Second-order Harmonic Component Research Articles

Online fault-detecting scheme of an inverter-fed permanent magnet synchronous motor under stator winding shorted turn and inverter switch open

To detect faults in an inverter-fed permanent magnet synchronous motor drive under the circumstance having faults in a stator winding and inverter switch, an online basis fault-detecting scheme during motor operation is presented. The proposed scheme is achieved by monitoring the second-order harmonic component in q-axis current and the fault is detected by comparing these components with those in normal conditions. The non-fault harmonic data in an arbitrary operating condition are determined using the linear interpolation method with several sample harmonic data pre-measured in the stage of the initial drive setup. Once the fault is detected, the operating mode is changed to identify a fault source using the phase current waveform. To verify the effectiveness of the proposed fault detecting scheme, a test motor to allow inter-turn short in the stator winding has been built. The entire control system including harmonic analysis and fault detecting algorithm is implemented using digital signal processor TMS320F28335. Without requiring an additional hardware, the fault can be effectively detected by the proposed scheme during operation so long as the steady-state condition is satisfied.

전류 고조파 관찰을 통한 영구자석 동기전동기의 권선 단락 고장 진단 기법

To diagnose a stator winding fault caused by a short-circuited turn in a permanent magnet synchronous motor (PMSM), an on-line based fault detecting scheme during motor operation is presented. The proposed scheme is based on monitoring the second-order harmonic components in q-axis current obtained through the harmonic analysis and a winding fault is detected by comparing these components with those in normal conditions. The linear interpolation method is employed to determine harmonic data in arbitrary normal operating conditions. To verify the effectiveness of the proposed fault detecting scheme, a test motor to allow inter-turn short in the stator winding has been built. The entire control system including harmonic analysis algorithm and fault detecting algorithm is implemented using DSP TMS320F28335. The proposed scheme does not require any additional hardware and can effectively detect a fault during motor operation so long as the steady-state condition is satisfied.

Torque Ripple Suppression in Flux-Switching PM Motor by Harmonic Current Injection Based on Voltage Space-Vector Modulation

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The flux-switching permanent-magnet (FSPM) machine is a relatively novel brushless machine having magnets and concentrated windings in the stator instead of rotor, which exhibits inherently sinusoidal back-EMF waveform and high torque capability. However, due to the high airgap flux density produced by magnets and the salient poles in both stator and rotor, the resultant torque ripple is relatively large, which is unfavorable for high performance drive system. In this paper, instead of conventional optimization on the machine itself, a new torque ripple suppression approach is proposed in which a series of specific harmonic currents are added into <formula formulatype="inline"> <tex Notation="TeX">$q$</tex></formula>-axis reference current, resulting in additional torque components to counteract the fundamental and second-order harmonic components of cogging torque. Both the simulation and experimental results confirm that the proposed approach can effectively suppress the torque ripple. It should be emphasized that this method is applicable to all PM machines having relatively large cogging torque. </para>

권선 단락 및 스위치 개방 고장 시의 인버터 구동 영구자석 동기전동기의 고장 진단 기법

인버터 구동 영구자석 동기전동기에서 고정자 권선과 인버터 스위치에 고장이 존재할 때 동작 중 실시간으로 고장을 검출하고 고장의 유형을 판별할 수 있는 진단 기법이 제시된다. 제안된 기법은 q축 전류의 2차 고조파를 실시간으로 관찰함으로써 이루어지며 고장이 없는 정상 조건에서의 고조파 데이터와 비교를 통해서 고장을 판별한다. 임의의 정상 동작 조건에서의 고조파 데이터는 선형 보간법을 이용해 구해진다. 고장 검출 시 진단 알고리즘은 고장 유형 판별모드로 전환되어 상전류의 파형 분석을 통해 고장의 유형을 판별한다. 제안된 고장 검출 기법의 타당성을 입증하기 위해 내부 권선 단락이 가능한 전동기가 제작되었으며 전체 시스템과 고조파 분석 및 고장 검출 알고리즘이 DSP TMS320F28335에 의해 구현된다. 제안된 방법은 부가적인 진단 장비를 요구하지 않으며 정상상태 조건이 만족된다면 동작 중 실시간으로 고장을 검출할 수 있다.

The effect of nonlinear parameters in one-dimensional mixed Klein-Gordon/Fermi-Pasta-Ulam chain

The possible discrete breathers are obtained numerically in the system of one-dimensional mixed Klein-Gordon/Fermi-Pasta-Ulam chain on the basis of simplified motion equations by using extended rotating plane wave approximation. Furthermore，the effect of each nonlinear parameter on the static，first-order harmonic and second-order harmonic components of the discrete breathers is investigated.

Instantaneous Visualization of K-Band Electric Near-Fields by a Live Electrooptic Imaging System Based on Double Sideband Suppressed Carrier Modulation

This paper discusses instantaneous electric near-field imaging in the K-band. The imaging technique is based on the live electrooptic imaging (LEI) scheme, which was originally developed for electric near-field imaging in the microwave range. The measurement frequency of the LEI system is extended by using the second-order harmonic component of modulated light as a photonic local oscillator signal. We demonstrated electric near-field imaging over rather ordinary components such as an SMA connector and a microstrip transmission line at frequencies up to 25 GHz.

Sagnac-loop-based equivalent negative tap photonic notch filter

A new structure that can realize an all-optical equivalent two-tap negative tap photonic notch filter response is presented. It is based on a Sagnac fiber loop interferometer containing an optical phase modulator. An equivalent two-tap negative tap notch filter response is obtained by phase modulating the clockwise and counterclockwise propagating optical waves inside the Sagnac loop at different times. Results demonstrate a robust notch filter response using a narrow-linewidth optical source with no phase-induced intensity noise and no second-order harmonic component present at the output.

Rotationally invariant pattern recognition in a photorefractive joint transform correlator using circular harmonic filters and the wavelet transform

A photorefractive joint transform correlator using circular harmonic filters and the wavelet transform for high discriminant and rotationally invariant pattern recognition is reported. In the experimental implementation, a photorefractive crystal, BSO, is used as the dynamic holographic medium and a bank of wavelet functions, derived from a mother Mexican-hat wavelet have been selected to achieve a band-pass operation in the Fourier domain. The zero-order and second-order circular harmonic components are used in the investigation. It is shown that, with the proper dilation factors, there is a trade-off between peak correlation intensity and signal-to-noise ratio (SNR) with the wavelet transform filters. With the second-order circular harmonic, an improvement of 63% in the SNR is achieved with only a 4% loss in the peak correlation intensity.

Independent [formula omitted] and 2[formula omitted] Distortions in the Incommensurately Modulated Low-Temperature Structure of NiTa2Se7

The modulated low-temperature structure of NiTa1.98Nb0.02Se7 has been determined by X-ray diffraction using synchrotron radiation. The superspace group of the modulated structure at 15 K is C2/m (0, qb, 0) s0 with qb=0.483(2). The lattice parameters were determined to a=13.807(6) Å, b=3.483(1) Å, c=18.564(11) Å, and β=108.95(4)° with Z=4. Satellite reflections up to second order were measured. Refinement with first- and second-order harmonic components of the modulation functions converged to R=0.059. The first-order harmonic was found predominantly on the double chain of Ni and Se2 atoms. Shifts were found parallel to the a→ and c→ axes, in good agreement with earlier investigations. The major part of the second harmonic was found on the Ta2 atoms, with amplitudes of secondary importance on the surrounding Se atoms. Shifts of the Ta2 atoms were found parallel to b→, thus forming a longitudinal wave. It is argued that the modulations according to the first-order and the second-order harmonics should be considered as independent CDW's.

Nonlinear tidal waves in channels: A perturbation method adapted to the importance of quadratic bottom friction

Bottom friction plays an important role in propagation and damping of long waves in shallow water. A perturbation method, well adapted to the importance of this bottom stress, is presented and applied for channels with constant mean depth and mean cross-section area. The main idea results from a development of quadratic bottom friction in a Fourier series up to the third order of approximation. A quasi-linearization of the damping effect of bottom stress is deduced from this expansion, which allows one to introduce the second-order damping effects of friction into the first-order system defining the fundamental component of the spectrum, and the main part of the third-order damping terms into the computation of the second-order harmonic components. From this expansion, the generating role of the harmonic played by friction is also identified and taken into account in the second-order approximation. Analytical and analytico-numerical solutions are presented and compared to numerical solutions of the full nonlinear equations obtained by the Lax-Wendroff finite-difference integration technique. These comparisons show that the analytical solutions limited to the second-order approximation fit very well with the L.W. solutions. DOI: 10.1111/j.2153-3490.1980.tb00942.x