Citation: Trujillo Guajardo, L.A.; Platas Garza, M.A.; Rodríguez Maldonado, J.; González Vázquez, M.A.; Rodríguez Alfaro, L.H.; Salinas Salinas, F. Prony Method Estimation for Motor Current Signal Analysis Diagnostics in Rotor Cage Induction Motors. Energies 2022, 15, 3513. https://doi.org/10.3390/ en15103513 Academic Editors: Daniel Morinigo-Sotelo, Rene Romero-Troncoso and Joan Pons-Llinares Received: 18 March 2022 Accepted: 9 May 2022 Published: 11 May 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). energies Article Prony Method Estimation for Motor Current Signal Analysis Diagnostics in Rotor Cage Induction Motors Luis Alonso Trujillo Guajardo * , Miguel Angel Platas Garza, Johnny Rodríguez Maldonado, Mario Alberto González Vázquez, Luis Humberto Rodríguez Alfaro and Fernando Salinas Salinas Universidad Autónoma de Nuevo León, UANL, FIME, Av. Universidad S/N Ciudad Universitaria, San Nicolás de los Garza C.P. 66451, NL, Mexico; miguel.platasgrz@uanl.edu.mx (M.A.P.G.); johnny.rodriguezml@uanl.edu.mx (J.R.M.); mario.gonzalezvzq@uanl.edu.mx (M.A.G.V.); luis.rodriguezlf@uanl.edu.mx (L.H.R.A.); fernando.salinassln@uanl.edu.mx (F.S.S.) * Correspondence: luis.trujillogjr@uanl.edu.mx; Tel.: +52-818-329-4020 Abstract: This article presents an evaluation of Prony method and its implementation considerations for motor current signal analysis diagnostics in rotor cage induction motors. The broken rotor bar fault signature in current signals is evaluated using Prony method, where its advantages in comparison with fast Fourier transform are presented. The broken rotor bar fault signature could occur during the life cycle operation of induction motors, so that is why an effective early detection estimation technique of this fault could prevent an insulation failure or heavy damage, leaving the motor out of service. First, an overview of cage winding defects in rotor cage induction motors is presented. Next, Prony method and its considerations for the implementation in current signature analysis are described. Then, the performance of Prony method using numerical simulations is evaluated. Lastly, an assessment of Prony method as a tool for current signal analysis diagnostics is performed using a laboratory test system where real signals of an induction motor with broken rotor bar operated with/without a variable frequency drive are analyzed. The summary results of the estimation (amplitudes and frequencies) are presented in the results and discussion section. Keywords: Prony method; broken rotor bar; fast Fourier transform; current signal analysis 1. Introduction Electric motors, particularly rotor cage induction motors (RCIM) are considered for most of industry applications, because of its operation performance and low maintenance cost. According to statistical studies performed by IEEE and Electric Power Research Institute, a percentage of 8–9% of the total RCIM faults occur in the rotor [1], where broken rotor bars (BRB) or cracked/broken end rings (CBER) are the most common issues in RCIM operation. It is well-known that the cage of RCIM is made typically of aluminum and in some cases of copper [2]. BRB or CBER will have a high probability of appearing when, for example a RCIM is operated considering several direct-on-line (DOL) starts in a short period of time or RCIM with high inertial loads, these conditions will put the RCIM through an excessive centrifugal, thermal, and mechanical stress. It is important to mention that a BRB or CBER cause a reduction in RCIM operation performance, for example, having problems to move its load mainly due to an unbalanced flux in the rotor causing a reduction in the output torque [3] and heavy damage to the RCIM. So, to prevent a heavy damage situation, BRB or CBER must be detected early in a noninvasive way, where as a part of condition monitoring of RCIM, motor current signature analysis (MCSA) is used to determine problems such as BRB, CBER, or abnormal air gap eccentricity (AAGE) at the rotor cage when the motor is under normal operation. It is important that BRB or CBER are accurately detected using MCSA. However, in some cases there exist “false positives”, which means an unnecessary shut down and transportation to a qualified repair facility, and if the RCIM is a large machine there will Energies 2022, 15, 3513. https://doi.org/10.3390/en15103513 https://www.mdpi.com/journal/energies