Order Harmonic Components Research Articles

A near unity power factor input stage with minimum control requirements for AC drive applications

Conventional AC induction motor drives use a PWM voltage source inverter (VSI) fed from a diode rectifier. In retrofit applications, due to voltage drops and the inverter voltage gain, six-step operation of the inverter is required at rated speed, resulting in large low order harmonic current and torque components. To allow the inverter to operate in the PWM mode at rated speed, a synchronous rectifier is proposed in this paper to slightly boost the DC bus voltage. The resulting converter system presents all the advantages associated with active front-end rectifiers. However, since the DC bus control requirements are not stringent, a simple control structure is used, the main purpose being to ensure unity power factor operation. Furthermore, optimized PWM patterns and pattern synchronization can be used to reduce the switching frequency of the rectifier. The paper presents a complete analysis and design guidelines for the DC bus supply and inverter systems. Simulation and experimental results confirm the feasibility and advantages of the proposed structure. >

Non-linear dielectric spectra of ferroelectric liquid crystals

Abstract The non-linear dielectric relaxation spectroscopy has been recently developed and applied to soft materials such as polymers. We have applied this new method to the S*C phases of some ferroelectric liquid crystals. Under a weak AC electric field, the original and third order harmonic frequency components of electric displacement are proportional to the first and third powers of the applied electric field, respectively. The linear spectrum obtained from the original frequency component shows the relaxation of Debye type and the third order non-linear spectrum shows the relaxation with an extended form of Debye type to the non-linear case. The third order non-linear dielectric increment is found to be negative, which implies that the dielectric non-linearity of the liquid crystal in the S*C phase is due to the saturation of molecular dipole moments induced by the applied electric field. The temperature dependence of the linear and third order non-linear spectra in the S*C phase are also studied. Bo...

往復動内燃機関クランク軸の振動付加応力波形のシミュレーション

A numerical simulation method by the transfer matrix method is prorosed to compute the vibratiom stress wavef orms of a V-type, 8 cylinder Diesel engine crankshaft in this work. This method will be able to predict the conditions of vibration stresses and be useful to design a crankshaft.The accuracy of this numerical method is considered by comparing the reuslts of the computation with the measured data. As a result of the comparisons with the measured data, it has been assured that the vibration stress wavef orms can be computed with adequate accuracy by considering from 0.5th to 10th or 12th order per 0.5th order harmonic components of exciting forces for a 4 cycele engine.

Improved PWM method of forced commutated cycloconvertors

An unrestricted frequency changer (UFC), a well known forced commutated cycloconverter (FCC), is known to be suitable for variable speed AC drives, because it operates in all four quadrants and generates no subharmonic components. However, lower order undesired components in the output voltage and in the input current are still large and cause problems in practical applications. In the paper, an improved PWM method is proposed to reduce lower order harmonic components. The new method can completely eliminate two undesired harmonic components in the low output voltage ranges with a relatively low switching frequency. This harmonic elimination occurs both on the output voltage and on the input current simultaneously. The harmonic characteristics of the proposed FCC are shown by computer simulations and verified by experiments.

Ac Line Harmonics Caused by Three-Phase Half-Controlled Converters with DC Motor Load

ABSTRACT This paper gives a study of line harmonics generated by three-phase half controlled bridge converters feeding separately excited D.C. motor. Analytical expressions for line current are given and dominant current and voltage harmonics have been computed for a typical system. The study shows that current has predominant low order harmonics, the second harmonic being significantly large as compared to other harmonics. The line voltage, however, has significant higher order harmonic components as well Line current harmonics are dependent on motor operating speed, whereas the voltage distortion factor is nearly independent of speed. On the other hand, percent current harmonics are nearly independent of torque, but the voltage harmonics and voltage distortion factor are dependent on load torque.

The Effect of Efferent Stimulation on the Phase and Amplitude of Extracellular Receptor Potentials in the Lateral Line System of the Perch (Perca Fluviatius)

ABSTRACT Microphonic and summating potentials were recorded extracellularly from lateral line organs in the suborbital canal of the perch in response to sinusoidal movements of canal fluid. These potentials were changed in amplitude, shape and phase, relative to the mechanical stimulus, by electrical stimulation of efferent fibres in the lateral line nerve. The receptor potential amplitude/stimulus intensity relationships for the microphonic and summating potentials saturated at high levels of stimulation, and at progressively lower amplitudes with increasing frequencies of mechanical stimulation. Efferent stimulation tended to reduce this rate of saturation. Amplitude versus frequency relationships plotted at different stimulus intensities for the microphonic potential showed that the lateral line organs were most sensitive to frequencies between 35–65 Hz (centre frequency), and at these frequencies efferent stimulation caused the greatest increase in amplitude. Analysis of the second order and third order harmonic components of the microphonic showed that these were reduced by efferent stimulation and that the strongest reduction occurred at the centre frequency. The phase of the receptor potential led that of the mechanical stimulus at very low frequencies by nearly 90 °. This changed to zero phase at the centre frequency and to a phase lag at higher frequencies. Efferent stimulation caused no change in phase of the microphonic relative to the control state at the centre frequency, but caused a progressive phase lead and lag as the frequency was decreased and increased respectively about the centre frequency. In the linear response range, the lateral line organs responded as critically damped low frequency resonators to the velocity of the stimulus. Efferent stimulation appeared to alter the damping of this resonance. The possibility is discussed that efferent stimulation can alter the mechanical properties of the lateral line hair cells.

低次高調波成分の少ないPWMインバータ波形制御法

低次高調波成分の少ないPWMインバータ波形制御法

Quality improvement of bandlimited speech by adding higher‐order harmonic components produced by nonlinear circuit

In this paper, the system to improve the quality of the bandlimited speech (0.3–3.4 kHz) through a telephone channel by adding the higher order harmonic components (3.4–7.0 kHz) produced by the simple nonlinear circuit is described. The restoration of the bandlimited speech is made based on the fact that most of the voiced sounds have periodicity. At the receive side, the higher‐order harmonic components are produced from the transmitted bandlimited speech by the nonlinear circuit and are added to the bandlimited speech with shaping in tho frequency domain. This nonlinear circuit operates in the way that the periodicity of speech is preserved and the output level is directly proportional to the input level. This system mainly improves the naturalness of the bandlimited speech. The subjective evaluation test using the samples of the speech announced in Japanese proves that improvement of scale value 0.5 by the method of paired comparison with five quality categories is obtained. This system also will be applied to the quality improvement of bandlimited music.