An increasing number of pumps are now being run using speed control in order to be able to define the dynamic volume flow. The pump’s quadratic characteristic causes the motor load to decrease rapidly at lower speeds, which results in the level of efficiency decreasing significantly. Using the diagrams, it can be seen that the ideal workload for the existing asynchronous motor is not reached, due to operation at partial loads (approx. 30%) and speeds (75%).
If the pump is then equipped with a PMSM motor that has an extended efficiency range including partial load operation, the level of efficiency can be increased by approx. 12% in this example and savings of more than EUR 250 per pump per year can be achieved (depending on the number of hours‘ operation per year).
The PMSM technology offers a major benefit above all for applications that run at partial load levels and variable speeds, allowing energy savings to be made. This means that the slight price increase for a new technology is amortised within just 10 months. And not only the efficiency is increased, also the gear size and weight can be reduced thanks to the higher performance density. Using the “synchronous
operation“ that it imposes, an exact flow level can be achieved e.g. with piston pumps.