Detection of half broken rotor bar fault in VFD driven induction motor drive using motor square current MUSIC analysis

This paper presents a new method to diagnose half broken rotor bar (BRB) fault in induction motor drive, running under various load conditions using a variable frequency drive (VFD). VFDs are commonly used in industries to improve motor's efficiency, but at the same time it generates noise and this noise modulates with the line current. Noise leads to poor signal to noise ratio (SNR) as a result motor's fault diagnosis using current monitoring becomes a challenging task, especially when the fault is at incipient stage. One such case of half broken rotor bar (BRB), has been discussed in this paper. Conventional techniques like motor current signature analysis (MCSA) is found to be ineffective in detecting half BRB fault at normal load condition. In this paper authors have developed an algorithm that generates a pseudo-spectrum of square of the current signal, using multiple signal classification (MUSIC) techniques. The square of current signal generates more BRB fault frequency components and helps in easily diagnosing the fault. These fault frequency components are detected using the proposed algorithm. The work has been experimentally validated at various load conditions.