International Journal of Engineering and Technology Innovation, vol. 13, no. 1, 2023, pp. 28-39 Analysis of Outer Race Bearing Damage by Calculation of Sound Signal Frequency Based on the FFT Method Iradiratu Diah Prahmana Karyatanti 1,* , Ananda Noersena 1 , Firsyaldo Rizky Purnomo 1 , Rafli Setiawan Zulkifli 1 , Ardik Wijayanto 2 1 Department of Electrical Engineering, Faculty of Engineering and Marine Science, Hang Tuah University, Surabaya, Indonesia 2 Department of Electronic Engineering, Electronic Engineering Polytechnic Institute of Surabaya, Surabaya, Indonesia Received 05 February 2022; received in revised form 16 July 2022; accepted 17 July 2022 DOI: https://doi.org/10.46604/ijeti.2023.9411 Abstract This study aims to identify the outer race bearing needed to protect an induction motor from severe damage. Faults are diagnosed using a non-invasive technique through the sound signal from an induction motor. The diagnosis aims to assess the damage to the bearings on the fan or main shaft. Moreover, this study discusses the type of damage, loading variations, and the diagnostic accuracy with the damage to the outer race bearing placed on the fan or main shaft rotor. The disturbance detection approach is used to analyze the sound spectrum to identify the harmonic components near the disturbance frequency. The damage frequency characteristics are also calculated to determine the sound spectrum peak value. The results show that the detection is slightly affected by the damage severity and the incorrect placement of the bearings on the rotor shaft. The lowest detection accuracy in testing the outer race bearing damage on the fan shaft is 91.66%. However, the accuracy percentage is 100% with the outer race bearing damage on the main shaft. Keywords: bearing, sound, frequencies, FFT 1. Introduction The electric machine widely used in industries is the induction motor, a vital driving tool whose reliability should be maintained for efficient operations [1]. Induction motors have high efficiency, simple construction, low price, and easy maintenance [2]. However, the motors do not operate normally continuously because they have an aging period due to long-term use [3]. Bearings and eccentricity may suffer mechanical damage and the stator and rotor may sufferer electrical damage [4]. The Electric Power Research Institute (EPRI) and the Institute of Electrical and Electronics Engineers Industry Applications Society (IEEE-IAS) found that motor bearings suffered the biggest damage [5]. Bearings limit the relative motion of two or more machine components by being moved in the desired direction [6]. Damage to bearings causes vibration, overheating, and noise [7], while abnormal use of an induction motor results in financial losses, damages to other motor parts, or workplace accidents. These adverse effects are overcome by monitoring the bearing condition as periodic maintenance information using diagnosis by invasive and non-invasive techniques [8]. Motor current signature analysis (MCSA) is an invasive technique that requires expensive equipment and data collection through direct contact with motor parts [9]. However, MCSA applies to all motors, including pumps operated on wet media [10]. The technique is also recommended because the detection results are more accurate, though the signal processing is * Corresponding author. E-mail address: iradiratu@hangtuah.ac.id Tel.: +62 857-5525-5203; Fax: +031 5946261