🔍 Key Concepts

• Wound-rotor induction motor starting characteristics and why external starting resistance is used in the rotor circuit • How the manual drum controller positions in figure B gradually cut out rotor resistance as you move the handle • What happens to starting current and torque if you begin with little or no resistance in the rotor

💭 Think About

• Look at the contact segments on the right side of figure B: in which handle position is the maximum amount of starting resistance connected in the rotor circuit? • If you were to place the handle directly in a higher-speed position, what would the rotor current and mechanical shock on the motor be compared to starting in the first position? • Which controller position is specifically designed for the motor to be brought up from rest before resistance is cut out?

✅ Before You Answer

• Identify which speed position has all starting resistance in series with the rotor windings; that is the only safe starting position. • Check whether any of the higher speed positions momentarily place the rotor nearly across the line (very low resistance) when starting from rest. • Confirm that the correct choice matches the requirement that you must limit inrush current and mechanical stress when the motor starts from standstill.