Abstract: Cathodic protection of a deep well submersible pumping assembly against the corrosive effect of electrolysis is achieved by providing a DC voltage source at the downhole pumping assembly, the negative terminal of the source being electrically connected to the metal surfaces which are in contact with the well fluid while the source's positive terminal is electrically connected to a sacrificial anode submerged in the well fluid. Current flows from the anode to the metal surfaces to reverse the process of electron flow caused by the electrolytic corrosion, thereby inhibiting the corrosion process on the metal surfaces. In effect, the corrosion is transferred to the sacrificial anode.

Abstract: Overload protection of a three-phase submersible pump motor, such as the type used downhole in an oil well, is obtained with a solid state digital logic control system that monitors each of the three phase currents and shuts the pump motor down if any of those phase currents indicates an overload condition. A time delay is introduced before shutdown to avoid undesired nuisance shutdowns otherwise caused by transient or momentary conditions. The shutdown time delay is variable and is inversely proportional to the amount of overload in order that greater overloads result in faster shutdowns.

Abstract: The phase sequence of the phase currents supplied by a three-phase AC power supply to a phase-sensitive load (such as a three-phase AC motor) is monitored by developing three phase-displaced, rectangular shaped logic signals, respectively representing the three phase currents, and applying these logic signals to respective ones of the J, C and K inputs of a J-K flip-flop. When the load is correctly connected to the power supply, the phase relationship of the three logic signals will be appropriate to trigger the flip-flop to its set operating state. Any other sequence actuates the flip-flop to its reset state which, in turn, disconnects the load from the power supply.