Centrifugal Pump Load:
Centrifugal Pump Load are used as boiler feed pumps and for pumping water in water pipe lines. The former must be adapted to the variable output of the steam generator. In the latter, varying water requirements of an area decide the delivery rate. The delivery rate of a pump is regulated by its speed. A variable speed drive system is required to drive the centrifugal pumps.
The requirements of a Centrifugal Pump Load are:
- Starting: A smooth starting of the load may be imperative so that no pressure surges exist in the hydraulic system. Also, the starting of the motor must avoid current peaks in the supply system while providing starting torque required by the load.
- Operating safety—Flexibility: The system used should have operating safety and flexibility. In case of any failure in the system the system must be able to drive the load so that continuity is maintained.
- Available power and speeds: The Centrifugal Pump Load are developed for all powers and speeds. Speeds up to 1800 rpm are there. In some exceptional cases speeds of 3600 rpm, 6000 rpm are required.
- Power Consumption: The drive motor used is based on the power requirement. The speed control is required over a wide range. The power consumption must be optimum.
Based on the above requirements, wound rotor induction motors with sub-synchronous converter cascade in the rotor circuit and converter fed synchronous motors are used very widely as the drives for Centrifugal Pump Load. Even though dc motors fed from converters are, versatile in smooth starting and smooth speed control they cannot be developed for high power and high speeds due to the commutator. Hence they are very seldom used as drives for centrifugal pumps.