With pumps that are operated in partial load, the volume flow of the operating point is less than the operation under full load. While the largest possible torque is provided with given speed under full load, the operation in partial load effects a throttling. It is brought about by reducing the energy supply.
Partial load operation can be meaningful because the highest efficiency of the transporting unit is usually not close to the full load characteristic. If the speed is reduced, the result is generally a more efficient operation. With variable operation, a pump can also be controlled demand-driven – it requires only as much energy as necessary for transporting the desired or incurred quantity of the medium. On a long-term perspective, an operation with partial load also positively affects the operating life of a pump.
The easiest way to accomplish partial load operation is via a frequency converter. In such a setup, the speed of the transporting unit can be adjusted in a flexible way.