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

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.7 no.2
• /
• pp.31-37
• /
• 2008

In this paper, we analyzed the dynamic behavior of magnetic fluid in a circular pipe with multiple permanent magnets. Magnetic fluid react on magnetic field against the normal fluid. In other words, magnetic fluid flow has the electromagnetism and fluid mechanics. So magnetic fluids has studied about the fluids properties and experiment. In this paper we studied the magnetic fluids velocity and pressure distribution for the novel type actuator. Because the velocity and pressure distribution is the important element of the magnetic fluids flow. First, we analyzed the Maxwell equation for the multiple permanent magnet and then concluded the governing equations for the magnetic fluid flow using the equation of Navier-Stokes. And, we simulated the dynamic behavior of magnetic fluid flow using the FEM(Finite Element Method). And we illustrated the relation between magnetic field and dynamic behavior of magnetic fluid flow.

• Journal of the Korean Society of Industry Convergence
• /
• v.24 no.6_1
• /
• pp.659-667
• /
• 2021

This paper develops the theory for a novel fault-tolerant, permanent magnet biased, 4-active-pole, double plane, homopolar magnetic bearing. The Lagrange Multiplier optimization with equality constraints is utilized to calculate the optimal distribution matrices for the failed bearing. If any of the 4 coils fail, the remaining three coil currents change via a novel distribution matrix such that the same opposing pole, C-core type, control fluxes as those of the un-failed bearing are produced. Magnetic flux coupling in the magnetic bearing core and the optimal current distribution helps to produce the same c-core fluxes as those of unfailed bearing even if one coil suddenly fails. Thus the magnetic forces and the load capacity of the bearing remain invariant throughout the failure event. It is shown that the control fluxes to each active pole planes are successfully isolated. A numerical example is provided to illustrate the new theory.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.40 no.3
• /
• pp.181-188
• /
• 2003

In this paper, we introduce a magnetic noise shielding method to reduce the noise effects in permanent magnet based MRI systems. Through FEM electromagnetic analyses, we have shown that the magnetic noise component parallel to the main magnetic field is the major component that makes various artifacts in the images obtained with a permanent magnet based MRI. Based on the FEM analyses, we have developed an active magnetic noise shielding system composed of a magnetic field sensor, compensation coils, and a coil driving system. The shielding system has shown a noise rejection ratio of about 30dB at the frequency below several Hz. We have experimentally verified that the shielding system greatly improves the image quality in a 0.3 Tesla MRI system.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.3
• /
• pp.1025-1034
• /
• 2015

This paper presented an improved analytical method for calculating the open-circuit magnetic field in the surface-mounted permanent magnet machines accounting for slots and eccentric magnet pole. Magnetic field produced by radial and parallel permanent magnet is equivalent to that produced by surface current according to equivalent surface-current method of permanent magnet. The model is divided into two types of subdomains. The field solution of each subdomain is obtained by applying the interface and boundary conditions. The magnet field produced by equivalent surface current is superposed according to superposition principle of vector potential. The investigation shows harmonic contents of radial flux density can be reduced a lot by changing eccentric distance of eccentric magnet poles compared with conventional surface-mounted permanent-magnet machines with concentric magnet poles. The FE(finite element) results confirm the validity of the analytical results with the proposed model.

• Proceedings of the KIEE Conference
• /
• 2003.07b
• /
• pp.918-920
• /
• 2003

This paper presents the analysis of the permanent magnet overhang effect for permanent magnetic actuator. Generally, The overhang is often used to increase the force density in permanent magnet machineries. The overhang is especially profitable to reduce the volume after increasing the force density per volume when using the overhang effect of the permanent magnet. Therefore, 3D Equivalent Magnetic Circuit Network Method (3D EMCNM) has been used in this paper. According to the plunger position, flux distribution per the overhang length, and the holding force are quantitatively compared. Furthermore, an appropriate length of the overhang has been proposed. To confirm the accuracy of the analysis method, the results of 3D EMCNM and FEM(2D, 3D) are compared for the basic model.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.902-904
• /
• 2004

PMA(Permanent Magnetic Actuator)는 기존의 유압식, 공압식 또는 스프링 조작기에 비해 신뢰성과 내구성이 뛰어나며, 유지${\cdot}$보수의 비용이 적고, 전류의 ON/OFF로 조작기를 쉽게 제어 할 수 있다. 그래서 최근 중저압 진공 차단기에 많이 사용되고 있다. 그러나 상대적으로 접점 간극이 길고, 압점력이 큰 고압 진공차단기에는 기존의 PMA(Permanent Magnetic Actuator)가 적합하지 않다. 고압 진공 차단기에 PMA를 적용시키기 위해서는 새로운 형상 설계가 불가피한데, 본 논문에서는 새로운 형태의 PMA(Permanent Magnetic Actuator)를 제안하고 그것의 동작 특성 해석을 통하여 사용 가능성을 검증하고자 한다.

• Proceedings of the KIEE Conference
• /
• 2001.07b
• /
• pp.653-656
• /
• 2001

This paper describes the design and the analysis of permanent magnetic actuator "Magnetic Switch" using classical method and 2D finite element method. The classical method gives an outline of permanent magnet size and analysis is carried out by finite element method. Therefore we make use of the result in specific detail site of magnet. The transient state is simulated in order to calculate the response time of "Magnetic Switch". The simulation is based upon a step-by-step integration of the electric circuit equations and the tore movement. The contactor uses a permanent magnet for maintaining the closed state. The presented solution takes account of non-linear magnetic material property and spring force controlled by core position. The dynamic response of "Magnetic Switch" is predicted by the simulation agrees closely with the required condition.

• Journal of Magnetics
• /
• v.17 no.4
• /
• pp.280-284
• /
• 2012

This paper presents a method for evaluating interior permanent magnet synchronous motor (IPMSM) performance over the entire operation region. Using a d-q axis equivalent circuit model consisting of motor parameters such as the permanent magnetic flux, copper resistance, core loss resistance, and d-q axis inductance, a conventional mathematical model of an IPMSM has been developed. It is well understood that in IPMSMs, magnetic operating conditions cause cross saturation and that the iron loss resistance - upon which core losses depend - changes according to the motor speed; for the sake of convenience, however, d-q axis machine models usually neglect the influence of magnetic cross saturation and assume that the iron loss resistance is constant. This paper proposes an analysis method based on considering a magnetic cross saturation and estimating a core loss resistance that changes with the operating conditions and speed. The proposed method is then verified by means of a comparison between the computed and the experimental results.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.2
• /
• pp.34-38
• /
• 2008

Commercially available magnetic barrel machines equipped with permanent magnets have certain limitations: work can only be finished effectively in limited areas of the container because permanent magnets are arranged two-dimensionally on the magnet disk. We overcame this problem by developing a new magnetic barrel machine equipped with a three-dimensional magnet arrangement. The effectiveness of the new machine has already been reported; this study improved the machine's polishing ability by changing the polarity of magnets on a magnet block. Polishing experiments confirmed the most effective arrangement of magnets on the magnet block. An alternating arrangement of north and south poles produced far superior polishing characteristics than a uniform arrangement of the same pole facing outward. Alternating polarity probably causes increased quantities of barrel media to work together. Finally, we introduced stronger permanent magnets to the magnet block, and found that the increased magnetic field also improved polishing ability.