Abstract: A submersible pumping system which, in one embodiment, includes a motor, a pump and a control circuit, or unit, coupled to the motor for controlling the operation of the motor is described. Using motor and sensor signals, the control unit detects various conditions within the pumping system and alters motor operation. In an exemplary embodiment, the control unit initiates an oscillation sequence of applying a forward torque for a first preselected period of time, applying a reverse torque for a second preselected period of time, and then repeating the torque applying steps a selected number of times to eliminate an obstruction from the pump.

Abstract: A method and apparatus for detecting the presence of a ground leakage path in an electric motor system including an alternating current (ac) electric motor coupled for receiving electric power from a switching inverter of the type having, for each phase of the motor, a pair of serially connected electronic switching devices connected between relatively positive and negative direct current (dc) voltage buses with the switching devices being alternately gated into and out of conduction for providing switched electric power to the motor. The inverter includes a current detector for detecting current in the relatively negative voltage bus. The method comprises initially applying a gating pulse each time the motor is energized to the switching device of each phase connected to the negative voltage bus and identifying a ground leakage path when such gating pulse produces current at the current detector.