• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.834-839
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• 2007

This paper investigates the distortion of magnetic field of a brushless DC (BLDC) motor due to deformed rubber magnet. Global or local deformation of rubber magnet in the BLDC motor is mathematically modeled by using the Fourier series. Distorted magnetic field is calculated by using the finite element method, and unbalanced magnetic force are calculated by using the Maxwell stress tensor. The first harmonic deformation in the global deformation of rubber magnet generates the first harmonic driving frequency of the unbalanced magnetic force, and the rest harmonic deformations of rubber magnet except the harmonic deformation with multiple of common divisor of pole and slot introduces the driving frequencies with multiple of slot number ${\pm}1$ to the unbalanced magnetic force. However, the harmonic deformation with multiple of common divisor of pole and slot does not generate unbalanced magnetic force due to the rotational symmetry. When the rubber magnet is locally deformed, the unbalanced magnetic force has the first harmonic driving frequency and the driving frequencies with multiples of slot number ${\pm}1$.

• Journal of Power Electronics
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• v.13 no.5
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• pp.884-895
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• 2013

In this paper, the Fourier-based PLL (Phase-locked Loop) is introduced with a new structure, capable of selective harmonic detection in single and three-phase systems. The application of the FB-PLL to harmonic detection is discussed and a new model applicable to three-phase systems is introduced. An analysis of the convergence of the FB-PLL based on a linear model is presented. Simulation and experimental results are included for performance analysis and to support the theoretical development. The decomposition of an input signal in its harmonic components using the Fourier theory is based on previous knowledge of the signal fundamental frequency, which cannot be easily implemented with input signals with varying frequencies or subjected to phase-angle jumps. In this scenario, the main contribution of this paper is the association of a phase-locked loop system, with a harmonic decomposition and reconstruction method, based on the well-established Fourier theory, to allow for the tracking of the fundamental component and desired harmonics from distorted input signals with a varying frequency, amplitude and phase-angle. The application of the proposed technique in three-phase systems is supported by results obtained under unbalanced and voltage sag conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1554-1560
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• 2012

In this paper, the even harmonic current(2nd, 4th, 6th, 8th) of the arc fault current and normal current were measured in computer load and analyzed. The BPF with GIC was developed to detection of harmonic, the exact center frequency and a high degree of sharpness could be easily obtained. The total even harmonic distortion due to series arc fault in computer load was 31.2%, this value was increased 3.9 times better than the total even harmonic distortion of normal current. The results of analysis of arc fault current RMS variation rate and Peak variation rate per half-cycle, The RMS average variation rate are as follows ; the 2nd harmonic was 0.24, the 4th harmonic was 0.15, the 6th harmonic was 0.19, the 8th harmonic was 0.25, respectively. The Peak average variation rate are as follows ; the 2nd harmonic was 0.19, the 4th harmonic was 0.12, the 6th harmonic was 0.13, the 8th harmonic was 0.15, respectively. The results of this analysis utilize data to detect of series arc fault on wiring of computer load.

• Journal of Power Electronics
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• v.5 no.2
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• pp.160-165
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• 2005

In a parallel operation of UPS, there are two types of circulating currents between UPS. One is the low order circulating current with a fundamental frequency caused by the amplitude and phase differences of UPS output voltages, and the other is the harmonic circulating current with PWM switching frequency caused by non-synchronized PWM waveforms among UPS. The elimination of the low order circulating current is essential for optimal load sharing in parallel operations of UPS, which can be accomplished by the phase and magnitude control at each UPS. The harmonic circulating current may cause troubles and deteriorate in performance of the controller for optimal load sharing in parallel operation of UPS. This paper presents a PWM synchronizing method to eliminate the harmonic circulation current in parallel operation of UPS. The effectiveness of the proposed scheme has been investigated and verified through experiments by a 50kVA UPS.

• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.285-288
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• 2004

A canonical transformation changes variables such as coordinates and momenta to new variables preserving either the Poisson bracket or the commutation relations depending on whether the problem is classical or quantal respectively. Classically canonical transformations are well established as a powerful tool for solving differential equations. Quantum canonical transformations have been defined and used relatively recently because of the non-commutativeness of the quantum variables. Three elementary canonical transformations and their composite transformations have quantum implementations. Quantum canonical transformations have been mostly used in time-independent Schrodinger equations and a harmonic oscillator with time-dependent angular frequency is probably the only time-dependent problem solved by these transformations. In this work, we apply quantum canonical transformations to a harmonic oscillator in which both angular frequency and equilibrium position are time-dependent.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.1999-2001
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• 1997

The main two drawbacks of the Sin91e Stage PFC (SS-PFC) converters employing a DCM Boost PFC cell are relatively high voltage stress on the bulk capacitor and the input current harmonic distortion. The high voltage stress on bulk capacitor makes the SS-PFC converter impractical in a universal input application and the input current harmonic distortion lowers power factor. In this paper a selective variable frequency control that reduces the voltage stress on the bulk capacitor and the input current harmonic distortion is proposed. Computer simulation results of the proposed control method are presented.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.3
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• pp.257-262
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• 2009

Capacitor is basically used for the power-factor compensation and sometimes as the passive filter to reduce harmonics of nonlinear load. Since the impedance of capacitor is inversely proportional to the frequency. The harmonic current may result in the problems of voltage distortion and resonance. Capacitor has easily fall under by two harmonic components, a nonlinear load and a distorted utility voltage. The amplified harmonic current and voltage may damage power capacitor. Hence the pre-investigation of harmonic is needed before designing and application the power factor for reducing fault rate. In this paper, we analyzed that voltage and current with harmonics components act on the capacitor under the resonance condition. we concluded that both voltage and current harmonics have an bad effect on the capacitor and current harmonics is a bitter rather than effect by voltage harmonics.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.4
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• pp.473-479
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• 2008

With the advent of mobile phone, digital multimedia broadcasting(DMB) service is to be realized for multimedia data communication. For an acoustic part, a smaller and lighter microspeaker is also soon to be realized as an MP3 song player and a speakerphone. Sound quality in the microspeaker is becoming more important in mobile phones. It is evaluated by total harmonic distortion(THD). THD is the proportion of higher order frequencies output response to sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear response of diaphragm. In this paper, harmonic distortion is analyzed by considering magnetic and mechanical coupling effects. Simulated results of THD are compared with experimental data. Results show that THD in lower frequency range is higher due to high displace on voice coil and high mechanical response of high order frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.236-241
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• 2008

With the advent of mobile phone, Digital multimedia broadcasting (DMB) service is to be realized for multimedia data communication. For an acoustic part, a smaller and lighter microspeaker is also soon to be realized as an MP3 song player and a speakerphone. Sound quality in the microspeaker is becoming more important in mobile phones. It is evaluated by total harmonic distortion (THD). THD is the proportion of higher order frequencies output response to sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear response of diaphragm. In this paper, harmonic distortion is analyzed by considering magnetic and mechanical coupling effects. Simulated results of THD are compared with experimental data. Results show that THD in lower frequency range is higher due to high displace on voice coil and high mechanical response of high order frequency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1100-1103
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• 2004

The paper presents the results of using the fundamental and the low frequency harmonic components of leakage current to study aging of EPDM insulator for contaminated condition by kaolin. The largeer the leakage current during 200ms, the higher harmonic component at 60hz. The harmonic component at 60hz and the odd order harmonics is increase relation without Kaolin Conent. Arcing on the surface was always associated with distortion in the leakage current; hence the low frequency components of the leakage currnent can be used as a means to evaluate the surface degration. Both the fundamental and 3rd & 5th harmonics increase dry-band activity.