• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.903-905
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• 2002

According to the improvement of the HTS wires performance, several types of HTS superconducting machines, such as, transformer, motors, current limiters, and transmission cables are being developed. Degradation of the critical current in HTS tape owing to external field is very important subject in developing the HTS machines. Considering that stacked HTS tapes are widely used to develop the large HTS machines, the critical current characteristics of stacked HTS tapes in external field need to be examined. In this paper, we present critical current characteristics of 4-stacked HTS tapes which are exposed to the external field. HTS tape with critical current of 4-stacked HTS tape. Test results prove that four times critical current of single HTS tape is smaller than critical current of stacked HTS tape in high external field.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.666-668
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• 2002

Reluctance torque is generated by the rotor of the rugged construction in Synchronous Reluctance Motor. Its construction is simple, and it is very economic because a rotor in existed AC motor can be used. As the Synchronous inductance in Synchronous Reluctance Motor is an element that is proportional to torque, the exact value must be experimentally or analytically found for controlling and the performance development of motors. In this paper, direct torque control simulation to maximize the torque of the Synchronous Reluctance Motor and fast response characteristics was carried out with the inductance value by the Finite Element Method. For the simulation results, there are torques and fluxs response characteristics when controlling speed.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.756-760
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• 2002

This study presents a solution to control a Permanent Magnet Synchronous Motor without sensors. The control method is the presented superposition principle. This method of sensorless theory is very simple to compute estimated angle. Therefore computing time to estimate angle is shorter than other sensorless method. The use of this system yields enhanced operations, fewer system components, lower system cost, energy efficient control system design and increased efficiency. A practical solution is described and results are given in this Study. The performance of a Sensorless architecture allows an intelligent approach to reduce the complete system costs of digital motion control applications using cheaper electrical motors without sensors. This paper deals with an overview of sensorless solutions in PMSM control applications whereby the focus will be the new Controller without sensors and its applications.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1149-1151
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• 2002

In this paper, an auxiliary winding driving system of single-phase induction motors is described. Starting charateristics variations are obtained by controlling the auxiliary winding voltage magnitude and phase angle, while the motor's main winding is directly connected to the local utility. A variable auxiliary winding voltage phase angle is shown to yield significant torque control, providing starting and braking torque. The analysis includes the determination of the relationship between the auxiliary winding voltage phase angle and the phase angle difference between the main and auxiliary winding current. The paper proposed for adjusting an auxiliary winding voltage magnitude and phase angle. Experimental results of motor's starting characteristics with using the DC-AMP and PWM inverter for auxiliary winding power supply are shown. The drive is tested using a dynamometer to experimentally verify the results of the theory.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.867-869
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• 2002

A method for the time step analysis of single phase induction motors is proposed. The unknown variables in differential equations are the currents flowing through rotor bars. They are coupled with the distributed magnetic flux densities in the airgap instead of inductance matrix while applying Kirchhoff's and Faraday's induction laws. Two patterns for magnetic flux densities are necessary. One is given by ideal stator winding distribution. the other is produced by currents flowing a rotor bar with unit magnitude and is calculated by FEM. Formulated set of equations are solved for a simple three phase and single phase example model and the resultant speed torque curve is shown in this paper.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.848-850
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• 2002

Single phase induction motor is directly used usual source, it can be a source of an appliance such as mechanical fan, refrigerator, washing machine, etc. Especially capacitor-run single phase induction motor is suitable to make more inexpensive and high efficient products because it is more high efficiency, and good to start than other single phase induction motors. Generally, voltage and current of capacitor-run single phase induction motor transfer to the part of positive phase and negative phase based on two motor theory. In this paper, we simulate the torque characteristics to capacitance variation from single phase induction motor's equivalent circuit. Through the test using the real motor, we compare and investigate the maximum torque of run state related with capacitance and the adequacy of the converted model.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.973-975
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• 2002

Voltage Sags are the short-duration reductions in rms voltage caused by faults in the electric supply system and the starting of large loads, such as motors. In this paper, we use the dq transformation(dq stationary frame and dq synchronous rotating frame) for series voltage sag compensation algorithm. Analysis, simulation results are presented for voltage sags on a three-phase balanced voltage source.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.838-840
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• 2002

Most adjustable-speed drives (ASDs) designed to operate 220[V] induction motors incorporate voltage-source inverters (VSIs), which create motor voltages at high switching frequencies. The motor leads used to connect an ASD to a motor can behave like transmission lines for voltage pulses, which can be reflected at the motor terminals. The resulting oscillatory transient, known as the long-lead effect, can stress and consequently degrade the stator insulation system of a motor. This paper describes the results of tests to 1) determine the correlation between peak motor voltage and the length of motor leads and 2) determine the correlation between peak motor voltage and the switching frequency of the ASD

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.6
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• pp.1036-1041
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• 2008

Periodic disturbance is practically occurred in several engineering applications, especially in data storage systems. However, recently addressed controls for such problem were mostly dealt with its deterministic nature, which is rarely practical in real-time implementation. We present an adaptive control approach for DC motor systems with periodic stochastic disturbance whose frequency and magnitude are both random variables. We establish adaptive state feedback control which is linearly composed of nominal and corrective control parameter matrices. The former is derived from a nominal system model voiding disturbance and the latter is constructed from a disturbed system model by using Lyapunov stability theory. We carry out computer simulation to evaluate the proposed control methodology and compare to the recently addressed control method to demonstrate its superiority.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2714-2719
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• 2007

HANARO, an open-tank-in-pool type research reactor of 30 MWth power in Korea, has been operating normally since its initial criticality in February, 1995. For the last about ten years, A cooling tower of a secondary cooling system has been operated normally in HANARO. Last year, the cooling tower has been overhauled for preservative maintenance including fills, eliminators, wood support, water distribution system, motors, driving shafts, gear reducers, basements, blades and etc. This paper describes the results of the overhaul. As results, it is confirmed that the cooling tower maintains a good operability through a filed test. And a cooling capability will be tested when a wet bulb temperature is maintained about 28 $^{\circ}C$ in summer and the reactor is operated with the full power.