Joe Evans is responsible for customer and employee education at PumpTech, Inc., a pump and packaged system manufacturer and distributor with branches throughout the Pacific Northwest. He can be reached via his website, www.PumpEd101.com. If there are topics that you would like to see discussed in future columns, drop him an email.
The ratio of available motor HP to required pump HP increases exponentially as speed is reduced. Figure 2 shows this relationship for the same pump and a 10-HP motor. Here, the available HP does not meet the required HP until the speed is below 50 Hz. If the reader’s design point could have been met at 45 Hz, the 10-HP motor would have been adequate. The calculator that produced Figures 1 and 2 is available on the “Pump Evaluation, Selection & Testing Tools” on my website.