![]() When the motor attains normal speed, the three brushes are short-circuited so that wound rotor runs like a squirrel cage rotor. The external resistances are used during starting period only. These resistances are gradually reduced to zero as the motor runs up to speed. At starting, the external resistances are included in the rotor circuit to give a large starting torque. The three brushes are connected to a 3-phase star-connected rheostat. The open ends of the rotor winding are brought out and joined to three insulated slip rings mounted on the rotor shaft with one brush resting on each slip ring. The rotor winding is uniformly distributed in the slots and is usually star-connected. How rotor windings are connected to supply and why wound rotor type is preferred to squirrel cage type induction motor? While wound rotor consists of a laminated cylindrical core and carries a 3-phase winding, similar to the one on the stator. The rotor is not connected electrically to the supply but has current induced in it by transformer action from the stator. The entire construction (bars and end rings) resembles a. This forms a permanently short-circuited winding which is indestructible. All these bars are joined at each end by metal rings called end rings. ![]() One copper or aluminum bar is placed in each slot. Squirrel cage rotor consists of a laminated cylindrical core having parallel slots on its outer periphery. The winding placed in these slots (called rotor winding) may be one of the following two type :ĭifferentiate between Squirrel cage type rotor and Wound type rotor? What are the major types of Rotor Winding placed in 3 phase induction motor? motor where both stator winding (i.e., field winding) and the rotor winding (i.e., armature winding) are connected to a voltage source. In which motor both stator and rotor winding are connected to voltage source? The rotor, mounted on a shaft, is a hollow laminated core having slots on its outer periphery. With what material the rotor of 3 phase motor is made? This rotating field induces currents in the rotor by electromagnetic induction. When 3-phase supply is given to the stator winding, a rotating magnetic field of constant magnitude is produced. Greater the number of poles, lesser is the speed of the motor and vice-versa. The 3-phase WINDING stator winding is wound for a definite number of poles as per requirement of speed. In the stator slots and are suitably connected to form a balanced 3-phase star or delta connected circuit. The rotor is separated from the stator by a small air-gap which ranges from 0.4 mm to 4 mm, depending on the power of the motor. shunt motor.ĭescribe the construction of a three phase motor?Ī 3-phase induction motor has two main parts (i) stator and (ii) rotor. (ii) Its starting torque is inferior to d.c. (i) It is essentially a constant speed motor and its speed cannot be changed easily. (iv) It has high efficiency and reasonably good power factor. (i) It has simple and rugged construction. What are the advantages and disadvantages of three phase induction motor? machine in which electrical energy is converted into mechanical energy. The induction motor may be considered to be a transformer with a rotating secondary and it can, therefore, be described as a “transformer-type” a.c. The rotor winding derives its voltage and power from the externally energized stator winding through electromagnetic induction and hence the name acquired. Only the stator winding is fed from 3-phase supply. The stator carries a 3-phase winding (called stator winding) while the rotor carries a short circuited winding (called rotor winding). Like any electric motor, a 3-phase induction motor has a stator and rotor.
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