InfoWorks ICM and CS have a number of different ways to model pumps. The two most commonly used are:
- Fixed Pumps (a simplistic method where the discharge is independent of the head on the pump) and
- Rotodynamic Pumps (where a head-discharge curve is used to determine the flow rate of the pump, but there is no speed control of the pump).
Variable Frequency Drive Pumps allows the user to change the speed of a rotodynamic pump by use of an Real Time Control (RTC). These are not to be confused with the Variable Speed Pump – which regulates discharge, and not speed of the pump.
Step 1: Create the model and include the pump as type VFDPump.
Step 2: Define the Head Discharge Curve for the pump at its nominal speed, and specify the Switch On and Off levels. You can use these levels to control the pump, and then use the RTC only for the speed regulation, or if there are more complex rules these values can be included in the RTC rule.
Step 3: Enter the Regulator details – Minimum Speed and Maximum Speed are what sets the bounds on the pump operation
Step 4: Create the RTC. Rule Order is very important. The controller is used to determine how often the regulator is can implement a change, and the threshold defines a minimum change that can occur. In the example below the pump turns on when the level reaches 11m AD, then regulates it’s speed to maintain a target level of 10.5m AD and will turn off when the speed of the pump drops below 1270 rpm.
The results are then available in the usual graph views, but you can also access the pump operating points.