Fault detection at the early stage of development is of great importance in the maintenance of electric motors. In this regard, Motor Current Signature Analysis (MCSA) is cited in many articles to detect rotor bar fracture. The popularity of MCSA is due to its non-invasive and non-destructive nature, simplicity, and, compatibility with several signal processing tools. The vast variety of the signal processing tools which are commonly used for detecting the broken rotor bar fault is based on the Fast Fourier Transform (FFT) of the stator current signal and analysis of the produced Fourier spectrum; however, because of the small amplitude at the fault frequency relative to the main frequency amplitude, the former cannot be easily discriminated from the latter. Therefore, the peak at the fault frequency is hidden in the shadow of the main frequency component, hence the fault will not be detectable. As a solution to vanish the base frequency component, a method based on the Algebraic Identity of trinomial expansion is proposed in this paper which enables us to display the difference between the frequency of the fault signature and the base frequency. In this article, the fault of the broken rotor bars of the squirrel cage induction motor is revealed by the proposed method. In addition, a frequency weighting technique is presented to magnify the component at the fault related frequency compared to the lower frequencies. To validate the proposed methods, they are examined on the laboratory data obtained from three different operating conditions including the direct online start, the direct torque control, and the scalar control and the results show the ability of the proposed methods in fault detection of an induction motor.

Based on an ethnozoological study carried out from December 2018 to November 2019, this paper attempts to document the usage of squirrel species for various purposes by the Adi, Idu Mishmi, Miju Mishmi, Tangsa, Chakma and Monpa tribe living near the villages adjoining the protected areas located in the districts of East Siang, Lower Dibang Valley, Dibang Valley, Lohit, Changlang and West Kameng of Arunachal Pradesh, India. The paper also describes the use of certain squirrel species as a part of their traditional culture and lists their names in English, Vernacular and Latin names. The study has led to an understanding that eight squirrel species are used by the tribes for cultural, food and medicinal purposes. This work contributes to ethnozoological research by describing a knowledge system of squirrel species use and the association of squirrel species with the cultural believes of the tribes.