Cascade circuit – combination of soft starter and frequency converter

Monday, October 25, 2010

A drinking water supply has to guarantee maximum availability. To ensure this availability, several pumps are operated in a cascade circuit. A combination of variable and fixed speed represents the optimum solution in terms of investment and energy. While the fixed-speed pumps cover the base load, a variable-speed pump controls the variable delta (changing load).



Compared to versions with throttle valve, the cascade version based on a Sinamics G120P frequency converter which provides the base load supply for the Sirius switching devices facilitates the following cost savings:

  • 12.000€  Acquisition cost 

  • Approx. 5,000 Euro energy costs p.a.

  • Approx. 26 tons CO2 emission p.a.


Advantages at a glance

  • Avoidance of peak loads thanks to the application of SIRIUS soft starters

  • Corresponding peak load reduction by up to 60 %

  • Avoidance of stress factors such as water hammers  thanks to soft start-up

  • Prolonged motor service life thanks to soft start-up and ramp-down