Energy saving with pump's AC adjustable speed drives

The pumps are the most frequent type of working machine with consumption of ca. 30% of total produced electrical energy in highly developed countries. They are usually driven by AC motors-squirrel cage induction motor (SCIM), slip ring induction motor (SRIM) and synchronous motor (SM). The classic pump control systems (throttling, by pass, vanes rotation) do not contribute to energy saving. The only way for energy saving is adjustable speed drives with AC motors application. The most convenient power electronics converters suggested for pumps driven by AC motors are current source inverter (CSI), undersynchronous cascade (USC) and load-commutated inverter (LCI).