Patent ID: 7117120
Filing Date: 2006-10-03
Classification: E21B,F04B,F04D

Abstract:
1. A method of controlling a centrifugal pump for transferring fluid within a fluid system, the method comprising the steps of: determining a value of speed input to the centrifugal pump; determining a value of pump flow rate; using the value of speed input and the value of pump flow rate to calculate one or more values representing the performance of the centrifugal pump; using the centrifugal pump performance values to produce one or more command signals, including the steps of selecting a centrifugal pump performance parameter to control, determining a setpoint for the selected centrifugal pump performance parameter, calculating a control signal using the setpoint value of the selected centrifugal pump performance parameter, and calculating the one or more command signals from the control signal; and using the one or more command signals to control the speed of the centrifugal pump, wherein the selected centrifugal pump performance parameter is the pump flow rate and the step of using the one or more command signals to control the speed of the centrifugal pump includes repetitively switching the speed of the centrifugal pump between a set pump speed for a portion of a cycle period and zero speed for the remainder of the cycle period to achieve an average pump flow rate equal to the setpoint value of the pump flow rate.