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The position sensor registers a change in position of the shaft i.e. rotor.
This change in position is communicated back to the processor where the
signal is processed and the controller decides what the necessary response
should be, then initiates a response to the amplifier. This response should
increase the magnetic force in the corresponding electromagnet in order to
bring the shaft back to center. In a representative system, the radial
clearance can range from 0.5 to 1 mm. This process repeats itself over and
over again. The rotor on getting closer to the magnet, the force increases.
The system needs to continuously adjust the magnetic strength that is
being recieved from the electromagnets in order to hold the rotor in the
desired position.

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