Figure - available from: International Transactions on Electrical Energy Systems
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Relationship between total harmonic distortion in the current (THDi), total harmonic distortion in the voltage (THDv) and load ratio when only a single variable frequency drive system is energized
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A tremendous increase in the industrial and commercial applications of low voltage variable frequency drives (VFD) has been observed in the last decade. VFD are mainly used for energy saving and reliable speed control of industrial motors in an electrical system. However, power quality issues are becoming more apparent due to the installation of VF...
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Good power quality is required in health facilities since the increasing use of microprocessor-based equipment. Poor power quality in the electric power system can cause medical equipment in health care centers to malfunction and give incorrect medical diagnoses. Since 2020 we are facing a new type of Virus (Covid-19), this virus requires special l...
Citations
... And further analysis was conducted on the performance of cooling units under different field conditions [13,14]. Some scholars have also proposed using a physical-mathematical model to establish an energy consumption prediction model for chiller units [15][16][17][18]. They have explored solutions that involve utilizing intelligent algorithms for optimizing the operational parameters of chiller units [19][20][21]. ...
... The variable frequency drives (VFD) fed electric motors (EMs) are widely used in automotive, ship, aviation, and manufacturing industries due to their cost efficiency, reliable speed control, lightweight, high specific power, and energy-saving capabilities [1][2][3]. However, when VFD-fed EMs are in operation, the harmonic components in the applied voltage waveform may develop, which could lead to premature insulation failure of the stator winding over time [4]. Therefore, online condition monitoring of VFD-fed EMs is essential to detect any preemptive winding insulation failure and plan regular maintenance activities [5,6]. ...
... A test bench for online PD measurement is set up to study the PD activity with different voltage harmonic distortion levels by recording the PD sweep signals of 20 ms. Both the 5th and 7th harmonic components are generated during the operation of 12-pulse VFD [4]. Additionally, the concentration of these harmonic components in the applied voltage waveform increases when the speed of VFD slows down. ...
... During the first set of experiments, the VFD is manually adjusted to set the operating speed of the EM at 100% of the designed speed. Based on our previous experimental results [4], the THD V calculated at this speed is approximately 4.5%, meeting the standards [22], and a nearly sinusoidal waveform of voltage was produced. To ensure thermal stability, the VFDfed EM is operated at this speed for 10-15 min. ...
Partial discharge (PD) diagnostics test is a reliable solution for estimating insulation health conditions in power system components. During laboratory PD diagnostics, the effect of harmonic components in the voltage waveform generated by variable frequency drives (VFD) fed electric motors (EMs) is often overlooked. As VFD‐fed EMs operate at low speeds, the harmonic concentration in the voltage increases. It has been found that PD activity in VFD‐fed EM is significantly affected by the addition of harmonic components in the voltage, thus making it necessary to consider their impact when performing true PD diagnostics. This paper investigates the influence of voltage harmonic distortion produced in VFD‐fed EM on PD severity and the subsequent insulation degradation. Eight VFD‐fed EM are used to study the PD behaviour under different levels of harmonic pollution. The PD characteristics, such as inception voltage, pulse repetition rate, accumulated apparent charge, average discharge current, discharge power, and quadratic rate, are determined. Using probability distribution functions, PD activity and severity at various voltage harmonic levels are estimated. The proposed technique can be used to plan the maintenance activities that ensure the reliability for industrial applications dealing with the voltage harmonic distortion.
... As a new type of high-efficiency air-conditioning technology, centrifugal air-conditioning chillers have attracted a lot of attention in recent years due to their high energy-saving efficiency and excellent load performance (Hassan et al., 2020;Deng and Yang, 2020). As the core equipment of air-conditioning, chillers are widely used in all walks of life. ...
... In the commercial buildings, HVAC systems are designed with electric motors driven fans, pumps and compressors for the movement of air, water and refrigerant. HVAC systems account for approximately 40-50% of the total energy consumption in the commercial and residential buildings (3)(4). Hence, the overall efficiency of electrical energy utilization is directly related with the performance of the HVAC system in use (3). ...
... HVAC systems account for approximately 40-50% of the total energy consumption in the commercial and residential buildings (3)(4). Hence, the overall efficiency of electrical energy utilization is directly related with the performance of the HVAC system in use (3). As a result, it's critical to assess HVAC systems performance in commercial and residential buildings with the goal of improving their efficiency. ...
With the goals of a better power factor and reduction in energy use, variable frequency drives (VFDs) have been standardized in various industrial applications including Heating, Ventilation, and Air-conditioning (HVAC) systems. However, key issues related to the deterioration in the power quality associated parameters (voltage harmonic distortion and current harmonic distortion) due to the growing number of VFDs demand a wholesome analysis of the problems faced by the users. In this present work, an analysis has been performed to investigate the potential impact of using alternating current (AC) line reactor and direct current (DC) link choke combination on harmonic mitigation in a VFD driven water-cooled centrifugal chiller compressor. Using a combination of AC line reactor and DC link choke as one of the low cost solutions in harmonic mitigation of a VFD driven load in HVAC systems can be decided based on the investigation done in this research work.
... T HE variable-frequency drives (VFD)-fed electric motors used in industrial and commercial applications are widely used because of their reliable speed control and significant energy saving [1]- [3]. However, the nonlinear operation of the VFD system in terms of variable speed can not only cause power quality (PQ) problems, but can also lead to the premature failure of the stator's insulation over the prolonged operation time [4]- [6]. Therefore, the preemptive failure detection in the stator insulation based on condition monitoring is required to design appropriate maintenance strategies. ...
... For this purpose, 12-pulse VFD have been used in the experimental work and 8 motors have been prepared by artificially developing the contamination defect under laboratory conditions [26]. It has already been investigated that 12-pulse VFD mostly produces fifth and seventh harmonic orders and the concentration of harmonic pollution increases at low N r [6]. Therefore, a nonintrusive condition monitoring technique can be employed on the VFD system and harmonic contents may be measured at variable N r . ...
... The reduction in the applied voltage at the lower speed increases the overall harmonic contents. The experimental-based study to measure the THD v at variable operating conditions has already been carried out in [6]. Fig. 2 presents the relationship between THD v and variable N r for eight VFD-fed electric motors. ...
Typically, in partial discharges (PD) diagnostics tests carried out in laboratory, harmonic content in 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 additional spectral components in the applied voltage waveform can have a significant impact on the PD behavior in the insulation of electric motor. Therefore, during online PD monitoring, overlooking the harmonic regime in the applied voltage may lead to a false interpretation of partial discharge data. This paper 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 mechanisms using VFDs can be conditionally divided into two groups. The first one comprises units, in which the automatic speed control based on any process parameter (fluid pressure in the pipeline, fluid level in the sump, air depression in the ventilation duct, etc.) allows saving energy [12][13][14][15]; these include pumps and fans. The second group is the mechanisms, the speed of which should be controlled to ensure the required process unit operating modes [16,17]. ...
Mining enterprises are energy intensive facilities. The capacity of single technological units can reach 5 MW. Variable-frequency drive systems are often used to set them in motion. The paper analyzes the features of choosing and using variable-frequency drives under diamond mining conditions. The study objective is to formulate and formalize the problems of introducing and operating variable-frequency drives at diamond-mining enterprises to further develop and implement guidelines for improving the performance of this drive type. To achieve this objective, the use of variable frequency drives in various process units of diamond mining should be studied and analyzed. The units are considered, for which in recent years, electric drive systems have been groundlessly (according to the authors) chosen by the engineering staff of enterprises. A technical and economic comparison of low-voltage frequency converters with the same power but different control modes is performed. The economic indicators of introducing high-voltage and low-voltage frequency converters into an existing electric drive system are calculated and represented as a comparative table. Conclusions are made on the need to proceed with the research and develop guidelines for implementing frequency converters at diamond-mining enterprises.
... Many papers in the literature have studied the diagnosis and condition monitoring of the IM rotor, but most only deal with machines operating at a constant speed and whole broken rotor bars. Nowadays, variable speed systems where the IM is driven by voltage source inverters (VSIs) are more common; they are used in a wide range of applications-namely, material handling, lifting, textile, compressors, pumps, mills, winders, and lifts [4]. These VSIs are usually pulse width modulators (PWM) that produce non-sinusoidal voltages using a solid-state inverter by rapidly switching the output voltage on and off. ...
The fault diagnosis of electrical machines during startup transients has received increasing attention regarding the possibility of detecting faults early. Induction motors are no exception, and motor current signature analysis has become one of the most popular techniques for determining the condition of various motor components. However, in the case of inverter powered systems, the condition of a motor is difficult to determine from the stator current because fault signatures could overlap with other signatures produced by the inverter, low-slip operation, load oscillations, and other non-stationary conditions. This paper presents a speed signature analysis methodology for a reliable broken rotor bar diagnosis in inverter-fed induction motors. The proposed fault detection is based on tracking the speed fault signature in the time-frequency domain. As a result, different fault severity levels and load oscillations can be identified. The promising results show that this technique can be a good complement to the classic analysis of current signature analysis and reveals a high potential to overcome some of its drawbacks.
... Electric motors play a vital role in process industries because of their reduced operational cost and energy consumption. The performance of the motors is improving with the advanced technologies and design, as compared to the mechanical and pneumatic systems [1][2][3][4][5]. However, the reliability of motors is mainly dependent on the stator insulation condition. ...
Partial discharge (PD) diagnostics is a reliable technique for the health assessment of electrical motors. This paper presents a unique methodology for the failure risk assessment of the low voltage motors containing various insulation defects based on PD measurements. The severity of PD in the motors increases with the time during their operation due to electrical and environmental stresses. In this work, several artificial PD defects have been created in low voltage induction motors under laboratory conditions. Accordingly, the characteristic parameters of PD measured in the laboratory for the artificial defects are evaluated to identify their impact on the resulting degradation of the insulation. Furthermore, the classification of these defects has been carried out based on cumulative energy function using K-mean clustering algorithm followed by the estimation of insulation lifetime. In this regard, Weibull distribution has been employed to quantify the probability of failure and risk evaluation corresponding to the severity of PD defects. The proposed risk assessment framework may be utilized to support asset managers in scheduling the regular maintenance activities and assist them in decision making about the type of actions required to eliminate the latent threat.
