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Pump control responsive to voltage-current phase angle

  • US 5,362,206 A
  • Filed: 07/21/1993
  • Issued: 11/08/1994
  • Est. Priority Date: 07/21/1993
  • Status: Expired due to Fees
First Claim
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1. A process of controlling an inductive, alternating current, electric motor of a well-pumping unit cyclically operating to reciprocate a subsurface pump by means of a sucker rod string, comprising:

  • (a) during each reciprocation cycle, repeatedly measuring phase angle between voltage applied to and current drawn by the motor;

    (b) producing a control function related to the measured phase angle for a predetermined portion of the reciprocation cycle;

    (c) comparing a value of the control function with predetermined limit value; and

    (d) if the value of the control function exceeds the limit value, shutting off the motor at least temporarily.

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