• Journal of Magnetics
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• v.18 no.3
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• pp.297-301
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• 2013

Flux-reversal machine (FRM) is cost effective and suitable for mass production due to its simple structure. However, there is a notable permanent magnet flux leakage which deteriorates the performance. To compensate this drawback with a design method, an Inset-Permanent-Magnet-Type FRM (ITFRM) has been proposed. The ITFRM has permanent magnets perpendicular to the stator teeth surface, and thus, is much more difficult to demagnetize. In this paper, we deal with the iron losses and irreversible permanent magnet demagnetization characteristics of the ITFRM according to various design variables and driving conditions. To analyze the characteristics, a two-dimensional finite-element method (2D-FEM) considering nonlinear analysis of permanent magnets is used. As a result, we propose the design variables that have the largest effects on the iron losses and irreversible magnet demagnetization.

• Journal of Magnetics
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• v.18 no.3
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• pp.268-275
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• 2013

This paper shows the characteristics of performance for interior permanent magnet machine (IPM) considering driving conditions such as maximum torque per ampere (MTPA) and flux-weakening control especially in terms of harmonic loss. In particular, based on finite element analysis (FEA), permanent magnet (PM) eddycurrent loss and the harmonic iron loss have been computed where the models have been intentionally designed to identify the effects of pole-slot combinations on the loss while maintaining the required power for electric vehicle. From the analysis results, it was shown that the rotor iron loss and PM eddy-current loss of machine employing fractional slot winding are extremely large at load condition. Furthermore, it was revealed that the harmonic iron loss at high-speed operation is mainly distributed over stator teeth and rotor surface, which may aggravate cooling system of the rotor structure in the vehicle.

• Journal of Power Electronics
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• v.6 no.4
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• pp.290-297
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• 2006

Various methods have been discussed to reduce detent force in a tubular permanent magnet type linear single phase AC generator. In particular, the proposed methods depend on variations of the permanent magnet construction. These methods include two approaches in the form of sloped magnets, and conical magnets in addition to the conventional method of optimizing the magnet length. The undesired detent force ripples were calculated by a two dimensional Finite Element Method (FEM). Moreover, the generated electromotive force in the stator coils was calculated for each configuration of the permanent magnet. The experimental results agreed well with those obtained from the FEM-based simulations. Sufficient reduction in the detent force was achieved over the range of 40% while the root mean square of the output voltage was maintained. It was found that sloping the permanent magnet decreased the detent force and at the same time increased the generated rms voltage of the AC generator. The performance of the designed linear AC generator was evaluated in terms of its efficiency, total weight, losses, and power to weight ratio.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.715-721
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• 2010

This paper deals with the design and characteristic analysis of electro-magnet/permanent-magnet (EM-PM) hybrid levitation and propulsion device for high-speed magnetically levitated (maglev) vehicle. The machine requires PMs with high coercive force in order to levitate the vehicle by only PMs, and propulsion force is supplied by long-stator linear synchronous motor (LSM). The advantages of this configuration are an increasing levitation airgap length and decreasing total weight of the vehicle, because of the zero-power levitation control. Several design considerations such as machine structure, manufacturing, and control strategy are described. Moreover, the levitation and propulsion device for high-speed maglev vehicle has been designed and analyzed usign the electromagnetic circuit and FE analysis. In order to verify the design scheme and feasibility of maglev application, 3-DOF static force test set is implemented and tested. The obtained experimental data using the static tester shows the validity of the design and analysis approaches.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.773-778
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• 2001

This paper describes the implementation of the vector control schemes for a variable-speed 131kW PMSM (Permanent Magnet Synchronous Motor) in super-high speed application. The vector control with synchronous reference frame current regulator has been implemented with the challenging requirements such as the extremely low stator inductance$(28^{\mu}H)$, the high dc link voltage(600V) and the high excitation frequency(1.2kHz). Because the conventional position sensor is not reliable in super-high speed, a vector control scheme without any position sensor has been proposed. The proposed sensorless algorithm is implemented by processing the output voltage of the PI current regulator, and hence the structure is simple and the estimated speed is robust to the measurement noise. The experimental system has been built and the proposed control has been implemented and evaluated. The test result, up to the speed of 60,000 r/min, shows the validity of the proposed control.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.424-429
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• 2003

A reciprocating compressor with a rotary motor used in a refrigerator has low efficiency, because it has the large mechanical losses due to the crank mechanism. The linear compressor which has the free piston driven by a linear motor, was developed to increase the efficiency of compressor by reducing mechanical losses. The TRIAC has been widely used for controlling the piston, because it has simple structure. However, as it is able to control only stator voltage, it is very difficult to obtain good efficiency. Recently, PWM inverter which is able to control the voltage as well as the frequency, is applied to linear compressor drive system to overcome above problem. In this paper, the variations for efficiency and power factor of linear compressor are investigated by changing both the mechanical resonant frequency and electrical resonant frequency of linear compressor, and also the inverter frequency The optimum relationships between both resonant frequencies and the inverter frequency is derived in order to obtain the maximum efficiency and also good power factor.

• Progress in Superconductivity and Cryogenics
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• v.13 no.1
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• pp.12-16
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• 2011

In this paper, the prototype of the HTS motor with an on-board cryocooler, is fabricated and tested. The overall system is composed of the stator with conventional copper winding, the rotor with superconductor, and the rotating cryocooler designed from the on-board concept. The rotor is fabricated as the race-track coil with 2G, YBCO tape and contacts with the on-board cryocooler while being rotated together. An inline-type pulse tube refrigerator is used as the on-board cryocooler. The cryocooler is fabricated from optimal process to satisfy the structure and thermal stability of the on-board system. Each component is integrated according to carefully defined sequence. Specially, a combining method of torque tubes is an important part for sustaining stability of the rotor and the cryocooler. In the rotating test, the HTS motor is successfully operated with 240 rpm of rotating speed when 75 A current is supplied to the superconducting rotor. In this paper, potential problems of the HTS motor system using the on-board cryocooler are proposed and solved, and realistic possibility of this concept is also confirmed.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.363-366
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• 2009

The maximum output torque developed by the machine is dependent on the allowable current rating and maximum voltage that the inverter can supply to the machine. Therefore, to use the inverter capacity fully, it is desirable to use the control scheme considering the voltage and current limit condition, which can yield the maximum torque per ampere over the entire speed range. This controller is controlled speed and current using hybrid PI(HBPI) controller and estimation of speed using ANN. Also, this paper is proposed control of maximum torque per ampere(MTPA) of induction motor. This strategy is proposed which is simple in structure and has the honest goal of minimizing the stator current magnitude for given load torque. The performance of the proposed induction motor drive with maximum torque control using HBPI controller is verified by analysis results at dynamic operation conditions.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.29-37
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• 2016

Fast and accurate fault diagnosis of the position sensor is of great significance to ensure the reliability as well as sensor fault tolerant operation of the Switched Reluctance Wind Generator (SRWG). This paper presents a fault diagnostic scheme for a SRWG based on the residual between the estimated rotor position and the actual output of the position sensor. Extreme Learning Machine (ELM), which could build a nonlinear mapping among flux linkage, current and rotor position, is utilized to design an assembled estimator for the rotor position detection. The data for building the ELM based assembled position estimator is derived from the magnetization curves which are obtained from Finite Element Analysis (FEA) of an SRWG with the structure of 8 stator poles and 6 rotor poles. The effectiveness and accuracy of the proposed fault diagnosis method are verified by simulation at various operating conditions. The results provide a feasible theoretical and technical basis for the effective condition monitoring and predictive maintenance of SRWG.

• Journal of Electrical Engineering and Technology
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• v.3 no.1
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• pp.60-67
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• 2008

The vibrations and noise origin in electric material is due to several coupled physical phenomena. The revolving electric machine complete modeling is complex; it does not allow simple parametric machine structure studies for various operation modes. This work presents a simple electromagnetic model which makes possible the machine principal parts flow estimation from flux density. Special interest is given in determining Switched Reluctance Machine (S.R.M) radial acceleration in accordance with the current supply. Our focus will be only on the magnetic origin efforts that are dominating in the S.R.M. The efforts calculation versus the current is presented in the case of a machine with a linearized rate. These efforts are considered as a tangential force producing the torque and a radial force that generates no torque. The application is realized on a 6/4 low power S.R.M type (6 stator teeth and 4 teeth rotor). The mechanical response is substituted in a transfer function. The model takes account of the power supply of the machine, the relation between the current supply and the efforts as well as the vibratory response of the machine to these efforts. Finally, the model is validated by comparison with similar experimental results within the framework of the definite assumptions.