Starting of induction motor by insert resistance

Starting a three-phase induction motor by inserting resistance is a method specifically used for wound-rotor induction motors (WRIM)

Why Use Resistance for Starting?

Purpose:

• Reduce starting current
• Increase starting torque
• Provide smoother acceleration

🛠️ How It Works (Rotor Resistance Starting)

1. Additional resistors are inserted into the rotor circuit via slip rings.
2. At startup, maximum resistance is inserted → reduces current, increases slip, and improves starting torque.
3. As the motor gains speed, the resistors are gradually removed (stepped or continuous control).
4. Once the motor reaches near full speed, the rotor is shorted (like a squirrel cage).