Abstract: A method and apparatus for controlling the operation of an oil well pumping unit in which the prime mover is a polyphase AC electric motor. The system comprises means for generating a plurality of signals representative of motor fault parameters including a motor winding overtemperature fault, undervoltage fault, and a phase imbalance fault. Upon occurence of a fault, a contactor in the motor supply leads is open to shut down the motor. After such shutdown because of undervoltage or phase imbalance faults the fault parameters are continuously scanned and once the fault has been cleared the motor is restarted. Where motor shutdown occurs because of an over temperature fault, the motor is maintained in a latched off shut down condition until an operator implemented reset occurs. An accessible counting memory is provided having separate registers for each of the fault conditions.

Abstract: This is a method and apparatus for controlling a downhole, hydraulically actuated pump. Two fluid flow monitoring means generate signals which are a function of the power fluid flow rate to the downhole pump and the return fluid flow rate from the well. An automatic controller causes the power fluid flow rate to be maintained essentially directly proportional to the return flow. Thus, the power fluid flow is not varied in the opposite direction of any change in return flow to maintain the return fluid flow constant, but conversely, is changed in a manner which will tend to accentuate any changes in the return fluid flow.

Abstract: This is a method and apparatus for a control system for a well-fluid hydraulic pumping unit. The system senses level in the suction vessel and operates an underflow throttling valve to control both the level in the suction vessel and the flows of the cyclone separator. The system maintains the level in the horizontal suction vessel and simultaneously maintains flows to the cyclone in a range for effective cleaning of the fluid and for self-cleaning of the underflow. The cyclone and its associated hardware are sized based on the above-ground pump flow and any bleed flow from the suction vessel. The system is generally applicable to hydraulic units in which the speed of the above-ground pump is not varied over a wide range.