Fundamental frequency

About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.

Discrete Rotor Flux and Speed Estimators for High-Speed Shaft-Sensorless IM Drives

Abstract: In numerous motor drive applications, high rotor speed is the key factor for system cost, performance, and overall energy efficiency. As a result of energy crises and global market competition, the specified rotor speed and fundamental frequency of the induction motor (IM) in many drive applications noticeably go up. For the same cost and efficiency reasons, that increase of inverter fundamental output frequency cannot be followed with the increase of pulsewidth modulation (PWM) frequency. Therefore, a very low ratio between the PWM and motor fundamental frequencies is to be expected in the near future. In this paper, the shaft-sensorless drive performance is investigated at high speeds, with a very low sampling to fundamental frequency ratio. As a result, two main problems with rotor flux estimators were discovered: the integration problem in the current-based rotor flux model and the phase error in the voltage-based rotor flux model. Both problems were addressed, and a proper joint solution is suggested. The effectiveness of the proposed solution is tested in a model-reference-adaptive-system-based high-speed shaft-sensorless IM drive. The experimental results collected from the digitally controlled IM drive with a low frequency ratio validate the proposed solution.

Application of MEMS Accelerometer for Detection and Diagnosis of Multiple Faults in the Roller Element Bearings of Three Phase Induction Motor

Abstract: This paper presents a simple, non-electrical contact approach to detect and analyze multiple faults in the roller element bearings of three phase induction motor by vibration analysis using microelectromechanical systems (MEMS) accelerometer. The ability of the proposed method has been investigated experimentally under no load, single phase and unbalanced voltage conditions. The frequency analysis of motor vibration due to bearing fault has been carried out by fast Fourier transform algorithm. The appearance of fault frequencies in vibration spectrum will indicate multiple faults in the bearings and also the existence of side-band frequency components around fundamental frequency component indicates air gap modulation due to bearing fault. Experimentally obtained fault frequencies are compared with analytical values and found that both are closely matching. This indicates that the proposed method can be reliably employed to detect from simple to complex faults in the bearings of induction motor using MEMS accelerometers.

Free vibration analysis of composite beams with overlapping delaminations

Abstract: The free vibration of composite beams with two overlapping delaminations have been solved analytically without resorting to numerical approximation. The delaminated beam is analyzed as seven interconnected Euler–Bernoulli beams using the delaminations as their boundaries. The continuity and equilibrium conditions are satisfied between the adjoining regions of the beams. Lower and upper bounds of the natural frequencies of the delaminated beams are identified by assuming totally ‘free’ and totally ‘constrained’ deformations of the delaminated layers, respectively. The influence of the delaminations on the natural frequencies and mode shapes of the cantilever and clamped–clamped beams are investigated. Results show the dominating influence of the longer delamination on the natural frequency of the beam. Similar trends are observed for the second mode frequency and mode shape of the cantilever beam and the fundamental frequency and mode shape of the clamped–clamped beam. Comparison with analytical and experimental results reported in the literature verifies the validity of the present solution.

Fundamental plasma emission involving ion sound waves

Abstract: The theory for fundamental plasma emission by the three-wave processes L + or - S to T (where L, S and T denote Langmuir, ion sound and transverse waves, respectively) is developed. Kinematic constraints on the characteristics and growth lengths of waves participating in the wave processes are identified. In addition the rates, path-integrated wave temperatures, and limits on the brightness temperature of the radiation are derived.

Multiple fundamental frequency estimation of polyphonic music signals

Abstract: The article is concerned with the estimation of fundamental frequencies, or F0s, in polyphonic music. We propose a new method for jointly evaluating multiple F0 hypotheses based on three physical principles, harmonicity, spectral smoothness and synchronous amplitude evolution, within a single source. Based on the generative quasiharmonic model, a set of hypothetical partial sequences is derived and an optimal assignment of the observed peaks to the hypothetical sources and noise is performed. The hypothetical partial sequences are then evaluated by a score function which formulates the guiding principles in a mathematical manner. The algorithm has been tested on a large collection of artificially mixed polyphonic samples and the results show the competitive performance of the proposed method.