Electrical submersible pumps with permanent magnet motors are migrating to Oil & Gas with a lot of excitement. The motors in these ESP’s have twice the horsepower as conventional induction motors.
Often overlooked though, is the complexity of these systems. The control algorithm that is required to maximize performance adds another system on top of the original electromechanical system creating more complexity and points of failure. We believe that the optimal approach for operators is an ESP that gets the horsepower gains without advanced controls.
All of the permanent magnet motors available in ESP’s to date require a closed-loop control to drive the motor, except sensors cannot be ran down-hole, meaning the control is pseudo-closed-loop. That means that the control uses an algorithm to calculate the state of the motor. So, the drive is outputting power to the motor according to the controller, which is operating on feedback from the motor, except the feedback is an approximation and not real data. Check out our other blogs for more information.
For now, consider this analogy: You have a modern gasoline truck which has an engine control module that adjusts the valve timing and the fuel injectors as well as the throttle body valve opening in order to keep the engine running optimal for the conditions. The whole thing is drive-by-wire. Except for oil & gas ESP’s, the engine control module would be a mile away from the car. Because of this distance the ECM could not use O2 sensors, and throttle positions sensors or intake manifold pressure sensors, it would only be able to determine adjustments based on the amount of fuel being used by the engine. It sounds complicated because it is. Subsurface motor applications are just different from other surface operations.
It would be much better if the engine could self-regulate, and the control module wasn’t so responsible for everything. This would be a simpler solution because the mechanism would be inherently easier to operate. That is the ElectromagnetiX technological approach. We have integrated an induction winding into a permanent magnet motor design so that only a standard variable frequency drive (VFD) is needed. We simplified the controls by having a self-regulating machine. It is still a permanent magnet motor capable of high horsepower except it works with the existing surface equipment. Since it is inherently more stable, like the induction motor, it can run on an open-loop control, no approximating algorithm necessary.
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