• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.4
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• pp.31-39
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• 2001

Composite propeller shafts for a vehicle have major advantages such as reduction of vibration, noise, and weight. A propeller shaft was designed with a carbon/epoxy composite material using the finite element method(FEM), and prototype shafts for tests were manufactured by the filament winding manufacturing process. In order to verify the design procedure by FEM, Two kinds of experimental tests were carried out using a FFT analyzer with impact hammers and a critical speed measuring apparatus for measurement of natural frequencies and critical speeds. The difference between the FEM analysis result and the test result was less than 3.4%, showing FEM analysis results to be acceptable. The parametric study was focused on determining the factor affecting the vibration and strength characteristics of the propeller shaft based on FEM. In investigation of the change in natural frequency without an increase in propeller shaft weight, it was found that the winding angle is the most significant factor affecting the vibration and strength characteristics.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.511-514
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• 2004

Proposed about new inverter that can use in PV system in this paper. Multi_level inverter that used inverter makes use of 4 transformers is basis, primary winding of each transformer voltage as can do step_up or step_down to appropriate voltage space tap lake. Put circuit that tap that turn in transformer connects properly according to inhibit signal that sense change of input voltage (output voltage of solar cell place) and transformer secondary voltage controls point of contact of relay so that get into fixed output voltage. As a result, can minimise relative harmonic content despite change width of input voltage are wide because number of output voltage level of multi_level inverter does not decrease. Because proposed circuit manufactures is easy and control is easy and is no burden of cost price rise economically, commercialization expected to do easily and this study examined propriety of action as that compose and experiments proposed circuit.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.291-294
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• 2001

This paper presents the circuit modeling and control methods of PWM DC/DC converter with isolated dual outputs. The dual output converter consists of a transformer with a single secondary winding and two switches. The proposed control algorithm is that required inductor current according to the loads is feed-forwarded to the PI current controller. The proposed control method has better response characteristics than conventional PI control method at load change.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2061_2062
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• 2009

Within serviced period of time in transformer, thermal stress is the most influential parameter affecting the aging behavior of an insulation system. The thermal stress on the insulation system may occur from operation in a high temperature environment due to Joule's heat at winding coils. This paper describes a development of capacitive sensor and preventive diagnosis techniques for electrical insulating oil, widely used for power and distribution transformer. To survey the dielectric properties of the virgin and used mineral insulating oil, we utilized the highly precise measuring system of KRISS. And the results were used to determine the design factors of the sensor. To evaluate diagnosis by the sensor, we performed accelerated aging test about insulating oils. The condition of aged specimens were investigated by measurements of relative permittivity i.e. capacitance change by capacitive sensor.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1163_1164
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• 2009

AC AT feeding method consists return circuits of electric train inserting in parallel between trolly line and feeding line and connecting neutral line to rail and FPW. Due to increasing train number, electric load at feeding system are increasing and collecting voltage of train are going down. To increase electric load and collecting voltage between trolly line and rail, the usefulness of new autotransformer are considered which variation of short impedance and change of line voltage is simulated with modified winding ratio of autotransformer from 1:1 to variable tab.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.892-893
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• 2015

This paper deals with a characteristic that varies the number of magnetic pole in permanent magnet (PM) motor in order to reduce energy consumption. The pole changing memory motor (PCMM) can change the number of magnetic poles and produce two types of torque. When the motor operates with eight poles, it produces a magnetic torque at low rotational speeds. When the motor changes to four poles, it produces both magnetic torque and reluctance torque at high speeds. The paper explain the principle and basic characteristics of the motor by using a finite element method magnetic-field analysis, which consists of a PM magnetized by a pulse d-axis current of the armature winding. The results of our experiment show that the proposed motor reduces core loss by 10% and 55% under no-load and load conditions, and doubles the speed range of the motor.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.195-197
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• 2001

This paper presents the circuit modeling and Control methods of PWM DC/DC Converter with Isolated dual outputs. The dual output converter topology is consisted of the two switch and single secondary winding. The control algorithm which is used by an adjusted PI control methods, of Dual Output PWM DC/DC converter is proposed in this paper. The proposed adjusted PI control method has faster response characteristics than conventional PI control methods at load change. The validity of the proposed adjusted control method is verified with the several interesting simulation results.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1374-1376
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• 2000

In this paper, sample coils for stator form-wound winding of traction motor were tested by the accelerative thermal degradation, which composed of heat, vibration, moisture and overvoltage applying. Reliability and expected life were evaluated on the insulation system for 200 class traction motor. After aging of 10 cycles, insulation resistance and PI properties were investigated as diagnosis tests in the range of $20{\sim}160^{\circ}C$. Analysis of polarization properties was performed on the base of do current-time change.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.6
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• pp.103-110
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• 2000

Experimental study of drilling for duralumin A2024 was conducted with intermittently accelerated and decelerated feedrate. It is achieved through a programmed periodic increase and decrease in the feedrate using a machining center. The following experimental results were performed with the objective of solving chip to disposal problems. In conventional drilling of aluminum, long continuous chips are produced with winding around the drill and causing difficulties in eliminating chips from the cutting zone. In order to acquire the basic data necessary to regulate the chip profile, the relationship between cutting variables and chip shape was investigate. The following conclusions are established from the experimental results. At a suitable feed fluctuation ratio, intermittently decelerated feed drilling proved successful in braking chips to appropriate lengths while maintaining stable cutting. Thus, it is an effective method for improving chip disposal. The amplitude of the dynamic component of cutting force in intermittent feed drilling is influenced by the feed fluctuation ratio.

• Proceedings of the KIEE Conference
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• summer
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• pp.1046-1048
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• 2004

Inductance is an important parameter determining the characteristics of current waveform in electric motors. There are many kinds of inductances, however, self and mutual inductances are the major components. These inductances are changed under the variation of the magnetic circuit, current, frequency etc., even in the same winding distribution. Therefore this paper deals with the characteristics of inductance according to the shape of stator tooth. The analysis model is newly developed motor made of SMC(Soft Magnetic Composite) to reduce the core loss in high speed. the result of this paper gives the basic understandings of inductance to extend the applications of the motors.