Power output and derating factor of oil well motors

ELECTRIC MOTORS that drive oil well pumping units are subjected to a continuously varying load characterized by high peaks and wide and rapid load variation. The exact load-vs-time relationship is influenced by many factors and is different for each installation. Load peaks may occur from 8 to 60 times per minute. Valleys between peaks are frequently negative where the motor momentarily acts as an induction generator and transfers energy from the pumping system to the electric power system. Ratio of peak load to average load ranges from 1.8 to 4.0.