A Bearing is a machine
element which support
It permits relative
motion between the
contact surfaces of the
members while carrying
Most bearings support
rotating shafts against
either radial or axial
A Magnetic bearing is a
bearing which supports
a load a load using
A Magnetic bearing
levitate a rotating shaft
and linear moving
with rotor,this is
accomplished by electro
attracts a ferromagnetic
principle rotor can be
suspended in magnetic
field which is generated
It is difficult to build a
magnetic bearing using
permanent magnets due
to the limitation imposed
and techniques using
As a result, most
magnetic bearing require
continuous power input
and an active control
system to hold the load
stable. Because of this
An active magnetic
bearing (AMB) works on
suspension and consists
an electromagnet assembl
y, a set of power
amplifiers which supply
current to the
electromagnets, a controll
er, and gap sensors with
•The power amplifier supplies equal bias
current to two pairs of electromagnets on
opposite sides of a rotor. This constant
tug-of-war is mediated by the controller
which offsets the bias current by equal and
opposite perturbations of current as the
•The gap sensors are usually inductive in
rotor deviates from a differential mode.
nature and sense in its center position.
The power amplifiers in a modern
commercial application are solid state
devices which operate in a pulse width
modulation (PWM) configuration. The
According to Control action
According to Forcing action
According to Sensing action
– Sensor sensing
– Self sensing
•According to Load support
– Axial or Thrust
– Radial or Journal
•According to Magnetic effect
– Electro magnetic
– Electro dynamic
MAGNETIC BEARING PERFORM
Clean & Contamination Free
High Surface Speed
Low Energy Consumption
Highest speeds are possible even till the
ultimate strength of the rotor.
Absence of lubrication seals allows the
larger and stiffer rotor shafts.
Absence of mechanical wear results in
lower maintenance costs and longer life
of the system.
Adaptable stiffness can be used in
vibration isolation,passing critical
speeds, robust to external disturbances
Include High Cost.
Large in Size.
Magnetic bearings are increasingly
used in industrial machines such as
compressors, turbines, pumps, motors
Magnetic bearings are commonly used
in watt-hour meters by electric utilities
to measure home power consumption.
A new application of magnetic bearings
is their use in artificial hearts.
Magnetic bearings advantages and
applications have been discussed .
Electromagnetism and Control system
technologies have been introduced .
Design of thrust and radial magnetic
bearings have been studied .
Control of a rotor by rigid rotor and
flexible rotor models have been studied
Schweitzer, G., Bleuler, H. and
Traxler, “Basic Properties and
Applications of Active Magnetic
Chiba, A., Fukao, T., Ichikawa, O., Oshi
ma, M., Takemoto, “Magnetic Bearings
& Bearingless Drives.
Maslen, E., “Magnetic
Bearings”, University of Virginia.