The correct answer is: A. Shunt motor
A shunt motor is a type of DC motor that has a shunt field winding that is connected in parallel with the armature winding. This type of motor is preferred for elevators because it has a constant speed characteristic, which is important for maintaining a smooth ride.
A series motor is a type of DC motor that has a series field winding that is connected in series with the armature winding. This type of motor has a high starting torque, which makes it ideal for applications where a large amount of torque is required at startup. However, series motors have a poor speed regulation characteristic, which means that their speed varies significantly with load. This makes them unsuitable for applications where a constant speed is required, such as elevators.
A differential compound motor is a type of DC motor that has a series field winding and a shunt field winding. The series field winding is connected in series with the armature winding, while the shunt field winding is connected in parallel with the armature winding. This type of motor has a high starting torque and a good speed regulation characteristic. However, differential compound motors are more complex and expensive than shunt motors.
A cumulative compound motor is a type of DC motor that has a series field winding and a shunt field winding. The series field winding is connected in series with the armature winding, while the shunt field winding is connected in parallel with the armature winding. The direction of the current in the shunt field winding is opposite to the direction of the current in the series field winding. This type of motor has a high starting torque and a good speed regulation characteristic. Cumulative compound motors are more complex and expensive than shunt motors, but they are more efficient than differential compound motors.