• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.397-400
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• 1990

All the existing PWM voltage-controlled inverters, regardless of the advantages of the operation, have produced serious problems such as acoustic noise. In this raper, the PMW technique for acoustic noise reduction is implemented using randomly modulated carrier modulation. By modulating the triangular carrier in sinusoidal PWM with band-limited white noise, it is shown that the acoutic noise level and spectral density is reduced in a tone. This method shows great merit in application the AC motor drive system to particularly environment.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.3195-3197
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• 2000

Narrowband active noise control (ANC) techniques to reduce the noise in thermal power plant are considered. To reduce the computational burden of the ANC system, an adjoint LMS algorithm instead of a filteredx LMS algorithm is used for adaptive filters. The square wave signal is used for the reference signal of adaptive filters to reduce the higher order harmonics as well as the fundamental frequency of noise. A computer simulation has done to show the effectiveness of a proposed algorithm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.181-189
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• 2007

This paper presents a experimental evidence of the generation of the earth potential and communication line noise from the electric railway. There is a critical measurement err in case of measuring the electrical power induced noise voltage and degree of cable balance in the field of earth potential generated. As a results, it has been found that the conventional cable has more noise immunity than shielded cable near the railway where the earth current flows through the sheath layer.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1462-1467
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• 2013

A pseudo 480-Hz drive method has been proposed to reduce the dynamic false contour noise that occurs on flat panel displays with displaying grayscale image in the digital mode, such as plasma display panels. The proposed method makes the image movements nearly continuous by rearranging the 8-bit image data displayed for 1 TV field into 8 subfields. The position of the image data rearranged in subfields has been optimized on the basis of the speed of the moving image by computer simulations for the dynamic false contour noise. It is verified that a significant reduction in the dynamic false contour noise is achieved with the proposed method as compared to the conventional noise reduction technologies. Moreover, to reduce the noise in digital mode displays, the proposed technology requires only 8 subfields. Therefore, there is no reduction in the brightness of the image.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.9
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• pp.565-571
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• 2000

SRM has been applied to many commercial applications that require economical advantages and high performance abilities. But it has some drawbacks such as acoustic noise due to the abrupt change of mmf level when commutation. The abrupt change of a phase excitation produces mechanical stresses and it results in torque ripple and noise. This paper deals with an analysis of vibration and noise in SRM drive. Several types of excitation method are taken into account. The 1-phase and 2-phase excitation technique of short-pitch winding 2-phase excitation technique of full-pitch winding are tested. The acoustic noise is reduced remarkably through the sequential phase excitation in the 2-phase excitation. It is because that the scheme reduces abrupt change of excitation level by distributed balanced excitation with free-wheeling during commutation.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.36-39
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• 2004

Electrical impedance tomography (EIT) has been suffered from the severe ill-posedness which is caused by the inherent low sensitivity of boundary measurements to any changes of internal resistivity values. So, small noise occur unexpected reconstruction image. Generally in EIT system, if measured voltage includes noise, we can't find object location and resistivity values. In this paper, we propose digital filter for measured voltage in EIT. Newton-Raphson is the most..popular algorithm in EIT, but noise cause to blur image. We use Fourier transform (FT) in order to minimize the noise and design the filter. After filtering, result of reconstruction image is improved better than before filtering.

• Journal of electromagnetic engineering and science
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• v.15 no.2
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• pp.89-96
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• 2015

This paper describes the application of a passive noise cancellation method to a prototype inductor-inductor-capacitor (LLC) resonant converter by placing a compensation winding in a transformer to reduce common mode noise. The connection method for the compensation winding is investigated. A circuit analysis is implemented for the displacement currents between the primary and secondary windings in the transformer. The analyzed displacement currents are verified by performing a circuit simulation and a proper compensation winding connection that reduces common mode noise is found. The measurement results show that common mode noise is reduced effectively up to 20 dB in the 1 to 7 MHz frequency region for the prototype LLC resonant converter by using the proposed passive noise cancellation method.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.9
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• pp.8-13
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• 2008

Noise in homogeneous extrinsic semiconductor samples is calculated due to distributed diffusion noise sources. As the length of the device shrinks at a fixed bias voltage, the ac-wise short-circuit noise current shows excess noise as well as thermal noise spectra. This excess noise behaves like a full shot noise when the channel length becomes very small compared with the extrinsic Debye length. For the first time, the analytic formula of the excess noise in extrinsic semiconductors from velocity-fluctuation noise sources is given for finite frequencies. This formula shows the interplay between transit time, dielectric relaxation time, and velocity relaxation time in determining the terminal noise current as well as the carrier density fluctuation. As frequency increases, the power spectral density of the excess noise rolls off. This formula sheds light on noise in nanoscale MOSFETs where quasi-ballistic transport plays an important role in carrier transport and noise.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.6
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• pp.75-81
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• 2005

Recently an increase of sensor and power trandusers in control equipment system has caused many kinds of noise the mis-operation equipment and demage program memories of control circuits. In this paper, the noise character of the various control equipment system has been measured and analyzed. Additionally, the countermeasure to reduce noise like as Noise Cut Transformer, Equipotential Bonding, Power Noise Rejector, Noise Filter has been applied and confirmed the effective results to solve the trouble of noise.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.12
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• pp.91-99
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• 2010

HVDC converter station consists of a number of equipment such as converter transformer, ac filter, thyristor valve and so on. They can be acoustic noise sources. In this paper, we analyzed the simulation results of the outdoor acoustic noise for HVDC converter station. It shows that maximum noise level in boundary of HVDC converter station exceeds regulation value. The main factors in generating maximum noise level are ac filter and converter transformer. Then we applied some soundproof countermeasures in HVDC converter station. Shielding wall is enough to reduce transformer noise level but not enough to reduce ac filter noise level. In case of ac filter, soundproof building is effective in satisfying noise level regulation in boundary of HVDC converter station. In addition, we also studied effects of season, soundproof woods, ground.