The start-up process refers the process by which the drive is activated and accelerated until the operating point of the pump is reached. There are several starting methods to make this stage of operation as low in impact as possible.
The torque (Tp) of the pump that is transferred by the shaft coupling is directly related to power (P) and rotational speed (n). When the centrifugal pump is started up, the torque versus speed curve is almost a parabola. The starting torque provided by the asynchronous motor, however, must be greater for the rotor to reach operating speed.
This motor torque, together with the voltage, has a direct impact on the current drawn by the motor and thus also characterises the build-up of heat in the motor winding. Impermissible heat build-up in the motor should be avoided by limiting the run-up time and/or current.