MAGNETIC LEVITATIONPRECAP…………

• Introduction

• Summary

• Theorem related to its principle

• Uses and its Practical Application

Prepared By:13BEE110 SHETHNA VASAV

13BBEE111 SHINGALA TUSHAR

Guided by:Prof. Hormaz

Amrolia

Magnetic levitation, maglev or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields

Magnetic Levitation

Levitation and Suspension

Levitation: Force of

Repulsion

Suspension: Force of

Attraction

APPLICATION OF MAGLEV

• Magnetic Bearing • Maglev Train• Maglev wind turbine• Maglev Fan• StartRam• Flying Car• Flywheels

Area of Attraction

As a means of eliminating friction or

physical contact

Frictionless bearings

High speed Ground

Transportation

Magnetic Bearing

MEANING OF BEARING

• A bearing is a device that is used to enable linear or rotational motion of the shaft while reducing friction.

• It provides stability to the rotating shaft and frictionless rotation of the same.

• The contacting surfaces in a bearing may be partially or completely separated by a film of oil or any other liquid in order to reduce friction.

TYPES OF BEARING

Plain or slider bearing : - In which the rotating shaft has a sliding contact with the bearing which

is held stationary . Due to large contact area friction between mating parts is high requiring greater lubrication.

Rolling or anti-friction bearing : -Due to less contact area rolling friction is much lesser than the sliding

friction , hence these bearings are also known as antifriction bearing.

MAGNETIC BEARING

• A magnetic bearing system supports a rotating shaft, without any physical contact by suspending the rotor in the air, with an electrically controlled magnetic force.

• It works on the basic principle of Magnetic Levitation and Electromagnetism.

• We can call it as the future for upcoming generation of motors.

CONTINUE….

• Hence we can say Magnetic bearings are designed to support rotating and linear moving machinery elements without contact with rotor, this is accomplished by Electro-magnet (bearing) which attracts a Ferromagnetic material (rotor) , using this principle rotor can be suspended in magnetic field which is generated by bearing.

• Main components of magnetic bearing are Actuators, Sensors and Control Mechanism.

Classification of Magnetic Bearing

Based on

Control action

Based on Forcing action

Based on Load

supported

Based on Magnetic

Effect

ACTIVE MAGNETIC BEARING (AMB)• Because of Earnshaw’s Theorem it is not

possible to use permanent magnets in magnetic bearing. Even techniques that deal with diamagnets are under-developed.

• Hence electromagnets are used for magnetic bearing. Hence magnetic bearing requires a continuous power input & control system to stable the load. Even back-up powering is required in case of power failure.

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.

OPERATION

Gap

• The controller offsets the required bias current by equal but opposite perturbations of current as the rotor deviates by a small amount from its center position.

• The gap sensors are usually inductive in nature and continuously sensing the gap between rotor and the bearing.

• The sensor measures the position of the body. The control electronics then calculates the right current to suspend the ball.

• This current is set by the amplifier. The resulting force is within limits proportional to the square of the current and inversely proportional to the square of the position.

• )^2 • Controller uses Microprocessor to allow the whole

system function in a stable manner.

Digital Control System:

A-D ConvertorControl Algorithm

Processor

D-A Convertor

e.g. the position, is sampled. The data serves as input of the control algorithm, which runs on the processor. Then the calculated desired value is converted into an analog form. According to the application the data width lies between 10 and 64 bits.

APPLICATION• Turbo-blower: cooling gas

compressor (CO2) for a power laser, cutting metal sheets up to 25 mm. The laser needs uncontaminated gas.

• The speed is 54000 rpm, the rotor mass 3.6 kg, the motor power 12 kW.

CONTINUE………..

• Gas-turbine/Generator for power generation: 4 radial bearings and 1 thrust bearing, 6010 rpm, 9000 kW, bearing diameter 400 mm.

Magnetic Bearings are free of contact and can be utilized in vacuum techniques, clean and sterile rooms, transportation of aggressive media or pure media.

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.

ADVANTAGES

DISADVANTAGES

High Cost

Relatively LargeSize

PASSIVE MAGNETIC BEARING (PMB)

• Passive Magnetic Bearing differs from AMB in terms of magnets and electronic system.

• The rotor is stabilized only by permanent uncontrolled magnetic fields.

• Because of this PMB are less expensive then AMB.

BACKGROUND

• PMB can be constructed using:Permanent magnetsFerrofuilds(A liquid that gets strongly

energized under magnetic field)Diamagnetic materials eg copper, gold,

quartz, mercury, water, alcohol.

• Shown Prototype is built at GLENN RESEARCH CENTER.

PROTOTYPE

• A prototype has been realized. Levitation is assured by a 7 cm graphite disc and a 2D array assembled of 5mm cubic NdFeB magnets. Weight compensation uses a cylindrical magnet of Ø 5 mm placed on the rotor and a ferromagnetic counterpiece on the stator (2).

• The rotor mass is 92 grams and it levitates at 300μm.

PROTOTYPE FIGURE

• As far as the application is concerned it is limited as the diamagnetic or the permanent magnets can be damaged easily.

• It can only be used in application of flywheels.

• First PMB bearing was prepared at GLENN RESEARCH CENTER at the speed of 5500rpm.

Application of PMB

Disadvantages

Permanent Magnets are

used

Hence not economical

Gets Damaged Easily Due to heat

or some other Factor

• Used in industrial machines like compressors, turbines, pumps, motors and generators.

• Can be used in Watt-Hour Meter to measure home power consumption.

• Useful in high precision equipment & to support equipment in a vacuum.

• To support Maglev Trains for smooth & noise free ride.

• Useful in ARTIFICAL HEART.

• Anywhere where ROTATING part is used……………

APPLICATIONS Of MAGNETIC BEARING

REFERENCES

• Introduction to magnetic bearing by JAGU SRINIVASA RAO (Pdf)

• Magnetic Bearings by HILLYARD (Pdf)

• Design and Control of Active Magnetic Bearing Systems for High Speed Rotation by RENE LARSONNEUR (Pdf)

• PMB by Gerhard Schweitzer (PDF)

• Optimization of Repulsive Passive Magnetic Bearings Roland Moser, Jan Sandtner, and Hannes Bleule1.

THANK

YOU