Evaluation of Classic and Innovative Sideband-Based Broken Bar Indicators by Using an Experimental Cage and a Transformed (n, m) Complex Model

Abstract

In this work the results of a measuring and simulation campaign performed on an experimental induction motor with artificial broken bars are presented, aiming to extract spectral current components useful for fault detection. With nonsinusoidal feeding a lot of frequencies other than (1-2s)f (lowersideband, LSB) and (1+2s)f (upper-sideband, USB) arise, in proximity of low-order current harmonics, that can be good fault indicators. Current signature analysis-based techniques (CSABT) can take advantage by these harmonic current sidebands (HCSBs) since they are less dependent on load, frequency, drive inertia and motor parameters, so producing a better fault estimation. The measures were matched with simulations carried out by using a topologically complete mathematical complex model. Machine parameters were obtained by 2D and 3D FEA. A comparison between LSB/USB-based indicators (LUSBBIs) and HCSB-based indicators (HCSBBIs) suggests to use the latter whenever a broken bar diagnosis must be attempted for inverter-fed motors.Index Terms-Broken bars, finite elements, harmonic current sidebands, identification, spectral analyses, multiphase model.

Diagnosis-oriented sequence circuit-based modeling of eccentric rotor traction induction motors accounting for cage damping and split-phase currents

“…Appendix B. The complete model is reported in [7]. All the circulant matrices turn out in a diagonalized shape in this way, and the sequence circuits are easily decoupled.…”

“…The transformed stator-rotor mutual inductance matrices are as follows:L '-F* L F -b d d' IL (q) )SR -n SR m -an -lag I SR J sequence mutual inductances L,sR (q) , LRS (q) are complex functions of the rotor rotation angle 8:L ( q ) -L ( q ) *-;-A ( q ) j qB 511 -ILl' -'I nm ,1 e . (B24)Since the matrices LSR' and LRS' =(LsR') ' * are usually non-square matrices, their shape is band-diagonal[7] as shown in (B25)for LRS' in case of four-pole machines (n=12).Figs. 12, 13show the real and transformed mutual inductances, respectively.…”

“…Broken bars [1], [2], rotor misalignments [3], [4], stator faults [5], and gear faults [6] are not uncommon in traction motors, nonetheless these motors are required to offer an high degree of affordability, to avoid service interruption, delays, and incidents. Broken bars in squirrel-cage traction motors for high-speed trains were analyzed in [1], [2], [7]. Papers [6] reported a study of the gear drive train fault due to torsional vibrations in railway drives.…”

“…This paper resorts to a symmetrical component transformation of the motor phase-model including all the stator split-phase currents and rotor cage-loop currents [7]. The analysis leads to five equivalent circuits useful for split-phase current calculation and fault severity assessment, taking in account the cage damping.…”

Influence of stator and rotor geometric parameters on rotor bar current waveform and performance of IMs

“…The accurate prediction of rotor bar current in squirrel‐cage induction machines (IMs) is crucial both in terms of electromagnetic performance including the parasitic effects and control of IM drives. In general, it has been assumed that the bar currents are sinusoidal under the balanced three‐phase sinusoidal source and healthy operation conditions [1–3]. Nevertheless, it has been revealed that the bar currents can be non‐sinusoidal under a very low slip rate or excessively high electrical loading operations [4] or in the IMs whose air‐gap length is remarkably short [5].…”