Detection of birdcaging in steel wire rope of a hoisting winch system by analysis of load torque and stator current

The aim of this paper is to analyze theoretically and experimentally the stator current of a three phase induction machine and load torque signals in a hoisting winch system, in order to show how they are influenced by the wire rope faulty condition. When the wire rope is subjected to axial and torsional loads, the outer strands can separate from the core in permanent way and make the rope useless. The term birdcaging is used to describe this type of phenomenon giving a permanent appearance of a wire rope forced into compression. In a hoisting winch system the running rope is bent over drum and pulley and it is torsionally stressed by the fleet angle between them. In this paper, the effect of the fleet angle is observed in the stator current and load torque, in order to detect the wire rope birdcaging. This study is performed on a 22kW squirrel-cage induction machine and presents an original non invasive way to detect wire rope fault condition, by using the stator current of the electrical machine.