Quickly estimating the energy savings available by installing variable speed drives to motors is simple as their power consumption is governed by the cube law (see earlier article).   In the example given, a 10% speed reduction saves 27% of the running cost. Energy savings calculators are also available for more complex applications, but flow applications are particularly suited to this type of speed control.

Flow applications include centrifugal fans, pumps and blowers fans where speed control can be used as an alternative to valves and dampers.  Other similar ‘variable torque’ applications include turbine pumps, agitators, and axial compressors.
Because ‘variable torque’ duty is less demanding than high performance application the inverter drives manufacturers either offer fan and pump ratings for their products, or specific products as a lower cost option.

Variable speed drives for fan and pump duty applications are available from a range of manufacturers including:

Altivar 61 from Schneider Electric (Telemechanique)

FR-F700 from Mitsubishi Electric- Mitsubishi energy savings calculator

MX2 from Omron-Omron energy savings calculator

Jaguar VXR from IMO

Go to www.999inverters.co.uk for more information