aseminar on

“magnetic bearing”

PRESENTED BY : VIMAL SHARMA

MECHANICAL ENGINEERINGREGD. NO. : 1301230247

8th SEMESTERSYNERGY INSTITUTE OF ENGINEERING AND TECHNOLOGY,DHENKANAL.

CONTENTS:BEARINGMAGNETIC BEARINGDESCRIPTIONBASIC OPERATIONCLASSIFICATIONMAGNETIC BEARING PERFORMADVANTAGESDISADVANTAGESAPPLICATIONCONCLUSIONREFERENCE

BEARINGA Bearing is a machine element which support another moving element.

It permits relative motion between the contact surfaces of the members while carrying a load.

Most bearings support rotating shafts against either radial or axial loads.

MAGNETIC BEARINGA Magnetic bearing is a bearing which supports a load a load using magnetic levitation.

A Magnetic bearing support moving machinery without physical contact,for example,they can levitate a rotating shaft and permit relative motion without friction or wear.

• Magnetic bearing are design 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.

DESCRIPTIONIt is difficult to build a

magnetic bearing using permanent magnets due to the limitation imposed and techniques using diamagnetic materials are relatively undeveloped.

As a result, most magnetic bearing require continuous power input and an active control system to hold the load stable. Because of this complexity, the magnetic bearing also typically require some kind of back-up bearing in case of power or control system failure.

BASIC OPERATIONAn active magnetic bearing (AMB) works on the principle of electromagnetic suspension and 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 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 rotor deviates from its center position.

•The gap sensors are usually inductive in nature and sense in a differential mode. The power amplifiers in a modern commercial application are solid state devices which operate in a pulse width modulation (PWM) configuration. The controller is usually a microprocessor or DSP

Classification According to Control action – Active– Passive – HybridAccording to Forcing action – Repulsive – AttractiveAccording to Sensing action – Sensor sensing – Self sensing

•According to Load support – Axial or Thrust – Radial or Journal – Conical•According to Magnetic effect – Electro magnetic – Electro dynamic

MAGNETIC BEARING PERFORMLubrication FreeClean & Contamination FreeReliabilityHigh Surface SpeedLow VibrationLow Energy ConsumptionNon-ContactingSubmerged Operation

aDVANTAGES 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

DISADVANTAGES

Include High Cost.Large in Size.

APPLICATIONS Magnetic bearings are increasingly used in industrial machines such as compressors, turbines, pumps, motors and generators.

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.

CONCLUSIONMagnetic 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 .

REFERENCESSchweitzer, G., Bleuler, H. and Traxler, “Basic Properties and Applications of Active Magnetic Bearings.

Chiba, A., Fukao, T., Ichikawa, O., Oshima, M., Takemoto, “Magnetic Bearings & Bearingless Drives.

Maslen, E., “Magnetic Bearings”, University of Virginia.

THANK YOU