The addition of variable speed drives is an excellent and low-cost solution to increase the differential pressure of â€œstandardâ€ centrifugal pumps. The head developed by a pump is increased by the square of the difference of the speed. For example, if the speed is increased by 10%, the discharge pressure is increased by 21%. If the speed is increased by 20%, the discharge pressure is increased by 44%. At the same time, pump flow rates will increase in direct proportion to the increase in speed.
When using variable speed drives, take care not to overload the motor since the horsepower required is directly proportional to the cube of the difference in the speed.
Standard canned motor pumps can operate between 1035 and 4140 RPM without any special considerations as long as the motor is not overloaded at the higher speeds. For speeds above 4140 rpm, special motors and bearing systems are available.