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 2 a), 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 2 b), 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.