Control System for Vertical Turbine Pumps

standard input frequency to a motor controller is 60 Hz. The speed of the pumps

is controlled by adjusting the output frequency of the motor controllers, using a

human interface module located on the front of each motor controller, shown

previously in Figure 17. The output frequency can be adjusted from 30 to 100

percent of the input frequency (i.e., output frequency = 18 to 60 Hz). Because

there is a linear relationship between output frequency, pump speed, and pump

discharge, the discharge from the pump can be controlled from 30 to 100 percent

of the maximum discharge rate. A detailed description of how to operate the

motor controllers can be found in, Allen-Bradley (1996).

Each of the motor controllers were equipped with optional serial

communication modules to provide a direct digital link between the 20 motor

controllers and a personal computer. Control software could be developed that

would allow the operator to enter the required discharge rates into the computer,

and the software would calculate the output frequency for each motor controller

based on the relationship between output frequency and pump discharge,

previously shown in Figure 19. The control software would then adjust the

output frequency of the motor controllers, based on the difference between the

measured flow rate and the required flow rate. This would automate the present

method of manually iterating to the required pump settings. Furthermore, using a

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Chapter 6

Experiment Control, Data Acquisition, and Analysis Packages