Study of Broken Rotor Bar Fault for Asymmetrical Six-Phase Induction Motor

A Comprehensive Survey on Fault Tolerance in Multiphase AC Drives, Part 1: General Overview Considering Multiple Fault Types

“…On the other hand, there are numerous faults that do not solely affect some of the stator phases, but all of them to similar extent. This occurs, e.g., in case of shortage [138,466,467], excess [131,132] or sensor failure [58] of dc-link voltage v dc (for single-dc-link drive), magnet demagnetization [75], as well as mechanical (e.g., eccentricity or damaged bearings/bars) [79,81,82,84,85], speed/position-sensor [182,199], or machine cooling-system failures (increasing temperature) [60,70,71,468], among others. The phase redundancy of multiphase machines, in principle, does not seem to offer inherent tolerance against these kinds of faults.…”

“…12.6.2. Broken Rotor Bars One or several bars of an IM cage rotor may crack or break due to phenomena, such as thermal (e.g., hot spots), mechanical (e.g., vibration), and environmental (e.g., humidity) stress [85,462,601]. Similarly to eccentricity faults, bar breakage also generates space harmonics (hence, voltage/current distortion), but with particular frequency characteristics that may be used to distinguish them [462,492,601].…”

“…Similarly to eccentricity faults, bar breakage also generates space harmonics (hence, voltage/current distortion), but with particular frequency characteristics that may be used to distinguish them [462,492,601]. The harmonics caused by broken bars also give rise to undesired torque and speed ripple [82,85].…”

“…The current signature for the asymmetrical WSA is further studied in [83], where it is concluded that special care should be taken to avoid misdiagnosis because of the non-ideal converter/machine asymmetries and the effect of the closed-loop current control. Abdel-Mageed et al [85] show that an asymmetrical six-phase IM exhibits larger stator-current symptoms with one or two broken bars than a similar three-phase IM (analogously to, e.g., rotor slot harmonics; see Section 7.3.2.1); in addition, they propose to use neural networks for the fault detection. On the other hand, Farag et al [62] show that the indices used for detecting phase OCs or high-resistance connections (based on x-y current) are robust to bar breakage in a symmetrical six-phase IM, while the broken bars could be detected from the α 1 -β 1 or phase current spectrum as in a three-phase IM.…”

“…The possibility of future work addressing the exploitation of the extra DOFs of multiphase machines to this end is particularly promising. In fact, the initial attempts that are available reveal that multiphase drives offer excellent features in this regard, such as enhanced tolerance to controller faults by using different control units for multiple modules [25,56], monitoring with reduced signal-to-noise ratio for eccentricity [84] or bar-breakage [85] detection, easier discrimination between fault symptoms thanks to the distribution of harmonics among a greater number of VSD subspaces [604], or the capability to compensate the effects of eccentricity [179,180]. Furthermore, even though the handling of some faults does not seem in principle easier than for three phases, it does anyway require specific analysis for higher phase numbers, because of the considerable differences; e.g., the current trajectories in VSD subspaces under current-sensor faults, which has only been addressed for asymmetrical six-phase machines so far [58].…”