Abstract: A pump control system and method employs a variable drive for controlling the speed of an AC electric motor driving a cyclic load. A real-time tuning of the frequency and voltage of the AC input to the motor allows a controlled variation of a cycle speed of the cyclic load. The control system and method adjusts motor speed according to a desired motor speed characteristic for different portions of a complete cycle and over multiple cycles of the cyclic load. The variable drive rectifies a poly-phase AC power input to provide a source of DC power on a DC bus and periodically samples the DC bus current and DC bus voltage across the DC bus to optimize the motor operation.

Abstract: An eddy current coupling with an electrically controllable field current is used to rotatably connect a drive motor to an oil well pumping mechanism where the eddy current drive speed is controlled to a reference speed using a speed feedback control system and operation can be limited in torque output by a torque feedback control system. In a first alternative embodiment, the eddy current coupling output speed is controlled by a stroke modulation unit using a first selected speed for the upward pumping stroke and a second selected speed for the downward pumping stroke. In a second alternative embodiment a controller is used to select torque or speed control for the upward or downward .pumping stroke.