Action model of an asynchronous machine
Asynchronous machines with flux vector control

Three-phase asynchronous machines are distinguished by the design of the rotor, which determines the motor torque characteristic as a function of speed.

In asynchronous machines with wound rotor (figure 2a), the rotor windings are accessible and can be connected to rings, and the resistance of the rotor circuit can be varied by inserting externally connected resistors.

In squirrel-cage machines (figure 2b), the rotor winding is inaccessible; it consists of aluminum or copper bars, the ends of which are joined on both sides of the rotor by short-circuiting rings of the same metal.