• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.95-99
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• 2005

This paper presents a general proposal to design and calculate the performance of a tubular permanent magnet linear generator treated here on the basis of the Finite Element Method. Optimizing the linear generator dimensions reduces the cogging force, which occurs due to the interaction between stator teeth and the permanent magnets. The generated AC voltage is analyzed and evaluated for both no load and load cases to take the armature reaction effects on the air gap flux density. A repetitive routine is followed to calculate the output AC voltage from the change of flux and the speed of the single-phase linear generator. The AC output voltage is calculated for different resistive loads, and hence, the linear generator load characteristic is obtained. The designed linear generator is capable to generate an output power of 5.3kW with AC output voltage of 222V with an efficiency of 96.8% at full load of 23.8A. The full load current is chosen based on the thermal properties of the coil wire insulations.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.1
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• pp.38-44
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• 2002

MFL method is a qualitative inspection tool and is a reliable, fast and economical NDT method. The application of MFL method to the inspection of storage tank floor plates has been shown to be a viable means. Examination of tank floors previously depended primarily upon ultrasonic test methods that required slow and painstaking application. Therefor most ultrasonic inspection of storage tank has been limited to spot testing only. Our NDE group have developed magnetic flux leakage system to overcome limitation of ultrasonic test. The developed system consists of magnetic yoke, array sensor, crawler and software. It is proved that the system is able to detect artificial flaw like 3.2mm diameter, 1.2mm depth in 6mm thick steel plate.

• Journal of the Korean Vacuum Society
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• v.16 no.5
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• pp.388-396
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• 2007

KSTAR (Korea Superconducting Tokamak Advanced Research) current lead system (CLS) has a role to interconnect magnet power supply (MPS) in room temperature (300 K) and superconducting (SC) bus-line, electrically. For the first plasma experiments, it should be assembled 4 current leads (CL) on toroidal field (TF) current lead box (CLB) and 14 leads on poloidal field (PF) CLB. Two current leads, with the design currents 17.5 kA, and SC bus-lines are connected in parallel to supply 35 kA DC currents on TF magnet. Whereas, it could supply $20\;{\sim}\;26\;kA$ to each pairs of PF magnets during more than 350 s. At the cold terminals of the leads, there are joined SC bus-lines and it was constructed helium coolant control system, aside from main tokamak system, to protect heat flux through current leads and enhanced Joule heat due to supplied currents. Throughout the establishment processes, it was tested the high vacuum pumping, helium leak of the helium lines and hardwares mounted between the helium lines, flow controls for CL, and liquid nitrogen cool-down of possible parts (current leads, CL helium lines, and thermal shield helium lines for CLB), for the accomplishment of the required performances.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.2
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• pp.144-151
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• 2013

This paper presents a result of the mechanical noise and vibration analysis as well as the electrical characteristics analysis of the permanent magnet(PM) motor according to the driving method that is Brushless DC(BLDC) drive and Brushless AC(BLAC) drive. To do that, the characteristics of the PM motor, which have the same output power but different driving method, are investigated. At that time, the characteristics such as torque, torque ripple and flux density, and so on, are obtained by finite element analysis(FEA). Besides, noise and vibration are obtained by spectrum analysis. The magnetic noise is defined as noise generated from vibrations due to electromagnetic excitation force. In this paper, the electromagnetic excitation force is analyzed and design process of noise reduction is proposed. Finally, The validity of the analysis results is verified by test.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2246-2253
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• 2011

This paper presents the error correction method of magnetic position sensor using recursive least square method (RLSM) with forgetting factor. Magnetic position sensor is proposed for linear position detection of the linear motor which has tooth shape stator, consists of permanent magnet, iron core and linear hall sensor, and generates sine and cosine waveforms according to the movement of the mover of the linear motor. From the output of magnetic position sensor, the position of the linear motor can be detected using arc-tan function. But the variation of the air gap between magnetic position sensor and the stator and the error in manufacturing process can cause the variation in offset, phase and amplitude of the generated waveforms when the linear motor moves. These variations in sine and cosine waveforms are changed according to the current linear motor position, and it is very difficult to compensate the errors using constant value. In this paper, the generated sine and cosine waveforms from the magnetic position sensor are compensated on-line using the RLSM with forgetting factor. And the speed observer is introduced to reduce the effect of uncompensated harmonic component. The approaches are verified by some simulations and experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.5
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• pp.411-417
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• 2016

Theoretical IPMSM control technique is complicated, and reliability is low because of the changing parameters. Further, in case of general look-up table designing method which obtains torque characteristics (according to current and speed) or torque characteristics (according to magnetic flux through the entire control region), obtaining a precise result can be difficult and has the disadvantage taking too much time to establish a current look-up table. In this paper, the new auto maximum torque point tracking (MTPT) algorithm that automatically finds the optimum stator d - q axis electric current reference through the entire speed region is devised; consequently, it could establish a 3D look-up table with torque characteristics according to current and speed. In case of using the devised auto MTPT algorithm, the result value detailed was obtained in comparison with the generalized look-up design technique, and checked to reduce the current look-up table establishment time.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.8
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• pp.717-726
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• 2010

For the application into a 1 kWh flywheel energy storage system(FESS), this paper presents the design scheme of radial and axial hybrid magnetic bearings which use bias fluxes generated by permanent magnets. In particular, the axial hybrid magnetic bearing is newly proposed in this paper, in which a permanent magnet is arranged in axial direction so that it can support the rotor weight as well as provide a bias flux for axial magnetic bearing. Such hybrid magnetic bearings consume very low power, compared with conventional electromagnetic bearings. In this paper, to stably support a 140 kg flywheel rotor without contact, design process is explained in detail, and magnetic circuit analysis and three-dimensional finite element analysis are carried out to determine the design parameters and predict the performance of the magnetic bearings.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.167-170
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• 1991

The back e.m.f. of PMSM is increased as the speed is increased and it saturates the current regulator because it counteracts the available output voltage of the inverter. In the PM motor, however, the required armature terminal voltage can be reduced within the maximum output voltage of the inverter by field weakening control, in which the air gap flux is weakened by the d-axis armature current. In this paper, the field weakening control of the surface PMSM fed by a hysteresis current control led PWM inverter based on the microprocessor is presented. To show the validity of the proposed control method, the simulation and experimental results are provided.

• Progress in Superconductivity and Cryogenics
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• v.22 no.3
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• pp.1-6
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• 2020

This paper presents the analysis results on the electrical output performance characteristics of a 746 W high temperature superconducting generator (HTSG). The HTS field winding is charged by non-contact excitation method, i.e., contactless superconducting field exciter (CSFE) which is originated by rotary flux pump based on permanent magnet. In this paper, the preliminary current charging test was carried out using a 70 A CSFE to evaluate the performance of field exciter and analyze its non-contact excitation characteristics for the full-scale HTS field winding of the 746 W HTSG. First, the various contactless current-charging tests were conducted using assembly with HTS field winding and CSFE. Then, in order to estimate the output power performance characteristics of the 746 W HTSG, finite element analysis was conducted based on field excitation information which is experimentally measured under various operating conditions. Finally, the electrical output characteristics in no-load and load models were simulated by two-dimensional transient solver in ANSYS electromagnetics 19.0 release.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.743-748
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• 2007

This paper describes a lens transmissive type tilting actuator for a projection TV. An electromagnetic analysis and a structural analysis of the tilting actuator system is necessary to design a tilting actuator for a projection TV. The tilting actuator is composed a permanent magnet, coil and yoke as the electromagnetic components and it needs a driving hinge part as the mechanical component. The design of the tilting actuator for the projection TV is performed by the following procedure. Firstly, a magnetic flux density of the tilting actuator system is analyzed by a mathematical theory and an electromagnetic FEM. Secondary, a magnetic circuit method is used to determine tilting force. Thirdly, the structural FEM is carried out with an FE model of a lens-transmissive type tilting actuator and then the prototype of the model is manufactured. The characteristic of the prototype is experimentally observed. Finally, a design for a new hinge configuration is suggested for better performance.