This paper presents the results of a study about the effects of unbalanced voltages on the energy performance of three-phase induction motors. The principal contribution of this paper is that presents a detailed analysis of the influence of positive and negative sequence voltage components and the angle between them on several characteristics such as: line currents, losses, efficiency and power factor under different voltage unbalanced conditions. A three-phase induction motor of 3 HP was used as a case study. The results of the investigation show that the positive sequence voltage must be considered together with the voltage unbalance factor (VUF) or percent voltage unbalance (PVU) index to evaluate the performance of the induction motor. It is also shown that the behavior of the motor load influences on the positive sequence parameters next to the voltage, while in the case of negative sequence only influences the negative sequence voltage. Keyword: Efficiency INTRODUCTIONThe analysis of induction motor operation is important because these represent most of the installed load in industrial systems due to its reliability, power to size ratio, ruggedness and relatively low cost [1]. In addition, they consume approximately 68% of the electric power in this sector [2]. The problems associated with energy quality, constitute an everyday phenomena. Unbalanced voltages, which in most cases occurs associated with voltage deviations, is one of the most common in terms of energy quality and has a direct influence on the increase of losses in electric motors and systems [3].The presence of unbalance is due mainly to the existence of unbalanced loads, unsymmetrical transformer windings or transmission impedances, large single-phase loads, incomplete transposition of transmission lines, open delta transformer connections, blown fuses on three-phase capacitor bank, operation of single-phase loads at different times, defective transformers in power systems, or when one of the threephases of the motor is open [4], [5]. These problems significantly affect the efficiency and other operational characteristics of the induction motors.The operation of induction motor under voltage unbalance conditions produce two rotating fields in the motor air gap, one in the forward direction of the motor rotation (positive sequence) and another in the opposite direction (negative sequence), giving as result an elliptical field [6]. Consequently for a given load and percentage of voltage unbalance, the phase currents and temperature rise much greater than when operating under the same load conditions and balanced voltages, affecting the motor performance.
Voltage Unbalance (VU) is one of the most common power quality problems in industrial electrical systems and it is a subject of systematic study. This problem affects the operation and the efficiency of Induction Motors (ims), which are the loads that demand more energy in the industrial sector with around 68%. The Voltage Unbalance Factor (VUF), defined by the international IEC standard, is the main factor used to characterize this problem. This article aims to present a theoretical analysis of VUF focused on its limitations for characterizing the effects of VU on ims. As a result of the analysis, it is shown that the use of the VUF indicator only is insufficient since it does not consider other aspects that affect the operation of the ims such as voltage variation. As an alternative, the use of the Complex Voltage Unbalance Factor and the Equivalent Voltage Magnitude Factor are suggested as parameters that, together with the VUF, allow deepening the characterization of the effects of the UV on the ims.
<p>Se fabricaron recubrimientos barrera térmica depositando polvos de CoNiCrAlY y YSZ, los cuales constituyeron las capas de enlace y superior, respectivamente. La primera se depositó sobre el acero inoxidable AISI 304 mediante un sistema de oxígeno combustible de alta velocidad; mientras que la segunda se depositó mediante un sistema de rociado por plasma atmosférico. Los recubrimientos se trataron térmicamente a 1200 °C por 8 y 16 h con el fin de determinar la evolución del estado de esfuerzos residuales en función del tiempo. Los perfiles de esfuerzos residuales se determinaron empleando el método de remoción de capa modificada y una adaptación de éste para recubrimientos bicapa, llamado método de remoción de capa modificada para recubrimientos dúplex. Se encontró que conforme el tiempo de exposición se incrementó los esfuerzos residuales de compresión incrementaron, siendo más notorios en las capas de enlace. Los recubrimiento sin tratamiento térmico revelaron esfuerzos residuales de tensión.</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
334 Leonard St
Brooklyn, NY 11211
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.