• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 하계학술대회 논문집 B
• /
• pp.920-922
• /
• 2002

This paper investigates the cogging torque reduction in a brushless DC(BLDC) motor having an inner-rotor with surface-mounted segment-type permanent magnets. The kind of magnets for the BLDC motor could have different waveforms of magnetization such as square, trapezoidal and sinusoidal form. This paper discusses the effect of the unsymmetrical magnetization distribution in the segment-type permanent magnet, which is able to obtain through a segment structure that the number of poles per segments is 2 ($N_p/N_s$), on the cogging torque and EMF waveform. Where the existing magnetizer fixture for the square-type magnetization is used to magnetize the magnets in two segment structures of $N_p/N_s$ = 1 and 2. The effectiveness of the proposed designs had been confirmed by comparing cogging torque, and EMF waveform between conventional and new models which are analyzed by Finite Element Method (FEM).

• 대한기계학회논문집A
• /
• 제33권9호
• /
• pp.938-948
• /
• 2009

In this paper, permanent magnets were used to remove magnetic sludge in the condenser of the power plant. To obtain the flow characteristics and magnetic information that are needed for determining a proper design of the magnetics sludge removal apparatus, numerical simulations were performed through the use of two commercial codes, ANSYS Workbench-Emag and CFX. Experiments were also performed on various kinds and sizes of magnets to obtain the magnetic information through a gauss meter. By analyzing the results of simulations and experiments, the minimum magnetic force that is able to remove the any size of the magnetic sludge in the condenser was calculated, and the design of the removal apparatus was confirmed. The test model which was confirmed by simulations and experiments was made. After testing, the test results were compared with those of numerical simulations and have good agreements.

• Journal of Magnetics
• /
• 제4권2호
• /
• pp.52-54
• /
• 1999

Injection molding is one of the methods to prepare dielectromagnets-permanent magnets made from hard magnetic powder (or from mixture of powders) bonded by dielectric materials. Magnetic properties of dielectromagnets are worse than those of sintered magnets made from the same hard magnetic powders, but this type of the permanent magnet has many advantages. One of them is simpler technology-easier in comparison to the technology of sintered magnets. The injection molded dielectromagnets do not need any final treatment. This technology permits to control magnetic, thermal and mechanical properties of dielectromagnets. The main chracteristics of dielectormagnets are magnetic properties, however mechanical properties have serious influence onto a range of their applications. The main factors shaping mechanical properties have serious influence onto a range of their applications. The main factors shaping mechanical properties of dielectromagnets are the kind and quantity of resin and the technology. The purpose of this investigateion was to find the correlation between infection conditions and the mechanical properties of dielectromagnets. Influence of two parameters of injection, temperature and pressure on mechanical and magnetic properties of dielectromagnets were not significantly changed. Increasing of pressure of injection also does not influence on mechanical properties of analysed samples, however increasing of temperature of injection significantly improved both compression and bending strength.

• 한국초전도ㆍ저온공학회논문지
• /
• 제14권1호
• /
• pp.14-19
• /
• 2012

Shimming, active and/or passive, is indispensable for most MR (magnetic resonance) magnets where homogeneous magnetic fields are required within target spaces. Generally, shimming consists of two steps, field mapping and correcting of fields, and they are recursively repeated until the target field homogeneity is reached. Thus, accuracy of the field mapping is crucial for fast and efficient shimming of MR magnets. For an accurate shimming, a "magnetic" center, which is a mathematical origin for harmonic analysis, must be carefully defined, Although the magnetic center is in general identical to the physical center of a magnet, it is not rare that both centers are different particularly in HTS (high temperature superconducting) magnets of which harmonic field errors, especially high orders, are significantly dependent on a location of the magnetic center. This paper presents a new algorithm, based on a field mapping theory with harmonic analysis, to define the best magnetic center of an MR magnet in terms of minimization of pre-shimming field errors. And the proposed algorithm is tested with simulation under gaussian noise environment.

• 한국초전도ㆍ저온공학회논문지
• /
• 제12권1호
• /
• pp.32-36
• /
• 2010

Superconducting current leads are indispensible for reducing power loss when subjecting current into superconducting magnets. HTS(High-Tc superconducting) current leads are divided into two types; one is bulk type and the other is tape type. In this paper, conceptual design on the HTS current leads which adopts tape type for nuclear fusion magnets is carried out using magnetic field analysis and thermal analysis. When large current flows through superconducting current leads, strong self magnetic field is generated and applied to the superconducting tapes. This phenomenon leads to the critical current decrease of the superconducting tape. Therefore, we analyzed magnetic field distribution of current leads and found the proper arrangement with respect to the various HTS tapes. In addition to the magnetic field analysis, heat leak through the current leads was also calculated to know which HTS tape is superior than others in thermal aspect. Magnetical field analysis and calculation of heat leak are performed to design 2 kA class HTS current leads.

• 한국초전도ㆍ저온공학회논문지
• /
• 제14권3호
• /
• pp.60-64
• /
• 2012

In this paper, an investigation of a room temperature active magnetic regenerative refrigerator is carried out. Experimental apparatus includes two active magnetic regenerators containing 186 g of Gd spheres. Four E-type thermocouples are installed inside the Active magnetic regenerator(AMR) to observe the instantaneous temperature variation of AMR. Both warm and cold heat exchangers are designed for large temperature span. The cold heat exchanger, which separates the two AMRs, employs a copper tube with length of 80 mm and diameter of 6.35 mm. In order to minimize dead volume between the warm heat exchanger and AMRs, the warm heat exchangers are located close to the AMRs. The deionized water is used as a heat transfer fluid, and maximum 1.4 T magnetic field is supplied by Halbach array of permanent magnets. The AMR plate, which contains the warm and the cold heat exchangers and the AMRs, has reciprocating motion using a linear actuator and each AMR is alternatively magnetized and demagnetized by a Halbach array of permanent magnet. Since the gap of the Halbach array of permanent magnets is 25 mm and two warm heat exchangers have the motion through it, a compact printed circuit heat exchanger (PCHE) is used as a warm heat exchanger. A maximum no-load temperature span of 26.8 K and a maximum cooling power of 33 W are obtained from the fabricated Active Magnetic Regenerative Refrigerator (AMRR).

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2008년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.92-94
• /
• 2008

The interest in permanent magnet synchronous motor is present in a wide area of applications, ranging from high-performance servo drive to line-start application[1]. The are mainly two reasons for this trend: first low rotor losses and second the foiling prices of high-energy magnets. In this paper the dynamic characteristic of the line-start permanent magnet synchronous motor are described and compared with those if the squirrel-cage induction motor through the simulation to find the characteristics of the permanent magnets and the rotor bar in the line-start permanent magnet synchronous motor.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
• /
• pp.756-760
• /
• 2001

Two different designs of permanent magnet motors as direct wheel-set drive for the German high speed train ICE 3 are designed, one with surface mounted magnets (SM) and one with buried rotor magnets (BM). The surface magnet motor has $17\%$ less mass and a slightly higher efficiency and was therefore chosen for further investigations. Compared with the conventional drive system of the ICE 3, consisting of geared inverter fed induction machines, the gearless permanent magnet direct drive yields about $16\%$ lower losses. This calculation is based on the route parameters of the high speed track between Frankfurt/Main and Cologne in Germany, which is currently under construction.

• 한국초전도저온공학회:학술대회논문집
• /
• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
• /
• pp.39-42
• /
• 1999

The characteristics of Nb3Sn strands shich will be used for the been investigated. The physics requirements for the KSTAR operation demands the two conditions, high non-Cu critical current density and low contradictory to each other. It is recent that superconductor manufacturers. IGC and Mitsubishi, have succeded in the production of the strand which satisfies the ITER HP-1 and HP-2 conditions at the same time. It has been determined that this type of strand, so-called HP-3, will be used for the KSTAR magnets and its properties, critical current density and hysteresis loss investigated by the several institutes are presented here. On the basis of the round robin tests for many strand samples under various optimized and the vendor will be seleted.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2001년도 ICCAS
• /
• pp.32.6-32
• /
• 2001

This paper describes the steering control and geomagnetism cancellation for an autonomous mobile robotusing MR sensors. The magnetic-resistive (MR) sensor obtains the vector summation of the magnetic fields from embedded magnets and the Earth. The robot is controlled by the magnetic fields from embedded magnets. So, geomagnetism is the disturbance in the steering control system. In this paper, we propose a new method of the sensor arrangement in order to remove the geomagnetism and robotbody interference. The proposed method uses two MR sensors located in a level plane and the steering controller has been developed. The controller has three input variables (dBx, dBy, dBz) using the measured magnetic field difference, and an output variable (the steering angle) ...