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Go to Editorial ManagerIn this work, a new computerized measurement system for multi-plane flexible rotor balancing has been designed and implemented. This system can be used to modernize and enhance conventional low-speed balancing machines or for field balancing applications. This system adds very important features to balancing machines such as multi-plane flexible rotor balancing, high accuracy, stability, and high dynamic range. Also, the proposed flexible rotor balancing technique permits accurate balancing of high-speed rotors utilizing low-speed balancing machines or field balancing at speeds lower than the critical speeds. The proposed digital Wattmetric technique in conjugation with advanced measurement circuitry have led to significant improvement in balancing accuracy even when the unbalance signal is buried into high level of noise.
A method based on experimentally calibrated rotor model is proposed in this work for unbalance identification of flexible rotors without trial runs. Influence coefficient balancing method especially when applied to flexible rotors is disadvantaged by its low efficiency and lengthy procedure, whilst the proposed method has the advantage of being efficient, applicable to multi-operating spin speeds and do not need trial runs. An accurate model for the rotor and its supports based on rotordynamics and finite elements analysis combined with experimental modal analysis, is produced to identify the unbalance distribution on the rotor. To create digital model of the rotor, frequency response functions (FRFs) are determined from excitation and response data, and then modal parameters (natural frequencies and mode shapes) are extracted and compared with experimental analogies. Unbalance response is measured traditionally on rotor supports, in this work the response measured from rotating disks instead. The obtained results show that the proposed approach provides an effective alternative in rotor balancing. Increasing the number of balancing disks on balancing quality is investigated as well.
In this work, a portable vibration analysis and diagnosis system is designed and constructed. The system is capable of doing most of the known analysis techniques such as FFT, time waveform, cepstrum analysis, dual channel analysis, orbit, envelope detection and other techniques. Furthermore, a new fast and efficient tracking analysis algorithm, suitable for portable instruments, has been proposed. This technique provides the data required to get accurate Bode and Nyquist plots for diagnostic analysis during machine run-up and coast-down tests. Moreover, FFT waterfall and spectrogram techniques have been included. Also, single-plane and dual-plane field balancing have been implemented in this system to execute field balancing tasks.
Low-voltage (LV) residential distribution networks are highly susceptible to voltage unbalance due to the stochastic and time-varying nature of residential single-phase loads. The assessment methodologies based on snapshots have a difficulty in allowing the spatial and temporal characteristics of the unbalance events. Based on 10-minute resolution time-series unbalanced power flow simulation in OpenDSS, this paper introduces a time-dependent evaluation framework. While the time-varying load profiles and Monte Carlo analysis represent the variance in daily load and uncertainty in phase allocation, respectively. The parameters include both voltage unbalance assessment indexes (i.e., Voltage Unbalance Factor (VUF), Phase Voltage Unbalance Rate (PVUR)), as well as temporal risk indicators (i.e., Time-at-Risk (TAR) and a TimeDependent Unbalance Risk Index (TD-URI)). The analysis produced shows voltage unbalance behaves transitory and locational, being most threatening during peak demand and faraway buses. The quantity and duration of unbalance events are reduced significantly with the help of phase balancing. The framework has been reconciled with the EN 50160 and it aims to buttress a tangible foundation for planning-oriented voltage unbalance evaluation and remediation in low-voltage residential networks.