Abstract: The present invention provides an algorithm that utilizes flow reference data which can be mathematically determined as a function of various pump and motor parameters such as speed, torque or power or from calibrated flow curves stored in an evaluation device, or from an external flow reference such as a flowmeter. Once the PID control valve has reached its steady state condition a calculated flow value is captured and compared to the current flow value obtained after the variable frequency drive has decreased in frequency (speed). The valve position is optimized just prior to the speed threshold where the flow condition of the algorithm is no longer true.

Abstract: A method and apparatus are provided for controlling the operation of a pump, such as a centrifugal pump, featuring steps of either adjusting the operation of the pump, or issues a warning to a user of the pump of an undesirable operating condition, or both, based on a comparison of an actual torque value and a corrected torque value either alone or in combination with a further step of compensating the corrected torque value based on a mechanical power offset correction. The corrected torque value may include a Best Efficiency Point (BEP) torque value and may also be compensated for based on at least the current operating speed of the pump. The pump has a controller for performing the steps of the method. The controller can compensate the corrected torque value based on the square of the speed change of the pump.