Rod pump beam position determination from motor power

An apparatus for coupling an electric power line to a cyclic load, the load having a continuous variation in power consumption while operating, due to periodic operation of the load at an operational frequency and over a 360.degree. span of phase, comprising:

• power sensing means producing a signal representing an instantaneous power drawn by the load, the signal of the power sensing means representing variations in said instantaneous power within the 360.degree. span of phase;
• a peak detector coupled to the signal, the peak detector developing an output signal representing a phase position of the cyclic load as determined by variation of the instantaneous power over an operational period of the cyclic load;
• a controller, the signal of the power sensing means being coupled to said controller;
• switching means responsive to the controller for coupling the line to the load, the switching means making and breaking a connection between the line and the load upon occurrence of at least one of overcurrent conditions and undervoltage conditions;
• and
• a control system having means to vary operation of the cyclic load, and wherein the control system is coupled to the peak detector and to at least one sensor operable to measure an operational parameter of the cyclic load, the control system further comprising means for assessing the operational parameter of at least one phase angle in the 360.degree. span referenced to the phase position determined by the peak detector.