Laboratory prototype for induction motor bar breakage experimentation and bar current measuring

An easy procedure for cage construction of induction motors used for experimental work is given in this paper. Usually, laboratory measurements about broken bars for diagnostic investigations need destructive tests that can be very laborious and time expensive. The test-bed proposed consists in a three-phase wound-rotor induction machine that has been converted in a squirrel-cage machine with current-measuring capability on two bars. Common multi-core copper cables have been used for cage fabrication; faults can be quickly produced and repaired without machine dismantling. The cage prototype was used to perform extensive tests about motor currents spectral characterization under severe rotor fault conditions (large number of broken bars). Full dependence of (1-2s)f sideband from load and fault gravity has been verified