Eddy current drive and motor control system for oil well pumping

An eddy current coupling control system for an oil well drive comprising:

• an AC electric drive motor for powering an oil well pump;
• an eddy current coupling assembly comprising a driven rotatable input shaft coupled to said AC electric drive motor, a driven rotatable output shaft, an inductor drum surrounding a peripheral surface of a pole member, said inductor drum being rotatable relative to said pole member, a coil means for inducing an electromagnetic flux for coupling said inductor drum and said pole member and said input shaft and said output shaft;
• oil well pumping means nonrotatably connected to said output shaft of said eddy current coupling for moving a sucker rod upward and downward;
• speed sensor means for generating a speed signal representing the rotational speed of said output shaft of said eddy current coupling;
• control means for supplying electrical power to said coil means for coupling said inductor drum and said pole member in response to said input control signal;
• a down speed signal means for generating a first speed signal representing the desired travel speed of said sucker rod in the downward direction;
• an up speed signal means for generating a second speed signal representing the desired travel speed of said sucker rod in the upward direction;
• direction sensor means for generating a direction signal indicating when said sucker rod is travelling in a downward direction and when said sucker rod is travelling in an upward direction;
• and
• a second control means for establishing a control signal in dependence on said first speed signal when said sucker rod is travelling downward and establishing a control signal in dependence on said second speed signal when said sucker rod is travelling upward as indicated by said direction sensor means where said control signal is connected to said electric drive motor for improving the production rate of said oil well pump by selecting an operating speed for said oil well pumping means when said sucker rod is travelling downward and another speed for said oil well pumping means when said sucker rod is travelling upward.

A method of controlling an eddy current drive coupling for use on an oil well pump comprising:

• providing an AC electric drive motor;
• providing an eddy current coupling comprising a driven rotatable input shaft electromagnetically rotatably coupled through an inductor member and a pole member where an electromagnetic field is generated by a coil means which travels through said inductor member and said pole member to a driving rotatable output shaft;
• providing an oil well pumping means nonrotatably connected to said output shaft for pumping subsurface oil to the surface for containment;
• providing an eddy current coupling output shaft speed sensor means for generating a speed signal;
• providing a desired operating speed signal;
• providing a summing junction means for generating an input control signal by adding and subtracting input signals and mathematically manipulating the result;
• providing a control amplifier means for supplying electrical power to said coil means according to said input control signal;
• providing a motor current sensor for generating a torque control signal representing the torque transferred by said output shaft based on said electrical power supplied to said electric drive motor and then mathematically manipulated;
• subtracting said speed signal from said desired operating speed signal to generate said input control signal;
• and
• subtracting said torque control signal from said desired operating speed when said torque control signal exceeds a present level thereby limiting the maximum torque transferred by said output shaft.

A method of controlling an eddy current drive coupling for use on an oil well pump comprising:

• providing an AC electric drive motor;
• providing an eddy current coupling comprising a driven rotatable input shaft electromagnetically rotatably coupled through an inductor member and a pole member where an electromagnetic field is generated by a coil means which travels through said inductor member and said pole member to a driving rotatable output shaft;
• providing an oil well pumping means nonrotatably connected to said output shaft for pumping subsurface oil to the surface for containment;
• providing an eddy current coupling output shaft speed sensor means for generating a speed signal;
• providing a desired operating speed signal;
• providing a summing junction means for generating an input control signal by adding and subtracting input signals and mathematically manipulating the result;
• providing a control amplifier means for supplying electrical power to said coil means according to said input control signal;
• providing a pump sensor means for generating an up signal and a down signal based on the direction of travel of said oil well pump;
• providing a reference speed switching means for electrically connecting and disconnecting an up speed signal and a down speed signal to said summing junction means;
• providing a stroke control means for controlling the state of said switching means for increasing the productivity of said oil well pump by supplying a first desired speed to said summing junction means when said oil pump is travelling upward and a second desired speed to said summing junction means when said oil pump is travelling downward;
• and
• subtracting said speed signal from said desired operating speed signal to generate said input control signal.

A method of controlling an eddy current drive coupling for use on an oil well pump comprising:

• providing an AC electric drive motor;
• providing an eddy current coupling comprising a driven rotatable input shaft electromagnetically rotatably coupled through an inductor member and a pole member where an electromagnetic field is generated by a coil means which travels through said inductor member and said pole member to a driving rotatable output shaft;
• providing an oil well pumping means nonrotatably connected to said output shaft for pumping subsurface oil to the surface for containment;
• providing an eddy current coupling output shaft speed sensor means for generating a speed signal;
• providing a desired operating speed signal;
• providing a summing junction means for generating an input control signal by adding and subtracting input signals and mathematically manipulating the result;
• providing a control amplifier means for supplying electrical power to said coil means according to said input control signal;
• providing a pump sensor means for generating an up signal and a down signal based on the direction of travel of said oil well pump;
• providing a reference speed switching means for electrically connecting and disconnecting an up speed signal and a down speed signal to said summing junction means;
• providing a stroke control means for controlling the state of said switching means for increasing the productivity of said oil well pump by supplying a first desired speed to said summing junction means when said oil pump is travelling upward and a second desired speed to said summing junction means when said oil pump is travelling downward;
• providing an external speed reference signal to said stroke control means;
• subtracting said speed signal from said desired operating speed signal to generate said input control signal;
• opening said reference speed switching means;
• and
• connecting said external speed reference signal to said summing junction means.