The correct answer is: A. Series motor
A series motor is a type of DC motor that has the field winding and the armature winding connected in series with each other. This means that the current flowing through the field winding is also flowing through the armature winding. This results in a high starting torque, which makes series motors ideal for applications where a large amount of torque is required at startup, such as cranes and hoists.
However, series motors also have a number of disadvantages. One disadvantage is that they are not very efficient, as the current flowing through the field winding also causes heating losses. Another disadvantage is that they are not very stable, as the speed of the motor is very sensitive to changes in load.
In the case of a load which is almost nil for certain part of the load cycle and peak value for short duration, a series motor is a good choice because it will provide the high starting torque required to get the load moving, and then it will be able to maintain a high speed even when the load is light.
A shunt motor is a type of DC motor that has the field winding connected in parallel with the armature winding. This means that the current flowing through the field winding is independent of the current flowing through the armature winding. This results in a more stable motor than a series motor, as the speed of the motor is not as sensitive to changes in load.
However, shunt motors also have a number of disadvantages. One disadvantage is that they have a lower starting torque than series motors. Another disadvantage is that they are not as efficient as series motors, as the field winding is always carrying current, even when the motor is not under load.
A compound motor is a type of DC motor that has both a series field winding and a shunt field winding. This gives the motor the best of both worlds, as it has the high starting torque of a series motor and the stability of a shunt motor.
However, compound motors are also more complex and expensive than series or shunt motors.
In conclusion, the correct answer is: A. Series motor.