Operation of propeller motors composed of ship electric propulsion systems with semiconductor converters

Abstract

The calculations of transient processes in ship electric propulsion systems (EPS) with semiconductor converters (SC) show that when the inverter transistors are locked, overvoltage occurs that may break through the insulation of propeller motors (PM). A feature of this overvoltage is its short duration and large value. Pulsed overvoltage of small duration and the EPS value of dozens or more kilovolts may occur in the circuits of the inverter supplying the PM winding. The main cause of overvoltage is the EPS self-induction resulting from rapid current reduction in circuits with inductances, including in motor windings, when the inverter transistors are locked. The paper presents the results of mathematical modeling of the processes arising when the inverter transistors functioning as part of the frequency converter are locked. The results of the analysis confirmed the possibility of overvoltage on the PM winding, which should be taken into account when designing the EPS and selecting equipment.