Using power measurements to diagnose degradations in motor drivepower systems: a case study of oilfield pump jacks

A study of diagnostics of faults in motor drive-power systems is reported. The study focuses on oil-field pump jacks and includes basic analysis, computer simulation, full-scale laboratory emulation and measurements in the oil fields. Spectrum analysis of instantaneous power and current delivered to the electric motor is used for diagnosis. An original electronic system for conditioning the input instantaneous power and current is explained. A model for the pump jack and its common degradations is given. A full-scale load control system emulates measured pump-jack loads in the laboratory.