• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_2
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• pp.1127-1134
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• 2023

In this paper, we proposes a study on air gap control for magnetic levitation of transverse flux permanent magnet electromagnets. In general, mechanical systems have a high failure rate of bearings. Bearings in particular are problematic because they have high surface wear rate and degradations. To solve this problem, replacing the bearing with a magnetic levitation electromagnet system can provide lightweight and efficiency improvements. However, precise air gap control is essential to control the magnetic levitation electromagnet system. Therefore, in this paper, we identify the instable cause of gap control through a mathematical modeling and verify through experiment a control algorithm that can use compensation.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.879-884
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• 2007

Flywheel energy storage systems have advantages over other types of energy storage devices in such aspects as unlimited charge/discharge cycles and environmental friendliness. In this paper we propose a millimeter scale flywheel energy storage device. The flywheel is supported by a pair of passive magnetic bearings and rotated by a toroidally wound electric motor/generator. The geometry of the bearings is optimized for the maximum dynamic performance.

• KSTLE International Journal
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• v.4 no.2
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• pp.37-42
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• 2003

One of the obstacles for a magnetic bearing to be used in the wide range of industrial applications is the failure modes associated with magnetic bearings, which we don't expect for conventional passive bearings. These failure modes include electric power outage, power amplifier faults, position sensor faults, and the malfunction of controllers. Fault-tolerant magnetic bearing systems have been proposed so that the system can operate in spite of some faults in the system. In this paper, we designed a fault-tolerant magnetic bearing system for a turbo-molecular vacuum pump. The system can cope with the actuator/amplifier faults which are the most common faults in a magnetic bearing system. We implemented the existing fault-tolerant algorithms to experimentally prove the adequacy of the algorithms for industrial applications. As it turns out, the system can operate even with three simultaneously failing poles out of eight actuator poles.

• Tribology and Lubricants
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• v.11 no.1
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• pp.20-26
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• 1995

Most magnetic bearings are based on the attractive force between the magnets and ferrous materials. One of the disadvantages of such attractive type magnetic bearings is the instability so that an active control device is necessary to operate bearing successfully. In this study a repulsive type magnetic bearing is analyzed which uses eddy current as a force source. The load capacities are analyzed for the various gap sizes, the rotor velocities and the frequencies of current supplied to electromagnet. Analytic Results show that as the gap size decreases, the levitation and drag forces increase, while the number of poles increasqs, the drag force decreases in the higher linear velocity region. Experimental results show that as the gap size decreases the levitation and the drag force increase, and as the velocity of rotor increases, the drag is larger than the levitation force up to certain velocity. But after that, the levitation is larger than the drag force. As the frequency of the current increases the levitation and drag decreases while the thickness of rotor gets thicker the forces decrease because of increase in eddy current loss.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.415-420
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• 2006

This paper introduces a new self-bearing motor which combines a homopolar step motor and a passive magnetic bearing. Compared with conventional self-bearing motors which are mostly based on the theory of active magnetic bearings and therefore have some difficulties in design of the complicated flux distribution and control of the levitation force and the torque independently, the proposed self-bearing motor has a very simple and novel structure and operating principle. for the levitation, it works just like passive magnetic bearings which use the repulsive force between permanent magnets. On the other hand, its rotation principle is quite similar to that of a conventional homopolar step motor. In this paper, we introduce the basic structure and the operating principle in detail, and show some results of FEM analysis to predict the performance of the proposed self-bearing motor and further, to get the optimal design parameters.

• Tribology and Lubricants
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• v.23 no.6
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• pp.283-287
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• 2007

Permanent-magnet (PM) passive bearings use the repulsive forces between the rotor and the stator magnets for the bearing function. It is desirable that the stiffness of the bearing is maximized with the given volume of the magnet. The stiffness is affected by the magnet strength, the number of layers, and the magnetization patterns. Previously, finite-element method (FEM) has been used to maximize the stiffness of the bearing. In this paper, we used the equivalent current sheet method to calculate the stiffness. The validity of this approach is checked against FEM results. The optimized bearing is applied to a micro flywheel energy storage system.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.1
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• pp.19-24
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• 2008

We propose a new miniature air-bearing stage with a moving-magnet slotless linear motor. This stage was developed to achieve the precise positioning required for submicron-level machining and miniaturization by introducing air bearings and a linear motor sufficient for mesoscale precision machine tools. The linear motor contained two permanent magnets and was designed to generate a preload force for the vertical air bearings and a thrust force for the stage movement. The characteristics of the air bearings, which used porous pads, were analyzed with numerical methods, and a magnetic circuit model was derived for the linear motor to calculate the required preload and thrust forces. A prototype of a single-axis miniature stage with dimensions of $120\;(W)\;{\times}\;120\;(L)\;{\times}\;50\;(H)\;mm$ was designed and fabricated, and its performance was examined, including its vertical stiffness, load capacity, thrust force, and positioning resolution.

• Progress in Superconductivity
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• v.14 no.1
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• pp.60-65
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• 2012

A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. A 35 kWh class SFES module was designed and constructed as part of a 100kWh/1MW class SFES composed of three 35 kWh class SFES modules. The 35 kWh class SFES is composed of a main frame, superconductor bearings, a composite flywheel, a motor/generator, electro-magnetic bearings, and a permanent magnet bearing. The high energy density composite flywheel is levitated by the permanent magnet bearing and superconductor bearings, while being spun by the motor/generator, and the electro-magnetic bearings are activated while passing through the critical speeds. Each of the main components was designed to provide maximum performance within a space-limited compact frame. The 35 kWh class SFES is designed to store 35 kWh, with a 350 kW charge/discharge capacity, in the 8,000 ~ 12,000 rpm operational speed range.

• Journal of Power System Engineering
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• v.16 no.3
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• pp.22-28
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• 2012

Active magnetic bearings(AMBs) present a technology which has many advantages compared to traditional bearing concepts. However, they require backup bearings in order to prevent damages in the event of a system failure. In this study, the dynamics of an AMB supported rotor during impact on backup bearings is studied employing a detailed simulation model. The backup bearings are modeled using an accurate ball bearing model, and the model for a flexible rotor system is described using the finite element approach with the component mode synthesis. Not only the influence of the support stiffness, clearance and friction coefficient on the rotor orbit, but also bearing load are compared for various rotor system parameters. Comparing these results it is shown that the optimum backup bearing system can be applicable for a specific rotor system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.12
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• pp.3909-3916
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• 1996

Magnetic bearing is the machine element that supports the shaft without mechanical contact using the magnetic force induced by permanent magnet of electromagnet. Active magnetic bearing system is composed of sensor, controller, power amplifier, and electromagnet. If all the elements were dieal, shaft position could be controlled to sensor resolution, Because each elements inreal system have mechanical and electricla losses and nonlinearity, it is impossible to attain the desired performance using general control algorithm. So far it has been studied on improvement of the control algorithm of the electric characteristics of each elements. Another factors to affect shaft behavior are the manufacturing errors due to machine work, and assembling errors due to accumulate manufacturing errors of the radial magnetic bearing. This paper describes that the shaft behavior due to accumulate manufacturing errors and asymmetric bolting. This paper describes that the shaft behavior due to assembling errors of the radial bearings donot affect the rotaitonal accuracy of the shaft. But when the amplitude of the assembling errors increasees over the certain value, the bearing can not support the shaft properly.