• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.5
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• pp.437-442
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• 2013

For open-end permanent magnet synchronous machine(PMSM) with dual inverter system, where one inverter is connected to the source and the other is flying, the dc link voltage of the flying inverter can be boosted through the machine. For this reason, when compared with single inverter drive system, higher voltage can be applied to PMSM, and higher torque can be generated in the flux weakening region. In this case, however, active and reactive powers are separately supplied by each inverter to maintain the dc link voltage of flying inverter. Therefore, the required flux weakening control is different from the conventional method for a single inverter drive system. This paper proposes the novel flux weakening control method which maximizes the active voltage component in a dual inverter PMSM drive system. The proposed method was demonstrated and verified through experimental results.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.939-941
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• 2003

High Speed permanent magnet machines are currently being developed for a number of applications including gas turbine power plants, air conditioning systems, machine tools, gas pumps, high performance vacuum pumps, flywheel energy storage systems, aircraft fuel pumps, and so on. Using a high-speed machine eliminates the necessity of the mechanical gearbox and could certainly increase the system efficiency and reduce the total cost. In addition, a high-speed machine has the advantage of small dimension and low weight, i.e. low weight to power and volume to power ratio. This paper presents a review of some important applications (mostly still under development) where high-speed machines arc used, highlighting the advantages of the technology in each case.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.718-725
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• 2017

The method of stator segmentation is generally taken to enhance the electromagnetic performance of surface-mounted permanent magnet (SPM) machine and reduce its production cost. Based on the model with single slot, the expressions of cogging torque in machine with uniform or non-uniform segmentations are deduced and the optimal combination is given. Moreover, this paper discusses a structured skewing method and put forward a novel stator structure model to reduce the cogging torque in segmented permanent magnet machine. The model can reduce the cogging torque amplitude by shifting a proper angle of slot-opening. The shifting angle formula for analysis can also be suitable for other permanent machine with segmented stator. Finally the results of finite element simulation are given to prove that the method is effective and feasible.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.4
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• pp.399-404
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• 2013

The rotor overhang is used to enhance air-gap flux and improve power density. Due to asymmetry in the axial direction caused by the overhang, the time consuming 3D analysis is necessary to design the motor with overhang. To solve this problem, this paper proposes the equivalent magnetic circuit model (EMCM) that can consider overhang effects without the 3D analysis by using effective air-gap length. The analysis time can be reduced significantly via the proposed EMCM. The reduction of the analysis time is essential for the preliminary design of the motor. In order to verify the proposed model, the 3-D finite-element method (FEM) analysis is adopted. 3-D FEM results confirm the validity of the proposed EMCM.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1369-1379
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• 2018

In this paper, a model predictive torque control (MPTC) without the use of a weighting factor for surface mounted permanent-magnet synchronous machine (SPMSM) drive systems is presented. Firstly, the desired voltage vector is predicted in real time according to the principles of deadbeat torque and flux control. Then the sector of this desired voltage vector is determined. The complete enumeration for testing all of the feasible voltage vectors is avoided by testing only the candidate vectors contained in the sector. This means that only two voltage vectors in the sector need to be tested for selecting the optimal voltage vector in each control period. Thus, the calculation time can be reduced when compared with the conventional enumeration method. On the other hand, a novel cost function that only includes the dq-axis voltage errors between the desired voltage and candidate voltage is designed to eliminate the weighting factor used in the conventional MPTC. Thus, the control complexity caused by the tuning of the weighting factor is effectively decreased when compared with the conventional MPTC. Simulation and experimental investigation have been carried out to verify the proposed method.

• 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.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.135-137
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• 2005

In servo system demanding precision dynamic characteristics, application of the Permanent Magnet Linear Synchronous Machines (PMLSM) has advantage of analysis convenience by simple geometry and thrust ripple reduction from the sinusoidal back electromotive force and excited stator. Therefore, this paper presents design of surface-mounted PMLSM with slotless iron cored stator according to coil turns to satisfy the rate thrust. Also, from dynamic analysis for servo application of manufactured motor with heavy mass, we offer accurate range of the DC link voltage and acceleration in rate speed. This is applied to speed reference profile considering system characteristics in total length of moving position.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.112-118
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• 2004

Recently, development of rare earth permanent magnet with the high remanence, high coercivity allows the design of brushless motors with very high efficiency over a wide speed range. Cogging torque is produced in a permanent magnet by magnetic attraction between the rotor mounted permanent magnet and the stator teeth. It is an undesired effect that contributes to output ripple, vibration, and noise of machine. This cogging torque can be reduced by variation of magnet arc length, airgap length, magnet thickness, shifting the magnetic pole and varying the radial shoe depth and etc. In this paper, some airgap length and magnet arc that reduce cogging torque are found by finite element method(FEM) and Maxwell stress tensor method. The SPM(Surface Permanent Magnet) type of high-power Brushless DC (BLDC) motor is optimized as a sample model.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.216-224
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• 2013

This paper describes dual inverter drive for a fractional-slot concentrated winding permanent magnet synchronous machine (PMSM). PMSMs are widely used in many applications from small servo motors to few megawatts generators thanks to its high efficiency and torque density. Especially, fractional-slot concentrated winding PMSM is very popular in the applications where wide operation range is required because it shows very wide constant power speed ratios. High speed operation, however, requires lots of negative daxis current for reducing back-EMF regardless of output torque. Field weakening current does not contribute to the torque generation in surface mounted PMSM case and causes inverter and copper loss. To reduce the losses from field weakening current, this paper proposes PMSM with split stator and parallel dual inverter drive. Proposed parallel dual inverter drive reduces back-EMF and enables efficient drive at high speed and light load situation. Control strategy of proposed dual inverter system is established through loss analysis and simulation. Proposed concept is verified with practical experiment.

• Journal of Industrial Technology
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• v.31 no.A
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• pp.129-133
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• 2011

In this paper, a surface mounted permanent magnet synchronous motor(SPMSM) drive system for industrial sewing machine was developed. Even through a lowr-esolution encoder is used for a low cost, using a full order observer enables to estimate accurate speed and position. And it also compensates a disturbance torque caused by the belt between a load and a motor. In order to control precisely stop positions of a needle, a speed trajectory is calculated from the acceleration pattern which is obtained from the position reference. The performance of the developed system is verified by experimental results.