magnetic bearing
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jeevanlalmalayil
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29-10-2009, 03:29 PM


pls send me this seminar and presentation report
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computer science crazy
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31-10-2009, 04:48 PM

A control device for controlling displacement of a magnetically supported moving member according to a command, comprising:

a feedback circuit for detecting the displacement of the moving member to control the moving member to ensure stability and robustness of the magnetic support in response to the detected displacement, the feedback circuit comprising a closed loop composed of a displacement detector receptive of an output from a displacement sensor, an integral compensator coupled to the displacement sensor, a phase advancing compensator coupled to the integral compensator, and an electrical power amplifier coupled to the phase advancing compensator for effecting the magnetic support; and a feedforward circuit having an input terminal receptive of a command and an output terminal connected to the feedback circuit, and cooperative with the feedback circuit without disturbing the stability and robustness of the magnetic support for controlling the displacement of the moving member according to the command.

2. A control device according to claim 1; wherein the feedforward circuit has an output terminal connected to an input port of the electric power amplifier.

3. A control device according to claim 1; wherein the feedforward circuit comprises a low-pass filter connected to the input terminal, a high-pass filter connected to the input terminal, a compensative filter for effecting compensation of an output of the low-pass filter, a gain regulator for regulating a gain of an output of the high-pass filter, and a differential amplifier for differentially processing the outputs from the low-pass and high-pass filters to each other.

4. A control device according to claim 3; wherein the low-pass filter has a transfer function including a polynomial denominator preset according to desired response characteristic to the command, and the high-pass filter has another transfer function including another polynomial denominator having coefficients identical to those of the polynomial denominator of the transfer function of the low-pass filter.

5. A control system for controlling displacement of a movable member supported by magnetic support means, comprising: feedback control means for stabilizing the movable member in response to a displacement thereof caused by an undesired disturbance, the feedback control means comprising means for sensing a displacement of the movable member and for producing an output signal representative thereof, and compensating means receptive of the output signal for applying a compensating signal to the magnetic support means to stabilize the movable member; and feedforward control means responsive to an input command for controlling the displacement of the movable member without disturbing the stability thereof, the feedforward control means comprising input means receptive of the input command for producing a displacement signal corresponding thereto, the input means comprising a low-pass filter and a high-pass filter each receptive of the input command, and output means for combining the displacement signal with at least one of the output signal and the compensating signal of the feedback control means for receipt by the compensating means and the magnetic support means, respectively, the output means comprising means for combining an output signal from the low-pass filter with the output signal form the sensing means and for combining the difference between an output signal from the high-pass filter and the output signal from the low-pass filter with the compensating signal.

6. The control system according to claim 5, wherein the feedback control means comprises a closed loop including the sensing means and the compensating means.

7. The control system according to claim 5; wherein the input means comprises a compensative filter for effecting compensation of an output of the low-pass filter, a gain regulator for regulating a gain of an output of the high-pass filter, and a differential amplifier for differentially processing the outputs from the low-pass and high-pass filter with respect to each other.

8. The control system according to claim 7; wherein the low-pass filter has a transfer function including a polynomial denominator preset according to a desired response characteristic to the input command, and the high-pass filter has another transfer function including another polynomial denominator having coefficients identical to those of the polynomial denominator of the transfer function of the low-pass filter


use this links to get it
scribddoc/7749477/Magnetic-Bearing-and-Bearing-Less-DrivesAchiba-Et-Al
Use Search at http://topicideas.net/search.php wisely To Get Information About Project Topic and Seminar ideas with report/source code along pdf and ppt presenaion
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04-03-2010, 01:02 PM


.pdf   magnetic bearing.pdf (Size: 169.29 KB / Downloads: 703)

MAGNETIC BEARING.

Introduction
A magnetic bearing is a bearing which supports load using magnetic levitation.
The application of magnetic bearings is based upon the principle that an electromagnet will attract ferromagnetic material.
from conventional bearing

Presented By:GEEVARGHESE P.JOY.
S-7-M-A.
ROLL NO: 37
GUIDE: SHREEJITH T.V.

NON-CONTACTING TECHNOLOGY.
LUBRICATION IS ELIMINATED.
CAP
mWFR
AMP. IFIFHS
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Components and Operation
GAP SENSOR: ELECTRONICS
CONTROLLER

Magnetic bearing system incorporates 3 technologies
Bearing & sensors
The control system
Control algorithms
Benefits
1. High Reliability.
2. Clean environments.
3. High speed applications.
4. Position and vibration control.
5. Extreme Conditions.
6. Machine diagnostics.
Limitations

1. Larger bearings
2. Higher complexity and cost.
3. Requires electrical power.
Applications

^^WfflCWIUUUui manufacturing.
Vacuum pumps.
High speed turbo machinery and drives.
Process equipment and high speed machine tool spindles.
Reference:
skfmagneticbearings.com
Schweitzer, G (2002). "Active Magnetic Bearings - Chances and Limitations"
Kasarda, M. An overview of Active magnetic bearing Technology and Applications
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21-05-2010, 09:13 PM

read scribddoc/7749477/Magnetic-Bearing-and-Bearing-Less-DrivesAchiba-Et-Al for getting more information of magnetic bearing
Use Search at http://topicideas.net/search.php wisely To Get Information About Project Topic and Seminar ideas with report/source code along pdf and ppt presenaion
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projectsofme
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27-09-2010, 05:15 PM


.pptx   Magnetic Bearings.pptx (Size: 452.23 KB / Downloads: 263)
INTRODUCTION

Bearings
A bearing is a device to allow constrained relative motion between two or more parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can handle.

Magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials like iron and attracts or repels other magnets.

Permanent Magnet
A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field.

Magnetic Bearing
A magnetic bearing is a bearing which supports a load using magnetic levitation. Magnetic bearings support moving machinery without physical contact, for example, they can levitate a rotating shaft and permit relative motion without friction or wear.
Principal of operation :-

Magnetic levitation
Magnetic levitation, maglev, or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields. Magnetic pressure is used to counteract the effects of the gravitational and any other accelerations.



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05-04-2011, 11:26 AM


ACTIVE MAGNETIC BEARING

Presented by
PRANEETH MAXIM NORONHA


.pptx   ACTIVE MAGNETIC BEARING.pptx (Size: 506.27 KB / Downloads: 112)
INTRODUCTION
Active magnetic bearings (AMB) have been designed to overcome the deficiencies of conventional journal or ball bearings. They have the ability to work in vacuum with no lubrication and no contamination, or to run at high speed. Today, magnetic bearings have been introduced into the industrial world as a very valuable machine element with quite a number of novel features, and with a vast range of diverse applications. Let us discuss key features such as load, size, stiffness, temperature, precision, speed, losses and dynamics.
PRINCIPLE
An Active Magnetic Bearing (AMB) consists of an electromagnet assembly, a set of power amplifiers which supply current to the electromagnets, a controller, and gap sensors with associated electronics to provide the feedback required to control the position of the rotor within the gap. The power amplifiers supply equal bias current to two pairs of electromagnets on opposite sides of a rotor. This constant tug-of-war is mediated by the controller due to control current as the rotor deviates by a small amount from its center position.
Schematic Diagram of AMB
LOAD
 The term load touches upon basic properties of magnetic bearings. The load capacity depends on the arrangement and geometry of the electromagnets, the magnetic properties of the material, and of the control laws.
 The load carrying capacity of an AMB depends on the magnetomotive force i.e., the product of the maximum current imax and winding number n.
 The load that can be carried depends on possible heat dissipation. Therefore, one limitation for a high static load is the adequate dissipation of the heat generated by the coil current due to the Ohm resistance of the windings.
 This is called soft limitation on load.
 When the current imax reaches a value where the flux generated will cause saturation then the carrying force has reached its maximal value. Any overload beyond that will cause the rotor to break away from its centre position and touch down on its retainer bearings.
 This is hard limitation
 It has been found that the maximum specific carrying force of 32 N/cm2 (or 0.32 MPa) can be generated which is considerably lower than that for oil lubricated bearings, which is about four times as high.
 Using expensive cobalt-alloys with a saturation flux density of over 2 Tesla, from which a specific carrying force of up to 60 N/cm2 will result
 Geometry of a radial bearing
 d Inner diameter (bearing diameter)
 da Outer diameter
 dr Rotor diameter
 c Leg width
 di Shaft diameter
 l Bearing length
 h Winding head height
 b Bearing width (magnetically active part)
 An Slot cross section (winding space)
 p Pole shoe width
 s0 Nominal air gap
STIFFNESS
 The stiffness of a bearing is the ratio of the supported load with respect to the resulting displacement of that load
 High stiffness can be obtained by using PID controller
 The PID controller brings the position the shaft to the same position after the load and thus the rotor shows a behavior that cannot be obtained with classical bearings
SPEED
 It can be discussed under 3 categories
 Rotational speed
 Circumferential speed
 Supercritical speed
Rotational speed
 In today’s industrial applications rotational speed range of about 3kHz to 5kHz has reached. Problems arise from eddy current and hysteresis losses in the magnetic material, air losses, and the related requirements for power generation and adequate heat dissipation if the rotor runs in vacuum.
Circumferential Speed
 The circumferential speed is a measure for the centrifugal load and leads to specific requirements on design and material. The centrifugal load leads to tangential and radial stresses in the rotor.
 The tangential stress is the most critical one. Highest stress values occur at the inner boundaries of a rotor disc
 Rotor speeds of up to 340 m/s in the bearing area can be reached with iron sheets from amorphous metal (metallic glass), having good magnetic and mechanical properties.
Supercritical Speed
 A rotor may well have to pass one or more critical bending speeds in order to reach its operational rotation speed. In classical rotor dynamics this task is difficult to achieve. In AMB technology it is the controller that has to be designed carefully to enable a stable and well-damped rotor behaviour.
SIZE
 In principle, there appears to be no upper limit for the bearing size, it can be adapted to any load. Small bearings are of special interest to micro-techniques. Potential applications are video heads, medical instruments, hard disk drives, and optical scanners. The challenge lies in simplifying the design and in the manufacturing process.
HIGH TEMPERATURE AMB
 In order to utilize the full advantages of active magnetic bearings, operation in gas turbine and aircraft engines requires that the magnetic bearing should work properly at high temperatures
 Challenges in designing such bearings consist in material evaluation, manufacturing process and high temperature displacement sensor development.
 Operating temperatures of up to 550º C have been reached, at rotor speeds of 30,000 rpm. Such a performance cannot be reached by any other kind of bearing.
 Experimental tests were quite successful, but the long-term exposure to high temperature needs further research, as the actual results are not yet convincing
 Test Rig For High Temperature AMB
LOSSES
 With contact-free rotors there is no friction in the magnetic bearings. The operation of active magnetic bearings causes much less losses than operating conventional ball or journal bearings
 Losses can be grouped into losses in
 Stator part
 Rotor part
Stator Loss
 Stator losses are mainly from copper losses in the windings of the stator and from losses in the amplifiers. The copper losses are a heat source, and, if no sufficient cooling is provided, can limit the control current and hence the maximal achievable carrying force
Rotor Loss
 These losses comprise iron losses caused by hysteresis and eddy currents, and air drag losses. The losses heat up the rotor, cause a breaking torque on the rotor, and have to be compensated by the drive power of the motor
 In general, the eddy current losses are the largest ones.
 The iron losses depend on the rotor speed, the material used for the bearing bushes
 The iron losses in the rotor can limit operations, as in particular in vacuum applications it can be difficult to dissipate the generated heat.
 The hysteresis losses arise if the B-H-curve travels along a hysteresis loop
 The eddy-current losses arise when the flux density within the iron core changes. A compact core acts like a short circuit winding and generates large eddy currents. The eddy-current losses can be reduced by dividing the iron core in insulated sheets or in particles (sinter cores). The smaller these divisions, the smaller the eddy-current losses.
 a) Iron Core b) Sheet
PRECISION
 Precision in rotating machinery means most often how precise can the position of the rotor axis be guaranteed
 Active magnetic bearings levitate an object, with feedback control of measured displacement sensor signal. The performance of AMB systems is therefore directly affected by the quality of a sensor signal
MATERIALS
Common AMB materials are
Silicon alloys
Cobalt alloys such as Hiperco
ADVANTAGES OF AMB
 Lubrication free
 Reliability
 Operation in vacuum
 Reduced energy consumption
 Condition monitoring
 High speed capability
 No oil contamination
 Precision
DISADVANTAGES
 Requires auxiliary bearing
 Load carrying capacity is limited
 Requires continuous power supply
APPLICATIONS
 Refineries and petrochemical plants
 Offshore and under sea gas extraction
 Cryogenic pumps, compressor and expanders
 Industrial refrigeration and air conditioning
 Turbo blowers, Turbo booster pumps, Turbo molecular pumps etc
CONCLUSIONS
 The maximal load depends on design
 The specific load depends on the available ferromagnetic material and its saturation properties, and is therefore limited to 32 to 60 N/cm2
 Circumferential speeds, causing centrifugal loads, are limited by the strength of material. Values of about 250 to 300 m/s have been realized with actual design
 Supercritical speed means that one or more critical speeds can be passed by the elastic rotor. It appears to be difficult to pass more than two or three
 High temperature bearings have been realized, running in experiments at an operating temperature of 550º C.
 The losses of magnetic bearings at operating speed are much smaller than that of classical bearings. Eddy current losses will limit the rotation frequency of massive rotors, the air drag will be crucial at high circumferential speeds
 A high precision of the position of the rotor axis (in the range of mm) requires high resolution sensors and adequate signal processing to separate disturbance signals from the desired ones
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09-04-2011, 10:07 AM

Presented By
B.V.S.Phanindra


.doc   magnetic bearing2.doc (Size: 102 KB / Downloads: 103)
Magnetic Bearings
INTRODUCTION:
Bearings

A bearing is a device to allow constrained relative motion between two or more parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can handle.
Magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials like iron and attracts or repels other magnets.
Permanent Magnet
A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field.
Magnetic Bearing
A magnetic bearing is a bearing which supports a load using magnetic levitation. Magnetic bearings support moving machinery without physical contact, for example, they can levitate a rotating shaft and permit relative motion without friction or wear.
Principal of operation:
Magnetic levitation

Magnetic levitation, maglev, or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields. Magnetic pressure is used to counteract the effects of the gravitational and any other accelerations.
DESCRIPTION:
It is difficult to build a magnetic bearing using permanent magnets due to the limitations described by Earnshaw’s theorem and techniques using diamagnetic materials are relatively undeveloped. As a result, most magnetic bearings require continuous power input and an active control system to hold the load stable. Many bearings can use permanent magnets to carry the static load, and then only use power when the levitated object deviates from its optimum position. Magnetic bearings also typically require some kind of back-up bearing in case of power or control system failure and during initial start-up conditions.
Two sorts of instabilities are very typically present with magnetic bearings. Firstly attractive magnets give an unstable static force, decreasing with greater distance, and increasing at close distances. Secondly since magnetism is a conservative force, in and of itself it gives little if any damping, and oscillations may cause loss of successful suspension if any driving forces are present, which they very typically are.
With the use of an induction-based levitation system present in maglev technologies such as the Inductrack system, magnetic bearings could do away with complex control systems by using Halbach Arrays and simple closed loop coils. These systems gain in simplicity, but are less advantageous when it comes to eddy current losses. For rotating systems it is possible to use homopolar magnet designs instead of multipole halbach structures, which reduces losses considerably. An example of this - that has solved the Earnshaws theorem - is the homopolar electro dynamic bearing invented by Dr Torbjorn Lembke.
Magnetic bearing system incorporates 3 technologies:
1) Bearing & sensors
2) The control system
3) Control algorithms
A control device for controlling displacement of a magnetically supported moving member according to a command, comprising:
1. A feedback circuit for detecting the displacement of the moving member to control the moving member to ensure stability and robustness of the magnetic support in response to the detected displacement, the feedback circuit comprising a closed loop composed of a displacement detector receptive of an output from a displacement sensor, an integral compensator coupled to the displacement sensor, a phase advancing compensator coupled to the integral compensator, and an electrical power amplifier coupled to the phase advancing compensator for effecting the magnetic support; and a feed forward circuit having an input terminal receptive of a command and an output terminal connected to the feedback circuit, and cooperative with the feedback circuit without disturbing the stability and robustness of the magnetic support for controlling the displacement of the moving member according to the command.
2. A control device according to claim 1; wherein the feed forward circuit has an output terminal connected to an input port of the electric power amplifier.
3. A control device according to claim 1; wherein the feed forward circuit comprises a low-pass filter connected to the input terminal, a high-pass filter connected to the input terminal, a compensative filter for effecting compensation of an output of the low-pass filter, a gain regulator for regulating a gain of an output of the high-pass filter, and a differential amplifier for differentially processing the outputs from the low-pass and high-pass filters to each other.
4. A control device according to claim 3; wherein the low-pass filter has a transfer function including a polynomial denominator preset according to desired response characteristic to the command, and the high-pass filter has another transfer function including another polynomial denominator having coefficients identical to those of the polynomial denominator of the transfer function of the low-pass filter.
5. A control system for controlling displacement of a movable member supported by magnetic support means, comprising: feedback control means for stabilizing the movable member in response to a displacement thereof caused by an undesired disturbance, the feedback control means comprising means for sensing a displacement of the movable member and for producing an output signal representative thereof, and compensating means receptive of the output signal for applying a compensating signal to the magnetic support means to stabilize the movable member; and feed forward control means responsive to an input command for controlling the displacement of the movable member without disturbing the stability thereof, the feed forward control means comprising input means receptive of the input command for producing a displacement signal corresponding thereto, the input means comprising a low-pass filter and a high-pass filter each receptive of the input command, and output means for combining the displacement signal with at least one of the output signal and the compensating signal of the feedback control means for receipt by the compensating means and the magnetic support means, respectively, the output means comprising means for combining an output signal from the low-pass filter with the output signal form the sensing means and for combining the difference between an output signal from the high-pass filter and the output signal from the low-pass filter with the compensating signal.
6. The control system according to claim 5, wherein the feedback control means comprises a closed loop including the sensing means and the compensating means.
7. The control system according to claim 5; wherein the input means comprises a compensative filter for effecting compensation of an output of the low-pass filter, a gain regulator for regulating a gain of an output of the high-pass filter, and a differential amplifier for differentially processing the outputs from the low-pass and high-pass filter with respect to each other.
8. The control system according to claim 7; wherein the low-pass filter has a transfer function including a polynomial denominator preset according to a desired response characteristic to the input command, and the high-pass filter has another transfer function including another polynomial denominator having coefficients identical to those of the polynomial denominator of the transfer function of the low-pass filter
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dngandhi
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09-04-2011, 11:47 AM

explin its working and list out components
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09-04-2011, 12:34 PM

dear dngandhi,
download th above attachments .. then read it ...
most of attachment included diagram to explain ideas easily
Use Search at http://topicideas.net/search.php wisely To Get Information About Project Topic and Seminar ideas with report/source code along pdf and ppt presenaion
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17-03-2012, 11:13 AM

i need this topic magnatic bearing ppts and doqument for my technical seminar and presentation
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