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Pump or Fan Affinity Laws Calculator


A variable speed drive (VSD), also known as a variable frequency drive (VFD), is an electronic device used to control the speed and torque of an electric motor. It works by adjusting the frequency and voltage supplied to the motor, which in turn varies the motor’s speed and power output.

VSDs are commonly used in applications where electric motors are used for tasks such as pumping or fan operation. In these applications, the motor may not always need to run at full speed, and in fact, running the motor at full speed continuously can be inefficient and wasteful.


By using a VSD to adjust the speed of the motor to match the load requirements, the motor can operate at the optimal speed and power output for the task at hand. This can lead to significant energy savings compared to running the motor at a fixed speed or using traditional methods of controlling motor speed, such as throttling the flow of a fluid.

In addition to energy savings, VSDs can also help to prolong the life of motors and other equipment by reducing stress and wear caused by excessive speed or torque. They can also provide greater precision and control over motor operation, making it easier to optimise processes and improve performance.


The preliminary calculations for energy efficiency provided on this website are intended to serve as a guide only. They are not to be considered as a decision tool for making capital investments or for detailed design purposes.

While we make every effort to ensure the accuracy and reliability of the information presented, we cannot guarantee the completeness or applicability of the results obtained from these preliminary calculations.

It is important to note that actual energy efficiency and savings may vary based on factors such as equipment selection, building design, operating conditions, and other variables not accounted for in these preliminary calculations.

Therefore, we strongly advise that any decision to invest in energy efficiency improvements should be based on a thorough analysis conducted by a qualified professional. We would be happy to help you in this aspect if you require.

We disclaim any liability for any damages or losses arising from the use or reliance on the results of these preliminary calculations.