Contactor Selection for Motor Control
How to select contactors by current rating, coil voltage, and application. DOL, reversing, and star-delta configurations.
Current Rating
Size the contactor for motor full-load current at the operating voltage. For AC-3 duty (squirrel-cage motors), use the rated operational current. Typical sizes: 9A, 12A, 18A, 25A, 32A, 40A, 50A, 65A.
Coil Voltage
24V DC and 230V AC are common. Use 24V for PLC-controlled circuits; 230V for direct mains control. Ensure auxiliary contacts match your logic requirements (NO/NC).
Reversing and Star-Delta
Reversing: use two contactors with mechanical interlock. Star-delta: use three contactors (main, star, delta) with timer. All contactors must be same size.
