non contact magnet

DESIGN AND ANALYSIS OF POWER TRANSMISSION CAPABILITY OF NON CONTACT MAGNETIC GEAR

DESIGN AND ANALYSIS OF POWER TRANSMISSION CAPABILITY OF NON CONTACT MAGNETIC GEAR

INTRODUCTION A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine. Geared devices can change the speed, torque, and direction of a power source. The most common situation is for a gear to mesh with another gear, however a gear can also mesh a non-rotating toothed part, called a rack, thereby producing translation instead of rotation. The gears in a transmission are analogous to the wheels in a pulley. An advantage of gears is that the teeth of a gear prevent slipping. When two gears of unequal number of teeth are combined a mechanical advantage is produced, with both the rotational speeds and the torques of the two gears differing in a simple relationship. In transmissions which offer multiple gear ratios, such as bicycles and cars, the term gear, as in first gear, refers to a gear ratio rather than an actual physical gear. The term is used to describe similar devices even when gear ratio is continuous rather than discrete, or when the device does not actually contain any gears, as in a continuously variable transmission.MAGNETIC GEAR All cogs of each gear component of such gear are performed as a constant magnet with periodic alternation of opposite magnetic poles on mating surfaces and nearest poles of cogs of different gear components are similar. And gear components are mounted with a backlash with capability of mechanical gearing. At not too big load such gear works without touch of motive details and has a raised reliability without noise.

Material used Neodymium magnetsare the strongest permanentmagnetsknown Nd2Fe14B. A neodymium magnet of a few grams can lift a thousand times its own weight. These magnets are cheaper, lighter, and stronger thansamarium-cobalt magnets. However, they are not superior in all ways, as neodymium-based magnets lose their magnetism at high temperatures and tend to rust, while samarium-cobalt magnets do not. Another chief use of neodymium is as the free pure element. It is used as a component in the alloys used to make high-strength neodymium magnets the most powerful permanent magnets known. These magnets are widely used in such products as microphones, professional loudspeakers, in-ear headphones, and computer hard disks, where low magnet mass or volume, or strong magnetic fields are required. Larger neodymium magnets are used in high power versus weight electric motors (for example in hybrid cars) and generators (for example aircraft and wind turbine electric generators). Neodymium magnets appear in products such asmicrophones, professionalloudspeakers, in-earheadphones,guitarandbass guitarpick-upsand computerhard diskswhere low mass, small volume, or strong magnetic fields are required. Neodymium magnet electric motors have also been responsible for the development of purely electrical model aircraft within the first decade of the 21st century, to the point that these are displacing internal combustion powered models internationally. Likewise, due to this high magnetic capacity per weight, neodymium is used in the electric motors of hybrid and electric automobiles, and in the electricity generators of some designs of commercial wind turbines (only wind turbines with "permanent magnet" generators use neodymium). For example, drive electric motors of eachToyota Priusrequire one kilogram (2.2 pounds) of neodymium per vehicle.Permanent Magnets A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferromagnetic). These include iron, nickel, cobalt, some alloys of rare earth metals, and some naturally occurring minerals such as lodestone. Although ferromagnetic (and ferromagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of magnetism.

Working Principle of Magnetic Gears

principle of magnetic gears Although for many purposes it is convenient to think of a magnet as having distinct north and south magnetic poles, the concept of poles should not be taken literally: it is merely a way of referring to the two different ends of a magnet. The magnet does not have distinct north or south particles on opposing sides. If a bar magnet is broken into two pieces, in an attempt to separate the north and south poles, the result will be two bar magnets,eachof which has both a north and south pole.Based on the magnetic poles it tends to rotate. Based on the poles arrangement it tends to rotate.1. On discs of mild steel we provide two north poles opposite to each other and two south poles opposite to each other.2. One disc will be connected to a motor and the other disc will rotate on the basis of attraction and repulsive forces of the magnets.3. These are non-contact gears, they run on the principle of magnetic forces.4. A minimum gap of 5 mm should be maintained between the two discs.Limitations1. Not easy to control the power (force)2. Limited working depth (field depth)3. Cannot be switched off and forced to release load (except in very specialised applications)4. Heart patients should not operate very closely

LITERATURE REVIEWLiterature surveyFrank T. Jrgensen, Torben Ole Andersen, and Peter Omand Rasmussen The Cycloid Permanent Magnetic Gear IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 44, NO. 6, NOVEMBER/DECEMBER 2008 This paper presents a new permanent-magnet gear based on the cycloid gearing principle, which normally is characterized by an extreme torque density and a very high gearing ratio. An initial design of the proposed magnetic gear was designed, analyzed, and optimized with an analytical model regarding torque density. The results were promising as compared to other high-performance magnetic-gear designs. A test model was constructed to verify the analytical model.RECENTLY, magnetic gears have gained some attention due to the following reasons: no mechanical fatigue, no lubrication, overload protection, reasonably high torque density,and potential for very high efficiency. Focus have been addressed to a kind of planetary magnetic gear, probably already invented before the strong NdFeB magnets came into the market in the early 1980s . An active torque density is in the range of 100 N m/L, which is a very high torque density for a magnetic device. However, there is still a need for increased torque density and a better utilization of the permanent magnets. The torque density of a magnetic coupling is in the range of 400 N m/L and this is, in principle, a magnetic gear with a 1: 1 gearing ratio.In this paper, a magnetic gearing topology with better utilization of the permanent magnet is presented. This gearing topology makes it possible to increase the torque density to almost twice the state-of-the-art magnetic gears and, therefore, might be a useful alternative in applications using traditional mechanical gears or, at least, in gearing applications where some of the other advantages, e.g., overload protection, oil-free construction, and separation, is vital. This paper will first give a description of the cycloid permanent magnetic gear and how the idea is derived from the classical magnetic spur gear. Due to the fact that the cycloid permanent magnetic gear is a 2-DOF topology, description of gearing ratios with different fixed axes (1 DOF) is stated. In order to optimize the layout of the new cycloid magnetic gear, a parametric analytical model to calculate the torque density is developed. The construction of an initial test model is given, and measurement is performed in order to validate the analytical model. Next, an optimization is utilized with the analytical model to quantify the cycloid permanent-magnet gear capability, andFinally, a conclusion is given. A new cycloid magnetic-gear configuration has been presented. This magnetic gear is characterized by having high torque density and a high gearing ratio.Gareth P Hatch, PhD CEng FIMMM Director of Technology Recent Developments in Permanent Magnet Gear Systems & Machines Dexter Magnetic Technologies in 2010Overview of mechanical gearingBenefits of magnetic gear systemsOverview of mechanical gearing Primary purpose: speed torque conversionRotating input power source (typically)Increase or decrease input speedIncrease or decrease input torqueBenefits of magnetic gear systemsSeveral reasons for considerationNon-contact elements no friction between gearsHighly efficient multiple magnetic poles engagedUtilization of peak torqueInput and output shafts can be isolatedIncreased temperature range no elastomeric sealsInherent overload protectionIncreased tolerance of misalignmentMore detail on best in class devices laterHistorical overview of magnetic gearsMagnet spur gear Principle of magnetic spur gearKais Atallah Magnetic Gear EnergyThic New technologies in 2001Contactless, high-efficiency, high-torque transmission with inherent overload protectionThe high-torque magnetic gear was invented and demonstrated by Magnomatics co-founder Dr Kais Atallah in 2001. This pioneering research has been extended by Magnomatics to provide a mature range of gear technologies that are suitable for a very wide range of applications. A torque density in excess of 70 kN m/m3 can be achieved.

Advantages over mechanical gears Reduced maintenance and improved reliability Lubrication free Higher efficiency than conventional gears Precise peak torque transmission (up to 665 Nm of torque per meter of length of the gears)and inherent overload protection Physical isolation between input and output shafts Inherent anti-jamming transmission Significantly reduces harmful drivetrain pulsations Allows for misalignment/vibration of shafts Very low acoustic noise and vibrationA magnetic gear uses permanent magnets to transmit torque between an input and output shaft without mechanical contact. Torque densities comparable with mechanical gears can be achieved with an efficiency >99% at full load and with much higher part load efficiencies than a mechanical gear. For higher power ratings a magnetic gear will be smaller, lighter and lower cost than a mechanical gear. Since there is no mechanical contact between the moving parts there is no wear and lubrication is not required. Magnetic gears inherently protect against overloads by when the fault torque is removed.Observation from the Literature Survey The following conclusions may draw from the review of the literatures.i. Distance between the magnets should be maintained ii. Non-contact elements no friction between gearsiii. Highly efficient multiple magnetic poles engagediv. Reduced maintenance and improved reliabilityv. Lubrication freevi. Higher efficiency than conventional gearsvii. Very low acoustic noise and vibration AIM AND OBJECTIVESAim By concluding the literature survey it is known that the magnetic gears are more advantageous than conventional gears like reduced maintenance and improved reliability, lubrication free, higher efficiency than conventional gears, physical isolation between input and output shafts, very low acoustic noise and vibration. To overcome few of the disadvantages of the conventional gears like wear and tear of teeth, gear jamming, lubrication, high maintenance, noise and vibration this attempt has been made. It is observed that Magnetic gears have a higher efficiency than the conventional gears. These are lubrication free and have a lower noise as they are contact less gears. The following are the ultimate aim of the project. To design, manufacture, analysis and comparison of frictionless gear system to friction gear system by using magnetic gear and conventional gear.Objectives1. Investigation, identification, selection of suitable material for magnetic gear, conventional gears.2. Design of magnetic gear, conventional gear3. Manufacturing.4. Performance prediction and analysis.5. Comparison

EXPERIMENTAL SETUP The experimental setup consists of a base made of slotted angles which has provision to support all the components of magnetic gear system. It consists of Al supports that are fixed to the base by providing a thin rectangular mild steel plate which has a provision to vary the centre distance. The ball bearings are fixed to the Al supports and thus the shaft is carried by the ball bearings in both the driver and the driven. One shaft is coupled with the DC motor which is the driver shaft. The DC motor is supported at the end with the help of a thin rectangular mild steel plate which has provisions to be fixed to the base i.e slotted angles. The other shaft which is kept a certain distance from the driver shaft is the driven shaft which is supported by two Al supports freely. The smaller disc is fixed to the driver shaft using key and keyways and the bigger disc is fixed to the driven shaft using the same key and keyways as in the driver shaft. Magnets are fixed in the slots provided in both the discs, these are arranged in such a way that south poles of both the magnets face each other of all the magnets. This is done to ensure that if the driver shaft rotates in clockwise direction the driven shaft should rotate in anti-clockwise direction due to the repulsive forces between the similar poles. All the components are explained and their specifications are given below.Ball Bearing Aball bearingis a type ofrolling-element bearingthat usesballsto maintain the separation between thebearingraces. The purpose of a ball bearing is to reduce rotational friction and supportradialandaxialloads. It achieves this by using at least two races to contain the balls and transmit the loads through the balls. In most applications, one race is stationary and the other is attached to the rotating assembly (e.g., a hub or shaft). As one of the bearing races rotates it causes the balls to rotate as well. Because the balls are rolling they have a much lowercoefficient of frictionthan if two flat surfaces were rotating on each other. Ball bearings tend to have lowerload capacityfor their size than other kinds of rolling-element bearings due to the smaller contact area between the balls and races. However, they can tolerate some misalignment of the inner and outer races.

KEY Inmechanical engineering, akeyis amachine elementused to connect a rotating machine element to ashaft. Through this connection the key prevents relative rotation between the two parts and allowstorqueto be transmitted through. For a key to function the shaft and rotating machine element must have akeyway, also known as akeyseat, which is a slot or pocket for the key to fit in. The whole system is called akeyed joint.A keyed joint still allows relative axial movement between the parts.Commonly keyed components includegears,pulleys, andcouplings.Types There are three main types of keys:parallel,Woodruff, andtaperedkeys.Parallel keys Parallel keys are the most widely used. They have a square or rectangular cross-section. Square keys are used for smaller shafts and rectangular faced keys are used for shaft diameters over 6.5in (170mm) or when the wall thickness of the mating hub is of concern. Set screws often accompany parallel keys to lock the mating parts into place so they do not move.The keyway is a longitudinal slot in both the shaft and mating part. Shaft Shaft is a thin long piece of metal in an engine or machine that turns and passes on power or movement to another part of the machine Drive shafts are carriers oftorque they are subject totorsionand shear stress, equivalent to the difference between the input torque and the load. They must therefore be strong enough to bear the stress, whilst avoiding too much additional weight as that would in turn increase their inertia. Magnet Magnet is a material or object that produces amagnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on otherferromagneticmaterials, such asiron, and attracts or repels other magnets. Apermanent magnetis an object made from a material that ismagnetizedand creates its own persistent magnetic field. An everyday example is arefrigerator magnetused to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are calledferromagnetic(orferrimagnetic). These includeiron,nickel,cobalt, some alloys ofrare earth metals, and some naturally occurring minerals such aslodestone. Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types ofmagnetism.

Base Base is a part that supports all the components of the setup.

DC Servo Motor ADC motoris an electric motorthat runs ondirect current(DC) electricity. DC motors were used to run machinery, often eliminating the need for a local steam engine or internal combustion engine. DC motors can operate directly from rechargeable batteries, providing the motive power for the first electric vehicles. Today DC motors are still found in applications as small as toys and disk drives, or in large sizes to operate steel rolling mills and paper machines. Modern DC motors are nearly always operated in conjunction with power electronic devices.

DC motor PRO-E modelMild steel discs Discs made of mild steel which have a provision to carry the magnets and are machined using the milling machine which have keyways that help in connecting to the shaft rigidly. One disc will be on the driver shaft and another on the driven shaft. Supports These are made of Aluminum which are machined in the LATHE using the boring operation so that the bearings can be properly fixed in it. These are ball bearings used for free rotation of the shaft as well as act as a support. These Al supports are tapped to 8mm at the bottom to provide 8mm screw and nut to support it rigidly to the base of the assembly.

Isometric view of the Magnetic Gear experimental set up side view

EXPERIMENTATION The experiment is carried out as following The DC motor runs with a battery and when power is supplied the driver shaft rotates and which makes the other shaft also to rotate cause of the repulsive forces between the magnets. Varying the centre distance between the discs we measure the speed on the driven shaft for different weights as to calculate the torque. The whole assembly is placed on a surface and the centre distance between the two discs is measured using a vernier calipers, weights are added to the pulley which is connected to the shaft.(the pulley weight is negligible when weight is taken into account). The motor is connected to the battery and the speed of the driver shaft is measured using a tachometer and the respective driven shafts speed is also measured. The following variations are made for each measurement:1. The centre distance between the discs is adjusted to a minimum distance and with increasing weights the speed is measured and for each added weight the speed is taken.2. The centre distance between the discs is then increased by 1 cm and the same process is repeated with varying weights and the speed is taken .3. The centre distance between the discs is further increased by 1 cm and the same process is repeated with varying weights and the speed is taken . Since the above required parameter is obtained the torque is calculated with the above obtained results. Torque is obtained by the product of force into radius. Torque = (force) x (radius) The force is nothing but the weights added and the radius is nothing but the grove radius of the pulley, thus the torque is successfully obtained.After the torque is calculated the power required is known i.e Power=(2)x(pi)x(n)x(T)/ 60 Based on these parameters graphs are plotted between centre distance , speed for different weights and centre distance and power .

RESULTS AND DISCUSSIONS The project was to design and fabricate magnetic gears which can be used everywhere where conventional gears are used. The entire design was successfully completed. Selection of materials and approximation of the budget required for the project was aptly done. Preference was given to light weight but study and strong materials so as to reduce the weight and make it more compact. The dimensions required in designing the discs were taken initially. This helped a lot in material usage reduction and fabrication .The driver shaft is made adjustable so as to enable easy varying of the centre distance. An AC motor can also be used instead of a DC motor but steps to be taken to reduce the high speed of the motor. Steps were also being taken to overcome most of the limitations that we came across during the study of certain papers and journals. High powered magnets can also be used. Plans to increase the no. of magnets on t5he discs by providing more slots so as to increase the speed and high repulsion between the magnets. This can be proposed as a future work to the students. Further modifications and improvements possible are also being discussed. After the construction is completed, the magnetic gears can be finally tested for its ability and its other mentioned features. The experiment is conducted and the results are tabulated. The speeds in the driven shaft and the power transmitted are tabulated by varying the center distance between the magnetic gears. It is always observed that as if the center distance between the magnetic gears increases the power transmitted and the speed in the driven shaft will decrease. Various graphs have been plotted on center distance between the magnetic gears vs speed in the driven shaft with different loads kept on the driven shaft and also on center distance between the magnetic gears vs power transmitted to the driven shaft.

CONCLUSIONS Conventional gears have disadvantages like wear and tear of teeth, gear jamming, lubrication, high maintenance, noise and vibration. So to overcome the disadvantages of conventional gears, a gear is to be designed in such a way that it should have reduced maintenance and improved reliability, lubrication free, higher efficiency than conventional gears, physical isolation between input and output shafts, very low acoustic noise and vibration. It is observed that Magnetic gears have a higher efficiency than the conventional gears. These are lubrication free and have a lower noise as they are contact less gears. The focus of the project is to develop and predict the performance of magnetic gear system. The aim of the project is to design, manufacture, analysis and comparison of frictionless gear system to friction gear system by using magnetic gear and conventional gear.

REFERENCES1. Frank T. Jrgensen, Torben Ole Andersen, and Peter Omand Rasmussen The Cycloid Permanent Magnetic Gear IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 44, NO. 6, NOVEMBER/DECEMBER 2008 2. Gareth P Hatch, PhD CEng FIMMM Director of Technology Recent Developments in Permanent Magnet Gear Systems & Machines Dexter Magnetic Technologies in 20103. Kais Atallah Magnetic Gear EnergyThic New technologies in 2001