Energy efficiencies from variable speed motor control in pumps, fans and compressors

A large proportion of the electricity produced around the world is used to raise, move or pressurise liquids and gases with machines such as pumps, fans and compressors.  With energy consumption awareness, attention must be paid to machine operation and the energy savings that can be achieved through variable speed control of motors.

Numerous industrial sectors have pumping, ventilation and compression needs. It is estimated that in industrial processes and building utilities, 72 % of electricity is consumed by motors, of which 63 % is used to drive fluid flow in pumps, fans and compressors.

Traditional flow control

Traditional methods of flow control rate or pressure involve varying the effective cross-section of the pipe or circuit through which the fluid flows. Valves, taps and gates are the most commonly used devices.

Substantial energy savings can be obtained by using variable speed drives to control the flow rate or pressure in pumps, fans and compressors as opposed to the above physical or mechanical means. In pumping applications, the most significant savings are achieved with centrifugal pumps.

In a technical publication from Schneider Electric (Cahier technique No. 24) the writer considers how centrifugal pumps, fans and compressors function in different operating modes, and quantifies the energy savings that speed control can generate.  He demonstrates the use of variable speed in hydraulic machines such as pumps, fans and compressors is the key way of reducing energy consumption in numerous industrial and commercial installations.

The energy savings are particularly significant if reduced flow rates are used on a frequent basis. The sums invested in variable speed drives are paid back very quickly and subsequently generate considerable savings through their operating life.

Additional benefits

In addition to energy savings, variable speed drives bring many additional benefits to these applications. For example, mechanical constraints, such as water hammer, cavitation and torque surges, are greatly reduced by the gradual and controlled acceleration and deceleration of the motor. This extends the life expectancy of equipment; improves flow and pressure control, and reduces noise pollution

Download examples

The key principles of fluid flow control have been presented, together with examples that illustrate the extent of the energy savings that can be achieved through the use of Schneider Electric variable speed drives. The complete document is available for download from the Schneider Electric website

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