Test procedures have been developed to measure the amplitudes of the motor torque pulsations of a single-phase motor at two times the motor line frequency. The test procedures presented in this paper ...do not require the sue of a dynamometer. The motor was fixed to a torsionally flexible frame. A small centrifugal blower wheel attached to the motor shaft was used to apply a load to the motor. The amplitudes of the motor torque pulsations at specified motor speeds were obtained by first measuring the amplitudes of the torsional accelerations of the motor stator at specified motor speeds and the mass moment of inertia of the motor stator. These values were then substituted into an appropriate equation to calculate the corresponding amplitudes of the motor torque pulsations. For the results reported in this paper, the motor speed was varied by changing the amplitude of the line voltage to the motor. The amplitude of the line voltage to the motor was varied from 50--100% of the rated motor voltage. The motor was operated at its rated line frequency (50 Hz or 60 Hz).
Acoustic noise in the switched reluctance motor (SRM) is caused primarily by the deformation of the stator lamination stack. Acoustic noise is most severe when the periodic excitation of the SRM ...phases excites a natural vibration mode of the stack. The natural vibration modes and frequencies of a four-phase, 8/6 SRM are examined. Structural finite element analysis is used to compute the natural modes and frequencies. Impulse tests on the stator stack verify the calculations and show which modes are excited. Heuristic arguments are developed to predict the operating conditions that will excite the natural modes. Measurement of vibration while the machine is under load shows which operating conditions excite the natural modes and verifies the predictions. An approximate formula is derived to predict the frequency of the fundamental vibration mode in terms of lamination dimensions and material properties. The formula is validated by comparison with finite element calculations for several laminations, and hence is shown to be useful in design trade-off studies.
This paper describes an effective way of reducing acoustic noise in a motor supplied from an adjustable speed PWM drive. The PWM patterns are selected to eliminate the most acoustically sensitive ...harmonics in the motor's vibration spectra. This permits the PWM drive to use more economical yet slower switching devices while maintaining quiet operation. This method is applicable to both voltage source and current source inverters since the current waveform is used as the basis for eliminating the objectionable harmonics.< >
The aim of the paper is to compare the aerial electrodynamic forces on the windings of a large power step-up transformer for three coil designs of the helicoidal LV coil: single layer helix with ...smoothed or nonsmoothed ends and double layer helix. The evaluation of the axial component of the force is made after the leakage magnetic field has been computed by a 3D finite element code.< >
The rotation speed of a turbogenerator is disturbed by its shaft torsion. Obtaining a filtered measure of this speed is a problem of a great practical importance for turbine governors. A solution to ...this problem is explained in this paper. The proposed filter is designed using Kalman's theory. The principles of the design, simulations and tests on the Electricite de France Micro-Network laboratory are presented showing several improvements over the current filter. Moreover, the described solution could be used profitably in all applications where it is necessary to substantially reduce a signal at given frequencies without causing too great a phase shift in the pass-band.
FREE SURFACE MIXING WITH HEAT TRANSFER Road, Peter E.; Fadda, Dani
Numerical heat transfer. Part A, Applications,
11/1/1997, Volume:
31, Issue:
7
Journal Article
Peer reviewed
This study investigates the thermal mixing phenomenon as external rocking excitations are applied to a container partially filled with a thermally nonhomogeneous fluid. The aim of this work is to ...determine the effects of the rocking frequency on thermal mixing in free surface flows. Numerical results show that optimum mixing is achieved while rocking at the wave natural frequency of the tank where the free surface displacements are greatest. At this optimal frequency the strong mixing is observed to be highly concentrated in the area near the free surface.
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