Rotor bars breakage in railway traction squirrel cage induction motors and diagnosis by MCSA technique Part I : Accurate fault simulations and spectral analyses

Harmonic Current Sideband-Based Novel Indicators of Broken Bars for On-line Evaluation of Industrial and Railway Cage Motor Faults

“…Simulations about higher-order sidebands [7], Fig.2, confirmed their insensibility to inertia, moreover showing load insensibility and linear-like variation with fault gravity (number of broken bars). So, a deeper investigation on these sidebands was engaged in.…”

“…Some remarks about motor parameter identification for setting (29) has been given in the Appendix. Fig.3 shows that Γ (5) and Γ (7) are not sensibly dependent on slip, and their dependence on frequency is much less heavy with respect to Γ (1) . Moreover, Fig.3 shows that Γ (5) and Γ (7) perform a better fault severity assessment.…”

“…The pulse number can rove from one (square wave) to few tens. Obviously, the main drawback consists in large low-frequency harmonic voltages producing large harmonic currents and torques [7], with adjunctive stresses on the motor.…”

“…GTO-based inverters are very often used in variable-speed drives with multi-megawatt power rating, and the railway traction is a typical applicative field [7]. GTOs are components robust and affordable, but their switching frequencies hardly range up to few hundreds of hertz in power applications.…”

“…Due to the linearity of the model, superimposition principle permits to separately calculate every sideband amplitude. Computation of (1-2s)f current sideband was performed by posing system (1), (2) in complex form, matching in harmonic balance frequency 'f' with 'sf' and '(1-2s)f' with '-sf', and simulating the fault by increasing the rotor resistance matrix as follows: Eq.s (6), (7) can be reduced to 2 nd order components:…”