Energy savings with variable speed drives

Everyone today is interested in saving power (kW) where possible; the financial pressure applied to individuals, companies and governments has ensured that technology makes this achievable.

A simple solution is to replace conventional light bulbs with low-energy LED equivalents. This definitely saves energy, but many installations are required to make significant savings in energy consumption. In the commercial, industrial, and health service areas there are major savings available where standard three-phase motors are used.

The motor, while being an efficient workhorse, has two areas of power wastage:

  • the cost of power wastage due to a poor power factor
  • the cost of running a motor at full speed when a slower speed will suffice

Both these areas are addressed by the installation of a Variable Speed Drive (VSD). The VSD raises the power factor closer to unity and allows the speed of the motor to be reduced to meet the 'required' load conditions.

These load conditions may have been met with a motor running at full speed and the control of the 'load' defined by operation of dampers or valves.

Simple instant savings rules are:

  • reduce the speed of your motor by 20 per cent and save 50 per cent of your energy costs
  • reduce the speed of your motor by 50 per cent and save 80 per cent of your energy costs

*Originally published in Retrofit.