Which D.C. motor has got maximum self loading property?

Solution (By Examveda Team)

Self-loading property refers to a motor's ability to automatically increase its load when the speed decreases slightly. In simpler terms, it means how well a motor can handle sudden increases in the amount of work it needs to do.

Option A: Series motor This statement is correct. Series motors have a high starting torque and naturally increase their torque output as the speed decreases. This makes them ideal for applications requiring heavy loads from the start, such as cranes or electric trains. The self-loading property is especially high in series motors because as the load increases, the current increases, which in turn increases the magnetic field and torque. This is why series motors are commonly used in high-torque applications where the motor needs to handle sudden increases in load.

Option B: Shunt motor This statement is incorrect. Shunt motors maintain a relatively constant speed regardless of changes in load. While they are efficient and provide stable operation, they do not exhibit the self-loading property like series motors. The field winding in a shunt motor is connected in parallel to the armature, so the field current remains constant and does not increase as the load increases. This means that the torque does not increase significantly with load, leading to a poor self-loading property.

Option C: Cumulatively compounded motor This statement is incorrect. Cumulatively compounded motors combine both series and shunt motor characteristics. They have a good balance between starting torque and speed regulation, but their self-loading property is not as high as a series motor. While they do have some self-loading features due to the series winding, they are not as efficient at increasing torque when speed decreases, making their self-loading property less pronounced compared to a series motor.

Option D: Differentially compounded motor This statement is incorrect. Differentially compounded motors have poor starting torque and can even become unstable under heavy loads. They have the worst self-loading property of all the D.C. motor types. The field winding configuration in these motors causes the magnetic flux to oppose the armature flux, resulting in decreased torque and an inability to handle sudden increases in load effectively.

Therefore, the correct answer is Option A: Series motor, as it has the maximum self-loading property due to its high starting torque and ability to automatically adjust to load changes by increasing its torque output as speed decreases.