•Investigates losses and efficiency enhancement opportunities in pumping system.•Presents efficient component selection in pumping system.•Suggests energy optimised sizing and dimensioning of piping ...system.•Reviews optimal control and adjustment methods in parallel pumping.•Highlights ongoing research and developments for improving pumping efficiency.
The energy consumption across the globe is increasing at an alarming rate. This has already shown its impact in the depletion of energy sources and environmental issues (global warming, and weakening of the ozone layer). Certainly, this escalating tendency of energy insufficiency will get aggravated in the future. Efficiency enhancement initiatives are considered to be the key solution in reducing the energy utilization and eventually resisting the global environmental impacts. Of the world’s total energy generated, pumping systems, especially the centrifugal pumps consume about 20%. Consequently, the primary focus of global energy policy makers is to enhance energy efficiency in pumping systems. As per the literature, remarkable energy savings can be accomplished by controlling the speed of the pumping system using Variable Frequency Drives (VFDs). For this reason, studies and researches focus primarily on VFD control techniques to improve the efficiency of the pumping system. This article also focuses on component selection, and system dimensioning in addition to the control techniques. Comparison of recent research outcomes of energy efficiency improvements in pumping system has been made to provide an insight for future research.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This article proposes a high-level engineering guide to develop an integrated system model for power quality analysis in electrical submersible pump (ESP) applications with variable frequency drives ...(VFDs). Such analyses are troublesome in the industry due to the complexity of these systems. In this article, simple steps to perform system integration analyses of such arrangements, including torsional analysis, are developed. A simplified VFD-ESP model suitable for coupled electrical and mechanical analysis in steady state is proposed in all their configurations of practical interest. Such a model can be easily implemented in common simulation software, significantly reducing engineering efforts for implementation and analysis. The focus of the proposed model is the prediction of ESP failures that might result from a poor power quality caused by VFDs. Analytical expressions of different types of harmonics in these systems, as well as their accurate locations in the frequency domain, including their interharmonics and common-mode harmonics, are derived for this purpose. Further, the effectiveness of the proposed model is verified through offline and real-time hybrid simulation results. Finally, a comparison between simulation results obtained using the proposed model and measurements collected on a down-scale laboratory prototype is carried out to demonstrate the accuracy of the suggested modeling approach.
Partial discharge (PD) due to high dv/dt pulsewidth modulation has been identified as one of the leading causes of insulation failure in low voltage (LV) variable frequency drive (VFD) fed motors ...with random wound stator windings. With the recent increase in electrical stress with faster risetime wide bandgap power semiconductor devices and higher dc link voltage for higher efficiency and power density of the system, PD-induced insulation failures are expected to increase. Since LV motor insulation is not resistant to PD, an increasing number of VFD motors are being qualified for PD-free operation. However, the PD inception voltage of qualified motors decreases with insulation aging making LV motors susceptible to failure. In this article, an offline standstill test method is proposed for automated inverter-embedded PD testing under impulse excitation. The main concept is to perform the impulse PD test using the VFD at increased voltage levels for providing advanced warning of PD activity for preventing forced outage of VFD motors. Options for application of increased impulse test voltage and automated detection of PD for implementing the proposed concept are presented. Testing on an 800 V VFD driven motor shows that the proposed method can provide automated impulse PD testing whenever the motor is at standstill to warn the end user of impending PD activity that can lead to failure.
In this article, an effective machine learning-based fault diagnosis method is developed for induction motors driven by variable frequency drives (VFDs). Two identical 0.25 HP induction motors under ...healthy, single-, and multifault conditions were tested in the lab with different VFD output frequencies and motor loadings. The stator current and the vibration signals of the motors were recorded simultaneously under steady-state for each test, and both signals are evaluated for their suitability for fault diagnosis. The signal processing technique, discrete wavelet transform, is chosen in this article to extract features for machine learning. Four families of machine learning algorithms in the MATLAB Classification Learner Toolbox, decision trees, support vector machines, k -nearest neighbors, and ensemble, with 20 classifiers are evaluated for their classification accuracy when used for fault diagnosis of induction motors fed by VFDs. To allow fault diagnosis for untested motor operating conditions, the feature calculation formulas are developed through surface fitting using experimental data of a range of tested frequencies and loadings of the motor to provide training data for untested conditions.
Smart condition-based maintenance is a critical aspect of Industry 4.0, ensuring the reliable and long-term operation of devices powered by Variable Frequency Drives (VFDs). Detecting early signs of ...failures in VFDs involves analyzing input data from sensors, including temperature signals, among others. However, due to the complexity of VFD operation, there persists a need for unified approaches to effectively detect anomalies. In this paper, we propose a novel anomaly detection pipeline that integrates a diverse set of models and introduces an innovative anomaly metric called the "Out Of Bounds Anomaly Score" (OBAS). The OBAS metric simplifies model output interpretation and lays the groundwork for an easy-to-use ensemble learning framework. Our approach leveraged temperature signals obtained from both real-world and simulated VFD operation scenarios, specifically wind turbine and virtual drive, respectively. We explored four key methodologies: Hidden Markov Models, Deep Autoencoders, and Principal Component Analysis. These methodologies were employed to detect periodic temperature increases, temperature shifts, and temperature profile changes after retrofit. We compared these models against classical anomaly detection tools such as exponential smoothing, moving average, and Hampel Filter. Our study showed a comprehensive pipeline for anomaly detection, seamlessly integrating different machine/deep learning models with OBAS, which facilitated comparisons of their performance. Furthermore, OBAS fostered construction of ensembles of models of different architectures and outputs. This helped to stabilize anomaly predictions yielding 2-10% improvement in accuracy. This research contributes to advancing anomaly detection in VFDs, bridging the gap between existing techniques and the evolving demands of Industry 4.0.
Embedded variable frequency induction motor drives are now an integral part of any industry due to their improved speed regulation and fast dynamic response. Hence, their diagnosis becomes vital to ...avoid downtimes and economic losses. In this paper, a technique based on a recent enhancement on wavelets, known as complex wavelets, is proposed for identifying multiple faults in vector controlled induction motor drives (VCIMDs). Radial, axial, and tangential vibrations are analyzed for diagnostic purpose. Initially, a relatively simple thresholding based method is investigated for feasibility of diagnosis under variable frequency and load conditions. In the second part, the feature extraction and classifier modeling are discussed, in which the nearly shift-invariant complex wavelet based model is compared with the discrete wavelet transform (DWT) for its applicability in detecting multiple faults. The fault conditions considered here are the most prominent ones such as interturn fault, interturn fault under progression, and bearing damage. Comparable performances of support vector machine (SVM) based models and simple technique based on k-nearest neighbor (k-NN) show the importance of efficient representation of input space by analytical wavelet based feature extraction. The performance indexes show the applicability of the scheme for industrial drives under variable frequencies and load conditions.
Electrical stresses in industrial variable frequency drive (VFD) motors are increasing with the higher voltage and dv/dt levels, and with the advent of wide bandgap power devices. This increases the ...likelihood of partial discharge (PD) in VFD motors, and is expected to increase the risk of stator insulation failures in low voltage (LV) motors for which the insulation is not resistant to PD. To ensure that PD does not occur during operation, LV VFD motors are qualified for PD-free operation in the design or manufacturing stages. However, the PD inception voltage of qualified LV motors decreases with insulation aging exposing them to the risk of PD-induced insulation failure. In this paper, an automated off-line test method for VFD-embedded PD testing is proposed. The main idea is to perform PD testing whenever the motor is stopped at a voltage higher than the operating voltage to identify PD activity in the insulation before it occurs during operation. A series impulse and common mode voltage tests are proposed for stressing the different components of insulation for early identification of PD in terminal-/neutral-end ground, phase, and turn insulation. Testing on a LV, VFD motor verifies that PD can be identified whenever the motor is stopped to provide early warning of insulation failure.
This article proposes a high-level engineering guide to develop an integrated system model for power quality analysis in electrical submersible pump (ESP) applications with variable frequency drives ...(VFDs). Such analyses are troublesome in the industry due to the complexity of these systems. In this article, simple steps to perform system integration analyses of such arrangements, including torsional analysis, are developed. A simplified VFD-ESP model suitable for coupled electrical and mechanical analysis in steady state is proposed in all their configurations of practical interest. Such a model can be easily implemented in common simulation software, significantly reducing engineering efforts for implementation and analysis. The focus of the proposed model is the prediction of ESP failures that might result from a poor power quality caused by VFDs. Analytical expressions of different types of harmonics in these systems, as well as their accurate locations in the frequency domain, including their interharmonics and common-mode harmonics, are derived for this purpose. The effectiveness of the proposed model is verified through offline and real-time hybrid simulation results. Finally, a comparison between simulation results obtained using the proposed model and measurements collected on a down-scale laboratory prototype is carried out to demonstrate the accuracy of the suggested modeling approach.
Typically, in partial discharges (PD) diagnostics tests carried out in a laboratory, harmonic content in a voltage waveform is ignored. However, during the operation of variable-frequency drives ...(VFD)-fed electric motors, the distorted voltage waveform is produced due to the addition of harmonics components in the sinusoidal voltage waveform. The distortion level increases when the VFD is operated at a lower speed ratio. The additional spectral components in the applied voltage waveform can have a significant impact on the PD behavior in the insulation of the electric motor. Therefore, during online PD monitoring, overlooking the harmonic regime in the applied voltage may lead to a false interpretation of PD data. This article investigates the influence of voltage harmonics distortion produced during the variable-speed operation of VFD on PD characteristics. For this purpose, online PD measurements have been carried out by performing a series of experiments on eight VFD-fed motors under variable operating conditions. The PD severity at different harmonic compositions is experimentally investigated by determining various PD characteristic parameters including PD inception voltage, accumulated apparent charge, average discharge current, discharge power, and quadratic rate. Also, two terms Gaussian models have been mathematically developed using 288 data samples to quantify the variations in PD characteristic parameters against distortion parameters. The article proposes a framework for properly evaluating harmonics impact in PD for electric motors and correctly estimating stator insulation degradation.
This article investigates discharge bearing currents in inverter-fed electric motors. Industrial reports indicate that among prevalent bearing failures, bearing currents are one of the influent ...drivers leading to a variety of tribological issues and premature wear in bearings. While the root-causes of bearing currents have been extensively reported over the years, the response of bearing under voltage stress and the factors that influence bearing endangerment through electric discharges have been far less studied. An online measurement of the bearing voltage is proposed on a motor test-bench to estimate both the discharge activity and the energy of the discharges. The designed test bed allows reproduction of representative bearing currents leading to electrical micropitting. This paper presents extensive measurements results that highlight the critical operating conditions and parameters that worsen the discharge phenomenon inside bearings. Testing protocols are performed to quantify the influence of each parameter separately. While the bearing voltage magnitude play a significant role in the discharge phenomenon, other parameters such as successive startups, bearing temperature, and type of grease deserve appropriate investigations to avoid or mitigate the well-known shortened bearing life under inverter operation.
