Analysis of Electric Power Losses in the Course of Operation of a Group of Pumps Equipped with Adjustable Drive

Summary

Calculations of the power losses in pump units with aggregates operating simultaneously, one of them is adjustable, are presented. The main advantage of a control scheme with one adjustable pump is a relatively low cost of an apparatus part. But additional power losses connected with reduction of rotation frequency of a pump impeller of the adjustable pump in the course of operation of unregulated pumps under conditions of maximum output are unavoidable. Calculations of these losses made with the use of vector diagrams of hydraulic capacity of pumps make it possible to develop a structure of a power efficient pumping unut characterized by acceptable cost of equipment and minimal power expenditures to maintain the preset pressure in a pressure line.

Key words:

pressure , pump unit , frequency of pump impeller rotation , capacity , hydraulic capacity , frequency of feeding voltage , frequency converter

Economic efficiency of using pumping units with variable-speed drives at low water supply

Summary

In the process of operating pumps with variable-speed drive at low water flow rates the reduction of the pumping unit efficiency factor is observed. It is suggested to determine the amount of energy lost during the operation of such pumping units with actual efficiency factor differing from the rated one. In some instances operating with low water flow rate results in power consumption increase. In this context experimental studies on determining the pumping unit efficiency factor at different impeller speeds were carried out. The results of the studies provided for identifying the optimal operation zone where the pumping unit efficiency factor was reduced by less than 2% of the maximum value, and the less economic zone where the efficiency factor was reduced to 35% of the maximum value. To evaluate the economic efficiency and determine the optimal operation area of pumping units with variable-speed drives at low water flow rate the efficiency curves for different pump impeller speeds are required. It is appropriate to include this data in pump catalogues.

Key words

adjustable electric drive , water supply , flow rate , head , frequency of pump impeller rotation , pump , water disposal , lifting efficiency , electric motor power