The correct answer is: A. alternator type machines
Synchronous motors are a type of AC motor that runs at a constant speed, regardless of the load. They are used in a variety of applications, including pumps, fans, and compressors. Synchronous motors are typically more efficient than induction motors, and they can be used in applications where precise speed control is required.
Alternator type machines are a type of synchronous motor that uses a rotating magnetic field to induce current in the stator windings. The stator windings are connected to an external power source, which provides the current that flows through the windings. The rotating magnetic field is created by a rotor that is turned by an external source of power, such as a steam turbine or an electric motor.
Induction type machines are a type of AC motor that uses a rotating magnetic field to induce current in the rotor windings. The rotor windings are not connected to an external power source, and the current that flows through the windings is induced by the rotating magnetic field. The rotating magnetic field is created by a stator that is turned by an external source of power, such as a steam turbine or an electric motor.
Salient pole type machines are a type of synchronous motor that has a rotor with poles that are not evenly spaced around the circumference of the rotor. This type of rotor is used in applications where high starting torque is required.
Smooth cylindrical type machines are a type of synchronous motor that has a rotor with poles that are evenly spaced around the circumference of the rotor. This type of rotor is used in applications where high efficiency is required.