HOW IS MOTOR POWER DETERMINED FOR CENTRIFUGAL PUMPS?
The motor size for centrifugal pumps is selected according to the shaft power value of the pump. There are internationally accepted and used ISO standards regarding pump shaft power values and the minimum motor sizes required. Apart from these standards, the most common method used when selecting motor power is to select a motor capable of providing the required power all the way to the end of the pump's shaft power curve. For example, if the power requirement at the pump's selection point is 16 kW and the value at the very end of the power curve is 21 kW, a 22 kW electric motor can be selected. In such an application, there is no need to use a 30 kW motor.
Since shaft power is related to the density and viscosity values of the fluid being pumped, motor selection for pumps that will operate in hot applications in particular must also take into account the shaft power at start-up conditions, when the fluid to be pumped is cold.
