Maximise savings in water pump and waste applications

In water applications, centrifugal pumps are driven by an induction motor directly fed from the network. Flow regulation is accomplished by a few different means, namely throttling, a highly inefficient method as hydraulic losses increase dramatically when the flow is strangled by a valve; variable-frequency drives ensure flow regulation by controlling the rotational speed of the motor shaft; and alternatively, on and off pump operation following a precise duty cycle – the pump is not operated continuously, but switched on for the time needed for pumping the target water volume and disconnected for the rest of the time. Given that many different hydraulic systems recommend the use of frequency converters or cyclic control (ie softstarter technologies), which one of these two solutions is the most cost-effective in reducing energy consumption and providing the most satisfactory payback time?

 

Take note

  • Softstarters can provide energy saving in specific applications.
  • Variable frequency control is best in friction loss dominated systems.
  • Cyclic control is best for static head dominated systems.

 

Published as: Softstarters… VSDs… or both?

By J Sagarduy, J Kristensson, S Kling and J Rees, ABB, Sweden

Electricity+Control, March 2012 (pgs 30 – 37)

Email: juan.sagarduy@se.abb.com; jesper.kristensson@se.abb.com; soren.kling@se.abb.com; johan.rees@se.abb.com; Hendrik.Spies@za.abb.com