Preferred Motor for Heavy Duty Starting:

3-phase squirrel cage Induction Motor (IM):
- A 3-phase squirrel cage IM is preferred for heavy-duty starting due to its high starting torque capabilities.
- These motors are rugged, reliable, and can withstand high starting currents without overheating.
- The squirrel cage design also allows for smooth acceleration and reduced maintenance requirements.

DC Shunt Motor:
- While DC shunt motors have good starting torque characteristics, they are not as commonly used for heavy-duty starting applications.
- DC motors require regular maintenance and are less efficient compared to 3-phase IMs.
- The starting current of a DC shunt motor can be high, leading to potential overheating issues in heavy-duty applications.

DC Series Motor:
- DC series motors have high starting torque, making them suitable for heavy-duty starting applications.
- However, these motors have a tendency to draw excessive current during starting, which can cause overheating and reduce motor life.
- DC series motors are not as commonly used for heavy-duty starting compared to 3-phase IMs.

Single Phase Induction Motor (IM):
- Single phase IMs are not preferred for heavy-duty starting as they have lower starting torque compared to 3-phase IMs.
- These motors are less efficient and may struggle to start heavy loads, leading to potential overheating issues.
- Single phase IMs are more suitable for light-duty applications where high starting torque is not required.