Comparison among Methods for Induction Motor Low-Intrusive Efficiency Evaluation Including a New AGT Approach with a Modified Stator Resistance

Abstract

Induction motors consume a great portion of the generated electrical energy. Moreover, most of them work at underloaded conditions, so they have low efficiencies and waste a lot of energy. Because of this, the efficiency estimation of in-service induction motors is a matter of great importance. This efficiency estimation is usually performed through indirect methods, which do not require invasive measurements of torque or speed. One of these methods is the modified Air-Gap Torque (AGT) method, which only requires voltage and current data, the stator resistance value, and the mechanical losses. This paper approaches the computation of a modified stator resistance including the mechanical losses effect to be applied in the AGT method for torque and efficiency estimation of induction motors. Some improvements are proposed in the computation of this resistance by using a direct method, as well as the possibility to estimate this parameter directly from the nameplate data of the induction motor. The proposed methodology only relies on line voltages, currents, and nameplate data and is not intrusive. The proposed methodology is analyzed through simulation and validated through experimental results with three-phase induction motors. Also, a comparison of methods for in-service induction motors efficiency estimation is presented for the tested motors.

A Study of Fault Diagnosis Based on Electrical Signature Analysis for Synchronous Generators Predictive Maintenance in Bulk Electric Systems

“…A second peculiarity is related to the discrimination of faults whose effects occur in the same fault pattern. As one may note, the rotor rotation frequency pattern is indicative of rotor mechanical problems, and rotor winding inter-turn short circuit [11,13,19,25,29]. Thus, by analyzing only this fault pattern, it is possible to detect rotor problems, but not to distinguish if it is an electrical or a mechanical problem.…”

“…There are several published works about ESA-based methodologies for fault detection in synchronous machines. ESA has been used mainly for detection of stator winding inter-turn short circuit [11][12][13][14][15][16], rotor winding inter-turn short circuit [11,13,[17][18][19][20], air-gap eccentricity [21][22][23][24][25], and rotating diode failure [26,27]. There are also works approaching various electrical and mechanical faults in SGs [28].…”

“…There is also an issue related to faults that coincide in the same fault pattern. For instance, the rotor rotation frequency fault pattern is indicative of rotor winding inter-turn short circuit and rotor mechanical faults [9,11,13,19,29]. Thus, the analysis of only the rotation frequency components allows the detection of rotor problems.…”

Assessment of the energy efficiency estimation methods on induction motors considering real-time monitoring

“…The study also considered the effects of voltage unbalanced for different load factors. [22] also compared different EEEM, focusing on the air-gap torque, and excluding the HTEA methods. In this study, the effects of voltage unbalanced and harmonics were not included in the assessment.…”

A PLL-Based Online Estimation of Induction Motor Consumption Without Electrical Measurement

“…If these data are not available, the characteristic P m = f (N m ) can be approximated by the slip method. In the same way, the efficiency curve can be approximated from models, database or standards [16][17][18][19]. One important point is the sensitivity of these two models to the accuracy of the speed estimation.…”