The main difference between a squirrel cage induction motor and a wound rotor induction motor is in the type of rotor they use. A squirrel cage motor uses a rotor with conductive bars, typically made of copper or aluminum, arranged in a cage-like structure. A wound rotor motor, on the other hand, uses a rotor with a set of windings that are connected to slip rings, allowing external resistors or other devices to be used for controlling the motor.