Precision Power Conversion: ABB 5SKA 280/20EH Module for Controlled Rectification

In a large cement plant, the raw mill’s 3000 kW synchronous motor requires a smooth, controlled start to prevent mechanical stress on the gearbox and power grid disturbances. A high-voltage liquid resistance starter is being replaced with a modern thyristor-based soft starter. The heart of this new starter is the ABB 5SKA 280/20EH​ module. Six of these modules (one per thyristor in a 3-phase anti-parallel configuration) are mounted on a water-cooled heat sink. During start-up, the control system gradually increases the firing angle of the thyristors, allowing more voltage to reach the motor windings and smoothly ramping up speed. The integrated diode provides a freewheeling path. The module’s rugged 280A current rating and high voltage withstand capability directly address the pain points of inrush current and torque jerks, enabling a soft, reliable start that extends mechanical lifespan and reduces peak demand charges on the plant’s electrical supply.