• The KSFM Journal of Fluid Machinery
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• v.2 no.2 s.3
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• pp.32-38
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• 1999

An experimental study is performed to investigate the frequency effects of the excitation force on the linear stiffness and damping coefficients of a LOP (load on pad) type five-pad tilting pad journal bearing with the diameter of 300.91 mm and the length of 149.80 mm. The main parameter of interest in the present work is excitation frequency to shake the test bearing. The excitation frequency is controlled independently, using orthogonally mounted hydraulic exciters. The relative movement between the bearing and shaft, and the acceleration of the bearing casing are measured as a function of excitation frequency using the different values of bearing load and shaft speed. Measurements show that the variation of excitation frequency has quite a little effect on both stiffness and damping coefficients. Both direct stiffness and damping coefficients in the direction of bearing load decrease by the increase of shaft speed, but increase with the bearing load.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1191-1192
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• 2011

We released new triple redundant digital excitation system with real time generator-turbine simulator. One of its great merits is the real time generator-turbine simulator when it was compared with the other products. If excitation system is tripped by unexpected faults, Maintenance man can do easily performance test of digital excitation control board, sequence relay and thyristor switching device of phase controlled rectifier without manufacturer's support. For the verification of this system, It was tested with an actual excitation system implemented on 5kVA M-G Set. After finishing the tests, the trial product will be installed and operated at a 500MW thermal power plant.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.173-179
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• 1998

An experimental study is performed to investigate the frequency effects of the excitation force on the linear stiffness and damping coefficients of a LOP (load on pad) type five-pad tilting pad journal bearing with the diameter of 300.91 mm and the length of 149.80 mm. The main parameter of interest in the present work is excitation frequency to shake the test bearing. The excitation frequency is controlled independently, using orthogonally mounted hydraulic exciters. The relative movement between the bearing and shaft, and the acceleration of the bearing casing are measured as a function of excitation frequency using the different values of bearing load and shaft speed. Measurements show that the variation of excitation frequency has quite a little effect on both stiffness and damping coefficients. Both direct stiffness and damping coefficients in the direction of bearing load decrease by the increase of shaft speed, but increase with the bearing load.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.8
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• pp.1449-1455
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• 2010

The excitation control system of an emergency diesel generator is classified as a kind of safety-related system. Compared with other control systems in a power plant, this system is required to be more reliable and have better performance. In this paper, the digital multi-redundant excitation system for a diesel generator was proposed. The signal processing system of the proposed system makes high speed signal processing and arithmetic in excitation control possible. The improved soft start algorithm and multiple PI parameters adaptation considering the diesel generator characteristics were implemented in the proposed system. The developed system was applied to a nuclear power plant successfully.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.46-49
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• 2004

Switched Reluctance Motor(SRM) has been researched for its superior characteristics. The SRM drive system has simple mechanical and magnetic structure, and it requires simple power electronic drive circuit. It is to be compatible to wide range adjustable speed drive system because it has the same driving characteristics of DC series motor's, easy control principle and high efficiency characteristics. In this paper, 2 types of excitation strategy are researched. Conventional 1-phase excitation and 2-phase excitation method are compared and tested. Though 1-phase excitation method is robust and has high performance, 2-phase excitation method has some merit in appling power device. Some simulation and test results are foaled with some analysis.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.8
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• pp.482-492
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• 2002

This paper deals with overvoltage stresses in the field circuit of synchronous machine connected to HVDC terminal. A load rejection of the HVDC may cause generator in the station to become self-excited, resulting in a severe system overvoltage. This paper shows that violent field current oscillations can be produced by resonance between the machine inductance and the terminal capacitance. As most conventional excitation system do not allow reverses current, new topology of excitation system to allow reverse current is proposed. the proposed system can limit the rate of rise of terminal voltage during conditions of self excitation. Apart from these simulations, the nature(Magnitude and frequency) of the field transient state is explained mathematically. Finally, the EMTDC program is used for the simulation studies.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2409-2413
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• 2007

Time resolved phosphorescence of Dibromobenzophenone (DBBP) choleic acid crystal was observed at 4.2 K as functions of excitation energy and delay time. The experimental results reveal that the energy transfer efficiency is dependent on the excitation energy, i.e. the density of acceptors sites. As the excitation energy or delay time increases, the resonance phosphorescence does not broaden and shift gradually, rather a broad luminescence band develops about 290 cm?1 to lower energy of the resonance phosphorescence. The observation implies that energy transfer from high to low energy sites in this system is controlled by emission of phonons or vibrons. The data of time resolved experiments were analyzed in terms of a mechanism involving direct donor-acceptor excitation transport by exchange coupling. It was concluded that an isotropic twodimensional exchange interaction topology is consistent with energy transfer in this system.

• Proceedings of the KIEE Conference
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• 2000.07e
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• pp.122-128
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• 2000

The SRM is a simple and robust machine which is finding applications over a wide power and speed range. To properly evaluate the motor performance, a reliable model design is required. This paper explains the various excitation mode and winding configuration to analyze the torque performance of SRM. A number of different idealized current excitation patterns are introduced, using unipolar, bipolar & square excitation, and the output torques produced by the various winding configurations are compared. The electromagnetic torque of the SRM was calculated from the rate of change of co-energy with respect to angular displacement. The simulation result shows that 3-phase square excitation mode models have revealed higher torque performance.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.241-244
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• 2002

Large eddy simulation of a circular jet at the Reynolds number of 10000 is performed to investigate turbulence suppression effect with single frequency excitation at the non-dimensional frequency of 0.017. Instantaneous flow fields show that, with excitation, naturally occurring energetic vortices are suppressed through earlier saturation and breakdown of the shear layer vortices into fine grained turbulence. Due to the excitation, the Reynolds stresses are larger for the excited case near the jet and turbulence suppression begins afterward. The Reynolds normal stresses show largest suppression in the shear layer near the jet and in the centerline further downstream, while the Reynolds shear stress shows largest suppression in the shear layer at all the downstream locations.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.371-375
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• 2003

In recent years, as the semiconductor and the optical industry grows, the necessity of the transporting system for semiconductor and precision optical lens without damage increases. The transport system using ultrasonic wave is very suitable for this area. In this paper the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave generators are performed. The effect of transporting speed according to the change of weight and amplification voltage are verified. In addition, the system performance for actual use is evaluated.