Short Circuit Fault at Delta Connection Induction Motor Using FRA Method: Experimental Analysis

Induction motors are indispensable in industrial systems, and their failure, especially from short circuit faults, can lead to substantial operational losses. This paper presents a novel application of Frequency Response Analysis (FRA), traditionally used in transformer diagnostics, for identifying short circuit faults in a 5.5 HP, delta-connected three-phase induction motor. Five fault types were artificially introduced: turn-to-turn (TT), coil-to-coil (CC), phase-to-phase (PP), phase-to-ground (PG), and open-circuit (OC) faults. FRA measurements were conducted before and after fault application, and deviations were analyzed across three frequency regions: low (20 Hz 1 kHz), medium (1 kHz 60 kHz), and high (60 kHz 1 MHz), and high (60 kHz 1 MHz). The trapezoidal rule was employed to calculate area deviations between normal and faulty conditions. Results show the highest deviations in the high-frequency region for CC (2.08 × 10⁶ a.u.), followed by OC (9.07 × 10⁵ a.u.) and PG (7.95 × 10⁵ a.u.). TT and PP faults showed moderate deviations in the medium frequency range. These distinct numerical signatures demonstrate the high sensitivity and diagnostic potential of FRA for early-stage fault detection in delta-connected motors. The approach is non-invasive, cost-effective, and practical for predictive maintenance applications.