This paper presents the application of a method to determine the output power, losses, and efficiency of induction motors, working in no-controlled conditions, in the presences of unbalanced and harmonics voltages. The method uses the steady state equivalent circuits, with some considerations for the analysis of motor performance, fed with unbalanced and harmonic voltages. The parameters of circuits are determined with low invasiveness, by applying a Bacterial Foraging Algorithm as technique of evolutionary search. With this, the efficiency and other operational parameters can be estimated at any operating point. The method was tested in a 12.6 kW motor working in an industrial network, with harmonics and voltage unbalanced.Index Terms--Equivalent circuits, energy management, harmonic analysis, induction motors, industrial power systems, power quality, parameter estimation, unbalanced voltage.Vladimir Sousa and Milén Balbis, are with GIOPEN of the Electrical Engineering program in Faculty of Engineering

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.

This paper evaluates the harmonic distortion generated by PWM motor drives in an electrical industrial system of a wheat flour mill company. For this, a comparative study between two industrial circuits connected at the same point of common coupling (PCC) with similar characteristics of load and transformers is presented. The difference is that one circuit has PWM motor drives and the other does not have them. In the study, a practical method based on the statistical characterization of the total harmonic distortion of voltage (THDV) and current (THDI), individual voltage distortion (IVD), individual current distortion (ICD) and K-Factor is applied. As result, it was observed that PWM motor drives generated voltage harmonics mainly of fifth and seventh order with values that exceed limits established by standards in both circuits. With these values, the operation of elements such as capacitors, motors and transformers can be affected. In the work is also demonstrated that in the analysis of harmonics is necessary to consider various parameters and not only one.

Distribution network reconfiguration (DNR) continues to be a good option to reduce technical losses in a distribution power grid. However, this non-linear combinatorial problem is not easy to assess by exact methods when solving for large distribution networks, which requires large computational times. For solving this type of problem, some researchers prefer to use metaheuristic techniques due to convergence speed, near-optimal solutions, and simple programming. Some literature reviews specialize in topics concerning the optimization of power network reconfiguration and try to cover most techniques. Nevertheless, this does not allow detailing properly the use of each technique, which is important to identify the trend. The contributions of this paper are three-fold. First, it presents the objective functions and constraints used in DNR with the most used metaheuristics. Second, it reviews the most important techniques such as particle swarm optimization (PSO), genetic algorithm (GA), simulated annealing (SA), ant colony optimization (ACO), immune algorithms (IA), and tabu search (TS). Finally, this paper presents the trend of each technique from 2011 to 2016. This paper will be useful for researchers interested in knowing the advances of recent approaches in these metaheuristics applied to DNR in order to continue developing new best algorithms and improving solutions for the topic.

This paper aims to evaluate the performance of synchronous reluctance motors assisted by a permanent magnet (PMa-SynRM) focused on efficiency and torque pulsations. PMa-SynRM shows high efficiency and power factor, compared to induction motors (IM), although they have a greater cost. These machines develop relatively high torque ripple, cogging torque, and torque imbalances. Consequently, the electromagnetic torque is reduced, the motor temperature is increased, and mechanical vibrations are induced. The optimal design of the machine structures such as flow barriers, permanent magnets, and stator slots, among others, allow reducing torque pulsations. A comparison is made between different designs of the PMa-SynRM reported in the scientific literature, and the effects on efficiency, torque pulsation, and operating costs are evaluated. A case study on the motor driving the air conditioner blower in a hotel room was made, to determine the best economic variant between IM or PMa-SynRM. A sensitive analysis was made to evaluate several uncertainties. The advantages of using one of the PMa-SynRM analyzed were demonstrated. Also, it was proved that the investment is feasible economically, although NPV and payback are not the best, due to low load factor in inverter-controlled motors in air conditioners.

This paper proposes the analysis of the effects of power electronics devices on the energy quality of an administrative building. For the study a method is applied that allows the analysis of the main problems of energy quality such as voltage variation, harmonics, flicker, and the effect of harmonics on the power factor. As a case study, the offices of an administrative building were used, where the measurements of the main energy quality parameters were carried out for a week. The results showed the presence of current harmonics and flicker problems due to non-linear loads such as the frequency inverters that drive the motors of the elevators and escalators, as well as the LED lamps. These problems cause systematic damage to the lighting system, UPS and improper correction of the power factor. The study also demonstrates the need to deepen the effects of energy quality not only in the industrial and residential sectors. In addition, attention must be paid to the tertiary sector, specifically to administrative buildings.

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In this paper the feasibility of energy saving by implementing flow regulation at constant load in feedwater pumps in a sugar industry is studied. As regulation strategy, the use of a variable speed drive in the hydraulic system is proposed. For the project evaluation, the Net Present Value and Payback Period techniques are used. Among the variables considered are the price of energy, the equipment useful life, financial data and those related to environmental impact. As a result, it was found that if only a commercial approach is considered, the energy saving strategy is profitable but not attractive, because investment is recovered in a period close to the useful life of technology. However, if a government focus that encourages the implementation of these energies saving strategies is considered, the investment of the project recovers in a short time.