Flow charts to assess the suitability of a VSD for a pump system are shown in Figures 9.1 for rotodynamic pumps and 9.2 for positive displacement
pumps. These are based on using a variable frequency drive, which will be more efficient than any speed control device, which uses slip to vary the speed. Having established that using a VFD is appropriate, Figure 9.3 is a flow chart for selecting the correct drive and making the life cycle cost calculation. Chapter 12 will help in making the financial justification.
Appendix A2.4 contains information on the factors to be considered in sizing a drive.