Inferring dynamic load of polished rod of oil well pumping unity from the motor current

This paper presents experimental results showing that the dynamic load supported by the polished rod of oil well pumping unity can be inferred from statoric current of a three-phase induction motor (which is given by sensorless vector AC-drive) using a Hammerstein-Wiener model with wavelet networks in series with an autoregressive model with exogenous input (ARX). The results obtained in the validation stage show that, on the basis of the experimental set used in this work, the best estimated model is suitable to represent the dynamic load of the polished-rod of the pumping unit.