Classification of Stator Electrical Faults in Rotary Machinery
The faults in Electro-mechanical rotary machinery or motors are divided into two major categories of electrical and mechanical faults. Here, the electrical faults that appear in the stator of motors are briefly explained. Basically two classes of stator winding failures can be considered namely asymmetry in the stator winding such as open phase and short circuit of a few turns in phase winding.
The former allows the machine to operate in a reduced torque while the latter leads to catastrophic failure in a short time. In case of winding asymmetry the motor parameters, and model changes, while in short turns the structure of equations changes because of increased number of state variables.
A short circuit fault is one of the most difficult faults to detect. The traditional protection circuit might not work and motor might keep running. The heating in the circuits will then results in the insulations to melt down. If undetected the fault will propagate and results in phase-phase or phase-ground faults. Ground current ultimately results in irreversible damage to the core and the machine should be removed from the process.