Eaton Corporation

Westinghouse Electric Corporation

Robert K London

David Glenn Loucks

Denis A Mueller

An electric contactor for the motor of a reciprocating pump such as an oil well walking beam pump, and other cyclic loads, uses the power drawn by the load to determine the phase angle of the pump without the need for a separate phase signalling sensor. The contactor couples the electric pump motor to a power line, and has a power sensor and peak detector. The power sensor can be responsive to RMS AC power or simply to current amplitude and polarity. The motor passes through a minimum power at the extreme top and bottom of a pump stroke, and the phase position at the top of the stroke is preferably detected by sensing for the power reversal that occurs as the momentum of the pump causes regeneration by the motor. The contactor can have overcurrent and/or undervoltage protection features, can include contacts for rearranging the motor windings to vary pump operation, and can report the phase to a pump control and monitoring system, whereby process variables are assessed as a function of phase.

Rod pump beam position determination from motor power

The extent to which a reciprocating pump for an oil well fills between successive pump strokes is determined indirectly from variations in the power consumption of an electric motor driving the pump. The power consumption is sampled numerically and a processor determines the phase of data in the samples from phase references defined by a peak and/or zero crossing in the cyclic operation of the pump and motor. When the pump fills incompletely between strokes, for example when the pump is operated at too high a frequency, the well rod moves against decreased resistance during the downstroke. The processor determines the point in the pump cycle at which the well rod encounters fluid from the increased power consumption, obtaining an indirect indication of fillage. The instantaneous power consumption preferably is measured by a module associated with an electrical contactor or motor starter included in an improved pump controller or 'pump panel' that includes a programmable controller effecting the processor functions and also functioning as an off-pump control for regulating activation of the pump.

Detection of rod pump fillage from motor power

A pump controller coupling the electric motor of a cyclically operating well pump to a power line is arranged to measure instantaneous power consumption of the motor, to integrate the power consumption over pump cycles, and to assess the performance of the well and/or pump by using the total power consumption to estimate fluid flow. The controller determines a phase reference in the cycle of the pump by monitoring for a peak or zero crossing in the instantaneous power level, specifically the point at which the pump changes over from a power stroke to regenerative operation due to pump momentum. The integrated total power consumption is reduced by an offset factor representing frictional losses, and scaled to obtain an approximate fluid volume determination for the pump and well. The factors used for offset and scaling can be adjusted by calibration using at least intermittent measurements of actual fluid flow and fluid density. The offset factor representing friction can be monitored for deciding when maintenance is needed on the pump.

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Bakersfield, CA, United States of America

Robert K London