Study of Start-up and Shutdown Modes of an Asynchronous Electric Drive for a Centrifugal Pump

Abstract

The aim of this study is to investigate the commutation processes of an asynchronous short-circuited electric drive for a centrifugal pump. The set goal is achieved by solving two tasks: analyzing the dynamic modes of connection to and disconnection from the network of the asynchronous motor of the centrifugal pump for a given power supply scheme; assessing the qualitative and quantitative indicators of the transient processes of the electric drive. Among the most significant results of the study, it is possible to highlight the ability to form practical recommendations on the operation peculiarities of electric drives for a wide class of mechanisms. The conducted research allowed asserting that in an electrical system with capacitors directly connected to the stator winding and during both the connection and disconnection of the drive motor of the centrifugal pump, voltages significantly exceeding the nominal ones may occur. It has been determined that considering the harsh operating conditions of pump units, such overvoltages represent a danger to the motor winding insulation. During the motor disconnection, significant overvoltages on the stator windings are possible if, for any reason, the capacitor's capacitance exceeds the calculated base value for the applied motor. The practical significance of the obtained results lies in the fact that the assumption of the motor transitioning to intensive braking mode and subsequent hydraulic shock upon disconnection from the network due to self-excitation did not prove to be true. The electric drive provides braking under the action of the load torque without mechanical overloads.