Star-Delta Starter Electrical Schematic for 3-Phase Motor Control

This electrical schematic depicts a star-delta starter configuration for a three-phase induction motor. The circuit features three main contactors: star contactor (KW1), delta contactor (KW2), and main contactor (KW3), all controlled through an MCCB (Molded Case Circuit Breaker) with terminal overload protection. The diagram illustrates the complete power circuit with three-phase supply lines (R, Y, B) and motor terminal connections (U1, V1, W1, U2, V2, W2). The star connection initially limits starting current by connecting windings in series, while the delta connection is engaged for normal operation, providing full voltage to each winding. This configuration is particularly effective for motors above 5HP where direct-on-line starting would cause excessive inrush current and potential voltage dips. The implementation includes overload protection circuitry, which is essential for preventing thermal damage during prolonged current surges or phase imbalances.