• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.377-382
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• 2016

In this paper, influence of vibration on cogging torque and Radial Magnetic Force(RMF) imbalance was investigated in the IPM type BLDC motor. Design of cogging torque reduction and the RMF equilibrium was proceed applied to Design of Experiment(DOE). Vibration test results, the RMF imbalance was confirmed that a significant impact of vibration.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.171-173
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• 1997

This paper presents analysis of the radial force density in brushless DC motor of which distribution is not uniform in the axial direction. The analysis considering 3D shape of teeth and overhang is not only important but essential to calculate the radial force density that acts on the teeth of stator, because it is frequent source of vibration and changes at the end of teeth. For the analysis, a new 3D equivalent magnetic circuit network method taking into account movement of the rotor without remesh is proposed. The radial force density is calculated by Maxwell stress tensor and analyzed by discrete Fourier transform.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.281-282
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• 2002

To reduce the spin-off of lubricants on a magnetic disk, which is caused by the radial component of shear force between the disk and air, we analyzed the air-velocity distribution and the air-shear force by three-dimensional large-eddy simulation (LES). This sensitivity analysis, on five design parameters, showed that disk/arm clearance and arm thickness have a greater effect on the mean radial air-shear force than the other parameters. The force on a disk optimized according to the optimum parameters is 12% less than the force on a conventional disk.

• Journal of Magnetics
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• v.18 no.4
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• pp.432-442
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• 2013

For magnetically suspended flywheel (MSFW) with gimballing capability, demerits of Lorentz force-type magnetic bearings and common reluctance force-type magnetic bearings are analyzed, a novel reluctance forcetype magnetic bearing (RFMB) including radial and axial magnetic bearing units with 4 separate biased permanent magnets and two conical stators is presented. By equivalent magnetic circuits' method, its magnetic properties are analyzed. To reduce the eddy loss, it was designed as radial poles with shoes and its rotor made of Iron-based amorphousness. Although the uniformity of magnetic flux density in the conical air gap determines mainly the additional tilting torque, the maximum additional tilting torques is 0.05Nm and the rotor tilting has no influence on its forces when the rotor tilts or the maximum changes does not exceed 14% when the rotor drifts and tilts simultaneously. The MSFW with this RFMB can meet the maneuvering requirement of spacecraft theoretically.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.12 s.243
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• pp.1561-1566
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• 2005

In this paper, a new compact active magnetic bearing(AMB) is proposed in which radial and axial bearings are integrated in one bearing unit. It consists of four U-shaped cores circumferentially connected by yokes and two-layer coils for radial and axial controls. For the radial control action, it has the same principle as conventional homopolar AMBs, while for the axial control, it uses the Lorentz force generated by the interaction of the bias flux for radial control and the axial control flux. The proposed structure makes it easy to design a compact AMB because it has no disk for axial control. This paper introduces the proposed structure, principle, and design process based on the magnetic flux analysis. By using a control algorithm with feedforward action to compensate the coupled flux effect, the feasibility of the proposed AMB is experimentally verified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.482-487
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• 2001

This paper introduces a Lorentz force type four-pole self-bearing motor, where the new pole arrangement of a stator is intended to function both as a synchronous PM motor and as a magnetic bearing. The Lorentz force type has some good points such as linearity of control force, freedom from flux saturation, and high efficiency unlike conventional self-bearing motors. Mathematical expressions of torque and radial force are derived to show that they can be separately controlled regardless of rotational speed and time. To verify the proposed theory, a prototype is made, where a ring-shape outer is actively controlled in two radial directions while the other motions are passively stable supposing the radial stability. Through some experiments, it is shown that the proposed scheme can provide high capability and feasibility for a small high-speed self-bearing motor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.321-326
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• 2013

This paper investigates the magnetic excitation force of a surface-mounted permanent magnet (SPM) motor according to the change of pole/slot combination. The characteristics of magnetic flux and radial magnetic force (RMF) due to pole/slot combination were analyzed by using magnetic circuit analysis. Also, the RMF of motors with the variable pole/slot combination was numerically simulated by using the finite element analysis to verify the result of the magnetic circuit analysis. This research shows that RMF ripple is reduced when the number of pole is smaller than the number of slot.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.11
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• pp.548-556
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• 2003

Switched reluctance motor(SRM) has simple magnetic structure, and needs simple power electronic driving circuit. It is very useful for wide range adjustable speed drive system. But, SRM drive generates large vibration and acoustic noise because it is commutated individually by step pulse m.m.f of each phase. In the vibration and acoustic noise characteristics. the considerable vibration and noise is induced by radial deforming of stator, so the frequency of dominant vibration and noise is coincident with the frequency of natural frequency of mechanical structure. This radial vibration force is generated by abrupt change of radial magnetic force in the phase commutation region. This paper studied about simple electromagnetic structure of SRM using auxiliary compensating winding for the reduction of noise and vibration. This auxiliary winding is coupled with all phase windings electromagnetically and absorb and transfer magnetic energy variation from phase to other phase. By this interaction of phase windings and compensating winding can reduce abrupt radial force change and vibration and acoustic noise. In this paper the improvement effect is examined by the test of prototype machine.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.5
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• pp.690-697
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• 2012

Novel 8/10 bearingless switched reluctance motor, which can control rotor radial positions with magnetic force, is proposed. The motor has combined characteristics of switched reluctance motor and magnetic bearing. This paper proposes a air-gap control system method of suspending force control in a bearingless switched reluctance motor (BLSRM). The proposed radial force control scheme is independent to the torque winding current. A PI direct current control (DCC) controller and look-up table are used to maintain a constant rotor air-gap. From the analysis and the experimental results, it is shown that the proposed strategy is effective in realizing a naturally decoupled radial force control of BLSRM.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.12 s.243
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• pp.1567-1573
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• 2005

This paper introduces a new active magnetic bearing(AMB) that can provide both radial and axial control functions in one bearing unit without axial disk. It has a structure of double four-pole AMB or a four-pole AMB where each core is split into two axially. The cores have two kinds of coil winding; they independently generate fluxes on the planes perpendicular or parallel to the shaft. For the radial control action, it works just like a conventional four-pole AMB. Meanwhile, for the axial control, it uses the Lorentz force generated by the interaction of the bias flux for radial control and the axial control flux. In this paper, the proposed structure, principle, and design process based on magnetic flux analysis are introduced, and its feasibility is experimentally verified by using a simple PD control algorithm with a feedforward loop to compensate the coupled flux effect.