Slip ring type or wound type rotor
In this type of rotor, a large no of rotor terms is used which increases the secondary voltage and reduces the current that flows through the slip rings. The rotor windings may be start or delta connected but the star connection is more preferable.
The 3 finished terminals are connected together to form a star point. The other point of the star is connected to 3 phosphorous bronze or brass slip ring mountain on but insulated from the rotor shaft. The three brushes which carry the current placed near the slip rings. These brushes are externally connected to a three phase star connected rheostat for the purpose of starting and speed control.
At the time of starting, the entire resistance is included in the rotor circuit and these resistances are gradually cutout as the rotor fine of the speed, when the rotor reaches near to the rotor speed the entire external resistance is cut out and the rotor windings are short circuited automatically by the slip ring with the help of metal collar. The rotor bars can be squired in this case also. It can produce high starting torque for the demerit is that a skilled operator is required.
3 supply is given to the motor stator produces magnetic field the resultant magnetic field established by the currents following in the 3 windings is of the magnitude 1.5 times of the maximum strength produced by individual phase windings and shifts around the stator surface.
If any two of the 3 supply lines to the stator winding is reversed, their by reversing the phase sequence of the stator currents.