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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

For driving constant loads in industry, the use of direct-on-line-start permanent-magnet-assisted synchronous reluctance motors with ferrite magnets (DOL-Start-PMa-SynRM) is proposed. The bibliographic search demonstrated that this new motor has greater efficiency than one similar induction motor (IM). It was evidenced that the main element that is required for direct starting is to insert a squirrel cage into the rotor of a PMa-SynRM, which does not produce negative operational effects in a steady state. An economic evaluation was carried out in a sugar mill company, applying the differential net present value (NPV) method, and a sensitivity analysis, considering the four factors that present the most variation. It was demonstrated, by means of a Pareto diagram standardized for the NPV that the most significant factors are fuel factor, lifespan and the multiplication of both. With response surfaces that are obtained with a multilevel factorial experiment, it was determined that, by varying the factors in the ranges considered, the NPV always remains positive and higher than 2200 USD. This is mainly due to the notable difference between the efficiency of the DOL-Start-PMa-SynRM and that of the IM. Consequently, is proved that an investment in the DOL-Start-PMa-SynRM may be feasible.

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.

More than 65% of electricity consumed worldwide by the industrial sector is used in electric-motor-driven systems. For this reason, the efficiency of electric motors is an important factor in improving the energy efficiency of the industry. Additionally, this contributes to reducing energy consumption, production costs, as well as CO2eq emissions. The replacement of motors with efficiency class IE1 by motors of efficiency class IE3 is one possible alternative to increase the efficiency of electric motor systems. When a program to replace motors with others of greater efficiency is initiated, it is necessary to casuistically evaluate all identified opportunities. Economic viability can be evaluated using a variety of methods. Often, the methods recommended by manufacturers or consulting entities focus on simple payback time without accounting for all influencing factors. This paper contributes to the academic discussion by proposing a methodology based on the calculation of energy-saving potential, by performing a preliminary an a priori evaluation and determining the economic opportunities. It avoids evaluating all motors in the studied facility and shows its effectiveness by using the cost of energy saved to distinguish which motors to evaluate. Finally, it provides a complete economic evaluation of the final decision on the basis of discounted cash flow methods. A short-production-cycle sugarcane industry was used in the case study.

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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