Correct Answer - Option 4 : 100 kW
Construction of a Synchronous Machine:
The alternator or motor consists of two main parts, namely the stator and the rotor.
The stator is the stationary part of the machine. It carries the armature winding in which the voltage is generated. The output of the machine is taken from the stator.
The rotor is the rotating part of the machine. The rotor produces the main field flux.
Stator Winding:
Slots are cut on the inner periphery of the stator core in which 3 phase or 1 phase winding is placed. Embedded copper is used as a winding material. The winding is star-connected. The winding of each phase is distributed over several slots. When the current flows in a distributed winding it produces an essentially sinusoidal space distribution of EMF.
Rotor Construction
The rotating part of the machine is called Rotor. There are two types of rotor construction, namely the salient pole type and the cylindrical rotor type.
Pole Core and Pole Shoe:
It is made of laminated steel sheet material. The Pole core provides the least reluctance path for the magnetic field and the pole shoe distributes the field over the whole periphery uniformly to produce a sinusoidal wave.
Field Winding or Exciting Winding:
It is wound on the former and then placed around the pole core. DC supply is given to it through slip rings. When direct current flows through the field winding, it produces the required magnetic field.
Damper Winding:
At the outermost periphery, holes are provided in which copper bars are inserted and short-circuited at both sides by rings forming Damper winding.
Conclusion: Due to very complicated construction, a synchronous motor is generally used beyond 100 kW.
