Electric current modal impulses to detect motor-driven equipment condition

Electrical current monitoring has been applied in recent years to gain insights into the condition of electric motors and generators. However, existing current monitoring systems and maintenance procedures, while they help to minimize failures and potential catastrophes, are relatively insensitive to many types of incipient faults. An approach is under investigation by the author's organization which is based on very low level broadband artificial stimulation of the electrical current feeding the motor, followed by experimental modal analysis of the resulting response current versus frequency spectrum. Such an approach in principle would be able to detect many problems that currently often go undetected, such as shaft cracking, bearing and seal deterioration, and rubs in the driven machinery as well as in the motor. In addition, the electromechanical response would also give an indication concerning the effectiveness of the process that the motor is driving, based on frequency curvefitting of the slope of the process parameter (e.g. cutting tool force as implied by driving current) as a function of the slight variation of speed that torsional response to the current impulse provides. There is also a strong potential for synergism between existing passive techniques and the proposed new "active" current monitoring method.