• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1832-1837
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• 2011

This paper presents the optimal permanent magnet shape on the rotor of an interior permanent magnet motor to reduce the core losses and improve the performance. As permanent magnet has conductivity inherently, it causes huge amount of eddy current losses by the slot harmonics with concentrated winding. This loss is roughly 100 times larger than that of distributed winding in high speed operation and it cannot be ignored, especially on traction motors. Each eddy current loss on permanent magnet has been investigated in detail by using FEM(Finite Element Method) instead of EMCNM(Equivalent Magnetic Circuit Network Method) in order to consider saturation and non-linear magnetic property. Simulation-based DOE(Design Of Experiment) is also applied to avoid large number of analyses according to each design parameter and consider expected interactions among parameters. Consequently, the optimal design to reduce the core loss on the permanent magnet while maintaining or improving motor performance is proposed by an optimization algorithm using regression equation derived and lastly, the core loss reduction on the proposed shape of the permanent magnet is verified by FEM.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.847-852
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• 2007

This paper investigates the characteristics of cogging torque and magnetic force of a brushless DC (BLDC) motor due to imperfect magnetization of permanent magnet (PM) numerically and experimentally which results in the magnetically induced vibration. A predicted magnetization pattern of the PM of the BLDC motor, which is derived from the measured surface magnetic flux density along the PM, is applied to the finite element analysis in order to calculate the cogging torque and the unbalanced magnetic force. This research also develops the experimental setup to measure the unbalanced magnetic force as well as the cogging torque. It shows numerically and experimentally that the imperfect magnetization of permanent magnet generates the driving frequencies of cogging torque with integer multiple of slot number in addition to the least common multiple of pole and slot. It also shows that the driving frequencies of unbalanced magnetic force are integer multiple of slot number ${\pm}1$ due to imperfect magnetization of PM even in the rotationally symmetric design.

• Journal of Magnetics
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• v.20 no.2
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• pp.176-185
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• 2015

We present the design optimization of the magnetic pole and slot design options that minimize the cogging torque of permanent-magnet (PM) brushless generators for small wind turbine generators. Most small wind-turbines use direct-driven PM generators which have the characteristics of low speed and high efficiency. Small wind-turbines are usually self-starting and require very simple controls. The cogging torque is an inherent characteristic of PM generators, and is mainly caused by the generator's geometry. The inherent the cogging torque can cause problems during turbine start-up and cut-in in order to start softly and to run a power generator even when there is little wind power during turbine start-up. Thus, to improve the operation of small turbines, it is important to minimize the cogging torque. To determine the effects of the cogging torque reductions, we adjust the slot opening width, slot skewing, mounting method of magnets, magnet shape, and the opening and combinations of different numbers of slots per pole. Of these different methods, we combine the methods and optimized the design variables for the most significant design options affecting the cogging torque. Finally, we apply to the target design model and compare FEA simulation and measured results to validate the design optimization.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.150-156
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• 2016

This paper compares the performances of permanent-magnet synchronous (PMS) and permanent-magnet vernier (PMV) machines for low-speed and high-torque applications. For comparison with the PMS machines, we consider two types of the PMV machine. The first one has surface-mounted permanent magnets (PMs) on the rotor and the other has PMs inserted on both sides of the stator and rotor. The PMS and PMV machines are designed to meet the condition of equal output power per unit volume. We analyze the magnetic fields of the machines using a two-dimensional finite element analysis (FEA). We then compare their performances in terms of the generated torque characteristics, power factor, loss, and efficiency.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.3
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• pp.138-145
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• 2006

It is well known that the accurate calculation of the field distribution is essential for the design of electrical machines. The analytical techniques for electromagnetic field can quickly and exactly determine airgap magnetic field distribution in electrical machines. Many analytical techniques have been investigated to predict the magnetic field distribution in PM machines equipped with permanent magnets. Using the analytical technique by transfer relations, D. L. Trumper and K. R. Davey already presented the design and analysis of linear permanent-magnet machines and induction machines, respectively. Using the transfer relations (Melcher's general methodology) to describe electromagnetic phenomena, this paper deals with the analysis on the magnetic field distribution due to PM and winding current, the induced voltage and the static torque characteristics in surface-mounted slotless type permanent magnet machine. The validity of the analysis results is confirmed by finite element (FE) analysis.

• Journal of Power Electronics
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• v.5 no.1
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• pp.1-10
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• 2005

This paper presents the application of a simple neuro-based speed control scheme of a permanent magnet (PM) dc motor. To validate its efficiency, the performance characteristics of the proposed simple neuro-based scheme are compared with those of a Neural Network controller and those of a Fuzzy Logic controller under different operating conditions. The comparative results show that the simple neuro-based speed control scheme is robust, accurate and insensitive to load disturbances.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.66-68
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• 2003

This paper is deal with the method of design for the optimum model using genetic algorithms in slotted Permanent Magnet Linear Synchrous Motor (PMLSM). The objective functions are maximum thrust and minimum detent force. Characteristic analysis method is used 2D space harmonic analysis method. Design parameters are PM width, PM height and slot width.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.6
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• pp.613-619
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• 2010

The stationary discontinuous armatures that are used in permanent magnet linear synchronous motors (PM-LSMs) have been proposed as a driving source for transportation systems. However, the stationary discontinuous armature PM-LSM contains the outlet edges which always exist as a result of the discontinuous arrangement of the armature. For this reason, the outlet edge cogging force generated between the armature's core and the mover's permanent magnet. This paper contemplated the outlet cogging for ceaccording to 2-D numerical analysis by FEM. We installed the auxiliary pole for in order to minimize the outlet cogging force.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.1
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• pp.54-60
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• 2012

In this paper, a new permanent-magnet (PM) linear motor is proposed, in which both the magnets and armature windings are placed in the short mover, while the long stator consists of iron core only. Hence, this new PM linear motor can be called a primary permanent-magnet linear motor. It exhibits the advantages of robustness, low cost, high efficiency, high power factor, and high thrust force density. It is especially suitable for long stator applications such as urban rail transit. In this paper, the topology and operation principle of this motor are discussed in detail. The steady-state characteristics including field distributions, flux-linkage, back-EMF, phase inductance and thrust force are investigated. In addition, the technique of skewing stator teeth is adopted to improve the electromagnetic performance. Results from finite element method (FEM) verified the theoretical analysis results.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.2
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• pp.168-172
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• 2005

A novel cogging torque reduction algorithm is presented for 2-pole permanent magnet DC motor. While the shape of the permanent magnet is changed in the conventional method, the pole shape of the magnetizing yoke is optimized in the presented algorithm. In order to parameterize the shape of the yoke, and the distribution of the residual magnetization of the permanent magnet, the Bezier spline is used. The shape of the magnetizing yoke is optimized using the design sensitivity analysis incorporated with the finite element method and Bezier spline.